CENTRE OF ADVANCED FACULTY - JNKVV · 14. Improving soil health through Green Manuring M.L.Kewat...

CENTRE OF ADVANCED FACULTYTRAINING

National Training Programme

on

Management of Soil Health: Challengesand Opportunities

(29th September to 19th October, 2014)

A.K. Rawat

B.L. Sharma

B. Sachidanand

R.K. Thakur

H.K. Rai

B.S. Dwivedi

Sponsored by

Indian Council of Agricultural Research

Organized by

Department of Soil Science and Agril. ChemistryJawaharlal Nehru Krishi Vishwa Vidyalaya

Jabalpur – 482 004 (M.P.)

PrefaceHealthy soil is the foundation of the food system. Soil health is the capacity of soil tofunction as a vital living system, within ecosystem and land-use boundaries, to sustainplant and animal productivity, maintain or enhance water and environmental quality andpromote plant and animal health. Soil health is critically important to sustain theagricultural productivity and environmental safety. Healthy soils provide a range ofenvironmental services including water infiltration, habitat provision and profitable andsustainable agriculture. In recent past anthropogenic reductions in soil health and ofindividual components of soil quality are a pressing ecological concern. There is a greatneed to increase awareness of the importance and utility of managing soil health forsustainable agricultural production system. Management of soil health involvesartistically combining a number of practices that enhance the soil's physical, chemical andbiological suitability for crop production. The key strategies for betterment of soil healthcould be the addition of abundant quantity of organic matter (crop residues, manures, andcomposts), suitable crop rotations, conservation tillage, mulching with living and deadresidue, reducing compaction and best nutrient and pesticide management practicesincluding biological components.Since the establishment of Centre of Advanced Faculty Training (erstwhile Centerof Advanced Studies) in 1995, 27 training programmes have been organized on variousthemes of Soil Science. The present training programme has been organized on“Management of Soil Health: Challenges and Opportunities” for Assistant Professors/Scientists and Associate Professors/ Senior Scientists of SAUs, ICAR institutes and otherAgricultural institutes with Masters degree in Soil Science & Agricultural Chemistry /Agronomy / Horticulture from 29th September to 19th October, 2014. This training willvirtually be helpful for better understanding how to maintain soil health for achievinghigher crop production and sustainability and also a better future for coming generation.I feel my proud privilege to acknowledge my sincere thanks to Dr. S. Ayyappan,Hon’ble Director General (ICAR), Dr. Arvind Kumar, Deputy Director General (Education)ICAR and Dr. Alok Jha, ADG (International Relations), ICAR for their keen interest in theCAFT project at JNKVV, Jabalpur. My sincere thanks are also due to Dr. V.S. Tomar, Hon’bleVice Chancellor, JNKVV, Jabalpur for his relentless efforts, keen interest and full support inCAFT activities.My sincere thanks to Dr. S.S. Tomar, Director Research Services, Dr. S.K. Rao, DeanFaculty of Agriculture, Dr. S.K. Shrivastava, Director Instructions and Dr. P.K. Mishra,Director Extension Services, JNKVV, Jabalpur for their valuable cooperation to CAFT.I would like to express my special thanks to all faculty members, guest speakersand other faculty members for imparting their expertise in their respective field ofspecializations.My thanks and appreciations also go to my colleagues and members of variousorganizing committees for successful organizing the training programme and people whohave willingly helped me out with their abilities.Jabalpur (A.K. Rawat)October, 2014 Director, CAFT

INDEXS.

No. Title Author Page No.

1. BIOFERTILIZERS: a tool towards soil healthmanagement A.K. Rawat 1-10

2. Soil Health and Food Security : Facts andReality

Sunil Bhaskar RaoNahatkar 11-19

3. Modeling Soil Erosion M.K.Hardaha 20-304. Test of Significance – I (Tests Concerning Mean) Ranbahadur Singh 31-405. Statistical Designs for Field Experimentation H.L. SHARMA 41-50

6. Biochar: A Potential Amendment for Soil HealthManagement

Anand Prakash Singh,Sumit Rai, PriyankaRani and Awtar Singh

51-64

7. Acid soil management for sustaining higher cropproductivity

Surendra Singh 65-67

8. Physical Indicators of Soil Health ForAgricultural Sustainability

H.S. Kushwaha 68-73

9. Effect of Plastic Mulch on Soil Properties andPlant Growth

Vijay Agrawal andS.S.Baghel

74-75

10. Diagnosis and Mitigation of Zinc Deficiency forSustainable Crop Production and Human Health

S.K. Singh 76-78

11. Micronutrient Application: Scaling up theproduction and storage quality of onion

Akhilesh Tiwari 79-82

12. INM: A key to improve and sustain soil health H.K. Rai 83-9013. Resource Conservation through Herbicide

Resistance managementM.L.Kewat 91-97

14. Improving soil health through Green Manuring M.L.Kewat 98-10315. Impact of continuous cropping with fertilizer and

manure application on soil fertility and cropproductivity

A.K. Dwivedi 104-107

16. Soil Pollution, its causes and remidial measuresfor sustaining soil health

B.L. Sharma and G.D.Sharma

108-114

17. Seed Priming: A Tool in Sustainable Agriculture F.C. Amule and N.G.Mitra

115-129

18. Integrated Nutrient management: way to forsustainable crop production

P.S. Kulhare 130-134

19. Screening and evaluation of plants for highwater-use efficiency

R.S. Shukla andNiharika Shukla

135-143

20. Role of Potassium in Sustainable AgriculturalProduction

A.K. Dwivedi 144-153

21. Microbial Indicators of Soil Health R.K. Thakur, F.C.Amule and N.G. Mitra

154-183

22. Soil Taxonomy: A New Trend of SoilClassification

G.P. Gupta 184-190

CAF T on M a n a g e m e n t o f S o i l H e a l t h : Ch a l l e n g e s a n d O p p or t u n i t i e s ” 2 9 S e p t . t o 1 9 O ct . 2 0 14

Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur – 482004 (M.P.) 1

BIOFERTILIZERS: a tool towards soil health management

A.K. RawatProfessor & Head,

Department of Soil Science & Agril. ChemistryJNKVV, Jabalpur

Green revolution brought selfsufficiency in food grain requirement ofthe country and made India selfsufficient in food grain production. ThePillars of green revolution were: Seed –Improved high yielding varieties; Water –Increase in irrigation ;Fertilizer – Use ofchemical fertilizers and Plant protection– Pests and disease management. TheAccomplishments (Since 1950-51 to2013-14) are: Food production: >5 times; Horticultural crops: >6 times; Fishproduction: >9 times; Milk production:>6 times and Egg production: >27 times.But Food requirements during 2025 willbe 320million tonnes while during 2050it will be 400+ million tonnes.

Challenges and responsibilities• To feed the ever growing population we

need to produce more and more foodfrom declining natural resources likeland and water.

• Experiments World over proved, can’tsustain productivity without externalsupply of nutrients.

• Intensification of agriculture with highyielding varieties accelerated in miningof native nutrients. Nutrient’s useefficiency is also a main concern.

• Improvement in soil health is verymuch essential to sustain ouragriculture. It is also our moralresponsibility to pass our naturalresources to next generation in abetter condition.

• Long term experiments are mostappropriate to address issues relatednutrients and soil health.

Low Nutrient use efficiency in Indiadue to poor soil health:Nutrient Efficiency (%)Nitrogen 30-50Phosphorus 15-20Potassium 70-80Zinc 2-5Iron 1-2Copper 1-2

Declining natural sesources:WHY SAVE WATER ?Demand by other sectors increasingPriority is drinking water10% saving in agriculture enhances theshare of other sectors by 40%Tentative estimates of waterconsumptionWe drink 2~3 litres/day (15-20 Glasses)We eat 1500 – 10000 litres/day1 kg rice – 3-4000 litres VIRTUAL1 kg wheat – 800 litres WATERVirtual Water (Allan, 1933) 15,000 litres of water for 1 kg of

beef. 5000 litres of water for 1 kg of

cheese. 40 litres of water for 1 slice of wheat

bread. Behind that morning cup of coffee

involve 140 litres of water used togrow, produce, package and ship thebeans i.e. roughly the amount ofwater used by an average persondaily for drinking and house holdneeds.

One single hamburger needs anestimated 2400 litres of water Percapita, an American consumesaround 6800 litres of virtual waterevery day, over triple that of aChinese.

SOIL It is well known fact that soil is oneof the most important natural resourceswhich facilitates the nutrition to plantsand directly related to productivity ofcrops and ultimately life on this planet. Soil is not just dirt, the life withinit make it live. Our soil is old and fragile,it can be damaged by farmingtechniques, poisoned by rising salts andlost by water and wind erosion. Caringfor the soil is the first principle of landcare. Unless soil health is cared, allother interventions of crop production,including improved varieties, plantprotection measures etc. are void.



India's food economy has gonethrough a complete cycle since itsindependence, starting with foodshortages via self sufficiency and willend with possibility of food insecuritysituation. Agriculture sector is witnessing aserious problem of deceleration andstagnation of crop yields which willprobably persist in the coming years. Diminished soil health is resultingfrom exploitative and intensiveagricultural practices which have puttremendous pressure on the soil causingsteady decline in soil environment andnutritional deficiencies which need to becorrected for sustaining agricultureproduction. The combination of anincreasing GDP, population growth,urbanization and industrialization arealso imposing a pressure on the qualityof our soils as well as shrinking theagricultural lands which are being usedfor non agricultural purposes. Disturbedecology is main concern for soil health.How ecology is disturbed ?? Industrialized agricultural techniques

are exacting a huge toll on surrounding environments, polluting waterways, creating dead zones in the oceans, destroying biodiverse habitats, releasing toxins into food chains, endangering public health Making soil unhealthy

Disturbing the agro-ecology??“Ecology is the scientific

discipline that is concerned with therelationships between organisms andtheir past, present, and futureenvironments.”

Agroecology is the study ofecological processes that operate inagricultural production systems. It isan interdisciplinary field thatincludes biology and Earth science”Soil Health• The health of soil is of great concern

to farmers and the mankind whoselivelihood depends on well managedagriculture.

• Soil fertility usually defined primarilyin chemical and physical term, whilebiological properties are neglected.Soil health is mainly determined byecological characteristics.

Soil Deterioration

• Environment Minister (GOI)conceded that about 25% of Indialand is degraded and turning todesert (Times of India, New Delhi)

• In the beginning of the centurydesert was in 20% area of earth,which has increased over 30% andspreading rapidly

Nutrient Requirement for CropProduction

• In early years of green revolution-1kg of NPK produced 16 kg foodgrain

• Now in 2010-2011- 1kg of NPKproduced 6 kg food grain

• The requirement of nutrients haveincreased about three times

• The additional requirement of micronutrients have also increased.

Sustainable agriculture A whole-systems approach to food,feed, and fiber production that balancesenvironmental soundness, social equity,and economic viability among all sectorsof the public.

Sustainable Agroecosystems Maintain their natural resource

base. Rely on minimum artificial inputs

from outside the farm system. Manage pests and diseases through

internal regulating mechanisms. Recover from the soil disturbances

caused by cultivation and harvestthrough CA.

Principles of Agroecology andSustainability

Use of renewable resources

Use of renewable sources of energyinstead of non-renewable sources.

Use of agriculturally beneficialmicroorganisms.

Use of naturally-occurring materialsinstead of synthetic, manufacturedinputs.

Use of on-farm resources as much aspossible.

Recycling of on-farm resources ofnutrients.



Minimize Toxics

Reduce or eliminate the use ofmaterials that have the potential toharm the environment, soil andhuman health.

Use farming practices that reduce oreliminate environmental pollutionwith nitrates, toxic gases, or othermaterials generated by burning.

• Conserve Soil Sustain soil nutrient and organic

matter stocks. Minimize erosion.

1. use perennials2. use no-till or reduced tillage

methods.3. mulch.4. Soil water management.• Conserve Water Rain water harvesting. Use efficient irrigation systems.• Conserve Energy Use energy efficient technologies.• Conserve genetic resources Save seed. Maintain local landraces. Use heirloom varieties. Adjust to Local Environments Match cropping patterns to the

productive potential and physicallimitations of the farm landscape.

Adapt Biota• adapt plants and animals to the

ecological conditions of the farm.

Manage Ecological Relationships

• Reestablish ecologicalrelationships that can occurnaturally on the farm instead ofreducing and simplifying them.

• Manage pests, diseases, andweeds instead of “controlling”them.

• Use intercropping and covercropping

• Integrate Livestock• Enhance beneficial biota in soil

(flora and fauna). Recycle Nutrients

• Shift from through flow nutrientmanagement to recycling ofnutrients.

• Return crop residues andmanures to soils.

• When outside inputs arenecessary, sustain their benefitsby recycling them.

Minimize Disturbance• Use reduced tillage or no-till

methods.• Use mulches.• Use perennials

Diversify• Landscapes

1. Maintain undisturbed areas asbuffer zones.

2. Use contour and strip tillage.3. Maintain riparian buffer zones.4. Use rotational grazing.

• Biota1. Intercrop.2. Rotate crops.3. Use polyculture.4. Integrate animals in system.5. Use multiple species of crops and

animals on farm.6. Use multiple varieties and

landraces of crops and animalson farm.

• Economics1. Avoid dependence on single

crops/products.2. Use alternative markets.3. Organic markets.4. Community Supported

Agriculture5. Add value to agricultural

products.6. Process foods before selling

them.7. Find alternative incomes.8. Avoid dependence on external

subsidies.9. Use multiple crops to diversify

seasonal timing of productionover the year.

Value Health• Human Health• Cultural Health• Environmental Health• Animal Health• Plant Health• Soil healthSoil biota is majorly responsible for

healthy soil which is directly coorelatedwith the availability of soil organiccarbon which is considered to be as



'black gold of soil'. Beneficial biota insoil can be enhanced by using thepreparations made from beneficialmicroorganisms.

A biofertilizers (also bio-fertilizer) or bioinoculants areformulations which contains livingmicroorganisms which, when applied toseed, plant surfaces, or soil, colonizesthe rhizosphere or the interior of theplant and promotes growth byincreasing the supply or availability ofprimary nutrients to the host plant. Bio-fertilizers add nutrients through thenatural processes of nitrogen fixation,solubilizing phosphorus, andstimulating plant growth through thesynthesis of growth-promotingsubstances. Bio-fertilizers and biocontrol agents can be expected to reducethe use of chemical fertilizers andpesticides. The microorganisms in bio-fertilizers restore the soil's naturalnutrient cycle and build soil organicmatter. Through the use of bio-fertilizers, healthy plants can be grown,while enhancing the sustainability andthe health of the soil. Since they playseveral roles, a preferred scientific termfor such beneficial bacteria is "plant-growth promoting rhizobacteria" (PGPR).Therefore, they are extremelyadvantageous in enriching soil fertilityand fulfilling plant nutrientrequirements by supplying the nutrientsthrough microorganism and theirbyproducts.

Bio-fertilizers provide eco-friendlyorganic agro-input and are more cost-effective than chemical fertilizers. Bio-fertilizers such as Rhizobium,Azotobacter, Azospirillum and blue greenalgae (BGA) have been in use a long timein India. Rhizobium inoculant is used forleguminous crops. Azotobacter can beused with crops like wheat, maize,mustard, cotton, potato and othervegetable crops. Azospirilluminoculations are recommended mainlyfor sorghum, millets, maize, sugarcaneand wheat. Blue green algae belongingto a general cyanobacteria genus, Nostocor Anabaena or Tolypothrix or Aulosira,fix atmospheric nitrogen and are used asinoculations for paddy crop grown bothunder upland and low-land conditions.Anabaena in association with water fernAzolla contributes nitrogen and also

enriches soils with organic matter.Other types of bacteria, so-called

phosphate-solubilizing bacteria (Bacillusand Pseudomonas), are able to solubilizethe insoluble phosphate from organicand inorganic phosphate sources. Infact, due to immobilization of phosphateby mineral ions such as Fe, Al and Ca ororganic acids, the rate of availablephosphate in soil is well below plantneeds. In addition, chemical P fertilizersare also immobilized in the soil,immediately, so that less than 20percent of added fertilizer is absorbed byplants. Therefore, reduction in Presources, on one hand, andenvironmental pollutions resulting fromboth production and applications ofchemical P fertilizer, on the other hand,have already demanded the use of newgeneration of phosphate fertilizersglobally known as phosphate-solubilizing bacteria or phosphate bio-fertilizers.

Potential Characteristic features ofsome bio-fertilizersNitrogen fixersRhizobium belongs to familyRhizobiaceae, symbiotic in nature, fixnitrogen 50-100 kg/ ha in associationwith legumes only. It is useful for pulselegumes like chickpea, red-gram, pea,lentil, black gram, etc., oil-seed legumeslike soybean and groundnut and foragelegumes like berseem and lucerne.Successful nodulation of leguminouscrops by Rhizobium largely depends onthe availability of compatible strain for aparticular legume. It colonizes the rootsof specific legumes to form tumor likegrowths called root nodules, which actsas factories of ammonia production.Rhizobium has ability to fix atmosphericnitrogen in symbiotic association withlegumes and certain non-legumes likeParasponia. Rhizobium population inthe soil depends on the presence oflegume crops in the field. In absence oflegumes, the population decreases.Artificial seed inoculation is oftenneeded to restore the population ofeffective strains of the Rhizobium nearthe rhizosphere to hasten N-fixation.Each legume requires a specific speciesof Rhozobium to form effective nodules3.Azospirillum: belongs to familySpirilaceae, heterotrophic and



associative in nature. In addition to theirnitrogen fixing ability of about 20-40kg/ha, they also produce growthregulating substances. Although thereare many species under this genus like,A.amazonense, A.halopraeferens,A.brasilense, but, worldwide distributionand benefits of inoculation have beenproved mainly with the A.lipoferum andA.brasilense. The Azospirillum formassociative symbiosis with many plantsparticularly with those having the C4-dicarboxyliac path way ofphotosynthesis (Hatch and Slackpathway), because they grow and fixnitrogen on salts of organic acids suchas malic, aspartic acid. Thus it is mainlyrecommended for maize, sugarcane,sorghum, pearl millet etc. TheAzotobacter colonizing the roots not onlyremains on the root surface but also asizable proportion of them penetratesinto the root tissues and lives inharmony with the plants. They do not,however, produce any visible nodules orout growth on root tissue. Azotobacter:belongs to family Azotobacteriaceae,aerobic, free living, and heterotrophic innature. Azotobacters are present inneutral or alkaline soils and A.chroococcum is the most commonlyoccurring species in arable soils. A.vinelandii, A. beijerinckii, A. insignis andA. macrocytogenes are other reportedspecies. The number of Azotobacterrarely exceeds of 104 to 105 g-1 of soildue to lack of organic matter andpresence of antagonistic microorganismsin soil. The bacterium produces anti-fungal antibiotics which inhibits thegrowth of several pathogenic fungi in theroot region thereby preventing seedlingmortality to a certain extent. Thepopulation of Azotobacter is generallylow in the rhizosphere of the crop plantsand in uncultivated soils. Theoccurrence of this organism has beenreported from the rhizosphere of anumber of crop plants such as rice,maize, sugarcane, bajra, vegetables andplantation crops.

Blue Green Algae (Cyanobacteria) andAzolla: These belongs to eight differentfamilies, phototrophic in nature andproduce Auxin, Indole acetic acid andGibberllic acid, fix 20-30 kg N/ha insubmerged rice fields as they are

abundant in paddy, so also referred as„paddy organisms‟. N is the key inputrequired in large quantities for low landrice production. Soil N and BNF byassociated organisms are major sourcesof N for low land rice4. The 50-60% Nrequirement is met through thecombination of mineralization of soilorganic N and BNF by free living andrice plant associated bacteria. Toachieve food security throughsustainable agriculture, the requirementfor fixed nitrogen must be increasinglymet by BNF rather than by industrialnitrogen fixation. BGA forms symbioticassociation capable of fixing nitrogenwith fungi, liverworts, ferns andflowering plants, but the most commonsymbiotic association has been foundbetween a free floating aquatic fern, theAzolla and Anabaena azollae (BGA).Azolla contains 4-5% N on dry basis and0.2-0.4% on wet basis and can be thepotential source of organic manure andnitrogen in rice production. Theimportant factor in using Azolla asbiofertilizer for rice crop is its quickdecomposition in the soil and efficientavailability of its nitrogen to rice plants.Besides N-fixation, these biofertilizers orbiomanures also contribute significantamounts of P, K, S, Zn, Fe, Mb andother micronutrient. The fern forms agreen mat over water with a branchedstem, deeply bilobed leaves and roots.The dorsal fleshy lobe of the leafcontains the algal symbiont within thecentral cavity. Azolla can be applied asgreen manure by incorporating in thefields prior to rice planting. The mostcommon species occurring in India is A.pinnata and same can be propagated oncommercial scale by vegetative means. Itmay yield on average about 1.5 kg persquare meter in a week. India hasrecently introduced some species ofAzolla for their large biomassproduction, which are A.caroliniana, A.microphylla, A. filiculoides and A.mexicana.

Phosphate solubilizersSeveral reports have examined

the ability of different bacterial speciesto solubilize insoluble inorganicphosphate compounds, such astricalcium phosphate, dicalciumphosphate, hydroxyapatite, and rock



phosphate. Among the bacterial generawith this capacity are Pseudomonas,Bacillus, Rhizobium, Burkholderia,Achromobacter, Agrobacterium,Microccocus, Aereobacter, Flavobacteriumand Erwinia. There are considerablepopulations of phosphatesolubilizingbacteria in soil and in plantrhizospheres. These include both aerobicand anaerobic strains, with a prevalenceof aerobic strains in submerged soils. Aconsiderably higher concentration ofphosphate solubilizing bacteria iscommonly found in the rhizosphere incomparison with non rhizosphere soil.The soil bacteria belonging to the generaPseudomonas and Bacillus and Fungi aremore common.

Phosphate absorbers and mobilizers(Mycorrhiza)The term Mycorrhiza denotes “fungus

roots”. It is a symbiotic associationbetween host plants and certain groupof fungi at the root system, in which thefungal partner is benefited by obtainingits carbon requirements from thephotosynthates of the host and the hostin turn is benefited by obtaining themuch needed nutrients especiallyphosphorus, calcium, copper, zinc etc.,which are otherwise inaccessible to it(due to limited root surface area), withthe help of the fine absorbing hyphae ofthe fungus and these infected roots withfungal hyphae increases the root surfacearea by many fold. These fungi areassociated with majority of agriculturalcrops, except with those crops/plantsbelonging to families of Chenopodiaceae,Amaranthaceae, Caryophyllaceae,Polygonaceae, Brassicaceae,Commelinaceae, Juncaceae andCyperaceae.

Zinc solubilizers

The nitrogen fixers likeRhizobium, Azospirillum, Azotobacter,BGA and Phosphate solubilizing bacterialike B. magaterium, Pseudomonasstriata, and phosphate mobilizingMycorrhiza have been widely acceptedas bio-fertilizers. However these supplyonly major nutrients but a host ofmicroorganism that can transformmicronutrients are there in soil that canbe used as bio-fertilizers to supplymicronutrients like zinc, iron, copper

etc.,The zinc can be solubilized bymicroorganisms viz., B. subtilis,Thiobacillus thioxidans andSaccharomyces sp. Thesemicroorganisms can be used as bio-fertilizers for solubilization of fixedmicronutrients like zinc. The resultshave shown that a Bacillus sp. (Znsolubilizing bacteria) can be used as bio-fertilizer for zinc or in soils where nativezinc is higher or in conjunction withinsoluble cheaper zinc compounds likezinc oxide (ZnO), zinc carbonate (ZnCO3)and zinc sulphide (ZnS) instead of costlyzinc sulphate.

Silicate solubilizing bacteria (SSB)Microorganisms are capable ofdegrading silicates and aluminumsilicates. During the metabolism ofmicrobes several organic acids areproduced and these have a dual role insilicate weathering. They supply H+ ionsto the medium and promote hydrolysisand the organic acids like citric, oxalicacid, Keto acids and hydroxy carbolicacids which from complexes withcations, promote their removal andretention in the medium in a dissolvedstate.The studies conducted with a Bacillussp. isolated from the soil of granitecrusher yard showed that the bacteriumis capable of dissolving several silicateminerals under in vitro condition. Theexamination of anthrpogenic materialslike cement, agro inputs like superphosphate and rock phosphate exhibitedsilicate solubilizing bacteria to a varyingdegree. The bacterial isolates made fromdifferent locations had varying degree ofsilicate solubilizing potential. Soilinoculation studies with selected isolatewith red soil, clay soil, sand and hillysoil showed that the organismsmultiplied in all types of soil andreleased more of silica and the availablesilica increased in soil and water. Riceresponded well to application of organicsliceous residue like rice straw, ricehusk and black ash @ 5 t/ha.Combining SSB with these residuesfurther resulted in increased plantgrowth and grain yield. Thisenhancement is due to increaseddissolution of silica and nutrients fromthe soil.



Biofertilizer journeyBroth based inoculants:

The commercial history of bio-fertilizers began with the launch ofNitragin by Nobbe and Hiltner, alaboratory culture of Rhizobia in 1895,followed by the discovery of Azotobacterand then the blue green algae and ahost of other micro-organisms.Azospirillum and Vesicular-ArbuscularMicorrhizae (VAM) and other are fairlyrecent discoveries. In India the firststudy on legume-Rhizobium symbiosiswas conducted by N.V.Joshi and thefirst commercial production started asearly as 1956. During this initial stageliquid broth based inoculants wereprepared and were used. But theseformulations were faced with lot ofproblems like suitable packing,transportation, shelf life, loweffectiveness and their use at fieldswhich compelled researchers to thinkover for other alternatives.

Carrier based biofertilizers

Looking to constraints with brothbased biofertilizers attempts were madeto evaluate several solid carriers likepeat, lignite, coal, FYM, soil, fly ash andso many other carrier material whichwere locally available in different parts ofthe country were used considering theproperties like: (1) non toxic to bacterialinoculants (2) good moisture absorptioncapacity (3) easy to process and freefrom lump formation (3) easy to sterilize(4) available in adequate quantity (5) lessexpensive (6) good adhesion power toseed (7) good pH buffering capacity and(9) non toxic to plants. Looking to all thetested carriers with special reference tosurvival of impregnated microorganisms,peat soil was found to be most suitable.But looking to scanty deposits of peat inIndia the biofertilizer productiontechnology was concentrated on the useof lignite (a low grade coal) as a carrierfor beneficial microorganisms to be usedin agriculture and is still in use.

Liquid microbial consortium

Liquid formulation is a buddingtechnology in India and has very specificcharacteristics and uniqueness in itsproduction methods. Liquid biofertilizersare the microbial preparations

containing specific beneficialmicroorganisms which are capable offixing or solubilizing or mobilizing plantnutrients by their biological activities.

Carrier based biofertilzers hasalready shown their significance andhave been showing the tremendouseffect on the global agricultureproductivity since the past two decades.Rectifying the disadvantages of thecarrier based biofertilizers, liquidbiofertilizers have been developed whichwould be the only alternative for the costeffective sustainable agriculture. LiquidBiofertilizer Technology providingreliable reasons for their necessity,specificity and emphasizes that “Use ofagriculturally important microorganismsin different combinations i.e. Liquidmicrobial consortium (LMC) is the onlysolution for restoration of soil health”.Even though biofertilizers are beingproduced and distributed constantly byprivate agencies, NGO’s, State andCentral Government production unitsfor the last three decades, theircorresponding usage is not in thesatisfactory proportions. To cope withthe rising demands for foodcommodities, serious efforts are beingmade by the State and CentralGovernments (under the NationalProjects) for the sufficient agriculturalproduction by popularizing biofertilizersand making them available to the farmercommunity. In spite of these efforts, therate of consumption of biofertilizers isnot to the optimum level in comparisonwith the agrochemicals. The reasonattributed is the “non-availability of goodand suitable carrier materials” thatraises contamination problems andshorter shelf life. To cope with thisalarming situation, Liquid formulations(LFs) are being developed that ensuremore quality over the conventionalcarrier based biofertilizers inauguratinga new era in the Biological inputtechnology. These liquid formulationsfacilitate long shelf life (up to 2 years),minimum contamination, carrier freeactivity, handling comfort, storage andtransport convenience, easy qualitycontrol, enhanced export potentials andare preferred by the farmer communityas well as manufacturers.



LBF Vs CBBF

Liquid biofertilizer formulation isthe promising and updated technology ofthe conventional carrier basedproduction technology which inspite ofmany advantages over theagrochemicals, left a considerabledispute among the farmer community interms of several reasons major being theviability of the organism. Shelf life is thefirst and foremost problem of the carrierbased biofertilizers which is maximumup to 6 months as per BIS standards.LBF on the other hand facilitates thelong survival of the organism byproviding the suitable medium with cellprotectants which is sufficient for theentire crop cycle. Carrier based biofertilizers are not so tolerant to thetemperature which is mostlyunpredictable and uncertain duringtransportation and in the crop fieldswhile temperature tolerance is the otheradvantage of the liquid biofertilizers. Therange of possible contamination is veryhigh as bulk sterilization does notprovide the desirable results in the caseof CBBF, where as the contaminationcan be controlled constructively bymeans of proper sterilization techniquesand maintenance of intensive hygieneconditions by appropriate quality controlmeasures in the case of LBF. Moistureretaining capacity of the CBBF is verylow which does not allow the organismviable for longer period and the LBFfacilitates the enhanced viability of theorganism. The additional benefits of LBFover CBBF are: longer shelf life -12-24months, no contamination, no loss ofproperties due to storage upto 45ºC,greater potentials to fight with nativepopulation, better survival on seeds andsoil, very much easy to use by thefarmer, high commercial revenues.

However, the administration ofLBF in the fields is comparatively easierthan CBBF. The other disadvantages ofCBBF like poor cell protection, laborintensity, and dosage controversy,limited scope of export, expensivepackage and transport, very slowadaptation by the farmer community aresome of the strongest problems whichare being solved by the Liquidbiofertilizers very effectively. Therefore,LBF are believed to be the best

alternative for the conventional carrierbased biofertilizers in the modernagriculture research communitywitnessing the enhanced crop yields,regaining soil health and sustainableglobal food production. A dose of 4-5 mlof liquid inoculum having a populationof 3x109 cells per ml (which is notpossible to achieve in carrier basedinoculant) is enough to coat one kg seedand could satisfactorily retain themaximum number of viable cells on theseeds up to 24 hrs of bacterization atroom temperature.

Biofertilizer enriched Compost

Normal farm compost could beconverted into a superior bio-enrichedcompost by amending with 1% P asRock Phosphate together withinoculating Azospirillum/Azotobacterand PSB liquid culture @ 1% (v/w) each(108-109 cfu /ml) and subsequentlycuring about a month at 25% moisturelevel. The C:N ratio of final productstabilized at around 10.0-12.3:1, withincrease of Azospirillum/Azotobacterand PSB population by 300- 400 timesand 6 times, respectively.

Future generation biofertilizers(Promising New Technologies)Mixed biofertilizers

Mixed biofertilizers (BIOMIX)containing a consortium of N fixers, Psolubilisers and PGPR found to promotethe growth of cereals, legumes andoilseeds better and save 25% NPfertilizers in crops. Response is betterand there is 50% nutrient substitutionin crops like rice and legumes dependingupon soil type and yield level. Theresponse of biofertilizers is better whenused along with 75% chemical fertilizersand is seen even when full dose ofchemical fertilizers are applied. There isclear improvement in nutrient useefficiency and quality of produce whenbiofertilizers are applied.

Polymer-Based Carriers

The increased interest in theapplication of bacterial preparations haspromoted studies aiming at improvingtheir stability and increasing their shelflife. Among the new materials utilized ascarriers, organic polymers have been



evaluated. These are compounds (e.g.,polysaccharides) that in the presence ofions or by changing chemical conditions(e.g., a change in pH of the medium)form cross-links that create a complexstructure. The polymers encapsulate, or“immobilize”, the microorganisms in thematrix and release them graduallythrough a degradation process. Polymerformulations offer a long shelf life evenat ambient temperature since theyprovide protection againstenvironmental stresses and a consistentbatch quality due to standardizedproduction. Nevertheless, storage at cooltemperature (4°C) allows maintaining alonger viability of encapsulated cells.These inoculants can be added or mixedwith nutrients to improve the survival ofthe bacteria upon inoculation.

Alginate, a natural polymer of D-mannuronic acid and L-glucuronic acid,is the most commonly used substancefor microbial cell encapsulation. It isderived mainly from brown macroalgaesuch as Macrocystis pyrifera (kelp), butrecently also another macroalga(Sargassum sinicola) has been shown toproduce alginate of similar physicalcharacteristics. The reaction betweenalginate and a multivalent cation (e.g.,Ca2+) forms a gel consisting of a densethree-dimensional lattice with a typicalpore-size range of 0.005 to 0.2 mm indiameter; when the alginate solution isdropped into the cation solution beadsare formed. Alginate beads generallyhave a diameter of 2-3 mm, butmicrobeads with a size of 50 to 200 μmthat can entrap up to 108 to 109 CFU g−1

have also been proposed.

Inclusion of bacteria in alginatebeads has been utilized for differentspecies, either spore forming and nonsporulating. Different AMF structureshave also been entrapped into alginatematrixes or in beads formed withdifferent polymers. Spores ofmycorrhizal fungi were entrapped inalginate film formed in a PVC-coatedfibreglass screen, and roots of leekseedlings inoculated with this alginatefilm containing G. mosseae spores wereheavily colonized after few weeks ofgrowth in greenhouse conditions.Similar results were obtained withspores obtained from monoxenic

cultures embedded into beads. Inclusionof filamentous fungi such as Aspergillusand Actinomycetes has been also provedpossible.

Alginate beads can maintain asufficient amount of live cells to assureinoculation up to several months.However, improving the viability ofinocula is still an issue. To tackle it,several approaches have been tested.Adding nutrients (e.g., skimmed milk) tothe inoculum or freeze-drying gel beadsin presence of glycerol resulted in aprolongation of beads shelf life.Intraradical structures of G. intraradicesembedded in alginate beads were stillinfective after up to 62 months afterstorage in plastic vials at 4°C. However,it shall be considered that freeze-dryingof alginate beads can result in somecollapse of the matrix. Therefore, theaddition of fillers (material added to themoulding mixture to reduce cost and/orimprove mechanical properties) shouldbe considered when planning thistechnological process. Adding chitin tothe beads helped preserve their porouscellular structure resulting insignificantly higher porosity values whencompared to starch filled beads andresulted in higher bacterial efficacywhen evaluating their effect on plants.Addition of 0.5% kaolin to freeze-driedalginate-glycerol beads significantlyincreased bacterial survival also underUV light radiation.

Reducing the cost of theproduction process and enhancing thephysical characteristics of the beadswere also obtained by encapsulation andair-drying of bacteria into a mixturemade of alginate (3%), standard starch(44.6%), and modified starch (2.4%).This process allowed to obtain beadsthat after drying have a water content of7%, size of 4 mm, and a mechanicalresistance of about 105 Newton (featuressimilar to that of grain seeds). Storage atroom temperature or at 4°C did notaffect the viability of the encapsulatedbacteria, which were able to survive upto six months maintaining a finalpopulation size of about 108 CFU g−1

(corresponding to about 105 CFUbead−1). However, with this composition,some problems can arise whenstandardizing and automating the beads



formation due to the viscosity of themixture and the need of a continuousagitation of the stock medium. Recently,a process using starch industrywastewater as a carbon source for theproduction of Sinorhizobium meliloti withsimultaneous formulation using alginateand soy oil as emulsifier has beenproposed, showing a cell viability ofmore than 109 CFU mL−1 after 9 weeksof storage. Addition of synthetic zeoliteto the alginate mixture did not improvethe survival of the embedded microbialcells, nor the physical structure of thebeads.

Water-in-oil emulsions appear to be agood, yet underutilized, method forstoring and delivering microorganismsthrough liquid formulations. The oiltraps the water around the organism

and, therefore, slows down waterevaporation once applied. This isparticularly beneficial for organisms thatare sensitive to desiccation or in case ofthe use for horticultural crops whereirrigation systems are in place. Water-in-oil emulsions allow the addition ofsubstances to the oil and/or aqueousphases which could improve both cellviability and release kinetics. However,cell sedimentation during storage is amajor issue to be considered. Studiesare carried out aiming at solving thisproblem with the help of nanomaterials.Thickening the oil phase usinghydrophobic silica nanoparticlessignificantly reduced cell sedimentationand improved cell viability duringstorage.



Soil Health and Food Security : Facts and Reality

Sunil Bhaskar Rao NahatkarPrincipal Scientist (Ag.Econ)

Directorate of Research ServicesJawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur (M.P.), India

The world’s agricultural system faces agreat balancing act. To meet differenthuman needs, by 2050 it mustsimultaneously produce far more foodfor a population expected to reach about9.6 billion, 34 percent higher thantoday; provide economic opportunitiesfor the hundreds of millions of ruralpoor who depend on agriculture for theirlivelihoods, and reduce environmentalimpacts, including ecosystemdegradation and high greenhouse gasemissions. Population and income arethe major factors in determining foodconsumption; world food demand isgrowing at a rate of 2% per year, 1.8% ofthis because of population increase and0.2% because of rising incomes. Currentpopulation of the world is around 7.24billion (2nd June 2014), and grows bynearly 80 million per year(approximately the population ofGermany). The world population isexpected to rise throughout the 21st

century, although this growth isprojected to decelerate markedly in 2050to 2100.

Human population growth is perhapsthe most significant cause of thecomplex problems the world faces;climate change, poverty, food andnutritional insecurity and resourcescarcity and degradation complete thelist (Foresight, 2009b). The perceivedlimits to producing food for a growingglobal population have been a source ofdebate and preoccupations for ages.Already in the third century AD,Tertullian, a church leader, raised theissue. The debate gathered momentumin the late eighteenth century, followingMalthus (Malthus, 1798), and morerecently with Paul Ehrlich’s PopulationBomb (Ehrlich, 1968). Yet, world foodproduction grew faster than populationand per capita consumption increased.Thus, in principle, there is sufficientglobal aggregate food consumption fornearly everyone to be well-fed. Yet this

has not happened: some 2.3 billionpeople live in countries with under2,500 kcal, and some 0.5 billion incountries with less than 2,000 kcal,while at the other extreme some 1.9billion are in countries consuming morethan 3,000 kcal. The reasons are fairlywell known: mainly poverty, which hasmany facets, but many low-incomecountries linked to failures to developagriculture and limited access to foodproduced in other countries. 20% of theglobalpopulation consumes 70% of its materialresources and possesses 80% of thewealth. The majority of this 20%centered in Canada, USA, Saudi Arabia,Australia, and Japan.

Future global food demand

The Food and AgricultureOrganization (FAO) projects that by theyear 2050 population and economicgrowth will result in a doubling ofdemand for food globally. To sustainthis level of growth, food production willneed to rise by 70 percent. Foodproduction depends on croplands andwater supply, which are under strain ashuman populations increase. Pressureon limited land resources, driven in partby population growth, can meanexpansion of cropland. This ofteninvolves destruction of vital forestresources or overexploitation of arableland. Despite lower food demand growthrates, the absolute quantities of foodnecessary to feed the world in 2050 aresubstantial. Assuming no change inpopulation growth, food consumptionpatterns and food waste management,the following production increases musttake place by 2050: cereals production must increase by

0.90 billion tones(2.10 billion tonstoday) to reach 3 billion tonnes;

meat production must increase by200 million tonnes to reach 470million tonnes;



and oil crops must increase by 133million tonnes to reach 282 milliontones

The present and expected growthrates in world food production andpopulation is given in Table 1.

Table 1: Exponential growth rates inthe food production in the world

(%)Particulars 1970-

19901990-2007

2009-2017

Area 0.15 0.14 0.39Production 2.20 1.30 1.20Yields 2.0 1.10 0.8Population 1.70 1.40 1.10Per capitafoodavailability

0.56 0.11 0.02

Source: USDA Agricultural Projections to 2017.

Global economic growth has beenstrong since the late 1990s. Fordeveloping countries, growth has beenquite strong since the early 1990s.Growth in Asia has been exceptionallystrong for more than a decade.Unusually rapid economic growth inChina and India, with nearly 40 percentof the world’s population, has provided apowerful and sustained stimulus to thedemand for agricultural products. Theworld’s population growth rate has beentrending down since before the 1970s.This declining trend applies to nearly allcountries and regions of the world.However, the number of people on earthis still rising by about 75 million (1.1percent) per year. This rising populationadds to the global demand foragricultural products and energy. Theimpact on demand is amplified becausethe most rapid population growth ratestend to be in developing countries. Manyof these have rapidly rising incomes,again particularly important foragricultural demand due to diet-diversification.

World agriculture (aggregate value ofproduction, all food and non-food cropand livestock commodities) has beengrowing at rates of 2.1-2.3 percent p.a.in the last four decades, with much ofthe growth originating in the developingcountries (3.4-3.8 percent p.a.). Thehigh growth rates of the latter reflected,among other things, developments insome large countries - foremost amongthem China. Without China, the rest of

the developing countries grew at 2.8-3.0percent p.a. They also reflected therising share of high value commoditieslike livestock products in the total valueof production: in terms of quantities(whether measured in tonnage or caloriecontent), the growth rates have beenlower. Urbanization will continue at anaccelerated pace, and about 70 percentof the world’s population will be urban(compared to 49 percent today). Incomelevels will be many multiples of whatthey are now. In developing countries,80 percent of the necessary productionincreases would come from increases inyields and cropping intensity and only20 percent from expansion of arableland. But the fact is that globally therate of growth in yields of the majorcereal crops has been steadily declining,it dropped from 3.2 percent per year in1960 to 1.5 percent in 2000. Thechallenge for technology is to reversethis decline, since a continuous linearincrease in yields at a global levelfollowing the pattern established overthe past five decades will not besufficient to meet food needs.

Growth of world agriculture underzero population growthZero population growth at the globallevel will be the net result of continuingincreases in some countries (e.g. bysome 31 million annually in 2050 inAfrica and South and Western Asiatogether) compensated by declines inothers (e.g. by some 10 million annuallyin China, Japan and Europe together).In brief, zero population growth at theglobal level will not automaticallytranslate into zero growth in demandand cessation of the building-up ofpressures on resources and the widerenvironment. The need for production tokeep growing in several countries willcontinue to condition their prospects forimproved nutrition. In those amongthem that have limited agriculturalpotential, the problem of productionconstrained food insecurity andsignificant incidence ofundernourishment may persist, even ina world with stationary population andplentiful food supplies (or potential toincrease production) at the global level.Nothing new here: this situation prevailsat present and it will not go away simply



because population stops growing at theglobal level. Projections to 2050 providea basis for thinking about this possibleoutcome. We project increases to some 3billion tones by 2050 and this wouldafford some increase in world per capitaavailability to around 340 kg (for all foodand non-food uses), some 10 percentover present levels.

Indian ScenarioIndia’s population is expected to be

1.4 billion by the year 2025. Agricultureis the mainstay of the Indian economy.Two thirds of the Indian populationdepends on it. To feed the growingpopulation in India 300 million tonnes offood grains will be required by 2025.Presently; India is expected to producearound 264.38 million tons of foodgrains including 106.29 million tons ofrice and 95.85 million tons of wheat for2013-14. India need to raise its foodgrains targets at a rate of more than 3.6million tonnes per annum. It wouldrequire about 130 MT of rice whilerequirement of wheat would reach 110MT in 2020.

Demand-supply situation projectiongrowth rates for major food products foryear 2026 based on base year fordemand 1999-2000 and for supply2003-04 is given in Table 2.

Table 2: Demand –Supply Situationfor 2026 based on per cent annualRate of growth of projected estimates

(%)Food items Demand SupplyRice 1.53 1.01Wheat 1.42 1.34Total cereals 3.17 1.45Pulses 6.51 0.91Edible oil 5.95 2.13Sugar 8.22 0.41Source: Mittal (2008).

Scope for increase in area undercultivation is negligible. Agricultureproduction can only be achievedthrough efficient use of resources and byimproving soil fertility. To meet the foodrequirement of the growing populationin India, the country needs to boost thefood grain production by 1.34%annually.

Challenges facing India Depleting soil organic matter Imbalance in fertiliser use Emerging multi-nutrient

deficiencies particularly of secondaryand micronutrients

Declining nutrient use efficiency Declining crop response ratio

The information on crop response ratioto plant nutrient consumption duringdifferent five years plan is given in Table3.Table 3: Declining Crop response ratio inIndia

Period Response ratio(Kg grains per kg NPK)

5th Plan (1974-79) 15.08th Plan (1992-97) 7.59th Plan (1997-02) 7.010th Plan (2002-07) 6.5

11th Plan (2007-12) 6.0

Negative soil nutrient balance. Stagnation / slow growth in food

grain productivity.The data on production of major foodproducts over different decades alongwith growth rates are given in Table-4.Table 4: Trend in production of foodgrains and oilseeds

Production (million tons)ItemsTE

1980-81TE

1990-91TE

2000-01TE

2010-11Rice 49.90 72.80 86.90 94.50Wheat 34.60 53.00 72.40 82.50Cereals 113.30 158.80 190.30 215.60Pulses 10.50 13.70 13.10 15.80Foodgrains

123.80 172.50 203.40 231.40

Oilseeds 9.40 17.90 21.30 27.90Sugarcane 144.90 223.20 294.70 305.50

Decadal rate of growth (%)Items1980-90 1990-2000 2000-2011

Rice 3.70 1.80 1.30Wheat 4.10 3.40 1.40Cereals 3.10 2.0 1.60Pulses 2.20 0.30 2.10Foodgrains

5.30 2.30 3.70

Oilseeds 5.50 2.40 4.30Sugarcane 3.3 2.8 1.10

Source: Various issues of AgriculturalStatistics at a Glance, DES, GOI

Reasons



Inadequate and imbalanced fertiliseruse

Increasing multi-nutrient deficiency Lack of farmers awareness about

balanced plant nutrition Lack of varietal breakthrough Poor crop management (excess

fertiliser dose not be the substituteof poor management)

Population Growth and Soil HealthSoil has always been important

to humans and their health, providing aresource that can be used for shelterand food production. The link between arising world population and the ability ofthe soil to support an increasing foodsupply has been of concern sinceThomas Malthus wrote his first famousessay in 1798. At times, the over-exploitation of soils attributable to adesire to increase food production led toits serious degradation, failure toproduce sufficient food for people andthe collapse of societies (Hyams, 1976).For example, speculation on the declineof the Mesopotamian civilisations hasbeen attributed in part to soildegradation brought about by erosionand salinisation. The collapse of theMaya Empire in approximately A.D. 600may have been due to soil nutrientexhaustion, erosion and resultingmalnutrition (Olson, 1981). Humanpopulation growth and the maintenanceof an adequate food supply are certainlyancient problems but with a globalpopulation, that may increase to apredicted 10 billion before it stabilises,the challenge for a solution continues.All agricultural soils have been alteredfrom their natural state by humaninterventions which are aimed atmaximizing production functions andwhich, to some degree, always result ina loss of other ecosystem functions. Thesoil food web may also be substantiallychanged.

Franklin Roosevelt’s (Roosevelt 1937)statement, “The nation that destroys itssoil destroys itself,” is as true today as itwas 76 years ago. The main driver forsoil health deterioration was thequadrupling of world population over thepast 100 years, which demanded afundamental change in soil and cropmanagement in order to produce more

food. Over the past 40 years, mineralfertilizers accounted for an estimated 40percent of the increase in foodproduction (Jenkinson, 2010).Conventionally, the practice ofagriculture may be seen as providingonly a single service, namely foodproduction. Primary and secondaryproduction depends on soil-basedecosystem functions such as nutrientcycling, maintenance of soil structureand biotic population regulation. Societymay also require that other services,such as the supply of good qualitywater, protection of human health andreduction of greenhouse gas emissions,be maintained at acceptable levels. Amajor target of sustainable agriculturemust be to ensure that the full range ofecosystem services is conserved forfuture generations: agricultural soilsmust thus retain a multifunctionalcapacity. We use soil health as a term todescribe the capacity of soil to deliver arange of different ecosystem functionsand services. Despite the great variety ofbiophysical and socio-economiccircumstances that need to beaccommodated, a working hypothesis forsustainable agriculture may beadvanced that ‘agriculture can beproductively and profitably practicedwithout impairment of soil health. Soilhealth has been defined as: “thecapacity of soil to function as a livingsystem. Soil health is presented as anintegrative property that reflects thecapacity of soil to respond toagricultural intervention, so that itcontinues to support both theagricultural production and theprovision of other ecosystem services.Managing soil health a formidablechallenge to ensure productivity,profitability and national food security.The FAO defines food security as whenall people, at all times, have access tosufficient, safe and nutritious food tomeet their dietary needs and foodpreferences for an active and healthy life(WFS, 1996). The United NationsMillennium Development Task Force onhunger made Soil Health Enhancementas one of the five recommendations forincreasing agricultural productivity andfight hunger in India and therefore soilhealth is directly related to ensuringfood and nutritional security in the



country.Soil health matters because Healthy soils are high-performing,

productive soils. Healthy soils reduce production

costs—and improve profits. Healthy soils protect natural

resources on and off the farm. Healthy soils can reduce nutrient

loading and sediment runoff,increase efficiencies, and sustainwildlife habitat.

What are the benefits of healthy soil? Healthy soil holds more water (by

binding it to organic matter), andloses less water to runoff andevaporation.

Organic matter builds as tillagedeclines and plants and residuecover the soil.

One percent of organic matter in thetop six inches of soil would holdapproximately 27,000 gallons ofwater per acre!

Most farmers can increase their soilorganic matter in three to 10 years ifthey are motivated about adoptingconservation practices to achievethis goal.

Follow four basic soil healthprinciples to improve soil health andsustainability: Use plant diversity to increase

diversity in the soil. Manage soils more by disturbing

them less. Keep plants growing throughout the

year to feed the soil. Keep the soil covered as much as

possible.When soils are in good condition,

they have the potential to provide societywith a range of ‘ecosystem services’;resources or processes provided by thenatural environment, that benefitpeople. The Ecosystem Services providedby soils are: Supporting services, e.g. nutrient

cycling, water release / retention, soilformation, habitat for biodiversity (ofmicrobes and soil animals), exchangeof greenhouse gases with theatmosphere, degradation of complexmaterials.

Regulating services, e.g. theregulation of flooding, the retention ofpathogens, contaminants and

agrochemicals and the storage ofcarbon and other greenhouse gases.

Provisioning services, e.g. providinga basis for food and fibre productionand for recharging water supplies.

Cultural services, e.g. soils supporthabitats, recreational pursuits andprotect archaeological remains.

The ecosystem services provided bysoil are driven by soil biologicalprocesses, but our concept of soil healthembraces not only the soil biota and themyriad of biotic interactions that occur,but also the soil as a habitat (Young &Ritz, 2005). The major challenge withinsustainable soil management is toconserve ecosystem service deliverywhile optimizing agricultural yields.Healthy soils maintain a diversecommunity of soil organisms that helpto control plant disease, insect and weedpests, form beneficial symbioticassociations with plant roots, recycleessential plant nutrients, improve soilstructure with positive repercussions forsoil water and nutrient holding capacity,and ultimately improve crop production(FAO, 2008). If the organic matter isincreased or maintained at a satisfactorylevel for productive crop growth, it canbe reasonably assumed that a soil ishealthy. Healthy soil is resilient tooutbreaks of soil-borne pests. Forexample, the parasitic weed, Striga, isfar less of a problem in healthy soils(Weber, 1996). Even the damage causedby pests not found in the soil, such asmaize stem borers, is reduced in fertilesoils (Chabi et.al, 2006). To achieve thehigher productivity needed to meetcurrent and future food demand, it isimperative to ensure nutrient availabilityin soils and to apply a balanced amountof nutrients from organic sources andfrom mineral fertilizers, if required.Monitoring of soil health is a verychallenging task, efforts are under wayto implement it at global (Sachs, 2010)),regional and national scales (Steiner et.al, 2000). FAO and its partners havedeveloped a list of methods and tools forundertaking assessments andmonitoring tasks (FAO, 2010). Soilhealth is related to functional capacityrather than actual service outputs. Asargued above, an effective approachappears to be using a set of diagnostictests for soil system performance,



chosen to be indicative of habitatcondition, i.e. physical (e.g. bulk density)and chemical (e.g. pH, salinity), ofenergetic reservoirs (e.g. soil organicmatter content) and key organisms andcommunity structure (e.g. earthwormsand phenotypic profiling).

Under the climate change scenariothe importance of soil health isincreasing because: Most adaptation options build on

existing practices and sustainableagriculture, rather than newtechnologies (Jarvis et al. 2011).

Many adaptation options—such asagro-forestry— are also beneficial formitigation, though the exact balanceof benefits depends very much onlocal conditions (Jarvis et al. 2011).

Changes to water and soilmanagement will be central toadaptation for most farming systems.Pest and disease management willalso be critical (Vermeulen et al.2012).

The selection or development of newcrop varieties is an importantadaptation response, and entailsseeking out or breeding for specifictraits depending on the local changesin climatic conditions (e.g. toleranceto heat, water stress, salinity or waterlogging) (Thornton et al. 2012).

Breeding—such as breeding beans fordrought tolerance—may be a limitedadaptation option when climatechange is associated with multiple,interacting environmental stresses(drought, heat, and low soil fertility)(Beebe et al. 2008).

Breeding for future climates requiresaccess to sufficient genetic variabilityin farmers’ fields, the wild, andgenebanks. About 90% of all genetictraits for rice, wheat, and maize areavailable in genebanks across theworld, but only a much smallerpercentage is accessible for manynon-staple crops that supply vitalmicronutrients (Lobell 2009).

More work has been done to developdrought-tolerant crops than heat-tolerant crops, even though manycrops, including the major cereals,show major reductions in yields whenexposed to high temperatures withinthe range of current and near-termclimate change (Lobell 2009).

Supplemental irrigation could help tomitigate the negative impacts of waterscarcity, the most growth-limiting factfor wheat. It would allow for earlierplanting and thus avoidance of(terminal) heat stress during the grainfilling period. However, moreirrigation water would be required inthe future—on average 181 mm perseason from 2080 to 2099 comparedwith only 134 mm historically—tosatisfy basic crop water requirements(Thornton et al. 2012).

Adapting to long-term climate trendsmay need different adaptation actionsthan adapting to increasing climatevariability. In general, long-termclimate change requires advancepreparation such as long-termforecasting, anticipatory policies, andbreeding for future climates.Increasing climate variability requiresrisk management tools such asimproved seasonal climate forecastingand crop insurance (Vermeulen et al.2012).

About 336 million tonnes of cropresidues are produced per yearwhich can supply about 5.1 milliontonnes of K in addition to organicmatter

Operations Management Theory ofSoil health

Using concepts taken fromOperations Management Theory (Slack,1997), a healthy soil could thus bedescribed as one that presents asatisfactory system performance. A setof system performance curves can beimagined describing the relationshipbetween potential rates of outputs froma soil system to rates of inputs(Kibblewhite, 2005). Such curves definethe current capacity of a soil to supportrequired ecosystem services, includingagricultural production and correspondto the familiar form of response curves.The ‘working range’ of the soil system isthat over which there is no degradationof system performance in terms of input-to-output conversion efficiency withincreasing outputs.

Increased food production withhealthy soils

The increased production on



sustainable manner for keeping the soilhealth intact, there is a need forenhancement of total factor productivity(TFP) by identifying the constraints ofyield gap. Total Factor Productivity (TFP)is defined as the amount of output perunit of total factors (production inputs)used to produce the output. In otherwords it is the efficiency with which thefactor inputs are converted to outputwithin the production process. Fivefactors or inputs were used in the USDAanalysis – land (acres), labor (hours),tractors (number), head of livestock(number) and amount of inorganicfertilizer applied. The analysis showedthat global agricultural output grew byabout 2.2 percent per year from 1961 to2007. During this period, almost half ofthe growth in output was due toincreased use of production inputs andthe reminder was due to increasedproductivity. In other words, asubstantial amount of the growth inagricultural output was due to theincrease in the efficiency of productioninputs in producing agricultural outputsand efficiency of input to translate inoutput depends upon soilhealth. Essentially, productivity meansdeveloping new technologies thatincrease agricultural output per unit ofagricultural input, or decrease theamount of agricultural inputs needed toproduce a unit of agricultural output.Partial Factor Productivity is the ratio ofoutput to a single input while totalfactor productivity is a ratio of an indexof aggregate output to aggregate input.Factor productivity and sustainability ofproduction system can be explainedunder different conditions in terms offactor productivity.Condition I: (Unsustainable)• If output goes up by 10% and input

goes up by 6%, total factorproductivity goes up by 4%.

Condition II : (Sustainable)• If output stays the same and inputs

go down by 5%, total factorproductivity goes up by 5%.

Condition III : (More Sustainable)• If output goes up by 10% and inputs

stay the same, total factorproductivity goes up by 10%.

Condition IV: (Highly sustainable)

• If output goes up by 10% and inputgoes down by 5%, total factorproductivity goes up by 15%.

Bridging yield gapYield gaps occur where yields are

not at the level they could be with fullutilization of currently availableagricultural production technology.Yield gaps are a result of not fullyutilizing existing technology, thusdiffering from yield plateaus where theyield of a crop may have reached itsbiophysical limit. Therefore there is aneed to identify the major constraints ofyield gap before making blanketrecommendations which may harm thesoil health in the long run. Thisapproach of productivity Improvementon sustainable manner through bridgingthe yield gap I and II was exist indeveloping countries and this need to beachieved through improvement inproductivity using local resources andknowledge because:• It is an Economic necessity for

higher marketable surplus &multiple sources of income.

• It is an Ecological necessity withlimited land resources, otherwise wehave to use pasture and forest land.

• More thorough incorporation ofnatural processes and reduction inthe use of off-farm inputs

• Greater productive use of thebiological and genetic potential

• Matching cropping patterns andtheir production potential

• Profitable and efficient productionwith emphasis on improved farmmanagement and participatory NRM

Concluding remarksSoil health, population growth

and food production are interlinked tofood and nutritional security. Becausehigh growth in population results inhigh demand for food which ultimatelyresulted in high pressure on limited landavailable for cultivation. Thus, in thelong run this affects soil health.Therefore, there is a need to produce thefood on sustainable manner as perdemand of increasing population andother factors which affects food demand.The best sustainability indicator of soilhealth is to absorb maximum adverseeffects of biotic and abiotic stresses



under changing climate situation.Therefore, maintenance of soil health forsupply of required food for future foodand nutritional security is an issuecomes under the ambit of socio-economic, demography and politicalsciences.

References

Beebe SE, Rao IM, Cajiao C, Grajales M.(2008). Selection for droughtresistance in common bean alsoimproves yield in phosphorus limitedand favorable environments. CropScience 48(2):582–592.

Blas, J. (2009). Number of ChronicallyHungry Tops 1bn. Financial Times, 26March; Food and AgricultureOrganization of the United

Chabi-Olaye, A., Nolte, C., Schulthess, F. &Borgemeister, C. (2006). Relationships ofsoil fertility and stem borers damage toyield in maize-based cropping system inCameroon. Ann. Soc. Entomol. (N.S.), 42(3-4): 471-479.

Ehrlich, Paul R. (1968). Population Bomb,Buccaneer Books.

Roosevelt, Franklin D. (1937): "Letter to allState Governors on a Uniform SoilConservation Law.," February 26, 1937.Online by Gerhard Peters and John T.Woolley, The American PresidencyProject..

FAO. (2008). An international technicalworkshop Investing in sustainable cropintensification: The case for improvingsoil health, FAO, Rome: 22-24 July2008. Integrated Crop Management, 6.Rome.

FAO (2008). The State of Food Insecurity inthe World . Rome: FAO.

FAO. (2010). Climate-smart agriculture:Policies, practices and financing for foodsecurity, adaptation and mitigation.Rome.

FAO. (2010). The State of Food Insecurity inthe World 2010. Rome: FAO

Hyams E. (1976). Soils and Civilization.London: Murray, 1976. (312 pp.).

Jarvis A, Lau C, Cook S, Wollenberg E,Hansen J, Bonilla O, Challinor A. (2011).An integrated adaptation and mitigationframework for developing agriculturalresearch: synergies and trade-offs.Experimental Agriculture 47:185–203.

Jenkinson, D.S.(2010). Department of SoilScience, Rothamsted Research. Interview

with BBC World. 6 November.Kibblewhite M.G. (2005). Soil quality

assessment and management. In:McGilloway D.A, editor. Grassland: aglobal resource. Wageningen AcademicPublishers; Wageningen, TheNetherlands:. pp. 219–226.

Lobell D, ed. (2009). Climate extremes andcrop adaptation. Summary statementfrom a meeting at the program on foodsecurity and environment held on June

16‐18, 2009. Stanford, CA: Stanford

University.Malthus, Thomas Robert (1798). An Essay

on the Principle of Population, publishedat London.

Mittal, Surbhi (2008). Demand-SupplyTrends and Projections of Food in India,Working Paper 209, Indian Council ForResearch On International EconomicRelations, New Delhi

Olson G.W. (1981). .Archaeology: lessons onfuture soil use. J Soil Water Conserv ;36:261 –264

Sachs, J., Remans, R., Smukler, S.,Winowiecki, L., Sandy, J., Andelman,S.J., Cassman, K.G., Castle, L.D.,DeFries, R., Denning, G., Fanzo, J.,Jackson, L.E., Leemans, R., Lehmann,J., Milder, J.C., Naeem, S., Nziguheba,G., Palm, C.A., Pingali, P.L., Reganold,J.P., Richter, D.D., Scherr, S.J., Sircely,J., Sullivan, C., Tomich, T.P. & Sanchez,P.A. (2010). Monitoring the world’sagriculture. Nature, 466: 558-560.

Slack N. (1997). The Blackwell encyclopaedicdictionary of operations management.Blackwell; Oxford, UK.

Steiner, K., Herweg, K. & Dumanski, J.(2000). Practical and cost-effectiveindicators and procedures for monitoringthe impacts of rural developmentprojects on land quality and sustainableland management. Agriculture,Ecosystems and Environment, 81: 147-154.

Thornton P, Cramer L, eds. (2012). Impactsof climate change on the agricultural andaquatic systems and natural resourceswithin the CGIAR’s mandate. CCAFSWorking Paper 23. Copenhagen: CGIARResearch Program on Climate Change,Agriculture and Food Security.

Vermeulen SJ, Aggarwal PK, Ainslie A,Angelone C, Campbell BM, Challinor AJ,



Hansen JW, Ingram JSI, Jarvis A,Kristjanson P, Lau C, Nelson GC,Thornton PK, Wollenberg E. (2012).Options for support to agriculture andfood security under climate change.Environmental Science and Policy15(1):136-144.

Weber, G. (1996). Legume-basedtechnologies for African savannas:Challenges for research anddevelopment. Biological Agriculture andHorticulture, 13: 309-333.

World Food Summit (1996). November 13-17, Rome, Italy.

World Food Summit (1996).http:/www.fao.org/wfs/index-en.htm

World Bank (2007). World DevelopmentReport (2008). Agriculture forDevelopment.www.wwfindia.org

www.worldometers.info/world-population/Young I.M, Ritz K. (2005). The habitat of soil

microbes. In: Bardgett R.D, Usher M.B,Hopkins D.W, editors. Biologicaldiversity and function in soils.Cambridge University Press; Cambridge,UK:. pp. 31–43.



MODELING SOIL EROSIONM.K.Hardaha

Joint Director Extension,Directorate of Extension Services, JNKVV, Jabalpur

Soil erosion is defined as thedetachment, transportation anddeposition of soil particles from oneplace to another by the action of wind,water or gravity forces. Although, theterm erosion was in use in the 19th

century, the term soil erosion wasintroduced at the beginning of 20th

century, and did not come into generaluse until 1930s. The word erosion is ofLatin origin being derived from the worderodere-to eat away (rodere-to chew).The term erosion was first used ingeology to describe the forming ofhollows by water, the wearing away ofsolid material by action of river water;while surface wash and precipitationerosion was called “ablation” (abatio-tocarry away). In addition to erosion andablation, a number of other terms“corrasion” (corradere-to chew to gether),“corrosion” (corodere-to chew to pieces),“abrasion” (abrodere-to scrape off) and“denundation” (denundere- to strip) werealso used. Soil erosion can be classifiedon the basis of rate, agent causingerosion and process of erosion. Table.1presents the classification of soil erosionbased on agents causing erosion.

Table 1. Classification of erosion by theactive factors.

TermS.N FactorEnglish Internatio

nal1 Water Water

erosionAquaticerosion

1.1 Precipitation, Rain

Precipitationerosion,Rain erosion

Pluvialerosion

1.2 River Rivererosion

Fluvialerosion

1.3 Torrent Torrenterosion

Torrentialerosion

1.4 Lake Lake erosion Limnicerosion

1.5 Reservoir Reservoirerosion

Lacustrineerosion

1.6 Sea Sea erosion Marineerosion

2 Glacier Glaciererosion

Galcialerosion

3 Snow Snowerosion

Nivalerosion

4 Wind Winderosion

Aeolianerosion

5 Organisms Biologicalerosion

Organogenicerosion

5.1 Plants Erosioncaused byplants

Phytogenic erosion

5.2 Animals Erosioncaused byanimals

Zoogenicerosion

5.3 Man Erosioncaused byman

Anthropogenicerosion

Source: Zachar D.C. (1982).

Our discussion in this section isconfined to water erosion and hereafter erosion shall be understood aswater erosion unless specified.

Factors effecting erosionErosion is resulted due to dispersive andtransporting power of the water, as incase of splash erosion, first the soilparticles are detached from the soilsurface by the action of raindrop andthen transported with surface runoff.There is a direct relationship betweenthe soil loss and runoff volume. Themajor factors, which affect the amountof, soil erosion in large extent, can besummarized as:

Climatic factors: The climatic factorswhich affect the soil erosion are rainfallcharacteristics, atmospherictemperature and wind velocity. Rainfallcharacteristic is the one of the mosteffective factor among them. Rainfallcharacteristic includes amount,intensity, frequency and duration ofrainfall. High rainfall intensity of rainfallhas bigger raindrop size, which hashigher kinetic energy and more erosivepower. Rainfall characteristics, whichproduce more runoff amount and ratecause more erosion. Frequent rainmaintains the soil moisture in adesirable range, which reducesinfiltration capacity of soil and thus



produces more runoff. A uniformdistribution of rainfall throughout theyear always reduces the total erosion bymaintaining the soil moisture within theoptimum range for good vegetation overthe land surface.Soil factors: Soil erosion has directrelation with runoff. All soil propertiesresponsible for higher infiltration ratelike, low bulk density, high porosity,large particle size, low moisture content,grainular structure etc. cause low runoffand soil erosion. High cohesive forcebetween soil particle results into lowerdetachability of particles as in case ofclayey soil. On the other hand largeparticle size reduces transportation ofthe detached particles.Topographic factors: The land slopeand length of the slope are the twotopographic factors, which stronglyinfluence the soil erosion. As the lengthof the land in the direction of slopeincreases, detachment of soil particlesgoes on increasing. When the slope ofthe land is doubled, the particle sizethat can be transported increasessixteen times.

Vegetation: Vegetation plays importantrole in reducing soil erosion. In presenceof good vegetation soil erosion can bereduced significantly. The vegetationhelps in reducing soil erosion infollowing ways Kinetic energy of falling raindrops is

absorbed by the leaves and stems ofthe vegetation, which reduces thedetachment of soil particles.

Some of the rainfall is intercepted byleaves and stems and reducesrunoff.

Vegetation physically obstruct thevelocity of flowing runoff

Roots of the vegetation binds soilparticles

In presence of good vegetation,evapotranspiration rate is faster,thus soil moisture reduces andinfiltration increases.

Decayed roots increase porosity ofsoil.

Growth of certain soil fauna likeearthworm is accelerated in presenceof vegetation. These soil faunaspulverize soil and increase porosity.

Soil Erosion Process Models:Several models have been developed toestimate soil loss from watershed as aresult of soil erosion process, outflow ofsediments carried by runoff to streams.Evaluation of soil loss from watershed isrequired while assessing the severity ofsoil erosion and its effect on agriculturalproduction. Soil loss can be estimatedas a function of parameters of watershedand rainfall. Some of the commonlyused soil loss models are discussedhere.

1. Universal Soil Loss EquationThere have been sincere attempts todevelop soil loss estimation models,beginning from the sixties of 20th

century. The most effective model on thesoil loss was presented by Wischmeierand Smith (1965) and improved byWischmeier and Smith (1978). Themodel is popularly known as UniversalSoil Loss Equation (USLE). This alsoopened a new chapter for research inthis field and formed the basic structureof most of the soil loss models after thisperiod. Ghanshyam Das (2000) statesthat USLE appears to have been basedon the Musgrave (1947) equation withnecessary modifications. The USLE canbe written as:

A = R K L S C PWhere : A = estimated gross soil erosion,t/ha/yrR = rainfall erosivity factor, joule/ha/yror t-m-cm/ha-sK = soil erodibilty factor, t/ha/unit of RS = slope factorL = slope length factorC= crop management or vegetative coverfactorP = supporting conservation practicefactor

Rainfall erosivity factor (R): is themeasure of erosive capability of rainfall.It is the function of rainfall intensity andamount of rainfall. Many indices havebeen developed for the R. EI30 index ismost commonly used to represent therainfall erosivity.

nEI30 = Ei.I30i/100

i=1Where Ei = total kinetic energy ofith rain storm



I30i = maximum intensity of ith rainstorm for 30 min durationn = number of rain storm havingrainfall more than 2.5 mm

E = KE . PWhere KE = kinetic energy of segmentof rain having uniform intensityP = amount of segment of rain havinguniform intensityKE = 201.3 + 89 log IWhere I = rainfall intensity, cm/h

Calculation of EI30 index requiresrainfall data recorded from automaticrecording raingauge. A simplifiedequation has been developed byHardaha et al. (1996) for the Malwaregion of Madhya Pradesh. The equationuses total erosive rainfall (ER) i.e.storms having rainfall more than 12.5mm and expressed as:

EI30 = 9.524 ER + 5.60

Rambabu et al. (1978) preparedan iso-erodent map of India from whichthe approximate erosion value can beobtained directly.

Soil erodibility factor: The soil erodibilityfactor (K), converts units of R to amountof erosion. It is the average soil loss froma standard plot with 9 % slope, 22.1 mlong kept fallow by periodic tillage up-and-down the slope per unit value of R.Value of K can be determinedexperimentally for any soil on standardplot. The value of K is estimated basedon soil characteristics as given by Fosteret al.(1981)

K = 2.8x10-7 M1.14 (12-a) +4.3x10-3 (b-2) + 3.3x10-3 (c-3)

Where, K = Soil erodibility, Mg/ha/(MJ-mm/ha-hr)M = Particle size parameter, (%silt +%very fine sand)(100-%clay)a = Organic matter content, %b = soil structure code(very finegranular-1; medium or coarse granular-3; blocky, platy or massive-4)c = profile permeability class (rapid-1;moderate rapid-2; moderate -3; slow tomoderate-4; slow-5; very slow-6)

Table 2 can be used whenorganic matter content and texturalclass of the soil is known.

Table2. Values for soil erodibiltyfactor for different types of soil

K based on percentorganic matter in soil

Soil type

0.5 % 2.0% 4.0%Fine sand 0.36 0.31 0.22Very finesand

0.94 0.81 0.63

Loamy sand 0.27 0.22 0.18Loamy veryfine sand

0.98 0.85 0.67

Sandy loam 0.60 0.54 0.42Very finesandy loam

1.05 0.92 0.74

Silt loam 1.07 0.94 0.74Clay loam 0.63 0.56 0.47Silty clayloam

0.83 0.72 0.58

Silt clay 0.56 0.51 0.43

Slope length factor (L): Length ofthe slope on which the overland flowoccurs, effects the rate of soil erosion.On large slope length, there is a higherconcentration of overland flow, and alsoa higher velocity of flow, which triggers ahigher rate of soil erosion. Slope lengthfactor is defined as ratio of soil loss froma given slope length to that from a landhaving slope length equal to 22.1 m, ifall other conditions remain unchanged.Mathematically it can be expressed as:

L = (Lp/22.1)mWhere Lp = Actual unbroken length ofslope (m).M = an exponent equal to 0.5 for slope >5%0.4 for slope 4-5%0.3 for slope < 3%

Slope gradient factor (S): Soil erosion isgreatly influenced by slope of the land.On steep slope the flow velocity of runoffis high resulting in increased scouring,cutting and transportability of soil. Soilgradient factor is defined as the ratio ofsoil loss from a given degree of slope tothat from land having 9.0% slope, if allother conditions remain unchanged.Empirically it can be expressed as:S = (0.43 + 0.30 s + 0.043 s2 )/6.613Where, s = slope of the filed inpercentage



Crop management factor (C): Cropmanagement factor or vegetative coverfactor is defined as the ratio of soil lossfrom a land with given crop rotation andcover to that from a land clean tilled and

kept permanent fallow. Vegetative coveracts many ways in reducing the soilerosion as discussed earlier. Table 3presents value of factor C for some ofthe vegetative covers.

Conservation practice factor (P): A barefallow land surface causes maximumsoil erosion, especially when it iscultivated along the slope. Conservationpractice factor is the ratio of soil lossfrom a land having specifiedconservation practice to the land

ploughed up and down the slope, if allother conditions remain unchanged. Anypractice adopted to reduce runoffamount and its velocity shall reduce thesoil erosion. Table 4 presents value of Pfor Indian conditions.

Table 3. Crop management factor for some crop/grass covers at few ICAR centersin India.

CentresCropKota Agra Lucknow

Moong 0.39 - 0.45Gram 0.54 - -Groundnut 0.41 - 0.42Soybean 0.42 - -Guar 0.59 0.42 -Guar + Arhar - - 0.35Maize 0.50 - -Jowar 0.62 0.64 -Jowar + Arhar 0.33 - 0.28Jowar + Gram - 0.32 -Bajra - 0.61 -Til - 0.51 0.39Natural vegetation 0.14 - -Grass (Cynodon dactylon) 0.22 - -Grass (Dicnanthium annulatum) 0.01 0.13 -

Source: Gurmel Singh et al.(1981)Table 4. Values of conservation practice factor for different types of conservation

practice.Conservation practice factorLand slope %

Contour cultivation Contour stripcropping

Bench terracing

< 1 0.80 - -

1-2 0.60 0.30 -2-4 0.60 0.25 -4-7 0.50 0.25 -

7-12 0.60 0.30 -12-18 0.70 0.35-0.40 ->18 0.80-0.90 0.40-0.45 0.28

2. Soil Loss Equation Model for SouthAfrica (SLEMSA)SLEMSA was developed by Elwell (1978)for the southern region of Africa and is amodification over USLE. This model hasbeen designed to predict mean annualsoil loss, rising from sheet erosion on

area of arable land. Framework ofSLEMSA is presented in fig1. Bhargav(1999) has modified the SLEMSA modelfor Indian conditions for conservationpractices in use by incorporatingconservation practice factor (P). Themodified model is Z = K.C.X.P



Fig.1. Framework of SLEMSA model. (Elwell, 1982)3. Soil Erosion Model forMediterranean Region( SEMMED)A soil erosion model SEMMED (SoilErosion Model for Mediterraneanregions) was developed for the test siteArdèche, France (De Jong, 1997).SEMMED comprises several modules,each of which describes a part of theerosion process such as soil particledetachment, moisture storage in the topsoil and transport of soil particles by

overland flow. SEMMED uses (multi-temporal) Landsat TM images to accountfor vegetation properties and it uses adigital terrain model in a GIS to accountfor topographical properties. Spectralvegetation indices allow a pixel-by-pixelassessment of vegetation properties andthe multi-temporal approach enables theassessment of the change of vegetativecover in one growing period. Fig 2.shows flow chart of the model..

Source: De Jong (1997)Fig.2. SEMMED Model.



4. Modified Universal Soil LossEquation (MUSLE)USLE has been modified by Williams(1975) for predicting sediment yield byreplacing its rainfall erosivity factor withrunoff factor. The model can estimatesediment yield on a per storm basisagainst the average soil loss on annualbasis. The MUSLE is:Y = 11.8 (Q qp)0.56 KLSCPWhere, Y = Sediment yield from anindividual stormQ = storm runoff volumeqp = peak runoff rateEstimation of sediment yield from verylarge watershed is not very accurate dueto variations in climatic factors, soilcharacterstics, land slope, cropmanagement, erosion control practicesand watershed hydraulics within thewatershed area. Such watershed isdivided into subwatersheds of les than25 sq. km and sediment yield can becomputed using routing model as:

nRY = = Yi.e-BTi (D50i)0.5

i=1Where, RY = sediment yield from entirewatershed, tYi = sediment yield from ith sub-watershed, tB = Routing coefficientTi = travel time from sub-watershed i tothe watershed outlet, h

D50i = median particle diameter of thesediment for sub-watershed i, mmDas and Chouhan (1990) observed thatthe value of B is equivalent to 1/K whereK is the storage coefficient.5. Morgan, Morgan and Finney Model: Morgan et al. (1984) developed a modelfor estimating annual soil loss from fieldsize area on hill slopes. Inputs and flowchart of the model is illustrated in fig.3.For determination of annual rate of soilloss, the model compares the predictionof splash detachment and transportcapacity of the overland flow. The lowerof these two is considered as annual rateof soil loss. Some of the limitations ofthe model are: The model is more sensitive to

change in the annual rainfall andsoil parameters, when erosion istransport limited and also sensitiveto changes in rainfall interceptionand annual rainfall, when erosion isdetachment sensitive.

It requires precise information onrainfall and other associatedparameters, for having accurateprediction.

This model can not be employed forpredicting the sediment yield fromthe drainage basin.

Like USLE, it is also not suitable forpredicting the soil loss, resultingfrom an individual storm.

Fig.3. Morgan et al. model for soil erosion.



6. WEPP Model: Water Erosion Prediction Project (WEPP)model (Nearing et al.,1989) hascapability of predicting spatial andtemporal distribution of net soilloss/gain for the entire hill slope for anyperiod of time. It contains its ownprocess based hydrology, water balance,plant growth, residue decomposition andsoil consolidation models as well as aclimatic generator and many othercomponents that broaden its range ofusefulness. The basic equation used forestimation of erosion from land isrepresented as:

if DDdx

dG

where, G = sediment concentration;x = distance down slope,Di = Inter-rill erosion,Df = Rill erosion.Di = Ki.Ie.ir.SDRrr.Fnozzle.(Rs/W);Where, Ki = inter-rill erodibility,Ie = effective rainfall intensity,ir = inter-rill runoff rate,SDRrr = sediment delivery ratio,Fnozzle = adjustment factor to account forsprinkler irrigation nizzle impactvariation,Rs = rill spacing, andW = width of the rill.Df = Dc (1-G/Tc) ;Where, Dc = rill detachment capacity =Kr (f-c),Tc = transport capacity of flow in rill,Kr = rill erodibilty of soil,f = flow shear stress, andc = critical shear stress.Tiwari et al. (2000) compared the WEPPpredictions with the measured naturalrunoff plot data and found that themodel efficiency is 0.71 % in terms ofannual soil loss with average magnitudeof error 2.01 kg m-2. It was concludedthat WEPP is comparable with USLEand MUSLE.7. Quasi Three-dimensional Runoffmodel for soil erosion:Victor Demidov (2001), used quasithree-dimensional runoff model for soilerosion modeling. The developed soilerosion model allows to simulate thetemporal and spatial variations inerosion by raindrop impact and overlandflow, sediment transport and deposition.

Structure of the Model:Quasi Three Dimensional Model ofRainfall Runoff Formation - A physicallybased model of rainfall runoff formationis based on using differential equationswhich describe the processes ofoverland, groundwater, subsurface,channel flow as well as vertical moisturetransfer in soil. The catchment isrepresented in the horizontal plane byrectangular grid squares. The mainchannel and the tributaries of differentorders are represented by theboundaries of grid squares.The model describes the followingprocesses:1. Vertical moisture transport in the

unsaturated zone (the one-dimensional Richard's equation isused; the calculations is carried outfor each grid square of hill slope);

2. Groundwater flow and theinteraction of surface andgroundwater on the hill slope and inthe river channel (the two-dimensional Boussinesq equationsare used);

3. Overland flow (the two dimensionalkinematic wave equations areapplied);

4. Unsteady flow in the river network(the one-dimensional kinematic waveequations are used).

The organization of the interactionbetween components of the hydrologicalmodeling system allows taking feedbackinto account. Coupling of thecalculations of the vertical moisturetransport with the overland andgroundwater flow is accomplished bymeans of a special procedure.Modeling Soil Erosion and SedimentTransport in the River BasinA soil erosion and sediment transportmodel was developed as a separate blockof the hydrological modeling system. Thesoil erosion model describes thetemporal and spatial variations of thesoil erosion and the sediment transportin the river basins during flood events(erosion by raindrop impact andoverland flow, sediment transportationand deposition).The erosion rate by raindrop impact, Dr

(kg m-2s-1), is expressed by the followingequation

Dr = Kr Ks i Fr R



where Kr = soil erodibility factor forerosion by raindrop impact, Ks = fraction of bare soil,i = ground surface slope,R = rainfall intensity (cm/s), = an exponent, andFr = is the factor reflecting influence ofthe water depth on erosion by raindropimpact that is expressed asFr = exp (1-h D-1) if h > D= 1 if h DWhere h is the flow depth (m); D is themedian diameter of raindrops that isdetermined from D = 0.0193 R0.182

The erosion rate by overland flowimpact, De (kg m-2s-1) , is calculated as :

De = Ke(/c-1) if > c

= 0 if c

Where Ke is the overland flow soilerodibility coefficient; is the shearstress(kg m-2s-1) and c is the criticalshear stress, which is taken to be :

c = g i (ni –0.5 Vp)-1.5

Where is the water density (kg/m3); gis the acceleration of gravity (ms-2) ; n isthe Manning roughness coefficient ; Vp

is the pickup velocity (m/s) that isdetermined by the equation

Vp = 1.14 (g a d )0.5

Where a ( = PT -1-1) and PT is thesediment density (kf/m3) ; d is the graindiameter (m).The sediment transport capacity,GT (kgm-1s-1), is calculated by means of theEngelund-Hansen's equation

GT = 0.04 (V V*2 PT)/( a g )Where, V is the flow velocity (m/s); V* isthe shear velocity (m/s); is thecriterion which is = a d h-1 i-1.The sediment transport by the overlandflow is described by two-dimensionalsediment continuity equation

Ey

G

x

G

t

hC yx

)()()(

t

zPE T

)()1(

Where C is the sediment concentration(kg m-3); Gx and Gy are the sedimenttransport rate in the x and y directionrespectively; is the soil surfaceporosity; z is the soil surface elevation(m); E is the erosion or deposition rateon surface slope (kg m-2 s-1).Sediment routing in channels isdescribed by the one-dimensional

sediment continuity equation. Numericalintegration of these equations is carriedout an implicit finite difference scheme.

8. LISEM MODELThe LISEM model (De Roo et al.2001) isone of the first examples of a physicallybased model that is completelyincorporated in a raster GeographicalInformation System. Incorporationmeans that there are no conversionroutines necessary; the model iscompletely expressed in terms of the GIScommand structure. Furthermore, theincorporation facilitates easy applicationin larger catchments, improves the userfriendliness, and allows remotely senseddata from airplanes or satellites to beused. If required, the model can belinked easily with other GIS’s. Processesincorporated in the model are rainfall,interception, surface storage in microdepressions, infiltration, verticalmovement of water in the soil, overlandflow, channel flow, detachment byrainfall, detachment by overland flow,and transport capacity of the flow. Also,the influence of tractor wheelings, smallpaved roads (smaller than the pixel size)and surface sealing on the hydrologicaland soil erosion processes is taken intoaccount.

After rainfall begins, some is interceptedby the vegetation canopy until such timeas the maximum interception storagecapacity is met. Besides interception,direct through fall and leaf drainageoccur, which, together with overlandflow from upslope areas, contribute tothe amount of water available forinfiltration. The amount of waterremaining after infiltration begins toaccumulate on the surface in micro-depressions. When a predefined amountof depressions are filled, overland flowbegins. Overland flow rates arecalculated using Manning’s n and slopegradient, with a direction according tothe aspect of the slope. When rainfallceases, infiltration continues untildepression storage water is no longeravailable. Soil detachment and transportcan both be caused by either raindropimpact or overland flow. Whether or nota detached soil particle moves, dependsupon the sediment load in the flow andits capacity for sediment transport.



When water and sediment reach anelement with a channel, they aretransported to the catchment outlet.Sedimentation within a channel appearswhen the transport capacity has beenexceeded.

When there are no sufficient fieldmeasurements available, thedistribution of a desired input variablecan be derived from digitized soil or landuse maps. A raster-based GIS is theideal tool to serve needs and fulfillrequirements associated with the DEMand the geostatiscal interpolationtechniques. Further advantages of usinga GIS are

1) the possibilities of rapidly producingmodified input-maps with differentland use patterns or conservationmeasures to simulate alternativescenarios,

2) the ability to use very largecatchments with many pixels, so thecatchment can be simulated withmore detail, and

3) the facility to display the results asmaps.

A series of maps can be producedshowing the variation with time ofspatial patterns of soil erosion,sedimentation and runoff over thecatchment. These maps can becompared by subtraction to yield mapsindicating how erosion or sedimentationmight be affected by certain controlmeasures within the catchment or theycan be viewed successively to create avideo of the modelled process. Runoffcan also be displayed as an overlay onthe landform surface

The main advantage of incorporatingmodels in GIS is that the ‘source code’ ofthe model then resides on thecomprehensible abstraction level of oneor two lines of source code, a GIScommand, per process (e.g. interception,infiltration and sediment routing). Sucha high level of abstraction simplifiesmodel modification, maintenance andreusability of parts of the model in othermodels. The current implementation ofLISEM is less than 200 lines (exclusivecomments).

INPUTLISEM needs a number of input files

and maps to run. These inputs aredescribed below.

Rainfall file: Data from multipleraingauges can be entered in an inputdata file. A map is used as input todefine for each pixel which raingaugemust be used. For every time incrementduring the simulation of a storm, themodel generates a map with the spatialdistribution of the rainfall intensity.Thus, the model allows for spatial andtemporal variability of rainfall. In thefuture, this approach allows for theinput of e.g. radar data indicatingrainfall intensity patterns changing inspace and time: e.g. to simulate athunder storm which moves over acatchment.Tables for the soil water model: Withinthe catchment, soil profiles are defined.The vertical soil water movement issimulated by subdividing a soil profile ina user defined number of layers. Foreach characteristic soil horizon, themeasured K-t3-h relations are read fromthe horizon specific tables.Maps of relevant topographical, soil andland use variables: To run LISEM, anumber of maps are needed in thePcRaster format-

a group of maps which describe thecatchment morphology:o an ‘area.map’, in which the

main catchment is defined;o an ‘id.map’, which defines the

spatial rainfall pattern;o a map with the locations of the

main outlet and subcatchmentoutlets;

o a map with the ‘Local DrainDirection’, which refers toaspect;

o a map with slope gradient;o a map with the Manning’s n for

overland flow;o a map with slope gradient of the

main channels;o a map with the Manning’s n for

channel flow;o two maps which describe the

channel morphology;o a map with the location and

width of roads; a map with the location and width of

wheel tracks from tractors;



a group of maps needed for the soilwater sub-model:o map with the soil profile types,

referring to the conductivitytables;

o a similar map, but then forprofiles under wheel tracks;

o maps with the initial soil metricsuction for each soil layer;

a group of maps with soil and landuse variables:o a map of the Leaf Area Index;o a map with the soil coverage by

vegetation;o a map with the crop height;o a map with the Random

Roughness of the soil surface;o a map with the aggregate

stability of the soil;o a map with the soil cohesion;o a map with the soil cohesion of

channels;Command file : When the model is run,the user is prompted for the selection ofthe catchment, the rainfall event, a fewtuning parameters and the desiredoutput. Alternatively, the user canspecify this information in a commandfile. This interface empowers the user to:

Select the catchment byspecifying the directory of thetopographical, soil and land usemap database;

Select the soil water modelparameters by specifying thedirectory of the soil water tables.Separating the map databaseand the soil water tables permitsoptional sharing of the soil watertables between differentcatchments;

Select the rainfall event byspecifying the rainfall file; Selectthe starting and ending time ofthe simulation;

Select the overall simulation timestep, and the minimum time stepfor the soil water sub-model;

Select a precision factor of thesoil water sub-model;

Select a number of parametersand coefficients used in thedetachment and transportformulas, such as settlingvelocity of the soil particles and asplash delivery ratio. Ifnecessary, a few of these

parameters could be used forcalibrating the sediment part ofthe model;

Select names of the output files:e.g. hydrograph files (main outletand outlets of predefined sub-catchments), runoff maps atseveral times, soil erosion mapand the ‘results’ file with totals.

OUTPUTThe results of the LISEM model consistof:

a text-file with totals (total rainfall,total discharge, peak discharge, totalsoil loss etc.);

a ASCII data file which can be usedto plot hydrographs and sedigraphs.

Pc-Raster maps of soil erosion anddeposition, as caused by the event;

PcRaster maps of overland flow atdesired time intervals during theevent.

VALIDATION OF LISEMThe model results are compared withobserved data (validation). Statisticalcriteria determine the ‘goodness of fit’.The model user has to decide whetherthe results are satisfactory. If so, thesimulations end and the ‘final results’are produced. If the validation is notsatisfactory, there are several options:

Modify the model; Re-calibrate the model;

Change the resolution (pixel-size orsimulation time step);

Collect more data; Collect better data (measurement

errors); Collect different data (other variables);This procedure is repeated untilsatisfactory results are obtained.

There are various erosion processmodels available and use depends uponthe data required in the model and thedata available.

References:Bhargav, K.S.(1999). A modified

SLEMSA model for Naurarsubcatchment of Ramgangariver. Unpublished master’sthesis. Submitted to GBPAUT,Pantnagar.

Das G. and Chouhan H.S.(1990)



Sediment routing formountainous Himalayan region.Trans. ASAE.

De Jong S. M. (1997) DeMon - SatelliteBased Desertification Monitoringin the Mediterranean Basin -www.geog.uu.nl/fg/demon.html.

De Roo A.P.J., C.G. Wesseling, N.H.D.T.Cremers, R.J.E. Offermans C.J.Ritsema and K. vanOostindie(November 2001).Lisem: a physically-basedhydrological and soil erosionmodel incorporated in a gis.www.odyssey.maine.edu/gisweb/spatd6/egis/eg94023.html

Elwell, H.A.(1978). Modelling soil loss insouthern Africa. Jl. of Agric.Engg. Res.

Foster G.R., McCool D.R., Renard K.G.,and Mobdenhaur W.C. (1981)Conversion of Universal soil LossEquation to SI Metric Units. Jl.Soil Water Cons.

Ghanshyam Das (2000). Hydrology andSoil Conservation Engineering.Prentice Hall of India. New Delhi.

Gurmel Singh, Ram Babu and SubhashChandra (1981) Soil lossprediction research in India.Bull. T 120/D-9, CSWCR & TIDehradun.

Hardaha M.K., Kale V.S. and Nema R.K.(1996). Erosive rains and erosionindex for Indore. Indian Jl. of SoilConservation. Vol. 24 no 3, p193-196.

Musgrave G.W.(1947) The quantativeevaluation of factors in watererosion, a first approximation. Jl.Soil Water Cons.

Nearing M.A., Foster G.R., Lane L.J. andFinkner S.C. (1989) A processbased soil erosion model forUSDA Water Erosion PredictionProject. Trans.ASAE 32(5).

Ram Babu, Tejwani K.G., Agrawal M.C.

and Bhusan I.S.(1978)Determination of erosion indexand Isoerodent map of India.Indian Jl. of Soil Cons. Vol. 6(1)

Williams,J.R.(1975). Sediment yieldprediction with universalequation using runoff energyfactor. In: Sediment yieldworkshop Oxford,Nov.1972.Present andprospective of technology forpredicting sediment yield andsources. Proceeding: Oxford,USDA Sedimentation Lab.

Wischmeir W.H. and Smith D.D.(1965)Predicting rainfall erosion lossesfrom cropland east of the rockymountains. USDA Handbook No.282, Washington D.C.

Wischmeir W.H. and Smith D.D.(1978)Predicting rainfall erosion losses– A guide to conservationplanning. USDA Handbook No.537, Washington D.C.

Tiwari A.K, Risse L.M. and Nearing M.A.(2000) Evaluation of WEPP andits comparison with USLE andRUSLE. Trans. ASAE vol.43(5)pp:1129-1135.

Victor Demidov (November 2001).Modeling Soil Erosion andSediment Transport onWatersheds with the Help ofQuasi Three-dimensional RunoffModel.www.epa.gov/OWOW/watershed/proced/demidov.html

Zachar D.C. (1982). Soil Erosion.Scientific Publishing Co.Amestrdam.



Test of Significance – I (Tests Concerning Mean)

Ranbahadur Singh

IntroductionIn applied investigations especially

in agriculture and allied Science, it maynot be possible to study the wholepopulation and thus the investigator isforce to draw inference about thepopulation on the basis of theinformation obtained from the sampledata (due to high operational cost andtime consideration), Which is called asstatistics inference . For Example, it isout of question to harvest and record theproduce from all the field growing thewheat crop which constitute thepopulation under study.

DefinitionStatistical inference is a branch

of statistics, which deals with drawinginference about the population on thebasis of sample information. Two majorarea of statistical inference are:I. Point and interval estimation of

parameters.

II. Test of significance (also called astest of hypothesis) Suppose we havean unreleased variety (V1) of wheatcrop. One may ask question such as:

i. What is the average yield of Varity(V1)? (It is a problem of estimation)

ii. Is the average yield of this variety(V1) = 65 q/ha or is the average yieldof (V1)>65 q/ha or < 65 q/ha (Testingof hypothesis).

Here we shall discuss various tests ofsignificance.Definition:

Any statement or assumptionbout the population or the parameters ofthe population is called as statisticalhypothesis.

The truth or falsity of statisticalhypothesis is never known withcertainty unless we examine the entirepopulation. This, of course, would beimpractical in most situations. Instead,we take a random sample from thepopulation of interest and use theinformation contained in this sample to

decide whether the hypothesis is likelyto be true or false. Evidence from thesample if inconsistent with statedhypothesis leads to the rejection of thehypothesis, whereas evidencesupporting the hypothesis leads to itsacceptance. The investigator shouldalways state his hypothesis in a mannerso as to test it for possible rejection. Ifhe is interested in a new vaccine, heshould assume that the new vaccine isnot better than the vaccine now in themarket and then set out to reject thiscontention. Similarly, to prove newplughing technique is superior to oldone, we test the hypothesis that is nodifference between these two techniques.Definition:

The hypothesis which is beingtested for possible rejection is referred isto as null hypothesis and is representedby H0 which as the hypothesiscomplementary to the null hypothesis isreferred to as alternative hypothesis andis represented by H1.

These hypotheses are such thatthe acceptance (or rejection) of one leadsto the rejection (or acceptance) of theother. Thus if we state the nullhypothesis as H0: µ (yield of c.v. WH-542) = 65 q/ha, then the alternativehypothesis might be H1 µ≠65 q/ha µ >65,q/ha µ< 65 q/ha.Let us consider an example…………

Example:Suppose the average yield 'of a

crop variety V1, is 55 q/ha. A newvariety V2 is evolved to increase theyield. Naturally before replacing thevariety V1 by V2, the breeder wants to besure (on the average) scientificallywhether the variety V2 is superior tovariety V1 in terms of yield. Here we aredealing with two populations of plots,those with varieties V1 and V2. Theaverage yield of V1 is known and is equalto 55 q/ha. To answer the abovequestion, the null hypothesis in thiscase is H0: µ= 55q/ha i.e. average yieldof variety V2 is equal to 55 q/ha and H1

= µ> 55 q/ha.



In testing of a statisticalhypothesis we have to choose betweentwo possible actions regarding thepopulation parameters. In the aboveexample we have to choose one of thetwo possible actions……..

(i) we accept the null hypothesis, inwhich case we retain the existingvariety V1, or..

(ii) we reject the null hypothesis inwhich case we recommend thenew variety V2.

Two types of errors:In order to make any decision to

accept or to reject the null hypothesiswe have to draw a random sample x1, x2

........xn of size n from the givenpopulation under study and on the basisof information contained in the samplewe have to decide whether to accept orreject the null hypothesis. Because ofthe random nature of the sample theabove decision could lead to two types oferrors.Decision

Accept Reject(i) H0 is true Correct decision (no

error) Type - 1 error I(ii) HO is false Type -II error

Correct decision (no error)

Definition:Type I error is made when we

reject a true null hypothesis, i.e. wereject the null hypothesis when it shouldbe accepted.

Definition:Type II error is made when we

accept a false null hypothesis, i.e. weaccept the null hypothesis when itshould be rejected.

The relative importance of thesetwo types of errors depends upon theindividual problem under study. Forinstance, in the above example, it isexpensive to replace the existing varietyV1 and so one should be very carefulabout the type I error. Whatever may bethe relative importance of these errors, itis preferable to choose a test for whichthe probability of both types of error isas small as possible. Unfortunately,when the sample size n is fixed inadvance, it is not possible to controlsimultaneously both types of errors.What is possible is to choose a test that

keeps the probability of one type of errora minimum when the probability ofother type is fixed. It is customary to fixtype I error and to choose a test thatminimize the probability of type II error.

Definition:Level of significance is the

probability of committing a type I error,i.e. it is the risk of rejecting a 'true nullhypothesis. It is denoted by the symbolα. On the other hand, the probability ofcommitting a type II error is denoted bythe symbol β and consequently (1- β) iscalled the power of the test. There is nohard and fast rule for the choice of α, itis customary to choose α equal to 0.05or 0.01. A test is said to be significant ifH0 is rejected at α= 0.05 and isconsidered as highly significant if H0 isrejected at α = 0.01.

Definition:Test statistic is a calculated numberfrom the sample data that is used todecide whether to reject or accept H0.

The formula for computing thevalue of test statistic depends upon theparameter we are testing. In general, theprocedure of testing any hypothesisconsists of partitioning the total samplespace in two regions. One is referred toas region of rejection or the criticalregion and other as region ofacceptance. If the test statistic on whichwe base our decision falls in the criticalregion, then we reject HO. if it falls inthe acceptance region, we accept HO.

One tailed and two tailed testsA test of any statistical

hypothesis where the alternative is onesided (right sided or left sided) is called aone tailed test. For example, a test fortesting the mean of a population HO: µ =µ0 against H1: µ > µ0 (right tailed) or H1:µ < µ0, (left tailed) is a one tailed test. Atest of statistical hypothesis where thealternative is two sided such as: H0 = µ =µo against H1: µ ≠ µ0 (µ>µ0 and µ<µ0), isknown as two tailed test.

Tests for the Single Mean:Here we will discuss tests fordetermining whether we should reject oraccept H0 about the population mean µ.

Case (i): Population S.D. (G) is known(Standard Normal Deviate Test – OneSample Z-test)



Let a random sample x1, x2 ....... xn ofsize n be drawn from a normalpopulation whose S.D. (σ) is known. Wewant- to test the null hypothesis thatthe population mean is equal to thespecified mean µ0 against the alternativehypothesis that the population mean isnot equal to µ0.

Assumptions:(i) Population is normal(ii) The sample is drawn at random(iii) Population S.D. (σ) is known

Procedure:1. Formulate the null hypothesis H1:µ=µ0

2. Formulate the alternative hypothesisH1: µ ≠ µo3. Choose the level of significance α =0.05 or 0.014. Compute the test statistic5. Conclusion: If |ZCal|>1.96, we rejectH0 at α= 0.05 (50/0 level of significance)otherwise we accept H0. If lZcall>2.58, wereject H0 at α = 0.01 (1% level ofsignificance).

Example: The average number of mangofruit per tree in a particular region isknown from a considerable experienceas 520 with a standard deviation 4.0. Asample of 20 trees gives an average'number of fruit 450 per tree. Testwhether the average number of fruitselected ln the sample is in agreementwith the average production in thatregion.A stepwise solution is as follows:1. H0: µ =µ0 = 520 fruit2. H1: µ ≠ 520 fruit3. α = 0.054. X= 450 n=20Conclusion: I Z (cal.) |> Z (tabulated),1.96 at <1= 0.05. Therefore, we reject H0and conclude that average number offruit per tree in the sample is not inagreement with the average productionin the region.Case (ii): if the population S.D. (σ) isnot known but sample size is large (say>30). Still we can use the one sample Z-testAssumptions: Same as in case (i)Stepwise procedure:Test statistic, we can use sample S.D. (s)in place of (σ)

Conclusion: If Zcal>Ztab, we reject H0and conclude that sample has not beendrawn from population with thespecified mean.Example: A sample of 900 plants hasthe mean height equal to 3.4 cms andS.D. 2.61 cms. is the sample height is inagreement with the mean height of theplants in the population equal to 3.25cms.

Step wise solution1. H0=µ=µ0

2. H1: µ ≠µ3. α= 0.05 = 3.4 n = 900 S = 2.614.

Since l Zcal l < 1.96, therefore, we acceptH0 at on = 0.05 and conclude that themean sample height is in agreementwith mean height of the plants in thepopulation.Case (iii): Population S.D. (σ) isunknown and sample size is small (onesample t-test)Let x1, x2 …………………. xn be a randomsample of size n from a normalpopulation with S.D. σ(unknown) and wewant to test the null hypothesis that thepopulation mean p is equal to aspecified value µ0 against the alternativehypothesis µ≠µ0. The stepwise testingprocedure is as follows:Assumptions:

i. Population is normalii. The sample is drawn at randomiii. Population S.D. (σ) is unknown and

sample size is small.1. HO: µ= µ0 .2. H1: µ≠µ0

3. Choose the level of significance α=0.05 or 0.01

4. Test StatisticObtain sample mean Y and sample

S.D.’s

nσ/0μx

calz

212;/

01

n

i

xixn

sns

calZx

X

73.161.2

3015.0

900/61.2

25.340.3

/0

ns

xcalZ

computeinallyfandXiXn

SandXn

x 21

121

ns

xcalt

/0



1. Obtain tabulated value of’t’distribution with (n-1) d.f. at thelevel of significance, α.

2. If l t (calculated) l > t (tabulated), wereject H0 at of level of significance,otherwise accept H0.

Example: A new feed was given to 25animals and it was found that theaverage gain in weight was 7.18 kg witha standard deviation 0.45 kg in amonth. Can the new feed be regardedhaving similar performance as that ofthe standard feed, which has theaverage gain weight 7.0 kg.Stepwise solution:1. H0 µ = 7.0 kg2. H1: p¢7.0 kg o= 0.05Here x = 7.18 kg and s = 0.45 kg

t (tabulated) at <1 = 0.05 with 24d.f. = 2.06Conclusion: As ltcal| <t tab, we acceptH0 at 5% level of significance therefore,we conclude that new feed do not differin performance than the existing feed.

TESTS OF SIGNIFICANCE – II

Tests for the Difference of Means:The Comparison of a sample

mean with its hypothetical value is not aproblem of frequent occurrence. Aproblem more commonly met with inagricultural and other biologicalresearch is the comparison of twosample means. Thus we may wish tocompare the mean yields of two varietiesof a crop, two diets to see their effect onthe increase in weight, the sucrosepercentage of two varieties of sugarcane,etc. Here we will like to test the nullhypothesis whether the two populationmeans are same against the alternativehypothesis that the two populationmeans are different ((HO 2 p1= iq)

Case (i): Population SD‘s are known(Two sample Z test).Let xl, X2 ………….xn and y1, y2 .......... yn

be the two independent random samplesof sizes n and m from the two normalpopulations with standard deviations σ1and σ2 (known) and we want to test thenull hypothesis H0 : µ1=µ2 against thealternative H1: µ1≠µ2

Assumptions:

(i) Populations are normal.(ii) Samples are drawn independentlyand at random.(iii) Population S.D.'s are known.(iv) Size samples may be small or large.

Stepwise procedure is as follows:1. Formulate the null hypothesis H0:µ1=µ2

2. Formulate the alternative hypothesisH0 : µ1≠µ2

3. Choose the level of significance α=0.005 or 0.014. Test statistic 1Obtain and from the two independentrandom samples of size n and mrespectively and compute.

Conclusion:Reject H0 at 5% level of significance if |Zcal l > 1.96 and at 1% level ofsignificance if l ZCal> 2.58, otherwiseaccept H0

Case (ii): Population SD‘s are unknownbut the samples sizes are large (Twosample Z-test).If the sample sizes are large, then wecan replace the population SD‘s withcorresponding sample values S1 andSQ.Assumptions:(i) Populations are normal.(ii) Samples are drown independentlyand at random.(iii) Population S.D.‘s are unknown.(iv) Sizes of the samples are large.Procedure is same as in case (i) exceptthe test statistic

2122

2112

22

21

yyn

sxixnwheres

m

s

n

s

yxcalZ

Conclusion is same as in case (i)

Example: A random sample of 90 birdsof one breed gave on average productionof 240 eggs per bird per year with a SDof 18 eggs. Another random sample of60 birds of another breed gave anaverage production of 195 eggs perbird/year with a SD of 15 eggs. Is thereany significant difference between thetwo breed with respect to their eggproduction.

0.225/45.0

7018.7

calt mn

yxcalZ

22

21



Stepwise solution is as follows:1. H0: µ1=µ2

2 H1:µ1≠µ2

3. α = 0.054. Test statistic = 240 n = 90 s1 = 18 =195 m=60 s2=15

Conclusion:Since l Z (cal) I > Z (tab), 1.96 at 5% levelof significance, therefore, we reject H0and conclude that there is a significantdifference between the two breea of birdswith respect to egg production.Case (iii) : Population SD's areunknown but same and sample sizes aresmall (Two sample I-test)Let x1, x2,……….xn and y1,y2………….. yn

in be two independent random samplesof sizes n and m (small) from two normalpopulations with standard deviationsσ1and σ2unknown but same. Here wewant to test the null hypothesis H0:µ1=µ2 against the alternative H1: µ1=µ2

Assumptions:1. Populations are normal.2. Samples are drawn independentlyand at random.3. Population S.D.'s are unknown butequalWe proceed by the following steps

• H0: µ1=µ2

• H1: µ1≠µ2

• α= 0.05 or 0.01

4. Test statisticCompute sample means , andsample variances s12 and S22 and obtain

2

22)1(2

112

mn

smsnwheres

mn

nm

s

yxcal

t

5. Obtain tabulated value of tdistribution (t-tab) at (n+m-2) at α levelof significance.6. If | tm l >ttab, reject H0 at ol level ofsignificance, otherwise accept Ho.

Example: For a random sample of 10pigs fed on diet A, the increase in weightin Kg. in a certain period were 10, 5, 16,17, 13, 12, 8, 14, 15, 9 Kg. and foranother random sample of 12 pigs fedon diet B, the increase in weights forsame period were 7, 13, 22, 15, 12, 14,18, 8, 21, 23, 10, 17 Kg.Test whether diet A and B differssignificantly as regards the effect onincrease in weight is concerned. How will we modify the testingprocedure if the population variancesare known to be 5 and 9 Kg2.Solution:1. H0: µ1=µ2

2. H1:µ1≠µ2

3. α = 0.05

4. 1210

120

n

xx

1512

180

m

yy

(n-1) S12=∑(x-x)2 =120(m-1) S12=∑(y-y)2 =314

S2= 1.2121210

134120

121

101

/1.21

1512

mn

nm

s

yxcalt

5. ttab at 5% level of significancewith 20 d.f. is 2.086.6. As l tcal| < 2086, we accept H0and conclude that the two dietsdo not differ significantly.(ii). Here the populationvariances are known, therefore,we can apply two sample Z-test[case (i)].

1. H0: µ1=µ2

2. H1:µ1≠µ2

3. α = 0.054. Test Statistic

68.2

129

105

151222

21

mn

yxcalZ

y

x

x y

61.162)15(

90

218

19524022

1

mm

s

n

s

yxcalZ



Conclusion:As | Zcal, l>Ztab = 1.96 at 5% level ofsignificance, therefore, we reject H0 andconclude that diet A differs significantlyfrom diet B as far as increase in weightis concerned.Case (iv) : Population variances areunknown but different…For testing the significance of thedifferences between two means, we havemade the assumption that the variancesof two populations are same. Beforeapplying the t-test, it is desirable to testthese assumptions by comparingvariances ratio s12/S22 (s12>s22) against Fdistribution with (n-1), (m-1) degrees offreedom. If the two variances aredifferent then in this case we -find outtcalas .

m

s

n

s

yxcalZ

2221

21

And compare it with tm, with v d.f. where

1)/(m2/m)22(s1)/(n2/n)2

1(s/m2

2s/n21s

v

Case (V) Test for the paired samples(paired t-test):

In above tests, we have that thetwo random samples are independent,but sometimes in practice we find thattwo random samples may be correlated.For instance in the above Example, itmay be possible that the pigs allotted atrandom to two diets may differ in theirages, sexes, initial weights, breeds,earlier nutritional standards etc. and theincrease in body weights apart from thedifferences in two diets may also affecteddue to these non-random factors. Insuch experiments, it is desirable thatbefore starting the experiments the pigsare paired in such a way that each pairis homogenous as far as possible, i.e.each pair contains the pigs taken fromsame body weight, same sex, samenutritional values. Other exampleswhere paired t-test may be used are, theneighboring plots of field for thecomparison of two fertilizers withrespect to yield assuming that theneighboring plots will have the same soilcomposition, branches of the same plantfor the comparison of nitrogen uptake.Let there be n pairs and the

observations are denoted by (x1,y1)(x2,y2)…… (xi,yi)………… (xn,yn) and letd1,d2……………….dn represents thedifferences of n related pairs ofmeasurements, where di =xi - yi ,

i = 1, 2,……………………………n.Assumptions:1. Populations are normal.2. Samples are dependent and atrandom.3. Population S_D.‘s areunknown but equal4. Size of the samples are small.Procedure:

1. H0: µ1=µ2

2. H1:µ1≠µ2

3. Choose the level of significance α

4. Test Statistic

5.

ds

dncalouttofindand

n

didd

sn

iddcompute0

1

22,

6. Obtain tm, at oi level ofsignificance with (n»1)d.f.

7. Reject H0 if l tm, l> tm, otherwiseaccept HO.

Example: An experiment wasconducted at a Research Station forcomparing two varieties of behind onneighboring plots of size 5 x 2 m2 ineach replication. The weight ofbehind per plot (in kgs) at harvestingtime was recorded on 7 replicates.

Test for significance of differencebetween the two varieties with respect totheir yield.Stepwise procedure:

1. H0: µ1=µ2

2. H1:µ1≠µ2

3. α = 0.05

Replicates

1 2 3 4 5 6 7

Variety–I

1.96 2.10 1.64 1.78 1.95 1.70 2.00

Variety-II

2.13 2.10 2.14 2.08 2.20 2.12 2.05



4.dS

dncalt

Corresponding differences between pairsare-0.17, O, -O.5O, -O.3O, -0.25, -0.42, -0.05 d=∑d i/n=-1.69/7=-024 d=∑d i/n=-1.69/7=-024

0337.021

12

ddndS

tcal=-3.46Conclusion:Since l t (cal) l> t (tab), 2.447 at 6 d.fand at 5% level of significance.Therefore, H0 is rejected and weconclude that there is significantdifference between the two varieties ofbehind with respect to yield.F-test is used:I. As a test for the equality of two

population variances i.e. whether thetwo samples may be regarded asdrawn from the normal populationhaving the same variance.

II. As. a test for the equality of severalpopulation means.

i. The F-test may be used to test theequality of two population variances.Let x1,x2…xn, and y1,y2,………yn; be twoindependent samples drawn randomlyfrom two normal population withvariances of and of. Let σ12 and σ22 bethe estimates of population variances.We want to test the null hypothesisthat the population variances areequal.

Assumptions:a. Populations are normal.b. Samples are drawn independentlyand at randomStepwise procedure is as follows1. H0: σ1 2=σ22

2. H1: σ1 2≠σ22

3. Choose the level of significanceα=0.05 or0.01

4. TestStatistic

Here numerator corresponds togreater variance

If FCal>F-tabulated at (v1, v2) d.f. (v1 =n1-1, v2 = n2-1) at α level ofsignificance, then we reject H0 andconclude that the populationvariances are significant different,otherwise we accept HO.

ii. The F-test can also be used to testthe equality of several populationmeans in the analysis of variancetechnique. The F-test has widerapplication as it provides an overalltest for the equality of severalpopulation means whereas t-testmay be used to test the equality ofonly two population means.

Example: Two random samples of 10and 12 equi sized plots treated withmanure I and II respectively in thebarley crop. The following results havebeen obtained regarding crop yields.

Manure No. ofplots

Av.Yield(q/ha)l

Sum ofsquares of

deviationsfrom

Manure I 10 50.0 180

ManureII

12 55.5 216

Other things remaining the same test ifthere is any significant differencebetween the crop yields due theapplication of two types of manures.Solution: Equality of means will betested by applying two sample t-test andhere we assume that σ12 = σ22therefore,we first apply F-test for the equality oftwo population variances.F-test1. H0 :σ12 =σ22 = σ2

2. H0 :σ12≠σ22

3. α=0.05 or 0.01

4. Test statistic 22

21

S

ScalF

n=10, x=50.0∑(xi - x)2 =180 m=12, y=55.5∑(yi - y)2 =216

018.1

112169

180

calF

212

12211

122

2

yiynySxixnxSwhereySxS

calF



Tabulated FD 05 (9, 11) = 2.90Since F(cal) < F (Tm), therefore we do notreject H0 and conclude that thepopulation variances are notsignificantly different.

Two sample t-test: After testing thenull hypothesis of equality of populationvariances, we now apply the t-test.

1. H0:µ1=µ2

2. H1:µ1≠µ2

3. α=0.05 or 0.01

4. Test Statistic

Conclusion:Since l tcall>ttab, therefore we reject Hgand conclude that there is significantdifference in the crop yield due theapplication of two types of manures.

Chi-square (χ2) test :Here, we shall discuss only twoapplications of χ2 test

1) Test of goodness of fit

2) Test of independence

Test of goodness of fit:The goodness of fit of any set of

data to any form of probabilitydistribution can be tested by a chi-square test. Suppose we are given a dataand we think that it should follow someknown distribution or some ratio i.e. wewant to test whether our assumption iscorrect. Suppose we know from theorythat in four groups the frequenciesshould be in the ratio of 9: 3 : 3: 1: 1 or1 : 1 : 1 :1 :1 and we want to test it withthe help of experimental trial. It is aproblem of testing of goodness of fit.

Here we will find the expectedfrequencies on the assumption that thedata follows a given distribution or ratioand the null hypothesis will be that thefit is good. To decide this we will applyχ2 test with (k-1) d.f. where k is thenumber of classes or groups.

Suppose we have got frequencydistribution of k classes and let Oibe theobserved frequencies of ith class (i = 1,2,………….. , k). Find out the expectedfrequencies (ei, i= 1, 2,………….. ,k) byfitting the desired probabilitydistribution.For carrying out this test we calculate,the test statistic

k

i ieieiO

1

22

which follows Chi-square distributionwith (k-1) degrees of freedom. It can beseen that for a complete agreement withthe hypothetical distribution the valuesof χ2 will be zero; but chance deviationsare bound to occur and we shall obtain

a positive value of χ2 due to samplingfluctuations. The test criterion is same

i.e. reject H0 if χ2Cal is greater than tablevalue of χ2 at oi per cent level ofsignificance with (l<-1) d.f.

Note: The expected frequencies in anyclass should not be too small, that is, 5or less. It is generally possible to poolthe frequencies in the adjacent classesso as to obtain the expectation of pooledfrequencies greater than 5. The pooledfrequencies will have to be treated asbelonging to single class and the degreesof freedom on which the χ2 is basedwould consequently be reducedTests: The expected frequencies arecalculated on the basis of thedistribution or ratio e.g. for testing aratio of 9: 3 : 3 :1, we expect a frequencyinIgroup 9/16*N; in II group 3/16 x N;in III group = 3/16*N and in the IVgroup = 1/16*N where N is the totalfrequency in the experiment.Example: In experiments on peabreeding, Mendal obtained the followingfrequencies of seeds: 315 round andyellow, 101 wrinkled and yellow; 108round and green; 32 wrinkled andgreen, Total 556. Theory predicts thatthe frequencies should be in the ration9: 3 : 3 : 1. Find χ2 and examinecorrespondence between theory andexperiment.Solution: H0 - The data follow the ratio9 : 3 : 3 :1 (or the fit is good)H1 - The data does not follow the ratio 9: 3 : 3 :1 (or the fit is not good)Expected frequencies for group I = 9/16x 556= 313

886.21210

1210

8.19

5.550.50

8.1921618020

122

2

12

calt

yi

yxixmn

s

mn

nm

s

yxcalt



Expected frequencies for group II = 3/16x 556 = 104Expected frequencies for group IH =3/16 x 556 = 104Expected frequencies for group IV =1/16 x 556 = 35

Total = 556I II II IV Total

O: 315 101 108 32 556

E: 313 104 104 35 556

..)14(51.0

35

23532

104

2104108

104

2104101

313

23133152 fd

The table value of X23 (0.05) = 7.82The calculated value is less than

7.82, hence we do not reject the null-hypothesis. We conclude that there is acorrespondence between the theory andexperiment or the data follows the ratio9: 3: 3: 1Test of independence:

Another common use of the Chi-square test is in testing independence ofattributes in what is known iscontingency table. Sometimes inagricultural and allied fields, attributedata are also considered equallyimportant for taking certain decisions asthe measurement data (grain yield, plantheight, No, of tillers etc.). This type ofattributed data is usually recorded in“words” instead of numeric values, forexample, colour classification (yellow,white), leaf shape (Narrow, Broad), yield(high, low) etc. are few examples ofattribute data. In social sciencesattribute data recorded more frequentlyfor example, social status, educationalclassification etc.

In testing of independence ofattribute data the null and alternativehypothesis are formed as follows:

H0: Attribute A and B areindependent

H1: Attribute A and B are notindependentSuppose there are `r' classification ofattribute A and `s‘ classification ofattribute B i.e. a r x s contingency tableis formed. Let Oij and eijare observed andexpected frequencies of ith row and jth

column respectively then

The test criterion is toreject H0 lf calculated χ2 is greater thantable value of χ2 at α per cent level ofsignificance with (r-1) x(s-1) d. f.

Special case: If two attributes aredivided only into two classes to form a 2x 2 contingency table and let a, b, c andd are respective observed frequencies ofthe classes then the test statisticbecomes;

)(,2

2 dcbawhereNdcdadbca

bcadN

and is used for testing HO. in casefrequencies in

2

x 2 contingency table are less than 5,Yates correction is useful for applyingChi-square test and the test statistic is

which is distributed as Chi-squaredistribution with 1 d.f. The test criterionremains same.

Example:Show that the conditions at

home has a bearing on the condition ofthe child on the basis of the followingobserved table:

CONDITION AT HOME

Clean Notclean Total

Clean 75 40 115Fairlyclean 35 15 50

Dirty 25 45 70

Conditions of

ChildTotal 135 100 235

Solution. H0 : Condition of child isindependent of condition at home. H1:condition of the child depends oncondition at home:The expected frequencies are :1. For clean-clean =

115 x 135/235=66.6

2. For clean-clean=50 x 135/235=28.73

..)1()1(2

22

1 1

fdsrwitheddistributisije

jieijOr

i

s

j

))((

2

22||

2dcbadbca

NbcadN



Expected frequency table

Clean Not clean Total

Clean 66.1 48.9 115

Fairly clean 28.7 21.3 50

Dirty 40.2 29.8 70

Total 135 100 235

95.18.).(2,

22

1 1

fdgetweije

ijeijOapplyBy

r

i

s

j

Now the table value of χ2 at 2 d.f. and at 5% level of significance (χ2 0.05) 5.99. Thecalculated value is more than the table value, hence the null-hypothesis is rejected, andour decision is that the condition at home has bearing on the condition of the child.



STATISTICAL DESIGNS FOR FIELD EXPERIMENTATION

H.L. SHARMA

DEPARTMENT OF MATHEMATICS AND STATISTICSCOLLEGE OF AGRICULTURE

J.N.K.V.V., JABALPUR-482004 (M.P.)

Experiments are performed byinvestigators in virtually all fields ofenquiry, usually to discover somethingabout a particular process or system.Literally, an experiment is a test. Moreformally, we can define an experiment asa test or series of test in whichpurposeful changes are made to theinput variables of a process or system sothat we may observe and identify thereasons for changes that may beobserved in the output response. Thus,statistical design of experiments refersto the process of planning theexperiment so that appropriate data thatcan be analyzed by statistical designswill be collected, resulting in valid andobjective conclusions. Data are thefundamentals of statistics. They can begenerated through two ways:

(i) Sample surveys (ii) Field experimentation

The theory of sample surveys has theobjective of deriving methods forcollection of sample observations from apopulation which exists in its own waysuch that the sample can adequatelyrepresent and accurately interpret thepopulation. In the case of experimentaldata no such population exists in its ownway. The experimentation is the merelyway to know an answer to the problem.Statistical design of experiment is verymuch useful in field experimentation totest the significant differences among thetreatment means. The following is anordered list of requirements for scientificexperimentation.1. Recognition of and statement of the

problem2. Choice of factors, levels and ranges3. Selection of the response variable4. Choice of experimental design5. Performing the experiment6. Collection of the data7. Statistical analysis of the data8. Conclusions and recommendations

Some of the terminology which areutilized in design of experiment, givenbelow: Experiment Treatment Experimental unit Experimental error Precision Layout

ExperimentExperiment is a means of getting

an answer to the question that theexperimenter has in mind. This may be todecide which of several pain–relievingdrugs that are available in the market isthe most effective or whether they areequally effective. An experiment may beplanned to compare the Chinese methodof cultivation with the standard methodused in India. In planning an experimentwe clearly state our objective andformulate the hypotheses we want to test.

Treatment

The different procedure undercomparison in an experiment is thedifferent treatments. e.g. in anagricultural experiment, the differentvarieties of a crop or the manures will bethe treatments. In a dietary or medicalexperiment, the different diets ormedicines etc. are the treatments.

Experimental unit

An experimental unit is the material towhich the treatment is applied and onwhich the variable under study ismeasured. In an agricultural fieldexperiment, the plot of land, and not theindividual plant, will be the experimentalunit; in feeding experiment of cows, thewhole cow is the experimental unit; inhuman experiments in which thetreatment affects the individual, theindividual will be the experimental unit.



Experimental error

A fundamental phenomenon inreplicated experiments is the variation inthe measurement made on differentexperimental units even when they getthe same treatment. A part of thisvariation is systematic and can beexplained, whereas the remainder is to betaken of the random type .Theunexplained random part of thevariation is termed the experimental error.This is a technical term and does mean amistake, but includes all types ofextraneous variation due to – (i) Inherent variability in theexperimental units(ii) Error associated with themeasurements made and(iii) Lack of representativeness of sampleto the population under study.

Precision The precision of an experiment ismeasured by the reciprocal of thevariance of the mean:

As n i.e. replication number increases,precision also increases. Another meansof increasing precision is to control σ2,smaller the value of σ2, the greater theprecision.LayoutThe term layout refers to the placementof treatment to the experimental unitaccording to the condition of design.

BASIC PRINCIPLES OF FIELDEXPERIMENTATION

There are three basic principles:

Randomization For an objective comparison, it isnecessary that the treatments be allottedrandomly to different experimental units.Statistical procedures employed inmaking inferences about treatment holdsgood only when the treatment areallocated randomly to the variousexperimental units . The purpose ofrandomness is to ensure that the sourceof variation not controlled in the

experiment operate randomly so that theaverage effect of any group of units iszero. In other words randomizationensures that different treatments on theaverage are subjected to equalenvironmental effect.

ReplicationThe repetition of treatments by

applying them to more than oneexperimental unit is known asreplication. It results in more reliableestimate of the treatment means than ispossible with a single observation. In anyexperimental situation, replication isnecessary in order to get an estimate ofexperimental error variation caused dueto uncontrollable factors. As it is, thisvariation, against which the variabilitydue treatments is compared. If we repeata single treatment a number of times themean of the treatment will be subjectedto standard error = σ/√r where σ is thenature error variability.

Local ControlThe reduction in the experimental

error can be achieved by making use ofthe fact that adjacent areas in the fieldare relatively more homogeneous thanthose widely separated. The entireexperimental material , if it isheterogeneous , may be divided intodifferent groups or blocks by takinghomogeneous units together and thetreatment may be allocated randomly todifferent units in each group by puttinga restriction that each treatment isapplied to one and only one units of theblock such that no treatment isrepeated in any group and no treatmentis absent from any group.

This procedure of blocking orgrouping is termed as local control.

The aim of the local control is toreduce the error by suitably modifyingthe allocation of treatments to theexperimental units.

BASIC DESIGNSCompletely Randomized Design

The simplest design using the twoprinciples i.e. .replication andrandomization is the completelyrandomized design (CRD). In this wholeof the experimental material assumed to

2

1

var ( )

n

iance mean



be homogeneous is divided into a numberof experimental units depending upon thenumber of treatments and theirreplication. The treatments are thenallotted randomly to the units /plots.This design is useful for laboratory, greenhouse and pot experiments. Missing plotsor unequal replication do not create anydifficulty in the analysis of this design .Ifwe have three treatment A ,B ,and C with5, 3 and 4 replication then the totalexperimental material is divided into 12experimental units .Then randomallotment of treatment A , B, C can bedone to 5 , 3 and 4 experimental units asshown below.

A B A BA A C CC B C A

Model – Yij = + i + e ij

(i = 1, 2 …..t, j = 1 ,2 ….r)Where -: yij denotes the observation of jthreplicate for the ith treatment is the general mean effect ,ti is the effect due to ith treatment and

eij is the random error .

Randomized Complete Block DesignWhen the experimental material is

not entirely homogeneous, the completelyrandomized design can not be used. Sohere we divide the whole material intohomogeneous groups/blocks ofexperimental units by adopting theprinciple of local control. Here thehomogeneous groups called blocks areformed perpendicular to the fertilitygradient. The randomization of thetreatments is done independently in eachblock. Let there be 5 treatments A, B, C,D and E and each replicated three times,the experimental area may be dividedinto three blocks B1, B2, B3 as shownbelow and then each block is divided into5 plots. The design is used frequently inagricultural field experiments.

B1 A C D B EB2 D C E A BB3 A E C D B

Model- Yij = + ti + bj + e ij; (i = 1, 2…..t, j = 1 ,2 ….r) Where -: Yij denotes the observation ofjth replicate for the ith treatment is the general mean effect,

ti is the effect due to ith treatment andbj is the effect of jth blockseij is the random error.

Latin Square DesignThe randomized block design is

intended to reduce error in respect ofone factor by forming homogeneousblock or groups. Often there is avariation among animals in respect tomore than one factor variation in respectof two factors can sometimes becontrolled simultaneously by anarrangement known as Latin square .Inthis design, the number of replicationsmust be equal to the number oftreatment. The txt unit is grouped in “t’rows and‘t’ column according to thevariation in two factors. Similarly in fieldexperiments, soil heterogeneity iseliminated in two ways by grouping theunits into rows and columns. If thefertility gradient is in the direction ofeast to west, then the grouping will bedone in the direction of North to South.The treatments are allotted such thateach treatment ‘occurs once and onlyonce in each row and in each column.The following are the examples of a LatinSquare Design

A B CB C BC A A

B C A DD A C BA D B CC B D AThe first is a Latin square of order 3 in astandard form. The second of order 4has been derived from a standard Latinsquare by permutation of rows andcolumns.

Model - Yij = + ri + cj+ tk +eijk

(i = 1, 2 …..t, j = 1 ,2 …. t, k=1,2….t )where Yijk denotes the observation onthe kth treatment jth column and in ithrow , is the general mean effect ,

ri is the effect due to ith row , cj is the effect due to jth Column the ithtreatment tk is the effect due to kth treatment and

bj is the effect of jth blockseijk is the random error which isassumed to be independently andnormally distributed with mean zero andconstant variance (2).



Factorial ExperimentsExperiment where the effects of

more than one factor, say varietymanure, etc. are considered together arecalled factorial experiments, whileexperiment with one factor, say onlyvariety or manure, may be called simpleexperiments. Consider a simple case of afactorial experiment. The yield of a cropdepends on the particular manureapplied .We may have two simpleexperiments, one for the variety and onefor the manure. First experiment will giveinformation on whether the differentvarieties of crop are equally effective orthere are some varieties which will givehigher yields than rest, similar type ofinformation may be obtained from thesecond simple experiment about themanures. Though the experiment withvarieties will be performed in thepresence of particular manure (not all themanure) and the experiment will beperformed with a particular variety (notall the varieties), they will not give us anyinformation about the dependence orindependence of the effect of the varietieson those of the manures. If there are pdifferent varieties then we shall say thatthere is p level of the factor ‘varieties’.Similarly, the second factor ‘manure’ mayhave q level, i.e. there may be differentmanures or different doses of the samemanure .Then this factorial experimentwill be called a p x q experiment.

Types of factorial experiment: Symmetrical factorial: where thelevels of each factor are the same in theexperiment.

Example- 22, 23, 24 …2n aresymmetrical factorial experiments offactors two, three, four… n, each it twolevels .The experiments 32, 33, 34 …3nare also symmetrical factorial consistingof 2, 3… n, factors each at three levels.Here in both type of experiments, thelevels of the factors are the same. In first,it is 2 and in second, it is 3.

Asymmetrical factorial: where the levelsof each factor are the different in theexperiment. In general, if there are n factors eachwith s levels than it is known as Sn

factorial (symmetrical) experiments. If thefactors consist of different levels i. e A

has 2 levels and B has 3 levels, then it isknown as 2x3 asymmetrical factorialexperiments and if there is another factorwhich is at four levels, then it called 2 x 3x 4 factorial experiment.

One factor at three levelsThe three levels of factor A may bedenoted by a0, a1, a2, with equalintervals. In dealing with factors at twolevels we have not mentioned the matterof equality of interval because there isonly one interval in that case. Levels withunequal intervals can also be analyzed.We observe the following:Increment form 0 to 1:a1 – a0

Increment from 1 to 2:a2 –a1

Sum of increments:(a2-a1)+(a1-a0) = a2-a0

Difference between increments: (a2-a1) –(a1-a0) = a2-2a1 +a0

The first contrast, a2-a0, measures thelinear effect of the factor. The secondcontrast, a2-2a1+a0, measures thedeviation from linearity, because if thethree points are collinear, this quantityequals zero.

Two factors, each at three levelsWhen there are two factors, each at threelevels, there will be nine treatmentcombinations.The seven contrastsFor factors at two levels, the symbolicexpressions and expansions for thevarious contrasts have been greatlysimplified by replacing a1 and a0 by a and1, etc. Unfortunately, there is no equallysimple notation for factors at three levels.We may, however, adopt a half-simplifiedsystem, writing a2, a1, a0, as a2, a, 1.Even this half-simplified notation willsave us a lot of writing labor. These fourcontrasts may be written symbolicallyA1 = (a2 - 1) (b2 + b + 1)

A2 = (a2 – 2a + 1 ) ( b2 + b + 1)B1 = (a2 + a + 1) (b2 - 1)B2 = (a2 + a + 1) (b2 - 2b + 1)

Where factors like (a2 + a + 1) and (b2 + b+1) simply mean marginal totals. Theremaining four expressions for differenttypes of interactions areA1B1 = (a2 - 1) (b2 - 1)A1B2 = (a2 - 1) (b2 – 2b + 1)A2B2 = (a2 – 2a + 1) (b2 – 2b + 1)

These eight expressions, when expanded,will form a set of orthogonal contrasts,



each with a single degree of freedom.Instead of lining the nine treatmentcombinations into a single file. Note thatthe coefficients for the interactions areactually products of correspondingcoefficients of the main effects involved.The 2 x 3 factorial

When one factor (say,a) is administeredat two levels (a1,a2) and another factor(say,b) at three levels with equal intervals(b0,b1,b2), we say breakdown of treatmenteffects of a 2 x 3 factorial (based onhypothetical data).

a2 a1 EffectZ

DivisorD x r

SsqZ2 / Dr

b2

144b1

138b0

108b2

162b1

90b0

78

A +1 +1 +1 -1 -1 -1 60 6 x 6 100B1 +1 0 -1 +1 0 -1 120 4 x 6 600B2 +1 -2 +1 +1 -2 +1 36 12 x 6 18

AB1 +1 0 -1 -1 0 +1 -48 4 x 6 96AB2 +1 -2 +1 -1 +2 -1 -84 12 x 6 98

Total treatment Ssq =912

Is a 2 x 3 factorial experiment. It is thesimplest example of factors with mixedlevel. The five contrasts among the sixtreatment combinations are,symbolically,

A = (a2 – a1) (b2 + b1 + b0)B1 = (a2 + a1) (b2 – b0)B2 = (a2 + a1) (b2 – 2b1 +b0)AB1 = (a2 – a1) (b2 – b0)AB2 = (a2 – a1) (b2 – 2b1 + b0)

The above table gives the coefficients ofthe treatment combinations after thesesymbolic expressions have beenexpanded. It is seen that the sum of thefive-component ssq is 912, as was foundin above table. Each component maythen be tested against s2 = 14.2 with20df.Zero level and dummy treatmentsWhen the lowest level of application ofthe factors is actually zero (that is, noapplication at all as an absolute control)and the factors involved are differentkinds of material such as differentderivatives of a basic chemicalcompound, different preparations of avaccine or antiserum, different varietiesor strains of organisms, different forms ofan active ingredient, etc., then the threetreatment “combinations’ at the zero levelare all identical, receiving no activeingredients at all. For convenience, let uschange the notations slightly and denotethe three different drugs by a, b, c

(aspirin, Bufferin, Coricidin; or Ajax,Babo, Comet, if you like) eachadministered at three levels – 0 (nonegiven), 1 (10grains per day), 2 (20 grainsper day). The nine combinations are thenas tabulated here. But the threecombinations at the zero level (a0, b0, c0)really represent the same condition(placebo): the patient receives no drug ofany king. There are actually only seven(not nine) distinct treatments.The factorial may also be regarded as a 2x 3 plus an extra control, instead of thesuperficial 3 x 3. The investigator may, ofcourse, conduct an experiment with justseven treatments; each replicated acertain number of times. In such a case,the number of observations at the zerolevel is only one-third of that at the othertwo levels and the quantitative effect ofthe drugs will not be as accuratelydetermined as when there are an equalnumber of replications at levels. In manyinstances, it is desirable to preserve thesuperficial 3 x 3 structure with equalnumber of placebos and treatments at 1and 2 levels. Then the treatments a0, b0,c0 are called dummy treatments. Theyare assigned at random to patients as ifthey were different. The analysis of thetreatment effects, however, requires asight modification.

CONFOUNDINGConfounding in experimental design isthen to denote an arrangement of thetreatment combinations in the block in



which less important treatment effectspurposively confounded with the block.This non-orthogonality is not a defect ofthe design; it is deliberately introduced inorder to get better estimates and tests onthe important treatment combinations.

Types of confounding Complete confounding:In complete confounding, we confoundthe same interaction in all thereplications and thus, we don’t have theinformation regarding get informationthat interaction from all the replicationwhere as unconfounding effects can beestimates and tested as any completeblock design.

Partial confounding:In partial confounding the differentinteraction is confounded in differentreplications .That is, if one effect isconfounded in first replicate, then othereffective will be confounded in second, inthird and so on.

• Systems of confounding in a 2n

experiments:Let us suppose that we have 5 factors A,

B, C, D and E each at 2 levels, giving 32combinations treatment combinations inall. .We wish to use blocks of 8

experimental units .The experimentwill consist of 4 blocks of 8 units andthere will be 3 effects or interactionsconfounded with blocks .

If we confound the interaction BCD,the treatment the combinations fallinto two groups, each groupsconsisting of 2 of the blocks namely:

() : (1), bc , bd, cd , a, abc , abd,acd, e, bce, bde, cde, ae, abce, abde,acde.

(): b, c, d, bcd, ab, ac , ad, abcd, be,ce, de, bcde, abe, ace, ade , abcde.

If we also confound, say, CDE, wedivided the treatment combinationsand again into 2 groups.

(): (1), cd, ce, de, a, acd, ace, ade, b,bcd, bce, bde, ab, abcd, abce, abde.

(): c, d, e, cde, ac, ad, ae, acde, bc,bd, be, bcde, abc, abd, abe, abcde.

If each of the comparisons () vs. ()and () vs. () are to be blockcomparisons, the blocks must containthe common treatment combinations of

the followings:(1)Treatment common in () and ()(2) Treatment common in () and ()(3) Treatment common in () and ()(4) Treatment common in () and ()

The four blocks will be represented asgiven below

(1) (2) (3) (4)(1) e b ccd cde bcd da ae ad ac

acd acde abcd bdbce bc ce aebde bd de bcdeabce abc ace abeabde abd ade abcde

SPLIT PLOT EXPERIMENT In field experimentation, sometimeswe need the large experimental area tothe test the treatment .In fact, when wego for testing the different methods ofploughing or irrigation. In this situation,it is difficult to manage both treatmentsin a small area. These treatments arecalled the whole plot treatments or mainplots. It is possible to test anothertreatment by splitting the main plot intosubplots which does not require largeplots. It may be possible that for subplottreatment expense may be slightly high.We introduce the second treatment insplit plot by splitting the whole plots. Wetest the treatments which are in subplots more efficiently rather than wholeplots.Model :-Yijk = + ri + m j + e ij + s k + (ms) jk + e ijk

where, Yijk is the observation on the kth

sub plot the jth main plot in the ithreplication. is the general mean effectri is the ith replication effectmj is the main plot treatment effecteij is the error first or main plot errorswhich are N(O,2e)sk is the kth sub plot treatment(ms)jk is the interaction effect due to mainand sub plot treatment eijk is the error second or sub plot errorwhich are N(O,2e).

STRIP PLOT EXPERIMENT



Another kind of split plot experiment isthe strip plot experiment. It is also knownas split block experiment because theblocks are spitted row wise and columnwise to accommodate the two sets oftreatments .This experiment is usuallyperformed where both treatmentsrequire large plot size .This is generallyhappened in agronomic experiments inwhich both experimental factors are noteasily applied to small areas like split plotFor example: The factors are tillage andwater management.In this experiment each block is dividedrow wise as per the first set of treatmentsand column wise as per the second. Thecolumn wise treatments are laid outeither in RCBD or LSD. Therandomization process is the same asthat for the standardized design. Thelayout plan of 1 replicate is be as shownin the following figure.

Replication 1A0 A2 A3 A1

B1

B2

B0

B4

B3

Where A and B are the level offirst and second set of treatments. In thisexperiment at least two replications arerequired. Such experiment providedrelatively low accuracy on both maineffects with relatively high accuracy onthe interaction.

Response surface If in an agricultural experiment, yieldis influenced by several factors likeheight of the plant, length of ear head,temperature, relative humidity, etc.,which are all quantitative variables thenthe yield (or response ) is a Function ofthe levels of these variables an is denotedby,

1 2( , ...... )j j j kj jY X X X E

Where j=1,2,…, n represent the jthobservation in the factorial experimentand i jX denotes the level of ith factor

of the jth observation and 'jE s are

experimental errors which are assumedto be independent and follow normal

distribution with mean zero andvariance 2k . The function ‘φ’ is called responsesurface. If φ is known then it is easy topredict (or forecast) the value for knowingthe different levels of factors. Further thecombination of levels of factors can bearrived at to attain the optimum andmaximum response once the function isknown. In the absence of knowledge ofthe function it can be assumed that theexperimental region can be representedby a polynomial of first or second degree.The designs used for fitting the firstdegree and second degree polynomialsare called first order and second orderdesigns respectively. The fitting of secondorder polynomial is illustrated here withan example. Example: An experiment was conductedwith nitrogen at four levels (40, 60, 80,100 kg/ acre) along with phosphorus atthree levels (15, 30, 45 kg/acre) in a lay-out of randomized block design havingthree replications for paddy. Thehypothetical yields are presented in thefollowing Table 16.70.

Table: ReplicationsTreatment 1 2 3 Total

n0p0 8 10 9 27

n0p1 10 14 12 36n0p2 11 9 10 30n1p0 13 12 15 40n1p1 15 14 13 42n1p2 18 16 19 53n2p0 14 12 10 36n2p1 20 22 22 64n2p2 24 26 25 75n3p0 16 15 18 49n3p1 22 20 23 65n3p2 28 27 29 84

199 197 205 601Fit the response surface for the abovedata.The two way table of nitrogen andphosphorus with plot yield totals of threereplications is given below:Nitrogen 15 30 45 Total

40 27 36 30 9360 40 42 53 13580 36 64 75 175100 49 65 84 198

The factorial analysis is presented in the ANOVA table below:



Source d. f. S.S. M.S. Fcal

Replications 2 2.89 1.45Treatments 11

N 3 711.42 237.14P 2 343.06 171.53 117.40**

NP 6 177.83 29.64 84.92**Error 22 44.44 2.02 14.67**Total 35 1279.64

** Significant at 1 % levelTo examine the trend in yield fordifferent levels of nitrogen andphosphorus, the linear, quadraticcomponents for phosphorus; linear,quadratic and cubic components fornitrogen as well as for NPInteraction were computed asfollows. The coefficients oforthogonal polynomials for linearand quadratic components forphosphorus levels (-1,0,1) and (1,-2,1)respectively, the coefficients fornitrogen levels for linear, quadraticand cubic components are (-3,-1,+1,+3), (+1,-1,-1,+1), (-1,+3,-3,+1)respectively.

Table: 16.2740 60 80 100 Total

(Linear) 3 13 39 35 90

(quadratic)-15 9 -

173 -20

It can be verified thatSimilarly the linear, quadratic andcubic components for nitrogen arecomputed as follows.

Table: phosphorus levels

15 30 45 Total

(linear) 62 109 184 355

(quadratic) 0 -5 -14 -19

(cubic) 34 -37 -12 -15

Source d. f. S.S. M.S. Fcal



Replications 2 2.89 1.45

N 3 711.42

NL 1 700.14 700.14 346.60**

NQ 1 10.03 10.03 4.97

NC 1 1.25 1.25

P 2 343.06

PL 1 337.50 337.50 167.08**

PQ 1 5.56 5.56

NP 6

NLPL 1 124.03 124.03 61.40**

NLPQ 1 2.18 2.18

NQPL 1 8.17 8.17

NQPQ 1 0.22 0.22

NCPL 1 17.63 17.63 8.73**

NCPQ 1 25.60 25.60 12.67

Error 22 44.44 2.02

Total 35 1279.64

** Significant at 1 % level From above table, it can be observedthat the yield is significantly affected bylinear and quadratic trend of nitrogen,linear trend of phosphorus, linear trendof nitrogen with linear trend ofphosphorus, cubic trend of nitrogen withlinear trend of Phosphorus, cubic trendof nitrogen with quadratic trend ofphosphorus.The response surface is the mathematicalrelation taking yield as the dependentvariable and the above mentioned factors

as independent variables. Let the relationbetween yield and and 'ib s areregression coefficients.In order to find out the regressioncoefficients 'ib s the coefficients oforthogonal polynomials will be usedsince,

Where Y is the estimated value of

Nitrogen levels

Phosphoruslevels

YieldTotal (Y)

NQ PL NLPL NCPL NCPQ



40 15 27 -3 +1 -1 +330 36 -3 +1 0 045 30 -3 +1 1 -3

60 15 40 -1 -1 -1 +130 42 -1 -1 0 045 53 -1 -1 1 -1

80 15 36 +1 -1 -1 -130 64 +1 -1 0 045 75 +1 -1 1

100 15 49 +3 +1 -130 65 +3 +1 045 84 +3 +1 1

601 35560

-1912

908

12240

-4640

96120

5.9167

-1.5833

11.250

3.0500

-1.1500 0.800

The response surface between yield and'iX s is given by

The same relation between yield and

is rewritten as:

The estimated yields can be obtained forthe given levels of nitrogen andphosphorus. For example, the estimatedyield, when the level of nitrogen is 80 andthe level of phosphorus is 45, is obtainedby substituting in the fitted equation for

ReferencesApplied Statistical Methods by Kaushik

et al (2003), Dhanpat Rai and Co.Delhi.

Practicals in Statistics by H. L.Sharma (2005), Agrotech PublishingAcademy, Udaipur.

Fundamentals of Statistics Vol. II byGoon, Gupta and Dasgupta, Calcutta.

Biochar: A Potential Amendment for Soil Health Management



Anand Prakash Singh, Sumit Rai, Priyanka Rani and Awtar Singh

Department of Soil Science & Agricultural Chemistry, Institute of Agricultural Sciences,Banaras Hindu University, Varanasi-221005, (U.P.), India.

AbstractBiochar is a new word for many, but thetechnology is a traditional one in severalregions of the world. Biochar refers to akind of charcoal made from biomass.Unlike charcoal made for fuel, biocharhas properties which make it a valuablesoil amendment. The decrease inbiomass production, decrease in organicmatter supply and increaseddecomposition rate are the primaryfactors to reduction in soil organicmatter. Biochar is a stable carboncompound created when biomass isheated to temperatures between 300and 1000˚C, under low oxygenconcentrations. Biochar is attractingattention as a means for sequesteringcarbon and as a potentially valuableinput for agriculture to improve soilfertility and sustainable production. Soilhealth management with biochar isevaluated globally as a means toimprove soil fertility and to mitigateclimate change.KeywordsBiochar, soil health, soil fertility andgreen house gassesIntroductionSoil health is the foundation of vigorouscrop productivity with higheropportunity for income and employmentwhich in turn provides sustainable foodsystem. Soil health management formsthe basis for sustainable system ofproductive agriculture as the Indianpopulation, which increased from 683million in 1981 to 1210 million in 2010,is estimated to reach 1412 million in2025 and to 1475 million in 2030. Tofeed the projected population of 1.48billion by 2030, India needs to produce350 million tonnes of food grains. Theexpanded food needs of future must bemet through intensive agriculturewithout any expansion in the arableland. The per capita arable landdecreased from 0.34 ha in 1950-51 to0.15 ha in 2000-01 and is expected toshrink to 0.08 ha in 2025 and to 0.07ha in 2030. The current food-grainproduction of 218 mt (2009-10) isobtained from the net arable land of 141

m ha.

Plants obtain their nutrition fromorganic matter and minerals found insoils. As the land is farmed, theagricultural processes disturb thenatural soil systems including nutrientcycling and the release and uptake ofnutrients (Bot and Benites 2005).Modern agriculture is apt to mine thesoil for nutrients and to reduce soilorganic matter levels through repetitiveharvesting of crops. This decline of thesoil continues until managementpractices are improved, additionalnutrients are applied, rotation withnitrogen-fixing crops is practiced, oruntil a fallow period occurs allowing agradual recovery of the soil throughnatural ecological development. As thenatural stores of the most importantnutrients for plant growth decline in thesoil, growth rates of crops are inhibited.Soil organic matter plays key role in soilfertility sustenance. In soybean-wheatsystem, without balanced input ofnutrients, organic matter status of soildeclined over a time in Alfisols ofRanchi. Whereas, balanced fertilizationwith NPK and NPK+FYM improved theorganic matter status in Vertisols undersoybean-wheat system at Jabalpur. It iscrucial to maintain a threshold level oforganic matter in the soil formaintaining physical, chemical andbiological integrity of the soil and forsustained agricultural productivity.Thus, assessing soil organic carbon(SOC) sequestration under intensivecropping with different managementpractices plays an important role inlong-term maintenance of soil quality.Efficient use of biomass, available ascrop residues and other farm wastes, byconverting it to a useful source of soilamendment/nutrients is one way tomanage soil health and fertility. Thecurrent availability of biomass in Indiais estimated at about 500 milliontons/year. These residues are eitherpartially utilized or un-utilized due tovarious constraints. It is estimated thatabout 93 million tons of crop residues



are burnt in each year in India. Residueburning traditionally provides a fast wayto clear the agricultural field of residualbiomass, facilitating further landpreparation and planting. However, inaddition to loss of valuable biomass andnutrients, biomass burning leads torelease of toxic gases including GHGs. Inthis context, biochar, a pyrolysisproduct of plant biomass offers asignificant, multidimensionalopportunity to transform large scaleagricultural waste streams from afinancial and environmental liability tovaluable assets. Use of biochar inagricultural systems is one viable optionthat can enhance natural rates ofcarbon sequestration in the soil, reducefarm waste and improve the soil quality.In India, about 435.98 million tons ofagro-residues are produced every year,out of which 313.62 million tons aresurplus. These residues are eitherpartially utilized or un-utilized due tovarious constraints (Murali et al., 2010).Koopmans and Koppejan (1997)estimated that about 507,837 thousandtons of field crop residues weregenerated in India during 1997 of which43% was rice and 23% wheat. Theestimates from Streets et al. (2003)reveal that 16% of total crop residueswere burnt. The results fromVenkataraman et al. (2006) suggest that116 million tons of crop residues wereburnt in India in 2001, but with a strongregional variation (Gupta, 2010). Studiessponsored by the Ministry of New andRenewable Energy (MNRE), Govt. ofIndia have estimated surplus biomassavailability at about 120–150 milliontons/ annum (MNRE, 2009). Of this,about 93 million tons of crop residuesare burned in each year (IARI 2012).Generation of crop residues is highest inUttar Pradesh (60 million t) followed byPunjab (51 million t) and Maharashtra(46 million t). Maharashtra contributesmaximum to the generation of residuesof pulses (3 million t) while residuesfrom fibre crop is dominant in AndhraPradesh (14 million t). Gujarat andRajasthan generate about 6 million teach of residues from oilseed crops.Among different crops, cereals generatemaximum residues (352 Mt), followed byfibres (66 Mt), oilseeds (29 Mt), pulses(13 Mt) and sugarcane (12 Mt). The

cereal crops (rice, wheat, maize, millets)contribute 70% while rice crop alonecontributes 34% to the crop residues(Fig 1). The surplus residues i.e., totalresidues generated minus residues usedfor various purposes, are typically burnton-farm. Estimated total amount of cropresidues surplus in India is 91-141 Mt(IARI, 2012). Cereals and fibre cropscontribute 58% and 23%, respectivelyand remaining 19% is from sugarcane,pulses, oilseeds and other crops. Out of82 Mt surplus residues from the cerealcrops, 44 Mt is from rice followed by24.5 Mt from wheat. About threefourthsof greenhouse gas (GHG) emissions fromagro-residues burning were CH4 and theremaining one-fourth was N2O. Burningof wheat and paddy straws alonecontributes to about 42% of GHGs.Hence, conversion of organic waste toproduce biochar using the pyrolysisprocess is one viable option that canenhance natural rates of carbonsequestration in the soil, reduce farmwaste and improve the soil quality(Srinivasarao et al., 2012, 2013).Biochar has the potential to increaseconventional agricultural productivityand enhance the ability of farmers toparticipate in carbon markets beyondthe traditional approach by directlyapplying carbon into the soil (McHenry,2009). Converting waste biomass intobiochar would transfer very significantamounts of carbon from the active toinactive carbon pool, presenting acompelling opportunity to intervene inthe carbon cycle. The use of biochar assoil amendment is proposed as a newapproach to mitigate man-inducedclimate change along with improving soilproductivity. The use of biochar inagriculture is not new; in ancient timesfarmers used it to enhance theproduction of agricultural crops. Inorder to sequester carbon, a materialmust have long residence time andshould be resistant to chemicalprocesses such as oxidation to CO2 orreduction to methane. It has beensuggested by many authors (Izaurraldeet al., 2001; McHenry, 2009) that theuse of biochar as soil amendment meetsthe above requirements; since thebiomass is protected from furtheroxidation as compared to material thatwould otherwise have degraded to



release CO2 into the atmosphere. Suchpartially burnt products, morecommonly called pyrogenic carbon orblack carbon, may act as an importantlong-term carbon sink because theirmicrobial decomposition and chemicaltransformation are probably slow.What is biochar?Lehmann and Joseph (2009) definebiochar as the carbon-rich productwhen biomass, such as wood, manure orleaves, is heated in a closed containerwith little or no available air. In moretechnical terms, biochar is produced byso-called thermal decomposition oforganic material with limited supply ofoxygen, and at relatively lowtemperatures (<700 oC) (Stockmann,2011). This process often mirrors theproduction of charcoal, which is one ofthe most ancient industrial technologiesdeveloped by mankind (Barrow 2012).However, biochar can be distinguishedfrom charcoal and similar materials inthat it is produced with the intent it beapplied to soil as a means of improvingsoil productivity, carbon (C) storage andpossibly filtration of percolating soilwater (to try and cut pollution of surfaceand groundwater bodies). Theproduction process and the intendeduse, forms the basis for distinguishingbiochar (Lehmann et al., 2006). Biocharis the appropriate term where charredorganic matter is applied to soil in adeliberate manner, with the intent toimprove soil properties. Thisdistinguishes biochar from charcoal thatis used as fuel for heat, as a filter, as areductant in iron making or as acolouring agent in industry or art(Lehmann et al., 2006). Biochar is themost widely used and arguably the bestterm. Biochar is very variable in quality,depending on raw material, pyrolysisconditions, whether it is enriched withother compounds and how finely it isground. The problem is that biochar is ageneric term and standards have notbeen established but are much needed(Barrow 2012).Slow pyrolysis is said to minimize therisk of producing dioxins and harmfulpolyaromatic hydrocarbons, which couldcontaminate biochar and/or escape withexhaust gases and solid or liquidwastes. Low temperature pyrolysis givesa material with more desirable soil

improvement properties than charcoal orash that is also richer in aromaticcarbon and humic substances (Barrow2012). The pyrolysis can generate usefulheat, biofuel or syngas as by-products.It may be possible to sequester morecarbon dioxide in the soil than isliberated to the atmosphere duringbiochar pyrolysis: making it a carbonnegative activity, which can enhanceprofitability (Fowles, 2007; Lal, 2007;Lehmann & Joseph, 2009; Matthews,2008b). Sohi, Loetz-Capel, Krull, andBoll (2009) noted biochar seems capableof remaining in soil without releasingcarbon for centuries, even millennia andit enhances microbial activity. The meansoil carbon residence time for buriedbiochar is likely to be at least 1000years, possibly longer (Nguyen &Lehmann, 2009).Some burnt materials like ash can behydrophobic; so if added to soil theyreduce moisture storage and enhancerunoff resulting in poorer crops andeven erosion; care needs to be exercisedto ensure biochar does not have thesequalities (Renner, 2007). So far theindications are that it enhances soilmoisture. Beneficial applications mightnot need to be very frequent (comparedwith fertilisers, compost or manures).Ideally, biochar should have a longresidence time in soil and activelysupport beneficial soil microorganisms.More research is needed to check thesequalities. Also, successful biocharprogrammes will require more thantechnical know-how if they are to avoidunwanted socio-economic impacts; theremust be political will, farmer support,organisational skills and the ability tocover the costs of raw materialtransportation and application to theland.Important Feedstock for BiocharBiochar can also be produced frommanures and other animal wastes,including bone (Fig 1.). For instance,dairy shed waste and chicken litter havebeen used to produce biochar (Cao &Harris 2010; Joseph et al. 2010;McHenry 2009). There are alsoobnoxious weed viz. Parthenium,Lantana etc. having characteristic woodystem can be used for making biochar.Many types of manure are anaerobicallydigested to produce biogas (a mixture of



methane and carbon dioxide) and it ispossible that the remaining solid by-products could be used in pyrolysisreactions to produce biochar. Whenconsidering a potential feedstock forbiochar production, biomass availabilityand moisture content must also beconsidered to ensure continualoperation of the processing plant, withminimal energy input requirements.Pyrolysis of these types of waste mayproduce both energy and a biocharproduct with relatively high levels ofplant nutrients, such as phosphorous,potassium, nitrogen, magnesium andcalcium. Containment and use ofnutrient-rich manures and animalproducts for production of biochar mayalso have positive environmental effectsincluding reduced nutrient run-off andcorresponding reductions in greenhousegas emissions, such as methane andnitrous oxide (He et al. 2000). Althoughmanure and municipal waste may beused in pyrolysis, the high risk ofcontamination from toxic chemicals andheavy metals may limit its use onagricultural soils. The mineral content ofpotential biomass feedstocks must alsobe considered. Nik-Azar et al. (1997)found that impregnating woody biomasswith sodium, potassium and calciumincreased biochar yields by up to 15 percent. These findings are in agreement

with other studies, where addition ofinorganic salts (magnesium chloride,sodium chloride, iron sulphate and zincchloride) increased production of charfrom 5 per cent (control feedstock; noaddition of salts) to 8, 14, 17 and 28 percent respectively (Varhegyi et al. 1988).However, addition of any minerals tofeedstocks to increase biochar yieldwould, from an agricultural productivityperspective, have to be weighed againstthe effect of those minerals on soilstructure, soil fertility and plant growth,and the cost of supplying thesenutrients through other means.Not all agricultural waste materials aresuitable for biochar production foragricultural purposes (Lehmann et al.2006; McHenry 2009). Some productionconditions and feedstock types cancause the resulting biochar to beineffective in retaining nutrients andsusceptible to microbial decay (McHenry2009). Depending on the biomasssource, some biochar products, such asmunicipal waste, may contain highlevels of toxic substances (heavy metalsand organic pollutants) which must alsobe considered in the context of addingbiochar to agricultural soils (Lehmann etal. 2006).

Fig 1. Potential biomass feedstocks for various pyrolysis conditions (Sohi et al. 2009)Potential benefits of biochar



Store recalcitrant form of carbonin soil. Compost and manures aresubject to rapid microbialbreakdown. Sequestration inbiochar is likely to be forcenturies, possibly for thousandsof years.

Enhance plant growth andsustain crop yields. Help improvegood and problematic nutrient-poor soils, including acidictropical humid and drierenvironment soils. (Table 2)

Help compensate for greenhousegas emissions associated withagricultural development.

Biochar may improve soilmoisture retention, increasingagricultural resilience andprovides support to intensivesustainable agriculture whichcould help to cut pressure for newforest clearances and enhancesbiodiversity conservation benefits.

Enable production of usefulmaterials from uncropped landmaking use of unused wasteswith increased adaptability toenvironmental change by makingproduction more resilient.

Reduce the need forfertiliser/manure/compost.Reduce costs of sewage andanimal waste treatment and cutemissions that they wouldotherwise cause if held in lagoonsor heaps. Application of manureor compost to the soil maystimulate bacteria and causemethane and N2O to theatmosphere. Composting alsoreleases greenhouse gases andcompost may have a limitedresidence time in soil. Pyrolysisdestroys microorganisms andsome veterinary pharmaceuticals.It also reported by manyresearchers worldwide toSuppress methane and N2O(nitrous oxide gas) emission fromcultivated soil thereby reducesglobal warming).

Offer a more environmentally-friendly way of processing plasticsand refuse if biochar is toocontaminated for agricultural usefor growing non-food crops or

send to landfill to sequestercarbon.

Nutrient affinity i.e. retention ofplant nutrients, notably retentionof N on permeable soils underrainy conditions is found higherwith biochar application. Biocharmay bind agrochemicals and helpreduce phosphate and nitrate andagrochemicals pollution ofstreams and groundwater. Thushelping resolve major problemshindering sustained and improvedagriculture. Reduce plant uptakeof pesticides from contaminatedsoils (Xiang-Yang Yu. et al., 2009).A form of bioremediation.

Reduce soil acidity/raise pH(Rodriguez et al. 2009). Reducealuminium toxicity and increasescation exchange capacity (Table1). The published data suggestthat biochars from woodymaterials tend to provide low CECvalues, while non-woody plantmaterials such as sugarcanetrash (leaf) or tree bark tend tohave higher CEC values(Yamamoto et al., 2006; Chan etal., 2007; Major et al., 2009;Singh and Gu, 2010; Van Zwietenet al., 2010).

By improving moisture retentionbiochar may reduce the demandfor irrigation and make croppingmore secure.

Support biofuel production andreduce its carbon footprint andeven enable it to move towardbeing carbon neutral.

Increase soil microbial biomassand support other beneficialorganism like earthworms.Support nitrogen fixation.Increase arbuscular mycorrhizalfungi in soil.

Opportunities for poor to benefitfrom carbon offset market andalso reduce dependency offarmers on input suppliers.

Periurban/urban agriculture:biochar may be a useful input tocounter harmful compounds likeheavy metals, dioxins, PAHs(polycyclic aromatichydrocarbons) present in sewageor refuse inputs.



Biochar and Soil PropertiesAvailable crop residues and other farmwastes such as obnoxious weeds can beconverted into a useful soil amendment/source of nutrients i.e. biochar. It is oneway to manage soil health and fertility.The use of biochar is reported toincrease the resilience of agriculturalsystems by introducing the recalcitrant

form of carbon with a reasonableincrease in the CEC (Yamamoto et al.,2006 and Glaser et al., 2002). There areso many published studies whichadvocate the beneficial effect of biocharon soil physical and chemical properties(Table 1).

Table 1. Effect of biochar on different soil properties (Srinivasarao et al. 2013)Some selected soil

properties Findings Reference

Cation exchange capacity 50% increase Glaser et al., 2002Fertilizer use efficiency 10-30 % increase Gaunt and Cowie, 2009

Liming agent 1 unit pH increaseCrop productivity 20-120% increase

Biological nitrogen fixation 50-72% increaseLehman and Rondon, 2006

Soil moisture retention Up to 18 % increase Tryon, 1948Mycorrhizal fungi 40 % increase Warnock et al., 2007

Bulk density Soil dependent Laird, 2008Methane emission 100% decrease Rondon et al, 2005

Nitrous oxide emissions 50 % decrease Yanai et al., 2007

Biochar and Plant GrowthMost of the currently published studies(Table 2) assessing the effect of biocharon crop yield, are generally small scale,almost all short-term, and sometimesconducted in pots where environmentalfluctuation is removed. These limitationsare compounded by a lack ofmethodological consistency in nutrientmanagement and pH control, biochartype and origin. It is not therefore

possible at this stage to draw anyquantitative conclusion, certainly not toproject or compare the impact of aparticular one-time addition of biocharon long-term crop yield. Nonetheless,evidence suggests that at least for somecrop and soil combinations, moderateadditions of biochar are usuallybeneficial, and in very few casesnegative.

Table 2. Effects of biochar on plant growth and yieldCrop Experimental

summary Findings Reference

Pea biomass increased by160%

MungbeanChar @ 0.5 t/ha biomass increased by

122%

Iswaran et al. (1980)

Soybean

Crops were grown onvolcanic ash loam,Japan with char @ 0.5, 5, 15 t/ha

Char @ 0.5 t/haincreased yield by151% whereas, Charat 5 t/ha and15 t/hadecreased yield by63% and 29%,respectively

Sugi trees

Crops were grown onclay loam, JapanWood charcoal, barkcharcoaland activated charcoalat 0.5 t/ha

increased biomass by249, 324 and244%, respectively

Kishimoto &Sugiura (1985)

Bauhinia trees Crops were grown onAlfisol/Ultisol

Charcoal applicationincreasedbiomass yield by 13%and height by24%

Chidumayo, (1994)



CowpeaGrown on xanthicferralsol char @ 67and 135 t/ha

Char @ 67 and 135t/ha increasedbiomass by 150% and200%, respectively

Glaser et al. (2002)

CowpeaPlanted in pots andrice crops inlysimeters, Brazil

Soil fertility andnutrient retention.Biochar additionssignificantlyincreased biomassproduction by 38to 45%

Lehmann et al. (2003)

Maize

Comparison of yieldsbetween disusedcharcoal productionsites and adjacentfields, Ghana

Grain and biomassyield was 91 and44% higher oncharcoal site thancontrol

Oguntunde et al.(2004)

Maize, cowpea andpeanut

Trial in area of low soilfertility Acacia barkcharcoal plus fertilizer

Increased in maizeand peanut yields butnot cowpea

Yamamoto et al.(2006)

Radish

Pot trial on heavy soilusing commercialgreen waste biochar(three rates) with andwithout N

Biochar at 100 t/haincreased yield 3times; linear increase10 to 50 t/ha, but noeffect without added N

Chan et al. (2007)

Beans

Enhanced biologicalN2 fixation (BNF) bycommon beansthrough biocharadditions, Colombia

Bean yield increasedby 46% and biomassproduction by 39%compared to control at90 and 60 gbiochar/kg,respectively

Rondon et al. (2007)

Four cropping cycleswith rice (Oryza sativaL.) and sorghum(Sorghumbicolor L.)

Charcoal amendedwith chicken manureamendments

Charcoal amendedwith chicken manureamendments resultedin the highestcumulative crop yield(12.4 t/ha)

Steiner et al. (2007)

Maize

Mitigation of soildegradation withbiochar. Comparisonof maize yieldsin degradationgradient cultivatedsoils in Kenya

Doubling of maizegrain yield in thehighly degraded soilsfrom about 3 to 6 t/ha

Kimetu et al. (2008)

Rice

Pot experiment inalluvial soil with ricehusk biochar @ 0, 4, 8and 16 t/ha

Non significantincrease in the grainyield and dry matteraccumulation due tobiochar application

Singh 2013

Rice

Pot experiment inalluvial soil with ricehusk biochar @ 5 and10 t/ha

Dry matter increasedby 11 and 17% ascompared to control @5 and 10 t/ha,respectively

Rani 2013

Biochar and GHGs emissionBurning of residues emits a significantamount GHGs. For example, 70, 7 and0.66% of C present in rice straw isemitted as CO2, CO and CH4,respectively, while 2.09% of N in straw isemitted as N2O upon burning. One ton

straw on burning releases 3 kgparticulate matter, 60 kg CO, 1460 kgCO2, 199 kg ash and 2 kg SO2. Thischange in composition of theatmosphere may have a direct orindirect effect on the radiation balance.Besides other light hydrocarbons,



volatile organic compounds (VOCs) andsemi-volatile organic compounds(SVOCs) including polycyclic aromatichydrocarbons (PAHs) andpolychlorinated biphenyls (PCBs) andSOx, NOx are also emitted. These gasesare important for their global impact andmay lead to a regional increase in thelevels of aerosols, acid deposition,increase in tropospheric ozone anddepletion of the stratospheric ozonelayer.Biochar production does emit carbondioxide and other greenhouse gases butcombined with waste disposal or biofuelproduction it appears to offer a practicalway to mitigate global warming. Soil is asignificant source of nitrous oxide (N2O)and both a source and sink of methane(CH4). These gases are 23 and 298 timesmore potent than carbon dioxide (CO2)as greenhouse gases in the atmosphere.Biochar is reported to reduce N2Oemission could be due to inhibition ofeither stage of nitrification and/orinhibition of denitrification, orpromotion of the reduction of N2O, andthese impacts could occursimultaneously in a soil (Berglund et al.,2004; DeLuca et al., 2006). Biocharpotential is attracting much attention asa safe, practical, technically simple, andaffordable method of sequestration,which has a chance of spreading fastenough to have real effect. If enoughfarmers, larger agricultural enterprises,biofuel producers, and waste treatmentplants a are established it could becomean important means of carbonsequestration. This potential is a littlebetter researched than biocharagricultural value; although, there isinsufficient data on biochar-burial soilcarbon mean residence times. However,according to Sohi et al. (2010), no peer-reviewed studies documentingsuppression of nitrous oxide emissionsin field experiments have been reported.There are, however, conferenceproceedings and laboratory-based peer-reviewed studies reporting reductions innitrous oxide emissions (Clough &Condron 2010). Rondon et al. (2005)found that adding biochar significantlyreduced net methane and nitrous oxideemissions when infertile Colombiansavannah soils were amended withbiochar at a rate of up to 30 grams per

kilogram of soil. Researchers found thatnitrous oxide and methane emissionswere reduced by up to 50 and 100 percent respectively, at an optimalapplication rate of 20 grams of biocharper kilogram of soil (Rondon et al. 2005).Similarly, Spokas et al. (2009) foundsuppression of both methane andnitrous oxide at levels up to 60 per centinclusion rates in laboratory trials(corresponding to 720 tonnes biocharper hectare). Yanai et al. (2007) alsofound that addition of biochar up to 10per cent reduced nitrous oxideemissions by 89 per cent, but only whenthe soil was rehydrated with 73 to 78per cent waterfilled pore space. However,biochar added to soils rehydrated at 83per cent water-filled pore spacesignificantly stimulated nitrous oxideemissions compared with the control(Yanai et al. 2007). Increased soil aerationfrom biochar addition reducesdenitrification and increases sink capacityfor CH4. Biochar addition inducesmicrobial immobilization of available N insoil, thereby decreasing N2O sourcecapacity of soil. Increased pH from biocharaddition drives N2 formation from N2O.When applied to the soil, biochar canlower GHG emissions of cropland soils bysubstantially reducing the release of N2O(Lehmann et al., 2003). Reduction of N2Oand CH4 emission as a result of biocharapplication is seen to attract considerableattention due to the much higher globalwarming potentials of these gasescompared to CO2 (Steiner, 2010). Rondonet al. (2005) reported a 50% reduction inN2O emissions from soybean plots andalmost complete suppression of CH4

emissions from biochar amended acidicsoils in the Eastern Colombian Plains.Yanai et al. (2007), however, reported an85% reduction in N2O emission from re-wetted soils containing 10% biochar,compared to soils without biochar. Biocharfrom municipal biowaste also caused adecrease in emissions of nitrous oxide inlaboratory soil chambers (Yanai et al.2007). Spokas et al. (2009) also found asignificant reduction in N2O emission inagricultural soils in Minnesota; while Sohiet al. (2010) found an emissionsuppression of only 15%. Additions of 15 gbiochar/kg of soil to a grass and 30 g/kgof soil to a soil cropped with soybeanscompletely suppressed methane emissions(Rondon et al. 2005).



Biochar and Soil BiotaBiochar has been described as apossible means to improve soil fertilityas well as other ecosystem services andsequester carbon (C) to mitigate climatechange (Lehmann et al., 2006;Lehmann, 2007a; Laird, 2008; Sohi etal., 2010). The observed effects on soilfertility have been explained mainly by apH increase in acid soils (Van Zwieten etal., 2010a) or improved nutrientretention through cation adsorption(Liang et al., 2006). However, biocharhas also been shown to change soilbiological community composition andabundance (Pietikäinen et al., 2000; Yinet al., 2000; Kim et al., 2007; O’Neill etal., 2009; Liang et al., 2010; Grossmanet al., 2010; Jin, 2010). Such changesmaywell have effects on nutrient cycles(Steiner et al., 2008b) or soil structure(Rillig and Mummey, 2006) and, thereby,indirectly affect plant growth (Warnocket al., 2007). Rhizosphere bacteria andfungi may also promote plant growthdirectly (Schwartz et al., 2006; Compantet al., 2010). Changes in microbialcommunity composition or activityinduced by biochar may not only affectnutrient cycles and plant growth, butalso the cycling of soil organic matter(Wardle et al., 2008; Kuzyakov et al.,2009; Liang et al., 2010). The materialproperties of biochar are very differentfrom those of uncharred organic matterin soil (Schmidt and Noack, 2000), andare known to change over time due toweathering processes, interactions withsoil mineral and organic matter andoxidation by microorganisms in soil(Lehmann et al., 2005; Cheng et al.,2008; Cheng and Lehmann, 2009;Nguyen et al., 2010). However, therelationships between biochar chemicaland physical properties and their effectson soil biota and potential concomitanteffects on soil processes are poorlyunderstood. The chemical stability of alarge fraction of a given biochar materialmeans that microorganisms will not beable to readily utilize the C as an energysource or the N and possibly othernutrients contained in the C structure.However, depending on the type ofbiochar, a fraction may be readilyleached and therefore mineralizable(Lehmann et al., 2009) and in some

cases has been shown to stimulatemicrobial activity and increaseabundance (Steiner et al., 2008a).Many soil microorganisms arespecialists living in microhabitats thatprovide resources for their specificmetabolic needs. For instance, aerobicmicrobes live at the surface of soilaggregates, while denitrifiers and semi-aquatic species dwell within the moistinterior of soil peds (Sexstone et al.,1985). Organic matter decompositionrates are higher at the surface of soilaggregates than in the core of aggregatesdue to higher influx of resources at thesurface (organic matter, moisture, andO2). This is evident from depleted Cconcentrations and C-to-N ratios, as wellas the oxidation of lignin phenols andthe accumulation of microbialpolysaccharides at the aggregate surfacerelative to the aggregate core (Amelungand Zech, 1996). Similarly, the exteriorsurfaces of biochar particles in the soilare significantly more oxidized than theparticle interior or core (Lehmann et al.,2005; Liang et al., 2006; Cheng et al.,2008). This is due to sorption of organicmatter on the biochar surface and theoxidation of the biochar C itself (Liang etal., 2006), both biotically and abioticallymediated via reactions with O2 (Cheng etal., 2006, 2008). Similar to soilaggregates, the preferential oxidation ofthe biochar particle surface relative tothe particle interior implies a limiteddiffusion of O2 to the interior of biocharparticles. Such differential redoxconditions not only influence organicmatter oxidation but also metaltransformation.ConclusionApplication of biochar to agriculturalland for soil amelioration andagricultural productivity improvementsis not a new phenomenon. A number ofbenefits have been identified within theliterature; biochar has been found toimprove agriculturally significant soilparameters such as soil pH, cationexchange capacity and soil waterholding capacity. Researchers havefound the increase in these performanceparameters has improved nitrogen useefficiency and therefore crop productivityin limited field trials. Further, biocharhas the potential to reduce greenhousegas emissions through carbon



sequestration, as well as potentiallydecreasing methane and nitrous oxideemissions from the soil. However, thevariable application rates, uncertainfeedstock effects, and initial soil stateprovide a wide range of cost formarginally improved yield from biocharadditions, which is often economicallyimpracticable. Long-term field researchfocusing on an optimal combination ofnutrient use, water use, carbonsequestration, avoided greenhouse gasemissions, and changes in soil qualityand crop productivity is needed beforelarge-scale biochar application to soils.The need for further clarity onoptimizing biochar application to variouscrop yields is necessary if it is to gainwidespread acceptance as a soil healthmanager.

ReferencesAmelung,W., Zech,W., 1996. Organic

species in ped surface and corefractions along a climosequence inthe prairie, North America.Geoderma 74, 193-206.

Berglund, L., DeLuca, T., Zackrisson,O., 2004. Activated carbonamendments to soil altersnitrification rates in Scots pineforests. Soil Biology andBiochemistry 36, 2067-2073.

Bot, A. and Benites, J. 2005. TheImportance of Soil Organic Matter:Key to Drought-Resistant Soil andSustained Food Production; FAOUN: Rome, Italy,.

Chan, K.Y., Van Zwieten, L., Meszaros,I., Downie, A. and Joseph, S. 2007.Assessing the agronomic values ofcontrasting char materials on anAustralian hard setting soil. Paperpresented in International AgricharInitiative (IAI) 2007 Conference, 27April–2 May 2007, Terrigal, NewSouth Wales, Australia.

Cheng, C.H. and Lehmann, J., 2009.Ageing of black carbon along atemperature gradient.Chemosphere 75, 1021-1027.

Cheng, C.H., Lehmann, J. andEngelhard, M. 2008. Naturaloxidation of black carbon in soils:changes in molecular form andsurface charge along aclimosequence. Geochimica etCosmochimica Acta 72, 1598-1610.

Cheng, C.H., Lehmann, J., Thies, J.E.,Burton, S.D. and Engelhard, M.H.2006. Oxidation of black carbon bybiotic and abiotic processes.Organic Geochemistry 37, 1477-1488.

Chidumayo, E.N. 1994. Effects of woodcarbonization on soil and initialdevelopment of seedlings inmiombo woodland, Zambia. ForestEcology and Management, 70, 353-357.

Clough, T.J., Bertram, J.E., Ray, J.L.,Condron, L.M., O’Callaghan, M.,Sherlock, R.R. and Wells, N.S.2010. Unweathered wood biocharimpact on nitrous oxide emissionsfrom a bovine-urine-amendedpasture soil. Soil Science Society ofAmerica Journal 74, 852-860.

Compant, S., Clément, S. and Sessitsch,A. 2010. Plant growth-promotingbacteria in the rhizo- andendosphere of plants: their role,colonization, mechanisms involvedand prospects for utilization. SoilBiology and Biochemistry 42, 669-678.

DeLuca, T.H., MacKenzie, M.D.,Gundale, M.J. and Holben, W.E.2006. Wildfire-produced charcoaldirectly influences nitrogen cyclingin ponderosa pine forests. SoilScience Society of America Journal70, 448-453.

Fowles, M. 2007. Black carbonsequestration as an alternative tobioenergy. Biomass and Bioenergy,31(6), 426-432.

Gaunt, J. and Cowie, A. 2009. Biochargreenhouse gas accounting andemission trading. In: Biochar forenvironmental management (J.Lehmann and S. Joseph eds.),Science and Technology,Earthscan, London. pp 317-340.

Glaser, B., Lehmann, J. and Zech, W.2002. Ameliorating physical andchemical properties of highlyweathered soils in the tropics withcharcoal – a review. Biology andFertility Soils, 35, 219-230.

Grossman, J.M., O’Neill, B.E., Tsai,S.M., Liang, B., Neves, E.,Lehmann, J. and Thies, J.E., 2010.Amazonian anthrosols supportsimilar microbial communities thatdiffer distinctly from those extant



in adjacent, unmodified soils of thesame mineralogy. Microbial Ecology60, 192-205.

Gupta, R. 2010. The economic causes ofcrop residue burning in WesternIndo-Gangetic plains. Paperpresented at conference held atIndian Statistial Institute, Delhicentre, December 2010, 1-26.

IARI, 2012. Crop residues managementwith conservation agriculture:Potential, constraints and policyneeds. Indian AgriculturalResearch Institute, New Delhi, 32p.

Iswaran, V., Jauhri, K.S. and Sen, A.1980. Effect of charcoal, coal andpeat on the yield of moong,soybean and pea. Soil Biology &Biochemistry 12, 191-192.

Izaurralde, R.C., Rosenberg, N.J. andLal, R. 2001. Mitigation of climatechange by soil carbonsequestration: issues of science,monitoring, and degraded lands.Advances in Agronomy, 70, 1-75.

Jin, H. 2010. Characterization ofmicrobial life colonizing biocharand biocharamended soils. PhDDissertation, Cornell University,Ithaca, NY.

Joseph, S.D., Camps-Arbestain, M., Lin,Y., Munroe, P., Chia, C.H., Hook,J., van Zwieten, L., Kimber, S.,Cowie, A., Singh, B.P., Lehmann,J., Foidl, N., Smernik, R.J. andAmonette, J.E., 2010. Aninvestigation into the reactions ofbiochar in soil. Australian Journalof Soil Research 48, 501-515.

Kim, J.-S., Sparovek, S., Longo, R.M.,De Melo, W.J. and Crowley, D.2007. Bacterial diversity of terrapreta and pristine forest soil fromthe Western Amazon. Soil Biologyand Biochemistry 39, 648-690.

Kimetu, J.M., Lehmann, J., Ngoze, S.O.,Mugendi, D.N., Kinyangi, J.M.,Riha, S., Verchot, L., Recha, J.W.and Pell, A.N. 2008. Reversibility ofsoil productivity decline withorganic matter of differing qualityalong a degradation gradient.Ecosystems 11, 726-739.

Kishimoto, S. and Sugiura, G. 1985.Charcoal as a soil conditioner. IntAchieve Future 5, 12- 23.

Koopmans, A. and Koppejan, J. 1997.

Agricultural and forest residues –generation, utilisation andavailability. Regional Consultationon Modern Applications of BiomassEnergy. 6-10 January 1997. KualaLumpur.

Kuzyakov, Y., Subbotina, I., Chen, H.,Bogomolova, I. and Xu, X., 2009.Black carbon decomposition andincorporation into microbialbiomass estimated by 14C labeling.Soil Biology and Biochemistry 41,210-219.

Laird, D.A. 2008. The charcoal vision: Awin-win-win scenario forsimultaneously producingbioenergy, permanentlysequestering carbon, whileimproving soil and water quality.Agronomy Journal 100, 178-181.

Lal, R. 2007. Farming carbon. Soil &Tillage Research 96(1), 1-5.

Lehmann, J. and Joseph, S. 2009.Biochar systems. In: Biochar forenvironmental management (J.Lehmann and S. Joseph eds.),Science and Technology,Earthscan, London. Pp 147-168.

Lehmann, J. and Rondon, M. 2006.Biochar soil management on highlyweathered soils in the humidtropics. In: Biological Approaches toSustainable Soil Systems (N.Uphoff et al. eds), Boca Raton, FL:CRC Press. pp 517-530.

Lehmann, J., Czimczik, C., Laird, D. andSohi, S. 2009. Stability of biocharin soil. In: Lehmann, J., Joseph, S.(Eds.), Biochar for EnvironmentalManagement: Science andTechnology. Earthscan, London,pp. 183-205.

Lehmann, J., Gaunt, J. and Rondon, M.2006. Biochar sequestration interrestrial ecosystems—a review.Mitigation and AdaptationStrategies for Global Change 11,403-427.

Lehmann, J., Liang, B., Solomon, D.,Lerotic, M., Luizão, F., Kinyangi,F., Schäfer, T., Wirick, S. andJacobsen, C., 2005. Near-edge X-ray absorption fine structure (NEXAFS)spectroscopy for mapping nano-scaledistribution of organic carbon forms insoil: application to black carbonparticles. Global Biogeochemical Cycles19, GB1013.



Lehmann, J., Pereira da Silva Jr. J.,Steiner, C., Nehls, T., Zech, W. andGlaser, B. 2003. Nutrientavailability and leaching in anarchaeological Anthrosol and aFerralsol of the Central Amazonbasin: fertilizer, manure andcharcoal amendments. Plant andSoil 249, 343-357.

Liang, B., Lehmann, J., Sohi, S.P.,Thies, J.E., O’Neill, B., Trujillo, L.,Gaunt, J., Solomon, D., Grossman,J., Neves, E.G. and Luizão, F.J.2010. Black carbon affects thecycling of non-black carbon in soil.Organic Geochemistry 41, 206-213.

Liang, B., Lehmann, J., Solomon, D.,Kinyangi, J., Grossman, J., O’Neill,B., Skjemstad, J.O., Thies, J.,Luizao, F.J., Petersen, J. andNeves, E.G. 2006. Black carbonincreases cation exchange capacityin soils. Soil Science Society ofAmerica Journal 70, 1719-1730.

Major, J., Steiner, C., Downie, A. andLehmann, J. 2009. Biochar effectson nutrient leaching. In: Biocharfor environmental management (J.Lehmann and S. Joseph eds.),Science and Technology,Earthscan, London. pp 271-287.

Matthews, J. A. 2008. Carbon-negativebiofuels. Energy Policy 36(3), 940-945.

McHenry, M.P. 2009. Agriculturalbiochar production, renewableenergy generation and farm carbonsequestration in Western Australia:Certainty, uncertainty and risk.Agriculture, Ecosystems andEnvironment 129, 1–7.

MNRE, 2009. Ministry of New andRenewable Energy Resources,Govt. of India, New Delhi.www.mnre.gov.in/biomassrsources.

Murali, S., Shrivastava, R. and Saxena,M. 2010. Greenhouse gasemissions from open field burningof agricultural residues in India.Journal of Environmental Scienceand Engineering 52(4), 277-84.

Nguyen, B., Lehmann, J., Hockaday,W.C., Joseph, S. and Masiello, C.A.2010. Temperature sensitivity ofblack carbon decomposition andoxidation. Environmental Scienceand Technology 44, 3324-3331.

Nguyen, B.T. and Lehmann, J. (2009).Black carbon decomposition undervarying water regimes. OrganicGeochemistry 40(8), 846-853.

O’Neill, B., Grossman, J., Tsai, M.T.,Gomes, J.E., Lehmann, J.,Peterson, J., Neves, E. and Thies,J.E. 2009. Bacterial communitycomposition in BrazilianAnthrosols and adjacent soilscharacterized using culturing andmolecular identification. MicrobialEcology 58, 23-35.

Oguntunde, P.G., Fosu, M., Ajayi, A.E.and Van de Giesen, N. 2004.Effects of charcoal production onmaize yield, chemical propertiesand texture of soil. Biology &Fertility of Soils 39, 295-299.

Pietikäinen, J., Kiikkilä, O. and Fritze,H. 2000. Charcoal as a habitat formicrobes and its effects on themicrobial community of theunderlying humus. Oikos 89, 231-242.

Rani, P. 2013. Potential appraisal of limeincubated sludge and biochar incurbing the bioavalability of heavymetals to rice. M.Sc. (Ag) Thesis,Banaras Hindu University,Varanasi, U.P., India.

Renner, R. 2007. Rethinking biochar.Environmental Science andTechnology 41(1), 5932-5933.

Rillig, M.C. and Mummey, D.L. 2006.Mycorrhizas and soil structure.New Phytologist 171, 41-53.

Rodríguez, L., Salaza, P. and Preston,T.R. 2009. Effect of biochar andbiodigester effluent on growth ofmaize in acid soils. LivestockResearch for Rural Development21(7), 110.

Rondon, M., Ramirez, J.A. andLehmann, J. 2005. Charcoaladditions reduce net emissions ofgreenhouse gases to theatmosphere. In: Proceedings of the3rd USDA Symposium onGreenhouse Gases and CarbonSequestration, Baltimore, USA,March 21-24, 2005.

Rondon, M.A., Lehmann, J., Ramirez, J.and Hurtado, M. 2007. Biologicalnitrogen fixation by common beans(Phaseolus vulgaris L.) increaseswith biochar additions. Biology andFertility of Soils 43, 699-708.



Schmidt, M.W.I. and Noack, A.G. 2000.Black carbon in soils andsediments: analysis, distribution,implications, and currentchallenges. Global BiogeochemicalCycles 14, 777-793.

Schwartz, M.W., Hoeksema, J.D.,Gehring, C.A., Johnson, N.C.,Klironomos, J.N., Abbott, L.K. andPringle, A. 2006. The promise andthe potential consequences of theglobal transport of mycorrhizalfungal inoculum. Ecological Letters9, 501-515.

Sexstone, A.J., Revsbech, N.P., Parkin,T.P. and Tiedje, J.M. 1985. Directmeasurement of oxygen profilesand denitrification rates in soilaggregates. Soil Science Society ofAmerica Journal 49, 645-651.

Singh, A. 2013. Effect of rice huskbiochar and PGPR on growth, yieldand nutrient uptake of rice. M.Sc.(Ag) Thesis, Banaras HinduUniversity, Varanasi, U.P., India.

Singh, J. and Gu, S. 2010. Biomassconversion to energy in India- acritique. Renewable & SustainableEnergy Reviews 14, 2596–2610.

Sohi, S. P., Krull, E., Lopez-Capel, E.and Bol, R. 2010. A review ofbiochar and its use and function insoil. In D. L. Sparks (Ed.),Advances in agronomy 105, 47-82.Burlington: Academic Press.

Sohi, S., Lopez-Capel, E., Krull, E andBol, R. 2009. Biochar’s roles in soiland climate change: A review ofresearch needs. CSIRO Land andWater Science Report 05/09, p 64.

Spokas, K.A., Koskinen, W.C., Baker,J.M. and Reicosk, D.C. 2009.Impacts of woodchip biocharadditions on greenhouse gasproduction andsorption/degradation of twoherbicides in a Minnesota soil.Chemosphere 77, 574-581.

Srinivasarao, Ch., Gopinath, K.A.,Venkatesh, G., Dubey, A.K.,Harsha Wakudkar, Purakayastha,T.J., Pathak, H., Pramod Jha,Lakaria, B.L., Rajkhowa, D.J.,Sandip Mandal, Jeyaraman, S.,Venkateswarlu, B. and Sikka, A.K.2013b. Use of biochar for soilhealth management andgreenhouse gas mitigation in India:

Potential and constraints, CentralResearch Institute for DrylandAgriculture, Hyderabad, AndhraPradesh. 51p.

Srinivasarao, Ch., Vankateswarlu, B.,Lal, R., Singh, A.K., SumantaKundu, Vittal, K.P.R.,Balaguruvaiah, G., Vijaya ShankarBabu, M., Ravindra Chary, G.,Prasadbabu, M.B.B. andYellamanda Reddy, T. 2012. Soilcarbon sequestration andagronomic productivity of an Alfisolfor a groundnut-based system in asemiarid environment in southernIndia. European Journal ofAgronomy 43, 40-48.

Srinivasarao, Ch., Venkateswarlu, B.,Lal, R., Singh, A.K. and SumantaKundu. 2013. Sustainablemanagement of soils of drylandecosystems for enhancingagronomic productivity andsequestering carbon. Advances inAgronomy, 121.

Steiner, C. 2010. Biochar in agriculturaland forestry applications. In:Biochar from agricultural andforestry residues – a complimentaryuse of waste biomass, U.S.-focused biochar report:Assessment of biochar’s benefitsfor the United States of America.

Steiner, C., Das, K.C., Garcia, M.,Förster, B. and Zech, W. 2008a.Charcoal and smoke extractstimulate the soil microbialcommunity in a highly weatheredxanthic ferralsol. Pedobiologia-International Journal of Soil Biology51, 359-366.

Steiner, C., Glaser, B., Teixeira, W.G.,Lehmann, J., Blum, W.E.H. andZech, W. 2008b. Nitrogen retentionand plant uptake on a highlyweathered central AmazonianFerralsol amended with compostand charcoal. J. of Plant Nutritionand Soil Sci. 171, 893-899.

Steiner, C., Teixeira, W.G., Lehmann, J.,Nehls, T., MaceDo, J.L.V., Blum,W.E.H. and Zech, W. 2007. Longterm effects of manure, charcoal andmineral fertilization on cropproduction and fertility on a highlyweathered Central Amazonianupland soil. Plant and Soil 291, 275-290.



Stockmann, U. 2011. Managing the soil-plant system to mitigateatmospheric CO2. DiscussionPaper for the Soil CarbonSequestration Summit Jan 31-Feb2, 2011. Sydney: University ofSydney, Food, Agriculture andNatural Resources and the UnitedStates Centre at the University ofSydney. 55 pp.

Streets, D., Yarber, K., Woo, J. andCarmichael, G. 2003. Biomassburning in Asia: Annual andseasonal estimates andatmospheric emissions, GlobalBiogeochemical Cycles, 17(4),1099.

Tryon, E.H. 1948. Effect of charcoal oncertain physical, chemical, andbiological properties of forest soils.Ecological Monographs 18, 81-115.

Van Zwieten, L., Kimber, S., Morris, S.,Chan, K.Y., Downie, A., Rust, J.,Joseph, S. and Cowie, A. 2010.Effects of biochar from slow pyrolysisof paper mill waste on agronomicperformance and soil fertility. Plantand Soil 327, 235-246.

Venkataraman, C., Habib, G., Kadamba, D.,Shrivastava, M., Leon, J., Crouzille, B.,Boucher, O. and Streets, D. 2006.Emissions from open biomass burningin India: Integrating the inventoryapproach with high-resolutionModerate Resolution ImagingSpectroradiometer (MODIS) active-fireand land cover data. GlobalBiogeochemical Cycles 20(2) GB2013.

Warnock, D.D., Lehmann, J., Kuyper,T.W. and Rillig, M.C. 2007.Mycorrhizal responses to biocharin soil – concepts andmechanisms. Plant and Soil 300, 9-20.

Xiang-Yang Yu, Guang-Guo Ying, &Kookana, R.S. 2009. Reducedplant uptake of pesticides withbiochar additions to the soil.Chemosphere 76(5), 665-671.

Yamamoto, M., Okimori, Y., Wibowo,I.F., Anshori, S. and Ogawa, M.2006. Effects of the application ofcharred bark of Acacia mangium onthe yield of maize, cowpea andpeanut, and soil chemicalproperties in South Sumatra,Indonesia. Soil Science and PlantNutrition 52, 489-495.

Yanai, Y., Toyota, K. and Okazani, M.2007. Effects of charcoal additionon N2O emissions from soilresulting from rewetting air-driedsoil in short-term laboratoryexperiments. Soil Science and PlantNutrition 53, 181-188.

Yin, B., Crowley, D., Sparovek, G., DeMelo, W.J. and Borneman, J.2000. Bacterial functionalredundancy along a soilreclamation gradient. Applied andEnvironmental Microbiology 66,4361-4365.



Acid soil management for sustaining higher crop productivity

Surendra Singh, FISSSDepartment of Soil Science and Agricultural Chemistry

Institute of Agricultural SciencesBanaras Hindu University, Varanasi 221005

Introduction Soil acidity is a major constraintfor crop production. The production ofacid in soils is a natural process,specially in the high rainfall areas. Thestagnation in crop productivity in acidsoil has been found due to deficiency ofseveral nutrients. At several place inacidic soils of India, application of liminghas become necessary for sustaininghigh crops yields, greater nutrients useefficiency and enhanced profit. Efficientsoil amelioration and nutrientmanagement methods are necessary forcrops susceptible to soil acidity Toachieve high benefits as well as cropproductivity, precise information onmanagement of acidic soil besides NPKis necessary and is the national priority.

Distribution of acid soil Acid soils are characterized by soilpH which varies from strongly acidic (4.5to 5.5) to extremely acidic (<4.5), lowcation exchange capacity and low basesaturation. The formation anddistribution of acid soils depend uponseveral factors like temperature,vegetation, parent material andhydrologic conditions etc. The variousprocess involved in the formation of acidsoils are laterization of varying degree,podsolization in temperate and subtemperate zones or intense baseleaching in light alluvial soils. Thelowest area under acid soils is coveredby laterites and latosols occurring inAssam, West Bengal, Jharkhand,Orissa, Andhra Pradesh, Kerala, MadhyaPradesh, Karnataka, Tamilnadu andMaharastra. Acid Podsol soils mostlyoccur in the Himalyan region while acidalluvial soils are mostly formed in WestBengal,Assam and Bihar. Peat and marshy soilare distributed in Assam, Kerela, coastaltracts of Orissa, South east coast ofTamilnadu and Trai region of UP andBihar. The acid soil (pH < 6.5) in Indiaoccupy approximately 90 million

hectares (M ha) of the geographical area(Sharma an Sarkar, 2005). Acidic soilsbelow pH 5.5 occupy around 25 Mha ofarbal land. These soils are primarilyconcentrated in the easterm part of thecountry comprising, Assam, Jharkhand,Orissa, West Bengal and North easternstates (Arunachal Pradesh, Manipur,Meghalaya, Mizoram, Nagaland, Sikkimand Tripura) with sporadic distributionin Himanchal Pradesh. In the north-eastern region the acid soils below Ph5.5 occupy 54 per cent of the total areaof the country. The toxicity of soil Al hasbeen recognized as one of the importantfactor limiting the productivity of cropson acid soils with pH less than 5.5. Red and lateritic soils of thecountry are in general low inproductivity. Such low productivity isattributed to a number of factors ofwhich nutritional disorders are mostimportant. The acid soils belonging togroups red, laterite and lateritic havedeveloped under conditions of intenseweathering and leaching of basesparticularly calcium and magnesiumThey not only suffer from the deficiencyof primary nutrient elements via; N, Pand K but also secondary nutrients (Ca,Mg and S)and micronutrients (Zn, Cu, Band Mo).

Selection of liming materialsIn principle, all liming materials

can be applied on all soils, but thechoice of a material depends mainly onsoil texture, local availability and cost.Medium to heavy soils (texture of loamand clay) can be neutralized rapidly withquick lime. However, to maintain theoptimal reaction slow-acting carbonatesare more suitable. In coarse texturedsoils (sand and loamy land) carbonatelime is preferable because of lower riskof over liming where an excessiveamount is applied or where thedistribution is not uniform. Anotheraspect of choice is the presence of by –products, some limes also containnutrients other than Ca, some clay



minerals, organic matter ormicronutrients, which makes them morevaluable for sandy soils.

Many industrial by-productshave neutralizing effect on soil acidityand can be used as amendments. Someare easily mobilizable, such as silicatesmixed with quick lime. Others contain acertain amount of phosphate and Mg,which makes them suitable foramelioration of acid soils that are alsodeficient in P and Mg. Pressmud fromsugar factories using the carbonationprocess is rich in lime can be used toimprove acid soils. Several RPs also haveneutralizing properties. Fly ash is apowery residues remaining after coalhas been burned (as in thermal powerstation). It has received considerableattention as a soil amendment forameliorating acid soils. However,caution is needed to avoid undueaccumulation of B, Mo, Se and solublesalts in fly ash treated soils.Liming materialsCommon liming materials are : Calcium carbonate: It generally

contains 75-95 per cent CaCo3

corresponding to 42-53 per centCao. Magnesium carbonate (MgCo3)concentration of more than 5 percent is useful. The particle size ofhard lime stone must be less than 1mm and that of soft material (chalk)less than 4 mm.

Calcium magnesium carbonate(dolomite) : Its different typescontain 15-40 per cent MgCO3 and60 -80 per cent CaCO3. Theseproducts are suitable for acid soilsthat are also Mg deficient.

Quick lime (Cao) and slaked limeCa(OH)2: These are quick-actingamendments for the neutralization ofsoil acidity. But they are generallymore expensive than natural limes.The common liming material isground natural limestone (CaCO3)which a definite fineness dependingon the hardness of the rock.Carbonate limes act slowly becausethey are only slightly soluble inwater and must be dissolved in toneutralizing forms.

Response of crops to liming Lime mainly provides calcium tothe soil where it is changed in to a form

available to plants. A substantialamount of calcium is removed by cropfrom the soil like N, P and K. Certainamount of lime is to be added tocompensate for the removal of calciumby plants like other nutrients.Calciumas a nutrient to soybean and ground nutin acidic soil of Jharkhand was studied.Furrow application each 2-4 q ha-1 ofcalcium carbonate and gypsumincreased grain yield of soybean and podyield of groundnut to the tune of 26.7and 47.6 percent respectively. Theimprovement in crop yield due togypsum was mainly due to Ca ratherthan increase in soil pH. On the basis ofresponse to lime, crops like pigeonpea,soybean and cotton have been classifiedas high responsive, chickpea, lentil,peas, groundnut and sorghum asmedium responsive and small millets,rice, potato etc as low or non responsive.Liming of acidic and red lateritic soil notonly ameliorate soil acidity relatedproblems but also supply lot of calciumto crops grown there. Lime application @1/10, 1/15 and 1/20 of limerequirement (LR) applied in rhizosphereat sowing time was compared with LRdose applied as broadcasting only onceas in the beginning. The mean yield ofUrad, Soybean, Groundnut, lentil andGram with 1/20th LR dose of lime was atpar with that of 1 LR dose. Lime (1/10 ofLR) has been applied to various crops indifferent states of India under ICAR network project on acid soils with primaryobjective of increasing crop yields overthe existing farmers practice. The cropsthat have responded well to lime aremainly legumes followed by crops likemaize, wheat and mustard.Goodresponse to liming in acid soils havebeen obtained for greengram in Assam,maize and wheat in Himanchal Pradesh,maize, pigeonpea, groundnut and pea inJharkhand, groundnut in Maharastraand pigeonpea in Orrisa and mustard inWest Bengal.

Magnesium is likely to bedeficient in acid soil and liming mayaccentuate this deficiency. Fieldexperiments were conducted in the year1992-95 in acidic soils of Ranchi ongroundnut, wheat, soybean and potatoto study the response of crops to addedmagnesium as magnesiumsulphate.Response of magnesium to



these crops was higher with applicationof 30 kg Mg ha-1. Groundnut andsoybean responded well to Mgapplication followed by potato andwheat. Field experiments conducted insoil of Kanpur revealed that response ofMg was found to be higher in wheat,chickpea and mustard with applicationof 60 kg ha-1 over control.

Response of crop to S applicationcan be judged based on nature andseverity of deficiency which can beknown either through visual symptomson plant foliage, plant analysis, soilanalysis and /or responses of crops tothe applied nutrients. The magnitude ofresponse differ widely among the cropsand their cultivars, soil types and degreeof S deficiency.

Beneficial effect of S applicationon increasing yield of several cereal,oilseed, pulse and cash crops has beenreported in S deficient soils of thecountry by several workers.There is anactive involvement of S in proteinsynthesis and oil production. Sulphur isa constituent of amino acid likemethionine, cystine and cysteine whichare building blocks of protein. Sulphurapplication not only enhances the grainyield but also improve the quality ofpulse crop.



PHYSICAL INDICATORS OF SOIL HEALTH FORAGRICULTURAL SUSTAINABILITY

H.S. Kushwaha

Professor, Department of Soil Science

College of Agriculture, G.B. Pant University of Agriculture & Technology,Pantnagar-263145, U.S. Nagar (Uttarakhand)

[email protected]

Agricultural production systems havebeen developed to meet the food, fiberand feed needs of the growing humanpopulation at the cost of naturalecosystem. Sustainable agriculture is away of farming that integrates threeprimary objectives viz. environmentalhealth, economic profitability, and socialand economic equity. It is expected that,over time, sustainable agriculture willmeet human needs for food and fiber,protect the natural resource base andprevent the degradation of soil andwater quality, use nonrenewableresources efficiently, use naturalbiological cycles and controls, assure theeconomic survival of farming and thewell-being of farmers, their families andsoil physical health. With increasingdemographic pressure coupled withscarcity of soil and water resources,sustainable agriculture is notsynonymous with “low-input” or organicagriculture. In some cases, low-inputsystem may be acceptable for a shorttime, but in others like major food graincrops it may not be acceptable at all. Asthere is no alternative to agriculturalintensification in our country, we mustensure using soil resources as per theircapability and adopting the practicesthat improve soil quality and maintain afavorable soil condition for plant growthand environmental health. The soilresources of India are enormous as 9,out of 12 Soil Orders which describe thesoils of the planet earth, occur in India.However, some of the soils have severeconstraints towards meeting thechallenges of 21st century. Soil-relatedconstrains are especially severe in arid,semiarid and hilly regions. Importantconstraints are low soil fertility andnutrient depletion, multi-nutrientdeficiency, physical degradation,accelerated soil erosion and poor soilhealth (Table 1). Apart from inherent

constraints, there are severe humaninduced constraints particularly inintensively cropped areas.Mc Graw Hill Dictionary of Scientific andTechnical Terms defines HEALTH as a‘State of dynamic equilibrium betweenorganism and its environment in whichall the functions of mind and body arenormal’. Drawing similar analogy, soilhealth would imply as being ‘a state ofdynamic equilibrium between flora andfauna and their surrounding soilenvironment in which all the metabolicactivities of the former proceed optimallywithout any hindrance, stress orimpedance from the letter.’Table 1 : Soil resources of India andsoil related constraints (Velayuthamand Bhattacharya, 2000)

S.N

Soilorder

Landarea,M ha*

% ofthe

totalarea

Soil-relatedconstraints

1. Alfisols 44.29 13.5

Weak soilstructure,crusting,compaction,erosion bywater

2. Aridisols 14.07 4.3

Droughtstress,nutrientdepletion,winderosion,desertification,secondarysalinization

3. Entisols 92.13 28.0

Erosion,nutrientdepletion,low soilorganicmatter

4. Inceptisols 130.37 39.8

Erosion, lowsoil organicmatter,nutrientimbalance



5. Mollisols 1.32 0.4 ?

6. Ultisols 8.25 2.5

Erosion bywater,nutrientimbalance,acidification, P fixation

7. Vertisols 27.96 8.5

Massivestructure,poor tilth,droughtstress,watererosion

8. Histosols 0.002 -

Highorganicmatter

9. Others 9.67 2.95Poor SoilPhysicalenvironment

Total 328.06 100

The terms soil health and soil qualityare currently used interchangeably inscientific literature and popular press.In general, Scientists prefer soil qualityand farmers prefer soil health.Alternative agriculture institutions suchas Rodale (PA) use soil quality and soilhealth without qualification. So,Scientists favour the joint term soilquality / health in the interest ofpromoting communication, knowledgesharing, and developing anunderstanding for managing soil quality/ health by farmers and Scientists.

1. Possible Soil management practicesand indicators of crop performance:

The adoption of specific soilmanagement practices is often driven bypractical or economic considerations,rather than the potential benefits ofimproved soil quality for crop productionand the environment. Without a highproductivity, agricultural profitability isdifficult to achieve and sustain, but highproductivity does not necessarily ensureenvironmental, economic or socialsustainability. On the other hand, theremay be cases in which soil managementpractices developed to lower productioncosts and reduce environmental impactsresulted in improved crop performanceand sustained economic performance(Table 2.) as reported by Mishra et.al.2002.

Table 2 : Strategies for sustainableagricultural management andproposed indicators of cropperformance, soil quality andenvironmental healthS.

No.Sustainability

strategyIndicators

1 Conserve soilorganic matterthroughmaintaining soil Cand N levels byreducing tillage,recycling plant andanimal manures,and /or increasingplant diversitywhere C inputs Coutputs

Direction/change inorganic matter levelswith time (visual orremote sensing bycolor or chemicalanalysis),Specific organicmatter potential forclimate, soil andvegetation,Soil and waterstorage

2 Minimize soilerosion throughconservation tillageand increasedprotective cover(residue, stableaggregates, covercrops, green fallow)

Visual (gullies, rills,dust, etc)Surface soilproperties (topsoildepth, organic mattercontent/texture,water infiltration,runoff, ponding,percent cover)

3 Balance productionand environmentthroughconservation andintegratedmanagementsystems (optimizingtillage, residue,water, andchemical use) andby synchronizingavailable N and Plevels with cropneeds during theyear

Crop characteristics(visual or remotesensing of yield,color, nutrient,status, plant vigor,and rootingcharacteristics),Soil physicalcondition/compaction,Soil and water nitratelevels,Amount and toxicityof pesticides used

4 Better use ofrenewableresources throughrelying less onfossil fuels andpetrochemicals andmore on renewableresources andbiodiversity (e.g.crop rotation,legumes, manures,integrated nutrientmanagement,integrated pestmanagement)

Input and outputratios of costs andenergy,Leaching losses/soilacidification,Crop characteristics(as listed above),Soil and water nitratelevels



Two-pronged strategy forachieving agricultural sustainability isneeded : i) preventing soil degradationand ii) enhancing soil quality. Althoughmanagement options for both thestrategies may be similar, enhancing soilquality requires information onthreshold levels of soil properties specificto soil functions. There is also a closerelationship between soil resilience andthreshold values which need to bedetermined for restoring degraded soils.

2. Possible ways for assessing soilhealth for sustainable cropproduction:

1. Identify key variables for establishingbaseline information to assessimpact later.

2. Develop a joint action planacceptable to farmers and otherstakeholders for implementation.

3. Understand the existing farmingsystems, available resources, andtheir patterns of utilization in thestudy area.

Analyze the various stakeholders andtheir roles in farming and relatedactivities of the study area.

4. Identify constraints to andopportunities for optimizing farmers’productivity with special focus onnutrient-related issues and soilhealth

5. Examine option to help farmers solvethe problems/issues and exploitingopportunities identified.

Soil quality indicates whethersoils are in good conditions for theircurrent use. The physical, chemical andbiological characteristics of differentsoils vary a great deal and, therefore,different soils are suited for differentuses. Soil quality is the "capacity of aspecific soil to function, within naturalor managed ecosystem boundaries, tosustain plant and animal productivity,maintain or enhance water and airquality, and support human health andhabitation" . Scientific controversy hassurrounded the concept because soilquality per se cannot be measured. Itmust be assessed by evaluating variousquantitative and qualitative indicators.Soil quality evaluation is complicatedbecause assessment must distinguishbetween inherent and dynamic soilquality. The inherent quality such as

texture, mineralogy etc., are innate soilproperties determined by the factors ofsoil formation - climate, topography,vegetation, parent material and time.They help compare one soil to anotherand evaluate soils for specific use. Forexample, all else being equal, a loamysoil will have a higher water holdingcapacity than a sandy soil. The loamysoil has higher inherent soil quality.This concept is generally referred to assoil capability. Map units descriptions insoil survey reports are based on theinherent properties of soils. However,The dynamic quality, the more recently,soil quality has come to refer to thedynamic quality - defined as thechanging nature of soil propertiesresulting from human use andmanagement.

3. Physical Indicators for soil health The soil as a physical systemcan be described in terms of bulkdensity, aggregate size, porosity andpore-size distribution, water content,temperature, aeration and friability. Allthese physical attributes of soilinfluence plant growth through theireffect on soil water, soil air, soiltemperature and mechanical impedanceto root development and shootemergence. As is known that soil is anatural body, synthesized in profileformed from a variable mixture ofbroken and weathered minerals anddecaying, organic matter, which coversthe earth in a thin layer and whichsupplies, when containing the properamounts of air and water, mechanicalsupport and, in part, sustenance forplants. One must look into reasons forvariation in the productivity of soils andto find means of conserving andimproving this productivity.

The main attention be focused onrole of soil as a storage place for waterand air, a medium for root growth, andanchorage for plants. A prime concern ofthe farmer has been to prepare aseedbed that would after least resistanceto seedling emergence and rootpenetration, and ensure optimal supplyof air, water and nutrients to the plant.Tillage has been considered as primetool to achieve these objective.



Since tillage rapidly alters soilstructure, studies be focused onimproving soil structure for increasingcrop production. A good soil conditionswas characterized as one which wouldafter minimum resistance to rootpenetration, permit rapid intake andmoderate retention of rainfall, provideoptimum soil aeration and optimum air-water balance in soil pares, providestable traction for farm implements andfacilitates organic farming Tillagedeteriorates soil structure as a result ofreduced organic matter, base saturation,porosity and granulation. However,become of its dynamic nature, soilstructure can probably be regenerated.Soil characteristics influencingbiophysical condition of soil are thosethat affect mechanical strength, waterand temperature relations. Therefore,efforts should made to relate plantgrowth with soil water, soil air, soiltemperature, and mechanical impedanceto seeding emergence and rootpenetration.

The physical properties of soils -texture, structure, density, porosity,water content, strength, temperature,and color, determine the availability ofoxygen in soils, the mobility of waterinto or through soils, and the ease ofroot penetration. Some of theseproperties are immutable (e.g., texture)and cannot be modified by culturalpractices, but bulk density, structure,water holding capacity, and porosity canbe improved using appropriate soilmanagement techniques. Soil physicalcharacteristics, having a vital role in soilproductivity are considered are given inTable 3. Soil depth is an easilymeasurable and independent propertythat provides direct information about asoil’s ability to support plants. Effectivesoil depth is the depth available for rootsto explore for water and nutrients.Layers that restrict root growth or watermovement include hard rocks, naturallydense soil layers. Soil depthrequirements vary with crop or species.For example, many vegetable crops, areshallow rooted while grain crops andsome legumes like alfalfa are deeprooted.

Table 3 : Physical indicators for soilhealth

Aeration Clay minerals Penetrationresistance

Aggregatestability

Depth of rootlimiting layers

Soil structure

Bulk density Poreconnectivity

Particle sizedistribution

Colour Oxygendiffusion rate

Soil tilth

Hydraulicconductivity

Pore sizedistribution

Total porosity

Consistence Soil strength Temperature

These physical properties of asoil play an important role indetermining its suitability for cropproduction. The characteristics likesupporting power and bearing capacity,tillage practices, moisture storagecapacity and its availability to plants,drainage, ease to penetration by roots,aeration, retention of plant nutrientsand its availability to plants are allintimately connected with the physicalproperties of the soil. Soil as a mediumfor plant growth should also bephysically fertile. The soil whichsupports plants is a variable mixture ofsolids (mineral and organic mixture),liquid (water) and gasses (air) and iscalled three phase system.

The inorganic solid phase iscomposed of discrete mineral particles ofvarious shapes and sizes as well as ofamorphous compounds such ashydrated iron and aluminum oxides.The proportion of amorphous material isgenerally small. The large soil particlesare generally visible to the naked eye,whereas the smaller are colloidal andcan be seen only with the aid of anelectron microscope. The liquid phase,consisting of soil water also containsdissolved salts and thus it is called soilsolution. The gaseous phase consistssoil air of varying composition of oxygenand carbon dioxide different from that ofatmospheric air.

Major Physical Indicators of soilhealth

a. Soil Textureb. Soil Structurec. Soil Porosityd. Soil strength, Consistency and

plasticity



e. Soil moisture content and watermovement

f. Hydraulic Conductivityg. Infiltration, percolation and drainageh. Soil Moisture Tensioni. Soil Aerationj. Soil Temperaturek. Ground water table, etc.

a. Soil texture as a physical indicatorfor soil health

The relative proportion of mineralmatter in a soil expressed as sand, siltand clay is referred to as soil texture. Soilsare often characterized in terms of theproportions of particles of different sizesperhaps because particle size is related tosoil behaviour and plant response.Although many soil properties vary withtexture but none of the relationships areuniversally applicable. At least two generalcauses of this ambiguity could bemaintained. Firstly, soil particles of agiven size are not necessarily similar intype and their characteristics. Forexample, a soil with same percentage ofclay may differ in kind of clay andtherefore, in swelling, plasticity etc. Weknow that montmorillonite is more plasticthan Kaolinite. Secondly swelling andplasticity are also dependent onconditions that are not inherent inparticle. For example, plasticity is highlydependent on type of ion such as Na+,Ca++, K+, H+ etc. and CEC.

Plant’s dependence on soil can berecognized from the fact that out of thesix commonly recognized external factorsviz. light, mechanical support, heat, air,water and nutrients soil supplies, eitherwholly or in part, all except light. Porespaces formed by arrangement of soilsolids and particle surface areaaccommodates roots through whichplants meet their requirements forgrowth and development. Soil also offersresistance against shoot emergence androot penetration for which a number ofphysical and biological manipulations arenecessary.

The soil texture may affect plantgrowth directly through resistance offeredagainst seedling emergence and rootpenetration but indirectly it affectsalmost all edaphic factors of plantgrowth.

Influence of texture on watersupply to plants is well known. Ingeneral, available water storagecapacity of medium to fine texturesoils is greater than those coarsetexture soils (Table 4).

Table 4 : Range of available water invarious soils

Soil texture Centimeter ofavailable water permeter of soil profile

Coarse sands, fine sandsand loamy sands

6.2-10.5

Sandy loams and finesandy loams

10.2-14.4

Very fine sandy loam,loams and silt loams

12.5-19.5

Clay loams, silty clayloams and sandy clayloams

14.4-20.6

Sandy clays, silty and clay 13.5-20.6In humid region, where rainfall is

sufficient to fill soils of all textures totheir capacity at certain intervals, theamount of water available to plants willbe greater in fine texture soils than incoarse texture soils. But in arid or semi-arid regions, where the rainfall is of highintensity and not sufficient to fill soils ofall textures to their capacity, theamount of water available to plantswould depend on the rates of infiltrationand evaporation. Because of highinfiltration rate, soils of coarse textureusually are superior to those of finetexture under such conditions. Thus,whereas soils of coarse texture aredraughty in humid regions, soils of finetexture are droughty in dry regions.

Crop yields are generally higherin soils of medium to fine texture thanin soils of coarse texture. However, allcrops do not respond to soil texture inthe same general way. Finances oftexture showed increase in yield of hempbut not of soybeans. Observationshowed that nitrogen deficiencysymptoms were not evident in soybeansbut were pronounced in hemp grown oncoarsest texture and becameprogressively less evident as the texturebecame finer. The differences in supplyof soil nitrogen were perhaps theprincipal cause of increase in yield ofhemp with fineness of texture. Thus it isquestionable to credit yield increase dueto texture alone because similar yieldscould have been obtained if nitrogen was



supplemented through other sources ashappened with soybeans which couldindependently fix nitrogen is rootnodules from the atmosphere.

b. Soil structure as a physicalindicator of soil quality

Physically a soil is a mixture ofinorganic particles, decaying organicmaterial, water and air. The inorganicprimary particles of various sizes (sand,silt or clay fraction) generally clustertogether to form complex and irregularpatterns of secondary particles whichare called aggregates at peds. The termsoil structure refers to the arrangementof these primary and secondary particlesinto a certain structural pattern. Soilstructure greatly influences many soilphysical processes such as waterretention and movement, porosity andaeration, transport of heat etc. Thevarious soil management practices suchas tillage, cultivation, application offertilizer and manures, amendments andirrigation etc., bring about changes insoil structure that influences other soilproperties, thereby affecting root growth,water and nutrient uptake, crop growthand yield.

The soil structure can becharacterized by evaluating the shapesand sizes and the strength of interparticle bonds within and amongaggregates. Under field conditions suchaggregates form and break into smalleraggregates during tillage and bydisruptive action of water and air. theaggregates maintaining their identity arethose in which the cohesive forcesamong particles were greater than thedisruptive forces. A quantitativecharacterization of aggregates is done bydetermining aggregates stability and sizedistribution of aggregates. The aggregatestability refers to the resistance of soilaggregates to breakdown by water , airand mechanical manipulations. Tillageoperations at lower or higher watercontents greatly decrease the aggregatestability and size distributions ofaggregates in a soil. The size distributionof wet and dry aggregates determineoverall tilth, size of pores andsusceptibility of aggregates to movementby water and wind. The stability ofaggregates is affected by differentamendments given in the field (Table 5)as well as by adoption of various croprotations (Table 6).



Effect of Plastic Mulch on Soil Properties and Plant GrowthVijay Agrawal* and S.S.Baghel

ScientistDeptt. Of Plant Pathology, College of Agriculture, JNKVV, Jabalpur (M.P)

Plastic Mulch is a similar product used asorganic mulch to conserve moisture and tosuppress weed growth in crop production.Under plastic mulch, soil properties likesoil temperature, moisture content,aggregate stability, bulk density andnutrient availability have been improved.Plant growth and yield also positivelyinfluenced by the plastic mulch due to themodification of soil micro climate.

Mulching is the process or practice ofcovering the soil surface around the plantsto make conditions more conducive forplant growth through in-situ moistureconservation, enhancement of microbialactivities in the root zone and weedcontrol. Mulching is in practice in theregion since ages in one or another form.Generally farmers use straw, dry leaves,hay, stones as mulching materials. Thisimplies that farmers of the region areaware of the benefits of mulching.However, introduction of the LDPE film asmulch increases the efficiency of water useby improved moisture conservation, soiltemperature and elimination of weedgrowth thereby increase crop yield. Itaccelerates plant growth by increasing thesoil temperature and stabilizing soilmoisture. Plastic mulches directly affectthe microclimate around the plant bymodifying the radiation budget of thesurface and decreasing the soil water loss.Plastic mulch comes in several colours,including red, white, black, yellow andblue, each having distinct reflectiveproperties which affect plant growth. Theuse of plastic mulches in conjunction withdrip irrigation increases the WUE

Soil temperature : Soil temperatureunder plastic film are depend on colour ofplastic film. Usually black plastic filmmulched plots had sitnificantly lower soiltemperature (1 to 2.8 deg C) than the clearplastic film mulched plots. Because muchof the solar energy abosorbed by blackplastic film mulch is lost to theatmosphere through radiation and forcedconvection (Schales and Sheldrake, 1963).

Nutrient availability :

The decomposition of organicresidues under plastic mulch adds organicacids to the soil resulting in low soil pH,which may increases the bio-availability ofmicronutrients (Mn, Zn, Cu and Fe). Thiswas also evident from the increased Feand Zn content in soil under plastic much.The mineral N content in soil is high dueto mineralization of organic N with time,thereby; it increases the availability of soilnitrogen. Breakdown of organic materialrelease soluble nutrients like NO3, NH4+,Ca+, Mg2+, K+ and fulvic acid to the soilintern increases the oil nutrientavailability under plastic mulch.

Reduced Leaching or Fertilizers :Because many fertilizer nutrients are notheld tightly in the soil, rainfall andexcessive irrigation may leach them belowthe roots of plants grown on bare ground.Nitrogen, potassium, magnesium, andsome formulations of micronutrients aresubject to leaching, especially in light,sandy soils. Plastic mulch covering thebed (or portion of it) prevents rainfall frompercolating through the soil and movingnutrients beyond the reach of plant roots.Preventing leaching improves the efficiencyof production by eliminating the need tomake several trips through the field toresupply leached nutrients, thereby savingtime, fuel, and fertilizer. In addition, ithelps prevent reduced quality and loweryields resulting from (1) hidden hunger -early stages of nutrient deficiency thatmay harm plants even before they begin toshow symptoms and (2) Zag time - thetime from when plants first showsymptoms of a deficiency until nutrientsare replenished in the plant tissues.Finally, minimizing the amount of leachinginto the soil helps protect groundwater fromfertilizer contamination.

Earlier Production : Probably the greatestbenefit of growing crops on plastic isearlier production. Plastic mulch raisesthe soil temperature, which helps plantsgrow more quickly and mature earlier.Spring vegetables grown on black plasticcan be harvested 7 to 21 days earlier thanthey can be on non-plastic mulch.



Harvesting one to two weeks earlier oftensignificantly increases market advantageand the prices growers receive.

Fewer Weed Problem : Black, white-on-black, reflective, and wavelength-selectivemulches will reduce light penetration intothe soil. Weeds generally cannot surviveunder the mulch. An exception isnutgrass, whose nut-like tubers provideenough energy for the seedling to puncturethe mulch and emerge. Clear plastic,however, does not prevent weed growthbecause light can penetrate it.

Increased Plant Growth : Plants grow morewith plastic mulch for two reasons. First,soil temperature at the 2-inch depth isincreased by up to 10°F to 15°F undermulch. Second, during growth, plant rootstake in oxygen and give off carbon dioxide.Plant leaves require CO2, which they getfrom the atmosphere. When plants aregrown on plastic, the CO2released fromroots accumulates under the plastic andeventually escapes through the holes inwhich the plants are growing. This“chimney effect” increases theconcentration of CO2to the leaves andenhances plant growth.

Reduced Evaporation : Because of the highdegree of impermeability of plasticmulches to water vapor, soil waterevaporative loss is reduced. Therefore, youactually need less water per unit ofproduction.

The use of drip irrigation in conjunctionwith plastic mulch reduces moistureevaporation from the mulched soil anddecreases irrigation requirements (Hanlonand Hochmuth, 1989). This has beenrelated to water savings of 45% comparedto overhead sprinkler systems (Clough etal., 1987;Jones et al., 1977).

Improved Quality : Vegetables grown onplastic mulch are cleaner and less subjectto rots because soil has not been splashedon the plants or fruit.

Reduced Soil Compaction : Soil under theplastic mulch remains loose, friable, andwell aerated. Roots have access toadequate oxygen and microbial activity isenhanced (Hankin et al., 1982).

Ability to double/triple crop : Once thefirst crop has been harvested, a secondcrop can be grown on the plastic mulch.This “intensive cropping” produces two orthree crops from the annual expenses forplasticmulch and drip irrigation tubing.

The second or third crop can be fertilizedthrough the drip irrigation line (fertigation)using soluble fertilizers and a fertilizerinjector (Clough et al., 1987; Marr andLamont, 1992).

Cleaner product : The edible product froma mulched crop is clean and less subjectto rots, because soil is not splashed on theplants or fruit. This is accomplished by araised bed that is firm and tapered awayfrom the row centre, and plastic mulchthat is stretched tightly to encourage waterrunoff.

Insect and Disease control : Mulches withaluminium or silver surface colours repelsthe sucking pests like aphids and reducethe incidence of aphid-borne viruses(Lament et al., 1990). Yellow plastic film isuseful in reducing whitefly populations(Bemisia tabaci) in young tomato andchillie plants. The flies are attracted by theyellow colour of the heated plastic as its isexposed to the sun, when the plants aresmall and the crop canopy does not shadeit. Soil solarization using transparentplastic mulch in nursery soil as well as ingreenhouses has been suitable for controlof soil borne diseases. The soiltemperature has been effective in reducingthe incidence of Fusarium, Verticilium andSclerotinia and significantly limiting thepresence of some weeds.

ConclusionUnder plastic much, soil properties likesoil temperature, bulk density, moisturecontent and nutrient availability improved.Plant growth and yield are also positivelyinfluenced by the plastic much due to themodification of soil microclimate. Withproper planning, attention to detail andcareful management of all aspects of thecropping sequence, earlier and higheryields are possible using plastic mulches.



Diagnosis and Mitigation of Zinc Deficiency for Sustainable CropProduction and Human Health

S.K. SinghProfessor

Department of Soil Science & Agricultural Chemistry,Institute of Agricultural Sciences B.H.U., Varanasi-221005

Micronutrients are essential forplants, animal and human health.Requirements of these nutrients are invery small amount but are indispensablelike any other essential nutrients.Decline in production of major crops is acause of concern that requiresimmediate attention. Production ofadequate food grain from the finite landresources to feed the burgeoningpopulation is a great challenge in theyears to come. The incidence ofmicronutrients deficiencies in crops hasincreased markedly in recent years dueto intensive cropping which is one of themajor factors limiting crop yieldaccompanied with human and animalhealth. Thus, micronutrient fertilizationfor sustaining crop production assumesimportance because of the twin benefits.It has now been well established thatquantum of micronutrients deficienciesin Indian soils are of a tune of 49, 33,12, 4 and 3 per cent for Zn, B, Fe, Mnand Cu,respectively.

Among micronutrients, zinc hasassumed greater importance in recent

years. It is estimated that about half ofthe agricultural soils of the world aredeficient in zinc leading to decreasedcrop production and nutritional value.Interestingly Zn deficient soils aredominant in developing countries likeIndia where cereal based food low in zinccontributes about 70% of the dailycalorie intake. This results in high zincdeficiencies in animal and humans. Zincis essential for normal structure andfunctioning of more than 300 enzymes.World Health Organization (WHO)recommends 12-14 mg zinc as dailydietary intake,45mgZn/day as the upperlimit and more than 150mg/day leads toZn toxicity .

Zinc is a trace element found invarying concentrations in all soils,

plants and animals and it is essential forthe normal healthy growth of higherplants, animals and humans. Zinc isneeded in small but criticalconcentrations and if the amountavailable is not adequate, plants and/oranimals will suffer from physiologicalstress brought about by the dysfunctionof several enzyme systems and othermetabolic functions in which zinc playsa part.

The essentiality of zinc for plantswas only scientifically established about70 years ago and in some parts of theworld the existence of deficiencies hasonly been recognized during the last 20or 30 years. The relatively recentdiscovery of widespread zinc deficiencyproblems in rice and wheat is linked tothe intensification of farming in manydeveloping countries. This has involveda change from traditional agriculture,with locally-adapted crop genotypes andlow inputs of nutrients, to growingmodern, high-yielding plant varietieswith relatively large amounts ofmacronutrient fertilizers andagrochemicals.

BIOFORTIFICATIONMicronutrient malnutrition is the

one among the most important globalchallenges affecting more than half ofthe world population, particularly in thedeveloping countries. According to aWHO report (World Health Organization2002), Zn deficiency ranks fifth amongstthe most important health risk factors indeveloping countries and eleventhworldwide. To alleviate the micronutrientmalnutrition several strategies areadapted including pharmaceuticalsupplementation, industrial fortification,dietary diversification andbiofortification.

Historically, most interventionshave involved people taking zincsupplements directly, or the addition of



zinc to foods (‘food fortification’).However, these approaches areexpensive, difficult to administer and, inmany cases, they have not beensustainable and have failed to reach allthe people at risk of zinc deficiency.Biofortification (enrichment of grainsand pulses) having some advantagesover others can be achieved in twodifferent ways; either by plant breeding(genetic biofortification), or by applyingzinc fertilizers to seeds, soil and/orfoliage, at rates greater than thoserequired for maximum yield, to increasethe uptake of zinc into the plants and itstranslocation into seeds (agronomicbiofortification).If the crops themselvesare enriched with zinc, the grains andpulses would enter the food chainnormally (and either be consumed, orprocessed etc.) and the whole populationwould benefit. From an agronomicviewpoint, apart from improving dietaryintake, zinc-enriched grains generallyresult in seedlings with increased vigourand greater stress tolerance. Thus, withseedlings having a greater chance ofsurvival and growing to maturity, it ispossible to reduce seed rates and,consequently, reduce the cost of cerealproduction.ROLE OF ZINC IN PLANTS Zinc exerts an effect on carbohydrate

metabolism through its effects onphotosynthesis and sugartransformations.

Zinc may play a role in themetabolism of starch because thestarch content, activity of the enzymestarch synthetase, and the number ofstarch grains are all depressed in zincdeficient plants.

The most fundamental effect of zinc isthrough its involvement in thestability and function of geneticmaterial.

In plants, zinc is considered to play acritical physiological role in thestructure and function of biomembranes.

Zinc is required for the synthesis ofauxin (a growth regulatingcompound-indole acetic acid, IAA).

ROLE OF ZINC IN HUMAN ANDANIMALS A review of a number of

investigations indicates that zinc

may be intimately involved inprotein, RNA, and DNA synthesis.

A number of physiological processesfor which zinc is required and over300 mammalian enzymes are zincdependent.

Zinc is especially important duringperiods of rapid growth, both preand post-natally, and for tissueswith rapid cellular differentiationand turnover, such as the immunesystem and the gastrointestinaltract.

Other critical functions that areaffected by zinc deficiency includepregnancy outcome, physical growth,susceptibility to infection andneurobehavioral developmen

FACTORS AFFECTING THEAVAILABILITY OF ZINC IN SOILS TOPLANTSZn deficiency can be caused by one ormore of the following factors:• Small amount of available Zn in the

soil.• Planted varieties are susceptible to

Zn deficiency (i.e., Zn-inefficientcultivars).

• High pH (close to 7 or alkaline underanaerobic conditions). Solubility ofZn decreases by two orders ofmagnitude for each unit increase inpH. Zn is precipitated as sparinglysoluble Zn(OH)2 when pH increasesin acid soil following flooding.

• High HCO3- concentration because ofreducing conditions in calcareoussoils with high organic mattercontent or because of largeconcentrations of HCO3- in irrigationwater.

• Depressed Zn uptake because of anincrease in Fe, Ca, Mg, Cu, Mn, andP after flooding.

• Formation of Zn-phosphatesfollowing large applications of Pfertilizer. High P content in irrigationwater (only in areas with pollutedwater).

• Formation of complexes between Znand organic matter in soils with highpH and high organic matter contentor because of large applications oforganic manures and crop residues.

• Precipitation of Zn as ZnS when pHdecreases in alkaline soil followingflooding.

• Excessive liming.



• Wide Mg:Ca ratio (i.e., >1) andadsorption of Zn by CaCO3 andMgCO3. Excess Mg in soils derivedfrom ultrabasic rocks.

• Zn deficiency is the most widespreadmicronutrient disorder in rice. Itsoccurrence has increased with theintroduction of modern varieties,crop intensification, and increasedZn removal. Soils particularly proneto Zn deficiency include the followingtypes:

• Neutral and calcareous soilscontaining a large amount ofbicarbonate. On these soils, Zndeficiency often occurssimultaneously with S deficiency(widespread in India andBangladesh).

• Intensively cropped soils where largeamounts of N, P, and K fertilizers(which do not contain Zn) have beenapplied in the past

• Sodic and saline soils• Peat soils• Soils with high available P and Si

status• Sandy soils• Highly weathered, acid, and coarse-

textured soils containing smallamounts of available Zn. Soilsderived from serpentine (low Zncontent in parent material) andlaterite.

• Leached, old acid sulfate soils with asmall concentration of K, Mg, and Ca

Higher concentrations of copper inthe soil solution, relative to zinc, canreduce the availability of zinc to aplant (and vice versa)

In waterlogged soils, such as paddyrice soils, reducing conditions resultin a rise in pH, high concentrationsof bicarbonate ions, sometimeselevated concentrations ofmagnesium ions and the formationof insoluble zinc sulphide (ZnS).

MECHANISMS OF ZINC UPTAKE BYPLANTS

Zinc appears to be absorbed byroots primarily as Zn2+ from the soilsolution and its uptake is mediated by aprotein with a strong affinity for zinc.

The transport of zinc across the plasma-membrane was towards a large negativeelectrical potential so that the process isthermodynamically passive. Thisnegative electrical potential of theplasma membrane is the driving forcefor zinc by means of a divalent cationchannel in dicotyledons andmonocotyledonsother than the Poaceae. In the Poaceaenon-protein amino acids called“phytosiderophores” form a complexwith zinc and transport it to the outerface of the root-cell plasma membrane.These phytosiderophores are releasedfrom the roots as a result of iron or zincdeficiency. This complex is thentransported to the cell via a transportprotein.

It has generally been recognizedthat zinc is transported in the planteither as Zn2+ or bound to organic acids.Zinc accumulates in root tissues but istranslocated to the shoot when needed.Zinc is partially translocated from oldleaves to developing organs.CORRECTION OF ZINC DEFICIENCYTHROUGH DIFFERENT ZINCSOURCES Organic Zn: Most organic wastes contain

small quantities of plant available zinc,typically ranging from 0.01 to 0.05%.

Inorganic Zn: Zinc sulphate is the most common Zn

fertilizer source, although use of Znchelates has increased.

Because of limited Zn mobility in soils,broadcasted Zn should be incorporatedwell especially in fine textured and lowZn soils.

Foliar Zn application is alsorecommended and is found to be moreeffective than soil applied Zn.

Damage to foliage can be prevented byadding lime to the solution or by usingurea with zinc sulphate solution.

Comprehensive soil testing isurgently needed to map the deficientareas so as the problem of hiddenmicronutrients deficiencies could betackled in advance to achieve the goal ofsustaining crop productivity and humanhealth.



Micronutrient Application: Scaling up the production and storage quality ofonion

Akhilesh TiwariSenior Scientist (Vegetable Science)

Department of Horticulture, JNKVV Jabalpur

Introduction:Onion is one of the most

important commercial vegetable cropsgrown in India. It is an important cropused raw, as a vegetable and spice allover the world. It is a bulbous biennialor perennial herb. Bulbs are formed bythe attachment of swollen leaf bases tothe underground part of stem vegetablecrops. It is grown in north as well asSouth India. The most important oniongrowing states are Maharashtra, TamilNadu, Andhra Pradesh, Bihar andPunjab. Characteristic flavor accountsfor its popularity. Onion are used assalad and cooked in various ways in allcurries, fried, boiled, baked, used insoup making, in pickles and for otherpurpose.

Fungicidal and insecticidalproperties of onion are well established.Dehydrated powder & flakes andpaste prepared out of onion provide richagro-industrial base for thesecommodities. This is one of thevegetables which are exported. Thenutritive value of onion varies fromvariety to variety. A general analysis isgiven below (Per 100 gm of edibleportion):

Moisture 86.8 gm Protein 1.2 gm

Fat Nil Minerals 0.4 gm

Fibre 0.6 gm Othercarbohydrates

11.0gm

Calories 49 Calcium 180mg

Phosphorus 50 mg Iron 0.7 mg

Riboflavin 0.01 mg Thiamine 0.08mg

Vitamin e 11 mg Nicotinic acid 0.4 mg

Small sized onions are more nutritive.The pungency in onion is due to avolatile oil (Allyl propyl disulphide).

Importance of micronutrientWhile much lower levels of

micronutrients are needed to satisfyyield and quality onion crop production,

the correct balance of these traceelements is essential. All micronutrientsplay a role in seedling and leaf growth.Without good leaf productivity, growthslows and yield suffers. Leaf tissueanalysis to assess micronutrient need,will enable deficiencies to be correctlydiagnosed and treated, and ensure thatonion production is maximized.

Role of Boron in Onion ProductionBoron is involved with carbohydratemetabolism and protein synthesis. Italso plays a key role in calciummovement within the plant.Boron and storage qualityBoron also influences storage quality ononions. This could be associated withthe micronutrient’s role in improvingcalcium accumulation in the bulb.

Boron effect at growth stages

Stage Boron effect

Pre-Planting Ensure good shootgrowth

VegetativeGrowth

Ensurephotosyntheticgrowth is notlimiting

Bulb Formation To maintain leafgrowth

Bulb Fill To improve storagequality and calciumuptake

General guidelines for BoronapplicationBoron is one of the essentialmicronutrients for onion production andshould not be limiting. While is quicklytaken up from the soil, it is relativelyimmobile in the plant, so foliar spraysare often more effective. It is importantto maintain the correct balance of



calcium, nitrogen and boron in the soil.High calcium and high nitrogen levelscan reduce boron uptake.

Boron deficiencies in onionYoung leaves develop yellow and greenmottling. Older leaves become yellowand dieback. Light yellow lines appearand develop into ladder-like transversecracks on the upper surfaces of olderleaves. They become brittle and deepgreen in color. Plants can be stunted ordistorted. Deficiencies are most commonon low pH and sandy soils as it is readilyleached.

Role of Zinc in Onion Production

Zinc is important for the developmentand function of growth regulators (e.g.auxin) that influence internodeelongation. It is also involved inchloroplast development and thusimportant for photosynthesis.

Zinc effect at growth stages

Stage Zinc effectPre-Planting Ensure good shoot

growthVegetative Growth Ensure

photosynthetic growthis not limiting

Bulb Formation To maintain leafgrowth

Bulb Fill Less critical, but tomaintain growth andprolong bulking

General guidelines for Zincapplication

Zinc uptake can be restricted byexcessive use of phosphorus. Thus it isimportant that zinc and phosphorus arebalanced, particularly during earlystages of growth.

Zinc deficiencies in onionDeficient plants are stunted and havetwisted, outward bending leaves. Olderleaves take on an orange mottledappearance. Younger leaves have a faintchlorosis and yellow striping. Bulbingcan be delayed and crops may not storewell. Problems are more common onhigh pH or calcareous soils or duringcold, wet weather.Role of Manganese in OnionProductionManganese is required for chlorophyllformation and oxide-reduction reactionsin cells. It is also involved in themetabolism and synthesis of proteins.

Manganese effect at growth stages

Stage Manganese effect

Pre-Planting Ensure good shootgrowth

VegetativeGrowth

Ensure photosyntheticgrowth is not limiting

Bulb Formation To maintain leaf growth




General guidelines for Manganeseapplication

As all other micronutrients, manganeseplays a role in seedling and leaf growth.Without good leaf productivity, growthslows and yield suffers.

Manganese deficiencies in onion Onions are very susceptible tomanganese deficiency. The outer leavesshow striped interveinalchlorosis. Thisdevelops into tip-burn and curlingleading to necrosis. Growth slows,plants become stunted and bulbformation is delayed. At maturity, bulbshave a thick neck. Deficiencies areworse on sandy soils and those with ahigh pH. Intermittent deficiencies arefound in poorly consolidated seedbeds orwhere soils are particularly dry.Role of Copper in Onion ProductionCopper has a key role to play in ligninformation. It is also linked to chlorophyllperformance.

Copper effect at growth stages

Stage Copper effect

VegetativeGrowth


BulbFormation

To maintain leaf growth

Bulb Fill For good skin quality

General guidelines for Copperapplication

Adequate supplies of copper areimportant for bulb skin and onion scaledevelopment, as a result of the element’srole in lignin production.

Copper deficiencies in onionA tip of young leaves turn white andtwist into a corkscrew or bend at rightangles. Bulbs have thin, yellow outerscales, are less solid, and are oftenearlier maturing. Deficiencies are morecommon on organic or sandy soils andwhere excessive nitrogen rates havebeen applied.Role of Iron in Onion ProductionIron is associated with chlorophyllformation and photosynthesis.

Iron deficiencyIron deficiency (left), complete nutrition(right)Iron effect at growth stages

Stage Iron effect

VegetativeGrowth


BulbFormation



General guidelines for Ironapplication

Applications of iron, such as foliar orfertigation, can be used to increase earlyleaf production and crop productivity.

Iron deficiencies in onionGenerally, onions appear insensitive toiron deficiency, with most soilssupplying adequate levels of iron to meetcrop needs. Under extreme deficiencies,leaves become completely chlorotic andbleached.



Role of Molybdenum in OnionProductionMolybdenum is an important componentof nitrate reductase and thus involved innitrogen metabolism as well as thesynthesis of pigments and chlorophyll.

Molybdenum effect at growth stages

Stage Molybdenum effect

VegetativeGrowth


BulbFormation



General guidelines for MolybdenumapplicationAs all other micronutrients,molybdenum plays a role in seedlingand leaf growth. Without good leafproductivity, growth slows and yieldsuffers.

Molybdenum deficiencies in onionDeficiency in new crops results in poorcrop emergence and seedling death. Inestablished crops, lack of molybdenumleads to leaf tip dieback with wiltedtissue between the necrotic and healthyareas. Problems are most common onacidic or sandy soils with low organicmatters.



INM: A key to improve and sustain soil health

Hitendra K Rai

Senior ScientistDepartment of Soil Science & Agricultural ChemistryJawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur

IntroductionThe high productivity levels to meet thechallenges of feeding the growing populationhas been achieved during few decades ofrecent past as a result of introduction ofhigh yielding inputs responsive cropvarieties, use of high analysis fertilizers andimproved pest management practices. Inlong term, continuous use of high analysisfertilizers leads to degradation of soil healthmainly because of excess mining of allessential plant nutrients which necessitatesrelooking the production system in terms ofsoil health for sustaining the productivity.Prior to the discovery of inorganic fertilizersin the nineteenth century, soil fertility andnutrient supply were maintained byreturning organic matter to the soil andthrough regular rotations and fallowperiods. Adequate plant nutrient supplyholds the key to improving the food grainproduction and sustaining livelihood.Nutrient management practices have beendeveloped, but in most of the cases farmersare not applying fertilizers at recommendedrates. They feel fertilizers are costly and notaffordable and due there is a risk. Therefore,a holistic approach of integrated nutrientmanagement (INM) by the application ofbalanced nutrients amalgamated throughinorganic and organic sources needs to beconsidered as a key for improving the soilhealth and its sustainability to reverse thetrend of yield decline. It will improve the soilhealth and sustainability and at the sametime also enhance the inputs (nutrient andwater) use efficiency and system’sproductivity. Therefore, integrated nutrientmanagement which involves integrated useof organic manures, crop residues, greenmanures and biofertilizers etc withinorganic fertilizers could be considered as akey for improving the soil health andsustainability.

The necessity for INM:There is a need to accept a widerconcept of nutrients use includinginorganic fertilizers and organic sourcesbased on several altering circumstancesand developments which may be asbelow: The need for a more rational use of

plant nutrient for optimizing cropnutrition by balanced, efficient, yield-targeted, site and soil specificnutrient supply.

A shift from use of inorganicfertilizers to combination of inorganicand organic sources of nutrientsobtained at on and off farm.

A swing from supply of nutrients onthe basis of individual crop tooptimum use for a cropping systemsor crop rotation.

A change of consideration for directeffect of fertilization to long termdirect plus residual effects. To a largeextent, this is accomplished wherecrop nutrition is on a croppingsystem basis rather than on a singlecrop basis.

A shift from static nutrient balanceto nutrient flows in nutrient cycles.

Emphasis on monitoring andcontrolling useless side–effects offertilization and possible adverseconsequences for soil health, cropdisease and pollution of water and air.

A shift from soil fertility managementto soil health management whichincludes amelioration of problem soilsand consideration of crop resistanceagainst stresses

An alteration from exploitation of soilfertility to its improvement or at leastmaintenance.

A swing from the ignorance of on-farm and off-farm wastes to theireffective utilization through recycling.

A. Concept of INM



The basic concept of integratednutrient management (INM) orintegrated plant nutrition management(IPNM) is the maintenance oreadjustment of soil fertility/productivityand of optimum plant nutrient supplyfor sustaining the desired cropproductivity through optimization of thebenefits from all possible sources ofplant nutrients including locallyavailable once in an integrated mannerwhile ensuring environmental quality.Practically a system of crop nutrition inwhich nutrients need of plants are metthrough a preplanned integrated use ofinorganic fertilizers, organic sources ofplant nutrients (green manures,recyclable wastes, crop residues, FYM,vermicompost etc.), and bio-fertilizers.The appropriate combination of differentsources of nutrients varies according tothe system of land use and ecologies,social and economic conditions at thelocal level. Integrated use of inorganic,organic and biological sources of plantnutrients and their differentmanagement practices have atremendous potential not only insustaining agricultural productivity andsoil health but also in meeting a part ofchemical fertilizers requirement fordifferent crop and cropping systems.

B. Goals of INM: The key goals of INMare:

i) To maintain soil productivityii) To ensure productive and

sustainable agricultureiii) To reduce expenditure on inputs

by using farm wastes, animalmanure, crop residues bio-fertilizers etc. at farm level.

iv) To utilize the potential benefits ofgreen manures, leguminouscrops and biofertilizers

v) To prevent degradation of theenvironment

vi) To meet the social and economicaspirations of the farmerswithout harming the naturalresource base.

C. Components of INM: The relativecontribution of each component toINM for a farming system dependsmainly on their local availability andsocio-economic factors. The majorINM components are as follows:

1. Chemical Fertilizers: There hasbeen a big gap between annual drain

of nutrients from the soil due to cropremoval and soil erosion and thenutrient inputs from existingsources. Present estimates show adeficiency of 10 million tones of NPKwhich is likely to grow with furtherintensification in agriculture andincreasing soil degradation. Keepingin view the conservative populationestimates and minimum calorierequirement of food, the country willneed to produce at least 300 milliontones of food grains by the year2020, which will necessitate the useof 30 to 35 million tones of NPK ofvarious sources. In addition, highvalue crops having export potential,which may even claim fertilizer useon priority basis, will need 14 to 15millions of NPK (Manna and Ganguli,1998). Thus from both organic andinorganic sources the country will berequired to arrange about 40-50million tones of primary nutrient andmost of this would have to comefrom indigenous sources. Apart of it,particularly all K and feed stock ofphosphatic and some nitrogenousfertilizer will continue to beimported. Wide deficiency ofmicronutrients such as Zn, Fe, Mn,Cu and B indicates that the cropdemand for these micronutrients by2025 will be very high.

2. Organic Sources: The productionof rural and urban compost hasbeen 297.2 million tones and 6.6million tones, respectively. Presentcontribution from organic sources isestimated to be 4-6 million tones N +P2O5 + K2O, through the totalnutrient potential of these resourcesranges somewhere between 10 and16 million tones. There are differentorganic sources for nutrients. Theseare - a) Farm Yard Manure (FYM)generated from the wastes of cattle,sheep, goat, etc. reared by farmers.b) Compost generated from theaerobic or anaerobic decompositionof farm wastes like leaf litter, stalksweeds, etc.) Vermi-compostgenerated from the excreta ofearthworms reared on farm wastes.d) Oil cakes of different oil seeds likepongamia, caster, neem, karanj etc.(most other edible oil seed cakes areused as animal feeds, poultry feeds



and fish feeds). Use of organicsources with fertilizers can take careof the widening N: P: K ratio andemerging problems of themicronutrient deficiency.

3. Green manure: Green manure hasa greatpotential tobe used forthebetterment ofthe IndianAgriculture.Raising agreen manure crop even for a shortperiod of 45-50 days would addsubstantial quantity of nutrientsupon incorporation in to the soil.Green manures crop include such asSesbania, Cowpea, Sunhemp, etc.and green leaf manures likeSubabul, Caliandra, etc. Green leafmanuring from the avenue and bundgrown trees like Pongamia, Neem,Glyricida and Leucaena should formpart of the crop managementsystem.

4. Biofertilizers: Several studiesclearly indicate that among thedifferent types of biofertilizersavailable at present, Rhizobium isrelatively more effective and widelyused. Considering an average Nfixation rate of 25 kg N ha-1 byapplication of Rhizobium. On theother hand Azotobactor, which isused in non –legume crops has giveninconclusive results. The use ofAzospirillum inoculation in non-legume crops as biotic N sourceshould be advocated. Similarly, BlueGreen Algae (BGA) applied at 10kg/ha fixes 20kg N/ha. Biofertilizersare also associated with theliberation of growth substanceswhich promote germination andplant growth. As regards phosphate,several phosphate solubilizingbacteria are known to mobilize thesignificant quantities of soilphosphate that would otherwise notbe available to the plant, but theireffectiveness is variable and notpredictable. VAM has also favorableeffect on P uptake and utilization.Thus, Rhizobium, Azotobactor,Azospirillum, Blue-green algae,Azolla are used for fixing the

atmospheric nitrogen by symbioticand non symbiotic means in plantavailable form. While, Phosphatesolubilizing bacteria and mycorrhizalfungi (VAM) are used for solubilizinginsoluble phosphorus to availableform.

5. Leguminous crops: Crop rotationinvolving legumes and spatialarrangement of crops toaccommodate legumes aid in fixingthe atmospheric nitrogen in t helegume rhizosphere in varyingquantities depending on the species.Major part of this can be madeavailable to the succeeding crop byfollowing appropriate technologies.Thus, the quantity of nutrientsrequired to be applied for thesucceeding crop can be substantiallyreduced.

6. Crop residues: Crop residues areparts of the plant left in the fieldafter crops have been harvested andthreshed or left after pasture aregrazed. In India about 100 milliontones of crop residues are availablefor recycling in agriculture annually.Crop residue when incorporated alsoimproves the physical, chemical andbiological properties of the soil.Management of crop residues iseither through of the following threemethods; removal, burning or



incorporation in soil. Burning is aminor practice in India and burnsthe residues causing loss of preciousorganic matter, plant nutrients andenvironmental pollution .Rainfedsoils are deficient in organic matter.There is need to replenish it by everypossible means to sustain soilproductivity. Crop residues arereservoir of plant nutrients(especially K) and improve soilphysical and biological propertiesand protect the soil from wind andwater erosion. Beneficial effects ofcrop residue incorporation in rainfedsoils on yields of crops have beenwidely reported.

7. Agro-industries: Agro–industries aredependent on agriculture for theirraw material. The byproducts ofthese agro industries can be utilizedas a source of organic manure forimprovement of soil fertility.Sugarcane is grown in 3.7 m ha inIndia. An estimated 12 million tonesof trash, 5 million tones of bagasseand 5 million tones of press mud canprovide substantial quantities ofnutrients and organic matter. Pressmud is a good source of organicmatter and phosphorus. Raw pressmud can be used as an amendmentin saline soil but composting it withearthworm and bio-inoculants willenhance its manorial value. Bagasse,though a high carbon material, canbe good organic manure, when it iscombined with FYM or green manureand applied to the field. Molassescan be applied to saline-alkali soilalong with press mud as anamendment. Coir pith is a byproductfrom coir industries. Raw andcomposted coir pith (inoculated withpleurotus spp. and 5 kg urea/t) is

presently used for increasing theyield of crops (10-45%) and forenhancing the soil moisture content(Parle, 1968). Distillery sludge, anagro-industrial waste, can also beprofitably utilized to the crop field forone or two years with reduced levelof fertilizers for higher crop yields(Rohilla, 2004). Use of industrial byproducts in rainfed acid soils canhelp in increasing the availability ofplant nutrients. Lime fromsugarcane and paper mills isavailable as suitable liming materialsfor managing acid rainfed soilbesides being sources of severalother plant nutrients. Limeapplication is considered to beadvantageous for increasingproductivity of various crops andcontent of Ca. Most commonly usedliming materials are burnt lime,quick lime, slaked lime, calcitic anddolomitic lime stone. Gypsum andphosphogypsum are potentialsources for S and Ca nutrition ofplants grown in acid soils.

D. INM in soil fertility and cropproductivity

The substitution of fertilizer Nrequirement to 50% by FYM has givenyield levels nearly similar to thoseobtained with complete fertilization. Theapplication of FYM not only increase thenitrogen use efficiency of urea, but alsoincreases the fertility status of the soilCombined use of organic manures andfertilizers is the ideal way to sustain soilproductivity. Panda and Sahoo (1989)summarizing the results of rice basedcrop sequence on Alfisols clearlybrought out the beneficial effect oforganic manure in enhancing nutrientuse efficiency. Results obtained so farpoint to the conclusion that 50 per centof the nutrient requirements can besupplemented by organic sources likeFYM. Organic sources provide additionalbenefits by improving soil physicalcondition. Hadimani et al (1982)observed in a six year study on anAlfisols increase in organic mattercontent of soil to 0.9 per cent from theinitial value of 0.55 per cent. In a long-term experiment on the Alfisols ofBangalore highest finger millet yieldswere maintained where FYM andfertilizers were used in an integrated



manner an excellent example ofenhancing rainfed finger millet grainyield at Bangalore due to FYM andfertilizer.

Green manure is one of the mosteffective and environmentally soundmethods of organic manuring thatoffers an opportunity to cut down theuse of chemical fertilizers. In situgrowing of green manure crop is ratherdifficult under dry land condition dueto loss of time for planting the maincrops, loss of valuable moisture and thedoubtful returns on the energy andinputs spent for growing the greenmanures crop especially when theseason is not favorable. However, greenmanuring as an inter cropping practicecould find place in red soils. Greengram grown in the inner space ofupland rice and cowpea beforetransplanting of medium land riceturned 6 weeks later showed a benefitequivalent to 30 kg N ha-1 in rainfedacidic red loam soils of Jharkhand. Thepractice of applying green leaves andlopping of N fixing trees has producedhigher yields in many situations thanapplying the same rate of fertilizer N. A5- year study on an Alfisols atBhubaneswar, Orissa showed that 30kg N through inorganic 30 kg organics(gliricida, water hyacinth or FYM) gavehigher yields of finger millet comparedto 60 kg N+40 kg P2O5+ K2O ha-1

through fertilizers.In Alfisols of Bangalore, it was

observed that incorporation of cropresidues in soil having low organicmatter content led to perceptibleimprovement in the fertility status andsoil physical properties. The maize yieldover a 5 year period increased by 25 percent with maize residue at 4 t ha-1 peryear. In an another study conducted onAlfisols at Hyderabad, on-farm residuemanagement was compared with otherbulky organic manures like cattlemanure and compost over seven yearswith per millet and cowpea as test crop.The crop residue enhanced the yield ofper millet. Yield of cowpea increasedwith all types of manures. Theincorporation of residues madesignificant improvement in soilstructure, stability of aggregate andhydraulic conductivity. Vekateswarlu(1984) also showed that residue

incorporation improved stability ofaggregates in both loam and sandyloam Alfisols. At Akola, crop residuesapplication increased sorghum grainyield by 20 per cent in Sorghum +Pigeon pea intercropping system.Hundekar et al (1999) reportedsignificant increase in Rabi Sorghumyield due to added six different cropresidues with 100% RDF in Vertisols.

Amelioration of soil acidity isindispensable to increase the fertilizeruse efficiency of crops and cropssequences. For economic and efficientuse of fertilizers, liming is important toincrease base saturation and inactive Al3+, Fe 2+ and Mn 3+ in soil solution. Forefficient N fixation and therebyincreasing P availability, liming isimportant. Review of plant research(Sarkar et al 1989) shows that forstability in crop production of Alfisols,fertilization with liming is crucial. Thetotal of NPK and micronutrients bywheat – soybean crop sequence on acidAlfisols of Ranchi indicates that there isneed to apply lime along with fertilizersto mitigate deficiencies of plantnutrients in rainfed acid soils ofJharkhand. The response of lime alongwith NPK application to different cropsin India is reported by several workers.The response of liming was 23.6 percent higher in pea when it was usedalong with recommended dose of NPKfertilizers Sarkar et al (2004). Sulphur is now accepted as thefourth major plant nutrient along withN,P and K. Inclusion of S is essentialalong with application of NPK fertilizersfor obtaining higher crop productivity.Sulphur deficiencies are being reportedmore and more in acid rainfed areas ofJharkhand (Singh et al 2000). Fieldexperiments on Niger, groundnut,mustard lentil, black gram and soybeanwith S along with recommended dose ofN, P and K fertilizers were conducted inS deficient acidic rainfed soils ofJharkhand. The sources of S weregypsum, phosphogypsum and lowgrade pyrites. Results reveal thatapplication of gypsum andphosphogypsum were superior for basalapplication compared to low gradepyrites in these soils. Significantremarkable increase these crop yieldsand quality was obtained due to S



added through gypsum andphosphogypsum. Gypsum was the mosteffective S source in groundnut due topresence of Ca which helps in podformation. Pyrites application isadvocated as broadcast 3-4 weeksbefore sowing the crop in order toprovide time for oxidation andconversion to plant available sulphateform. Rhizobium inoculation has nowbecome a practice for introducedlegume crops. In India, a lot of workhas been conducted on agronomic useof Azotobactor and Azospirillum. Duringthe crops tested sorghum, pearl milletand finger millet appeared to beconsistently responsive its inoculationat more than one location (Tilak andSubba Rao 1987). Azospirillum seedinoculation has been reported toincrease 20-30 kg N ha-1. Desal andKonde (1984) from field trials inMaharashtra observed that grain anddry matter yields of sorghum wereincreased by seed inoculation withAzotobactor chroocooccum andAzospirillum brasilense. Use ofAzotobactor has been tested for uplandrice in rainfed acidic soils of Jharkhand(Singh et al., 2002). Results reveal asignificant increase in grain yield ofupland rice due to Azotobactorinoculation. Capitalization of legume effectis one of the important strategies oftapping additional nitrogen throughbiological N fixation. The contributionof legumes in cropping systems towardsthe yield and soil fertility have beenreviewed by Singh and Das (1986) andReddy et al (1988).The effect ofpreceding crops on the succeeding nonlegumes crops have been studied at anumbers of locations. The legume waseither as a monsoon or a post –monsoon crop. Short duration fodderlegumes like cowpea, cluster bean,moth bean and soybean were found tobe enriching the soil fertility. Das et al(1990) in five year rotation of castorwith sorghum, sorghum + pigeon peaand green gram + pigeon pea in anAlfisols of Hyderabad observed thatgreen gram + pigeon pea intercropsystem had a positive balance of 97 kgha-1 total nitrogen in soil.Comprehensive study on the

contribution of legume crop in croppingsystem has also been made recently byKatyal and Das (1993).

E. Constraints in adoption in INM1. Non- availability of INM2. Difficulties in growing green

manure crops3. Non- availability of biofertilizers4. Non-availability of soil testing

facilities5. High cost of chemical fertilizers6. Non-availability of water7. Lack of knowledge and poor

advisory services8. Non-availability of improved

seeds9. Soil conditions10. Non-availability of credit facilities

F. Research gaps in INM1. Mismatching of INM practices

developed at research stations withthe farmers resources and theirpractices;

2. INM recommendations for differentcrops are not based on soil testingand nutrient behavior of themanures;

3. Nutrient balance/flow analysis vis-à-vis soil fertility managementpractices with special reference toINM at farm level needs to be workedout;

4. Nutrient release characteristics offarm residues in relation to theirquality to develop decision supportsystems;

5. Biofertilizers were not includedas component of INM in many cases;

6. Integrated Farming Systems (IFS)approach needs to be encouraged forsustaining livelihood in rural areasparticularly for small and marginalfarmers;

H. Adoption of INM During the adoption of INM, special

attention should be given to sources ofnutrients that may be mobilized by thefarmers themselves (manure, cropresidues, soil reserves, BNF, etc).Minimization of losses andreplenishment of nutrients from bothinternal and external sources of majorinterest. While INM strives for integratedapplication of diverse inputs, the use oforganic sources cannot replace the use



of mineral fertilizers. Although theeffects of organic inputs go beyond thenutritional aspects, by contributing toimproving soil physical properties and tobetter efficiency of fertilizers use, therecycling of organic materials does notsuffice to fully replenish the nutrientthat are removed by crop harvest.

I. Current status of INMKeeping the importance of

organic resources in view, a lot ofresearch has been done on integratednutrient management during last twodecades in natural resourcemanagement institutions and stateagricultural universities. Theseresearches will lead to:

Development of INM practices formajor crops

Understanding the enhanced role oforganic manures in increasing inputuse efficiency due to their favorableeffect on physical, chemical andbiological condition of the soil.

Establishing the beneficial role ofintegrated use of organic manures inimproving nutrient cycling in differentproduction systems in various types ofsoils.

Beneficial role of INM in improving soilchemical, physical and biologicalquality for sustainable cropproduction.

The work on INM has been compliedand published in the form ofbooks/bulletins by severalinstitutions.

Conclusions Soils in the rainfed agro eco-systemare invariably poor in moisture contentand fertility status of nutrients. There isneed for integrated use of inputs inagriculture such as nutrients and waterthrough synergistic combination in aholistic manner to improve nutrient useefficiency crop productivity in rainfedagro-ecosystem. The nutrient useefficiency in rainfed agro-ecosystemshould be improved through optimizingthe nutrient levels with the limitedavailability of water, and by followingintegrated plant nutrient supply system.The major sources of plant nutrients arechemical fertilizers, organic sources,green manures, biofertilizers,leguminous crops, crop residues andagro industries. No single source canmeet the increasing nutrients needs of

rainfed crops. There is need to integrateboth organic and inorganic sources ofnutrients for improving soil fertility andachieving higher productivity of rainfedcrops. There is also need to more thruston use of locally available sources ofnutrients and biofertilizers in order toreduce requirement of chemicalfertilizers so that nutritionalrequirement of rainfed crops is met at alow cost.References1. Das S. K, Rao, A.C. and Sharma, K.

L (1990) Legume based croppingsystem for sustainable yield of graincrops under dry land condition. In:International symposium on naturalresources management forsustainable Agriculture. New Delhi,6-10 February.

2. Desal, A. G and Konde, B.K (1984).J. Maharashtra Agril. Univ., 9: 169-170.

3. Hadimani, A.S. Hegde, B.R andSatanaryana, T (1982). In: Review ofSoil Science Research Part II, XIIInt. Cong of Soil Sci, New Delhi 689-700.

4. Katyal, J. C. and Rattan, R. K(1990) Micronutrient use inNintee’s. In: Soil Fertility andFertilizer use –Nutrientmanagement and Supply system forsustaining Agriculture in 1990’s vol.IV IFFCO, New Delhi, PP, 119-135.

5. Katyal, J.C. and Das, S.K. (1993)Fertilizer management in foodcrops. H.L.S. Tandon (Ed.) Fertilizerdevelopment and consultationorganization pp 61-78.

6. Panda, N and Sahoo, D (1989).Ferti. News 34 (4) 71.

7. Reddy G. Subba, Das S.K. andSingh R.P. (1988). Prospective ofgreen leaf manuring as analternative to fertilizer nitrogen indry land forming systems. Paperpresented at the nationalsymposium on recent advances indry land agriculture, CRIDA,Hyderabad.

8. Sarkar A.K., Mathur B.S., Lal S.and Singh K.P. (1989). Fert. News.34 (4) 71

9. Sarkar A.K., Singh Surendra, SinghR. N. and Saha P.B (2004)Integrated Nutrient ManagementPractices for Crops (Results from



farmers field trials of Jharkhand)SSAC (BAU) Tech. Bull. No.1/2004PP13-14

10. Singh R.N., Binod Kumar, PrasadJanardan and Singh Surendra(2002). Integrated nutrientmanagement practices on rice cropin farmer’s field. Journal ofResearch, BAU ,14 (1) 66-67.

11. Singh, R.N. (2007). In: Consolidatedreport –ICAR, Integrated nutrientmanagement in rice based croppingsystems in copper mines area ofeast Singhbhum for higherproductivity

12. Singh, R. P. and Das, S. K (1986)Prospects of fertilizer use in drylands of India. Fertilizer Industry,181- 190.

13. Singh, Surendra, Sarkar, A.K andSingh, K.P (2000) Sulphur researchin soils and crops of Bihar plateau.SSAC (BAU) Res bull. 1/2000.

14. Singh, Surendra, Singh, R. N.,Prasad, Singh, B.P and KushwahaA.K. (2008) Integrated nutrientmanagement for sustainable

productivity of rainfed rice. India J.of Fert. 4(3) pp 25-28&31-32.

15. Singh, Surendra, Singh, R.N.,Prasad, Janardan and Kumar Binod(2002). Effect of green manuring,FYM and Biofertilizer in relation tofertilizer nitrogen on yield andmajor nutrient uptake by uplandrice J. Indian, Soc. Soil Sci. 50 (3)313-314.

16. Tilak, K.V.B.R and N. S. Subba Rao(1987) Association of Azospirillumbrasilence with pearl millet(Pennisitum americanum L.). Biologyand Feril. of Soil. 4 ;97-102.

17. Venkateswarlu, J. (1984) In :Nutrient management in dry landwith special reference to croppingsystem and Semi arid Red soils. AllIndia Coordinated Research projectfor dry land Agriculture, Bull. No. 1-56.



Resource Conservation through Herbicide Resistance managementM.L.Kewat

Principal scientist (Agronomy)JNKVV, Jabalpur (M.P.)

[email protected]

1. IntroductionHerbicide resistance in weeds is aworldwide phenomenon, and thenumber and frequency of resistantbiotypes have expanded in recent years,particularly in developed countrieswhere herbicides are used intensively.Currently the use of herbicides in Indiais low. Yet wheat farmers particularlywhere rice-wheat cropping system isfollowed have been the victims of thisproblem in the recent past. Continuoususe of isoproturon since the last 15 to20 years to control Phalaris minor inwheat has resulted in the developmentresistant biotypes of the weed. This isbecoming a potential threat tosustainability in rice-wheat croppingsystem, which is an important,widespread and most remunerativecropping system followed in irrigated,fertile north-western plains of India.2. What is Herbicide Resistance?

Following application ofherbicides, three types of plantresponses are recognized i.e.susceptibility, tolerance and resistance.Susceptibility is the lack of capacity towithstand herbicide treatment so thatthe plant is damaged by the herbicides.Tolerance is the ability to continuenormal growth and function whenexposed to a potentially harmful agent,generally due to differences in uptake,translocation and metabolism of theherbicide. Tolerance of course is dose-dependent. At very high doses no plantmay be tolerant. Definitions ofresistance have been given by manyauthors. Holt and LeBaron (1990)opined that any definition of resistanceshould have some relevance to thedoses of herbicides recommended foruse in the field. Powles et al.(1997)defined herbicide resistance as theinherent ability of weed population tosurvive a herbicide application that isnormally lethal to vast majority ofindividuals of that species. Thus,

herbicide resistance is simply an alteredresponse to a herbicide by a specieswhich was earlier susceptible. It isnaturally occurring, irreversible andheritable.3. Cross , Multiple Resistance and Co-resistance

Cross resistance is aphenomenon whereby followingexposure to an herbicide a weedpopulation evolves resistance toherbicide from chemical classes to whichit has never been exposed. Multipleresistances are the phenomenon ofresistance to herbicides from more thanone chemical class to which apopulation has been exposed (Holt et al.,1993). Rubin (1991) considered that theterm cross-resistance should be used todescribe cases in which a weedpopulation is resistant to two or moreherbicides by the presence of a singleresistance mechanism For exampleCommon cocklebur resistant tochlorimuron may also be resistant toimazaquin with the same mode ofaction(ALS inhibitor) . In contrastmultiple resistance should be used incase where resistant plants possess twoor more distinct resistantmechanisms.For example Commonwaterhemp (Amaranthus tuberculatus)isresistant to both triazine and ALSinhibitor,which have two different modeof action. However , when weed developsresistance to both mixing partnerherbicides of a mixture appliedconcurrently called co-resistance/compound resistance. For exampleLolium rigidium developed resistance toAmitrol and Atrazine appliedconcurrently.4. Current Status of HerbicideResistant Weeds

In contrast to resistance toinsects, pests and pathogens, therecognition of herbicide resistance inweeds is a relatively recent one.However, since the detection of a triazine



resistant weed (Senecio vulgaris) in 1968(Ryan, 1970), there has been a steadyincrease in the number of resistant weedspecies and classes of herbicides towhich resistance has evolved.International Survey of HerbicideResistant Weeds in 1995-96 recorded183 herbicide resistant weed biotypes in42 countries. In 1997, there were atleast 61 weed species (43 dicotyledonous

and 18 monocot weeds) resistant totriazine herbicides. In addition, at least63 species had biotypes resistant to oneor more herbicides from 15 otherherbicide classes (Table 1). Today, over315 biotypes belonging to 183 species(110 dicots and 73 monocots) from 59countries are resistant to herbicides(http://www.weedscience.org.2007).

Table 1. Occurrence and distribution of herbicide resistant weed biotypes

Herbicide classYear of

first detection

Number ofresistant weed

biotypes

Number of

countries

ACCase inhibitors 1982 13 11

ALS inhibitors 1986 33 11Amides 1986 2 2

Aminitriazoles 1986 4 2

Arsenicals 1984 1 1Benzonitriles 1988 1 1

Bipyridiliums 1976 27 12Carbamates 1988 2 1Dinitroanilines 1973 6 4Phenoxyacetic acid 1962 14 11

Unclassified 1988 2 2Pyridazinones 1978 1 3Substituted ureas 1983 14 12Triazines 1968 61 20Uracils 1988 2 1

(Modified from Holt et al.t 1993; Heap, 1997)

Herbicide resistance is a worldwidephenomenon. Resistant weeds havebeen recorded in most states of the USA(49 biotypes), I most provinces ofCanada (22 biotypes), 18 European and22 other countries. The most widespreadtype of resistance, worldwide, is theresistance to triazine herbicides. Thespecies in which resistant biotypes havebeen detected most frequently are:Amaranthus hybridus, A. retroflexus,Kochia scoparia, Chenopodium album,Senecio vulgaris, Solarium nigrum andPoa annua.

The predominance of triazineresistant weeds was mostly due to thewidespread use and effectiveness of

atrazine for weed control in maize.Triazine resistant weeds accounted forabout 70% of the documented cases ofherbicide resistance by 1983. With theintroduction of herbicides with newmode of action, in the late 1970s andearly 1980s, the proportion has changedas greater number of cases of evolvingresistance to these herbicides weredocumented (Table2). Multipleresistance has evolved in somepopulations of Alopecurus myosuroidesin Europe (Moss, 1990; Kemp et al.,1990) and numerous populations ofLolium Hgidum in Australia (Hall et al.,1994).



Table 2. Global herbicide sales and cases of herbicide resistanceHerbicide group Percentage of

herbicide sale in1994

Percentage ofresistance biotype

(1997)

Percentage of newlyreported cases ofresistance (from

1984-97ALS inhibitors 17 18 27

Triasines 12 32 16

Amide and phenyl ureas 16 9 12

ACCase inhibitors 5 7 9

Dinitronni lines 5 3 4

Bipyridiliums 4 15 15

Synthetic Auxins 4 8 6

Glyphosate 11 0.8 0.7

Others 26 6.2 10.3

Simple resistance and crossresistance could be managed withreasonable success in many countries,usually by the use of alternativeherbicides. However, multiple-resistanceis of particular practical concernbecause it is complicated, intractableand least predictable, and resistancecan occur simultaneously to most or allherbicides options available to a grower.5. Resistance of Phalaris minor toIsoproturon in India

The use of herbicide is quite lowin India. Among the pests the losses dueto weeds are highest in India. But theshare of herbicide use is lower than thatof insecticides as opposed to that in theworld (Table 3) However, in some regionsthe herbicides have been in use andpopular since last 10 to 12 years but infuture it is likely to increase due to

labour shortase in India and in theworld.

Rice-wheat cropping system is animportant one in India food securitysystem and is followed in about 14.5 Mha. Littleseed canarygrass (Phalarisminor) a grassy weed, morphologicallysimilar to wheat plant in its vegetativephase and very competitive, hasestablished itself as number one pest inwheat from sixties particularly whererice-wheat system is followed. Herbicideisoproturon has been used mostcommonly for its control for more than15 years. However, from 1990 onwardsthere have been increased reports poorcontrol of this weed which was laterconfirmed as development of resistance(Malik and Singh, 1996; Yuduraju andSingh, 1997).

Table 3.Consumption pattern of pesticides in India and the worldItems Percentage use (India) Percentage use (World)Insecticides 70 30.0Herbicides 12 44.0Fungicides 8 21.0Others 10 5.0Source: Bami (1996)6. Development of HerbicideResistance

Over-reliance and continuousand repeated uses of a herbicide orherbicides having same mechanism ofaction in intensive agriculture orhorticultural systems involving cropmonoculture, and minimum tillage havebeen the major causes of occurrence of

herbicide resistance. Factors which aregenerally responsible for thedevelopment of herbicide resistance aredescribed as follows:6.1 Initial Frequency

It is generally believed thatresistant genotypes exist in naturalplant populations in varying frequency.The development of resistance on a field



scale depends on the rate of increase inthe proportion of the resistant genotypewithin a population. Repeated use ofsame herbicide, or herbicides havingsame mechanism of action, results inkilling of the susceptible biotypesallowing resistant individuals tomultiply. Thus, within a few seasons ofapplication the whole population isdominated by resistant biotypes. Theinitial number of resistant individuals ina population will dramatically influencethe rate of development of resistance.Darmency and Gasquez (1990) found anaverage frequency of 3 x 10-3 triazineherbicide resistant individuals in apopulation of Chenopodium album andPowles et al. (1997) reported an averagefrequency of 1 x 10-2 diclofop-methyl-resistant individuals in a population ofLolium rigidum.6.2 Selection pressure

All factors / measures that willresult in better and efficient control ofsusceptible weed population imposehigh selection pressure for thedevelopment of resistant population.Application of herbicides having singletarget site and specific mode of action,longer soil residual effect, and frequentapplication over several growing season,without rotating or combining with othertype of herbicides, impose high selectionpressure (Holt and LeBarron, 1990). Aherbicide the controls 95% of thesusceptible population will result indevelopment of herbicide resistance.6.3 Fitness

Fitness measures the potentialevolutionary success of a genotype thatcombines both survival andreproduction. Resistant populations maybe less fit as in case of triazine resistantweeds, more fit or remain unchanged ascompared to susceptible population.This is assumed to be the generalphenomenon and an inning feature ofthe herbicide resistance trait.Populations with higher ecologicalfitness are cause for greater concern.6.4 Seed bank in the soil

The seed bank in soil can exert astrong buffering influence in delayingappearance of resistance. For thespecies in which seeds remain residualin the soil seed bank, the appearance ofresistance will be delayed by thecontinued recruitment of susceptible

individuals from the seed bank. Thus,the importance of the buffer dependsmainly on the germination dynamicsand tillage or cultivation practicesfollowed. Minimum tillage is, therefore,expected to encourage fasterdevelopment of resistance as thebuffering of seeds (belonging to relativelymore susceptible population) burieddeep is prevented.

Among other factors, the mode ofinheritance of resistance, gene flow,mode of pollination and levels of geneticexchange with susceptible populationsare important. Most cases of herbicideresistance are due to the action of asingle gene with a high degree ofdominance.7. Herbicide Resistance Mechanisms

The resistance in weeds toherbicides could be attributed & eitherone or more of the followingmechanisms:7.1 Altered site of action

Herbicides inhibit or kill plantsby inhibiting or preventing a biochemicalreaction in the plant. The site at whichthe herbicide exerts its influence iscalled the biochemical site of action. Thebinding site in resistant biotype is somodified that the plant remainsunaffected. This mechanism is involvedin the resistance of weeds to most of thetriazines. acetelactate synthase (ALS)inhibitors and dinitroaniline herbicides.

Triazine herbicides are primarilyphotosynthesis inhibitors and inresistant biotypes, the loss of herbicidebinding ability occurs due to analteration of the binding site on thethylakoid membrane of the chloroplast.Site alteration results from a pointmutation in the chloroplast Pab a gene,encoding herbicide-binding protein, dueto single base change of serine to glycineat amino acid position 264 (Gronwald,1994).

The enzyme acetolactateaynthase (ALS) or acetohydroxy acetonesynthase (AHAS) catalyses the firstreaction in the production of branchedchain amino acids - isoleucine, leucineand valine. The ALS in plants resistantto ALS-inhibitor herbicides, such assulfonylureas or imidazolinones isaltered to make it less sensitive toherbicides (Chaleff and Ray, 1984; Saariet aL, 1990; Subramanian et al., 1990).



Dinitroanline herbicides inhibitthe formation of microtubles andthereby block mitotic cell division insusceptible plants. An altered target sitewas found in a biotype of Eleusine indicawhich is highly resistant todinitroanilines. Resistance in thisbiotype is conferred by an altered formof tubulin that results in microtubuleinsensitivity to the dinitroanilines(Vaughn and Vaughan, 1990).7.2 Enhanced metabolism

Rapid degradation and/orconjugation of herbicides into non-toxicor less-toxic forms are amongst themajor factors responsible for selectivityof crops to most herbicides. Similarmechanism is found to offer resistancein many weeds as well.

Triazine-resistance in Abutilontheophrostii has been attributed toenhanced herbicide metabolism(Gronwaid et al., 1989). The resistanceto chlorotoluron and isoproturon isbelieved to be due to rapid degradation,catalysed possibly by cytochrome P-450monooxygenase. Aryloxy phenoxypropionate (AOPP) herbicides, whichinclude diclofop-methyl and fluazifop-butyl, and substituted 1, 3cyclohexanedione (CHD) herbicides,including sethoxydium andtralkoxydium are called graminicides asthey selectively control grassy weeds inwheat and barley. These groups arepotent reversible inhibitors of plantacetyl co-enzyme-A carboxylase(ACCase), a biotin containing enzymefound in Plastids. ACCase catalyzes ATPand HCO3 dependent conversion ofacetyl Co-A to malonyl Co-A required forsynthesis and elongation of fatty acidsand number of secondary compounds.Resistance to these groups of herbicidesin A. myosuroides - other weeds is dueto enhanced activity of a cytochrome P-450 catalyzed detoxification system. InAustralia, in some populations of L.rigidum resistance has been found to bedue to increased metabolism in theplant (Christopher et al., 1991). In India,studies made on mechanism ofisoproturon resistance in P. minorrevealed that it was due to enhancedmetabolism (Singh et al.,1996).7.3 Sequestration and compartmentation

Compartmentation may be eitherby storage of the herbicide or its

metabolites in the cell vacuole or theirsequestration in cells or tissue, awayfrom the site of action. One of the majormechanisms of resistance to paraquat isby compartmentation, thoughalternative explanations such as rapidenzyme detoxification have also beensuggested (Dodge, 1991). Similarly,sequestration is also found in someresistant biotypes of L. rigidum inAustralia (Holtum et al., 1991).8. Herbicide Resistance Management

It is important to start managingherbicide resistant weeds in initialstages of detection itself; otherwise, itwill have serious consequences in a veryshort span of time. Use of alternativeherbicides, having different chemistryand mechanisms of action, isrecommended as a short-term measure.In India, pre-emergence application ofpendimethalin @ 1.0 kg ha-1 and post-emergence application of clodinofop,fenoxaprop, sulfosulfuron andtralkoxydim have been found to be veryeffective in controlling the resistantpopulations of P. minor. In some casesresistant biotypes are more effectivelycontrolled by an alternative herbicidethan are susceptible plants. This isknown as negative cross resistance. Theeffective management of herbicideresistance in weeds lies in reducing theselection pressure for evolution ofresistance. Therefore, the main focusshould be on modifying those factorsand practices which are responsible forquicker evolution of resistance, such asrepeated and continuous use of sameherbicide/ herbicide class, monocultureand reduced tillage.

The use of two or moreherbicides, having different mechanismsof action when used in a mixture or inrotation, reduces the selection pressurefor resistant biotypes and delays the rateof evolution. The record of herbicideresistant weeds reveals that few weedshave evolved resistance tochloracetamides, diphenyl ether andglyphosate despite extensive use of theseherbicides (Table 4). Therefore, these areconsidered as low risk herbicides. Onthe other hand, weeds have readilyevolved resistance to triazine, ALAinhibitors, bipyrildyliums, phenylureas,and ACCase inhibitors have greatpropensity for development of



resistance, hence these should be usedcautiously. Herbicides having lowresidual activity in soil, applied as post-emergence are ideal for reducingselection pressure for resistant biotypes.Application at higher rate and repeateduses of same herbicides should beavoided as far as possible.8.1 Role of non-chemical methods

In modern agriculture, non-chemical methods have been ignored orgiven a good bye. Age-old practices suchas crop rotation, tillage, inter cultivationand intercropping have been forgotten.In view of the adverse effect ofherbicides, it is heartening to note thatthese practices are staging a comeback,even in developed countries.

Crop rotation also facilitatesherbicide rotation. Many serious weedsare always associated with specificcrops. Changes in planting time andweed control measures can sometimeshave an adverse effect on the problemweed. Crop rotation may also reduce theoverall usage of herbicides and extendthe feasibility of using a wide range ofherbicides. Crop rotation could be aneffective tool for Phalaris minor controlas the problem is evident mostly in rice-wheat system. Investigations haveshown that changes in cropping ineither or both seasons would bringabout a drastic reduction in Phalarisminor problem. But crop substitutiondoes not always impress farmers due toa variety of reasons.

Other non-chemical methods ofweed control, such as stale seedbedpreparation, selection of competitivecrop / crop cultivar, modifying the timeof planting, optimum seed rate, bettercrop husbandry and increased seed ratecould find place in a holistic approach inmanagement of weeds. These reduce theover reliance on herbicides and thus theresistance problem. Use of certified cropseeds, and clean machinery will preventspread of resistant weed seeds or plantmaterials (Shaner, 1995).8.2 Integrated weed management

Integrated weed management(IWM) is by far the most viable strategyas it is based on the principle of using awide range of control methods inappropriate combinations. In most of thecases the resistance problem has beensolved by using alternative herbicides.

However, it is noticed that newherbicides have greater propensity fordevelopment of resistance (LeBaron,1991; Shaner, 1995). Besides, discoveryof herbicides having new and uniquemode of action, with all thecharacteristics necessary for regulatoryand commercial success, is becomingmore difficult. The IWM strategies arethe only solution in case of multipleresistance as it is the most complicatedone and in the worst cases virtually noselective herbicide remains effective.Thus IWM strategies involving physical,chemical and biological methods, in anintegrated fashion, without excessivereliance on any single method, can helpin successfully managing herbicideresistance while maintaining farmprofitability and sustainability .Forexample : summer deep ploughing +useof weed free seed for sowing+ stale seedbed +post emergence application offenoxaprop can dilute the resistanceagainst Phalaris minor in wheat.ReferencesBami, A.L. 1996. Pesticide use in India-ten

questions. Pesticide Information12:19-27.

Chaleff, R.S. and Ray, T.B. 1984. Herbicideresistant mutants from plant cells.Science 223:1148-1151.

Christopher, J.T., Powles, S.B., Lujegren,D.R. and Holtum, JAM. 1991. Crossresistance to herbicides in annualryegrass (Lolium rigidium) 11.Chlorsulfuron resistance involveswheat like detoxification system.Plant Physiology 95:1036-1043.

Darmency, H. and Gasquez, J. 1990.Appearance and spread of triazineresistance in common lambsquarter(C. album). Weed Technology 4: 173-177.

Dodge, A.D. 1991. Mechanism of paraquattolerance, pp. 165-175. In: HerbicideResistance in Weeds and Crops.(Eds) J.C. Caseley, G.W. Cussansand G.W. Cussans and RK Atkins.Butterworth-Heinemann, OxfordU.K.

Gronwaid, J.N.V., Anderson, R.N. and Yee,C. 1989. Atrazine resistance in velvetleaf (A. theopharisti) due toenhanced atrazine detoxification.Pesticide Biochemistry andPhysiology 34:149-163.

Gronwald, J.W. 1994. Resistance tophotosystem 11 inhibiting



herbicides, pp. 27-60. In: HerbicideResistance in Plants : Biology andBiochemistry. (Eds) S.B. Powles andJ.A.M. Holtum. CRC Press BocaRaton, Florida USA.

Hall, L.M., Holtum, J.A.M. and Powles, S.B.1994. Mechanisms responsible forcross resistance and multipleresistance for cross resistance andmultiple resistance, pp. 243-261. In:Herbicide Resistance in Plants:Biology and Biochemistry. (Eds) S.B.Powles and J.A.M Holtum. LewisPublishers, Boca Raton, FloridaUSA.

Heap, I.M. 1997. The occurrence of herbicideresistant weeds worldwide. PesticideScience 51: 235-243.

Holt, J., Holtum, J.A.M. and Powles, S.B.1993. Mechanisms and agronomicaspects of herbicide resistance.Annual Review of Plant Physiologyand Plant Molecular Biolology 44:203-229.

Holt, J.S. and LeBron, H.M. 1990.Significance and distribution ofherbicide resistance. WeedTechnology 4: 141-149.

Holtum, J.A.M., Mathews, J.M., Hansler,R.E., Lijjegren, D.R and ftonks, S.B.1991. Cross-Resistance to Herbicidein Annual Ryegrass (Loliumrigidum).111. On the mechanism ofresistance to diclofop- methyl. Plantphysiology 97: 1095-1034

Kemp MS, Moss, S.R. and Thomas, T.H.1990. Herbicide Reference inAlopecurus myosuroides, pp. 376-393. In: Managing Resistance toAgrochemicals: From FundamentalResearch to Practical Strategies (Eds)M.B. Green, H.M. LeBaron and W.K.Moberg. American Chemical SocietySymposium Series, 421 WashingtonDC USA.

LeBaron, .H.M 1991 Distribution andseriousness of herbicide-resistantweed infestations worldwide, pp. 27-43. In: Herbicide-resistant in Weedsand Crops.

Malik, R.K. and Singh S. 1995. Littleseedcanarygrass (Phalaris minor)resistance to isoproturon in India.Weed Tichnology 9(3): 419-425.

Moss S.R. 1990. Herbicide cross-resistancein slender foxtail (Alopecurusmyosurides) Weed Science 38: 492-496.

Powles, SB, Preston, C., Bryan, I.B. andJutsum, A.R. 1997. Herbicideresistance: Impact and management.

Advances in Agronomy 58: 57-93.Rubin, B. 1991. Herbicide resistance in

weeds and crops, Progress andProspectives, pp. 387-414. In:Herbicide Resistance in Weeds andCrops (Eds) J. C. Caseley. G.WCussans and R.K. Atkins.Butterworth -Heinemann, OxfordUK.

Ryan, G.F. 1970. Reaiatanee of commongroundsel to simazine and atrazine.Weed Science 18:614-616.

Saari L.L., Cotterman, J.C. and Primiani.M.M. 1990. Mechanism ofsulfonylurea herbicide resistance inthe broadleaf weed Kochia scoparia.Plant Physiology 93:55-61.

Shaner, D.L.. 1995. Herbicide resistance :Where are we? How did we get here?Where are we going? WeedTechnology 9: 850-856.

Singh, S., Kirkwood, R.C. and Marshall, G.1996. Uptake, translocation andmetabolism of l4C isoproturon inwheat, susceptible and resistantbiotype of Phalaris minor. SecondInternational Weed ControlCongress, Copenhegan Denmark.

Subramanian, M.V., Hung, H.Y., Dias, J.M.,Miner, J.H. and Butler. 1990.Properties of mutant acetolactatesynthase resistance to triazolo-pyrimiridine sulfananilide. PlantPhysiology 94: 239- 244.

Vaughn, K.C. and Vaughn, M.A. 1990.Structural and biochemicalcharacterization of dinitroanilineresistant Eleusine , pp. 364-375. In:Managing Resistance toAgrochemicals : From FundamentalResearch to Practical Strategies.(Eds) M.B. Green, H.M. LeBaron andW.K. American Society, WashingtonDC USA.

Yaduraju N.T. and Singh, G.B. 1997.Herbicide resistance in Phalarisminor – an emerging problem. IndianFarming 47: 20-25.



Improving soil health through Green ManuringM.L. Kewat

ProfessorDepartment of Agronomy, JNKVV,

Jabalpur – 482004 (M.P.)

Indian agriculture has gonethrough major changes during the lastcentury. It has developed from a more orless subsistence farming to a highlyintensive agricultural productionparticularly after green revolution. It reliesheavily on the inputs of energy and otherresources and production has becomedependent on chemical pesticides andcommercial fertilizers. With an increasepressure on farmland country wide,farmers are facing global problem such assoil erosion, wide spread deficiencies ofmacro and micro plant nutrients,salination, increasing pest problems.Besides these, damages to human beings,animals and nature from syntheticchemical pesticides have become moreapparent in the different statesparticularly in Punjab and Haryana.Therefore, a change from high-input andchemically intensive agriculture to a moresustainable form of agriculture likeorganic farming is not only desirable buturgently needed to rectify the ill effects ofchemically intensive agriculturalproduction (Tandon, 1995; Stockdale etal., 2000)

Organic farming is a newagricultural production system trying towork with the nature as much as possible.It involves us of locally and naturallyavailable organic materials or agro-inputsto meet out the need of the productionsystem without endangering our preciousnatural resources. In organic farming, thenutritional demands of crops are meet out

mainly through on farm organic wastes,biofertilizers and green manure crops. Inthe present article an endeavor has beenmade to compile the available literature onimportant green manures crops of India,their potential in terms of biomass andnutrients, techniques for harnessing themaximum benefits from green manuringand their complementary effects on cropsyields, physico-chemical properties of soiland quality of agricultural produce.

What is green manuring ?

Green manuring is the practice ofgrowing lush plants on the site into whichyou want to incorporate organic matter,then turning (tilling, ploughing andsoading) into the soil while it is still fresh.The plant material used in this way iscalled a green manure (GM). Generally thepractice of green manuring is adopted intwo ways:

(a) In-situ green manuring: In this systemthe short duration legume crops aregrown and buried in the same site whenthey attain the age of 60-80 days aftersowing. This system of on-site nutrientresource generation is most prevalent innorthern and southern parts of Indiawhere rice is the major crop in theexisting cropping systems. The mostcommon green manure crops which aregrown for in-situ green manuring arelisted in Table 1

Table 1. Common legume crops for in-situ green manuringS.No. Common Name Botanical Name Growing season

1 Dhaincha Sesbania aculeta Zaid / KharifSesbania rostreta Zaid / Kharif

2 Sunhemp Crotolaria juncia Zaid / Kharif3 Mung Vigna radiata Zaid / Kharif4 Cowpea Vigna unguiculata Kharif5 Guar Cyamopsis tetragonoloba Kharif6 Senji Melilotus alba Rabi7 Berseem Trifolium alexandrium Rabi8 Khesari Lathyrus sativus Rabi

(Singh et al., 1992)



Besides these, some weeds growing in the fields can be buried in the soil while they arestill fresh at the time of field preparation. The weeds which can be used for greenmanuring along with the common legumes to cater the nutritional requirement of cropsunder organic farming are presented in Table 2.

Table 2 . Mineral composition of certain weeds on dry weight basis

Nutrient content (%)S.No. WeedN P2O5 K2O

1 Amaranthus viridis 3.16 0.06 4.512 Cassia occidentalis 3.08 1.56 2.313 Chenopodium album 2.59 0.37 4.344 Cleome viscosa 1.96 1.53 5.815 Dactyloctenium aegyptium 2.78 0.24 1.656 Digitaria sanguinallis 2.00 3.36 3.487 Echinochloa crusgalli 2.98 0.40 2.968 Portulaca quadrifida 2.40 0.09 5.579 Solanum xanthocarpum 2.56 1.63 2.1210 Trianthema partulacastrum 2.34 0.30 1.1511 Eupatorium spp. 2.93 0.49 1.4712 Parthenium hysterophorus 2.66 0.88 1.2913 Eichhornia crassipes 2.83 0.90 1.79

(Gupta, 2000)

(b) Green leaf manuring: Green leaves and tender plant parts of the plants are

collected from shrubs and tress growing on bunds, degraded lands or nearby

forest and they are turned down or mixed into the soil 15-30 days before sowing

of the crops depending on the tenderness of the foliage or plant parts. The most

common shrubs/trees used for green leaf mauring are given below :

S.No. Common Name Botanical Name1 Subabool Leucaena Leucocephala2 Gliricidia Gliricidia maculata3 Wild daincha Sesbania speciosa4 Kranj Pongamia pinnata

Status of GM crops in India

At present only 6.7 millionhectares area is green manured whichaccounts for 4.5 per cent of net sownarea (142 million ha) of the country(Agril Ststistics, 2005). The practice ofgreen manuring is most common in ricegrowing states like A.P., U.P.,Karnataka, Punjab and Orissa whichcontribute 41, 16,11,6 and 5 per cent tothe total area under green manuring inIndia respectively. Whereas, the share ofGujrat (3%), M.P. (3%), HimanchalPradesh (2%) and Haryana (1.7%) is notvery encouraging and concentratedeffects are to be made out at all levels tobring more area under green manuringthat too in irrigated areas if nutritionalneed of organic farming is to be made.

Biomass potential of GM crops

The benefits deriving from greenmanure crops are directly related to theamount of biomass and nutrients addedin soil. Biomass production of greenmanure crops varies widely according tothe species of the legumes,environmental conditions, soil fertilityand crop management practices and ageof green manure crops (Palaniappan,1992). According to the estimates ofSigh et al. (1992), the Sesbania aculetaand Crotolaria juncia have higher rate ofbiomass production and both canproduce dry matter to the tune of 16.0to 19.0 t/ha within a short period of 45-60 days and on an average about5.0t/ha dry matter can easily beproduced which is sufficient for meeting



out the nutritional demand of a cropgrown either in Kharif or rabi season.Beside these, some weeds particularlyEichhronia crassipes have maximumrate of biomass production and one canget about 70 q/ha dry matter with in aperiod of 46-60 days and could be used

for ex-situ green manuring. Weeds likeTrianthema portulacastrum andParthinum hysterophorus are also foundabundantly in different habitat withbetter nutrient content and dry matterproduction to cater the need of theorganic agriculture (Table 3 and 4).

Table 3. Nutrient compositions of common green manure crops and weeds on drybasis

Nutrient contentMajor nutrients (%)* Total micro nutrients (mg/kg)**

S.No. Crop/weed

N P2O5 K2O Zn Fe Cu Mn1 Sesbania rostrata 2.62 0.37 1.25 40 1968 36 2102 Sesbania speciosa 3.98 0.24 1.30 50 480 44 1103 Crotolaria juncia 2.86 0.34 1.27 30 1190 24 1104 Eichhornia crassipes 2.83 0.90 1.79 50 470 19 4205 Trianthema spp. 2.34 0.30 1.15 30 1992 19 2006 Parthenium hysterophorus 2.66 0.8 1.29 70 470 19 1607 Gliricidia maculata 3.49 0.22 1.30 30 550 19 1508 Cowpea residue 1.70 0.28 1.25 - - - -9 Mungbean residue 2.21 0.26 1.26 - - - -

* Singh et al (1992) and ** Gupta (2000), Savitri et al (1999)

Table 4. Biomass and nutrient potentials of different green manures and weedsNutrient accumulation

Major nutrients (kg) Total micro nutrients (g)S.No. Crop Dry matter

in 45-60DAS (q/ha) N P2O5 K2O Zn Fe Cu Mn

1 Sesbania rostrata 50.0 131.0 18.5 62.5 200 9840 180 10502 Sesbania speciosa 30.0 119.4 07.2 39.0 150 1440 132 3303 Crotolaria juncia 52.5 150.2 47.3 93.9 262 2467 100 22054 Eichhornia crassipes 70.0 198.1 63.0 125.3 350 3290 133 29405 Trianthema spp. 25.0 58.5 07.5 28.7 75 4980 47 5006 P. hysterophorus 40.0 106.4 35.2 51.6 280 1880 76 6407 Gliricidia maculata 36.0 125.6 7.9 46.8 108 1980 68 540

Palaniappan (1992) ; Singh et al. (1992)

Nutrient potential of GM cropsAlmost all GM crops which are

used for in-situ or ex-situ greenmanuring contains all the plantnutrients which are essential forcompleting the life cycle of any palntgrown in community. Among thedifferent GM crops, dhainch (Sesbaniaaculeta) and Sunhemp (Crotolaria juncia)have higher accumulation of major andmicro nutrients on account of morebiomass production and better nutrientcomposition compared to food legumeswhich are inferior due to low contents ofnutrients coupled with less dry matterproduction (Table 3&4). Water hyacinthhas great nutrient potentials and itcould contribute 198 kg N, 63.0 kg P2O5,125.3 kg K2O and 350 g Zn, 3290 g Fe,133 g Cu and 2940 g Mn when about 70q/ha dry matter is added in the soil andcould serve as better source of plantnutrients through ex-situ greenmanuring.

Techniques for harvesting thebenefits of green manuring

The maximum benefit from greenmanuring can be obtained throughbetter knowledge of suitable sowing timeof GM crops, age or stage of GM crop forburial and time interval between burialand sowing of next crop.

(a) Sowing time of GM crops: Sowingtime of GM crops for in-situ greenmanuring varies according to localconditions and farming situations.The green manures can be grown ascatch crop during summer seasonparticularly in irrigated agro-ecosystem. The quick growing cropslike sunhemp and dhaincha etc. aresown in month of April-May andburies in the field in the month ofJune and July before the planting ofmain kharif crop. In rainfed areas aswell as in intensive farming areas,the dhaincha is intercropped withpaddy in 4:1 row proportion,



whereas sunhemp and cowpea areintercropped in between the rows ofwidely spaced crops like cotton,maize and sugarcane and buried inthe soil when these crops attain theage of 30-45 days with the help ofhoes or mould board plough. Inkharif fallow areas sunhemp, guar,cowpea and dhaincha are sown inJune, July and buried in the soilduring Ausgut-Spetember. Thispractice is most common in Punjab,U.P., Rajasthan, Bihar and M.P.

(b) Stage of GM crop at burial :Knowledge of time of burial of GMcrops is of utmost importance forderiving maximum benefit fromgreen manuring. The chemicalcomposition of most plants changesidentically during growing season.During early period of crop growthits content of N, protein and watersoluble constituents are maximum,while the amount of fiber, cellulose,hemicelluloses, lignin and the C:Nratio are also less. Therefore, tissuesof immature plants usuallydecompose more rapidly ascompared to those of maturedplants. Singh et al (1992) reportedwhile reviewing the nutrienttransformations in soils amendedwith green manures that the greenmanure crops are to be buried in thesoil when they are 2 months old andtwo weeks delay in the incorporationreduced their N content andincreased the C:N ratio, cellulose,hemicelluloses and lignin contents.

(c) Time interval between burial ofGM and sowing of next crop:Knowledge of time interval betweenburial of GM crops and sowing ofnext food crop for just to facilitatethe complete decomposition of theturned in green matter is essential.Ghose et al. (1960) reported fromtheir studies conducted at CRRI,(Cuttack) that the time interval wasnot so important when succulentgreen manure crop of eight weeks agewas buried because transplanting ofpaddy immediately after burying ofgreen manure crop was as good as anyother treatment. But it was necessaryto give the time interval of 4 – 8 weeksbefore planting paddy when the GMwas 12 weeks of age.

Effect of green manuring on cropyields

In most of the studies conductedin different parts of the world, the cropyields under organic management aresomewhat lower than conventionalsystems. In developing countries,organic farming methods providedsimilar outputs and income per labourday to that of high-input systems usinginorganic fertilizers (Andrew and Hidka,1998) In Sambalpur district of Orissa,the studies of Patra et al. (2000) revealedthat there was reduction in the yield ofrice to the tune of 15-23 per cent due toalone green manuring as compared to100% recommended dose of NPKthrough fertilizers which produced themaximum yield (42.97 q/ha) of rice. InSamastipur (Bihar), Thakur et al. (1999)assessed the impact of green manuringon yield of rice-wheat system andreported that green manuring withdhaincha significantly improved theproductivity of rice over other sources,whereas residual effect of greenmanuirng on succeeding wheat wasmarginal. Nair and Gupta (1999) alsorecorded 25% more yield of rice over no-green manuring which produced only34.94q/ha of rice at Pantnagar,Uttranchal. Similar views were alsoendorsed by Hemalatha et al. (2000) atMadurai in Tamil Nadu

Effect of green manuring on soilproductivity

The physico-chemical propertiesof soils are affected significantly due toaddition of organic matter in the form ofgreen manures particularly in plotsreceiving green manuring throughSesbania rostrata and Crotolaria juncia.Consequently, marked improvement insoil structures, infiltration rate, bulkdensity and water holding capacity ofsoil. It is evident from the results ofstudies of Badanur et al. (1990) thatincorporation of subabool, sunhemp andcrop residues were equally effective inincreasing infiltration rate of soil whilethe water use efficiency of sorghum wasincreased significantly with the greenleaf manuring of sunhemp, subabooland fertilizer application over cropresidues. Aggregate stability andporosity increased identically with the



addition of organic inputs particularlygreen manures and consequently itimproves the soil aeration and waterholding capacity of the soils underorganic management (Droogers et al.,1996). Lower rates of runoff and soilerosion have also been reported underorganic systems (Logsdon et al., 1993;Reganold et al.,1987). On the contrary inseveral studies no change in thephysical properties of soil have beenobserved when managed organically orconventionally (Niggli et al., 1995)

The changes in chemicalproperties of soil could be predicted wellthrough the nutrient budget. The resultsof several studies showed that nitrogen,phosphorus and potassium, organiccarbon etc. ranged from deficit tosurplus in organic farming systems(Fagerberg et al., 1996; Nguyen et al.,1995 and Hemalatha et al., 2000). Greenmanuring under submerged conditionsmarkedly increased Fe and Mnconcentration and partial pressure ofCO2 and decreased pH, Eh and Zn insoil solution. The increase in Fe and Mnconcentration attributed to theformation of complexes of Fe2+ and Mn2+

with organic acids produced duringanaerobic decomposition of greenmanure and also due to sharp decreasein Eh and pH and increase in partialpressure of CO2 (Sadana and Chahal,1995; Sadana and Nayyar, 2000).Effect of green manuring on productquality

There is no clear-cut scientificevidence with some studies showingincreases in vitamin C, minerals andproteins (Lampkin, 1990) because theseare controlled by a complex ofinteraction in added manures andfertilizers. Therefore, it is difficult todistinguish the effects of theenvironment and farming systems onquality of crop products. Studies ofStarling and Richards (1993) showedthat organic wheat had lower proteinlevels compared to conventionally growncrops. Results of studies conducted atMadhurai in Tamil Nadu have alsoindicated that incorporation of Sesbania12t/ha increased the optimum cookingtime, total amylose content, crudeprotein in rice and reduced the gruelloss (%) of grain Hemalatha et al., 2000.

References

Agricultural Statistics (2005).Agricultural statistics at aglance. Ministry of Agricultural,New Delhi.

Andew, D.A. and Hidaka, K. (1998).Yield loss in conventional andnatural rice farming system.Agric Ecosystem Environ. 70 :151-158

Badanur, V.P., Poleshi, C.M. and Naik,B.K. (1990). Effect of organicmatter on crop yield and physicaland chemical properties ofvertisol. J. Indian Soc. Soil Sci.,38 (3) : 426-429

Droogerss, P., Fermont, A. and Bouma,J. (1996). Effects of ecologicalsoil management on workabiltiyand trafficiability of a loamy soilin Netherlands. Geoderma 73:131-145.

Fagerberg, B., Salomon, E. and Jonsson,S. (1996). Comparisons betweenconventional and ecologicalfarming systems at Ojebyn :nutrient flows and balances.Swedish J. Agric. Res., 26:169-180.

Ghosh, R.L.M., Ghate, M.B. andSubrahmanyam, T. (1960) Ricein India. I.C.A.R. New Delhi-12

Gupta, O.P. (1984). Scientific weedmanagement in tropic andsubtropics. Today and TomorrowPrinters and Publishers, NewDelhi

Hemalatha, M., Thriumurugan, V. andBalasubramaniam, R. (2000).Effect of organic sources ofnitrogen on productivity, qualityof rice and soil fertility in singlecrop wetlands. Indian J. Agron.,45 (3) : 564-567

Lampkin, N. (1990). Organic farming.Farming Press, IPSWICH, U.K.,pp 715

Logsdon, S.D., Radke, J.K. and Karlen,D.L. (1993). Comparison ofalternative farming systems. I.Infiltration techniques Am. J. Alt.Agric., 8 : 15-20.



Nair, A.K. and Gupta, P.C. (1999) Effectof green manuring and nitrogenlevels as nutrient uptake by riceand wheat under rice wheatsequence. Indian J. Agron., 44 (4): 659-663

Nguyen, M.L., Haynes, R.J. and Goh,K.M. (1995) Nutrient budgetsand status in three pairs ofconventional and alternativemixed cropping farms inCanterbury, Newzealan. Agric.Ecosystems Environ., 52 : 149-162.

Niggli, U., Alfoldi, T., Mader, P., Pffiffner,L., Speciss, E. and Besson, J.M.(1995). DOK-VersuchVergleichende Longzeit-Untersuchungen in den dreiAnbausystemen biologish-dynamisch, Organish-biologishund Konventionell VI. Synthese1und 2 Fruchffloge periode.Schweiz Landw Fo. SnderheftDOK 4 : 1-34.

Palaniappan, S.P. (1992) Greenmanuring : nutrient potentialand management. (In) fertilizers,development and recyclablewaste and biofertilziers. Ed.Tandon, H.L.S. Development andconsultation Organization, NewDelhi

Patra, A.K., Nayak, B.C. and Mishra,M.M. (2000). Integrated nutrientmanagement in rice-wheatcropping system. Indian J.Agron., 45 (3): 453-457

Reganold, J.P., Elliot, L.F and Unger,Y.L. (1987). Long term effects oforganic and conventional farmingon soil erosion. Nature 330: 370-372.

Sadana, U.S. and Nayyar, N.K. (2000).Amelioration of iron deficiency inrice and transformations of sol

iorn in course textural soils ofPunjab. Indian J. Pl. Nutr. 23(11-12): 2061 – 2069.

Sadana, V.S. and Chahal, D.S. (1995).Iron availability, electrochemicalchanges and nutrient content ofrice as influenced by greenmanuring in a submerged soil(In) : Iron nutrition in soil andplants (Netherlands) Ed. J.Abadia pp 105-109.

Savithri, P., Poongothai, S., Joseph, Band Vennila, R.K. (1999). Non-conventional sources ofmicronutrients for sustainablesoil health and yield of rice-greengram cropping system. Oryza, 36(3) : 219-222.

Singh, V., Singh, B. and Khind, C.S.(1992). Nutrient transformationsin soil amended with greenmanures Adv. Soil. Sci., 20 : 238-298

Starling, W. and Richards, M.C. (1993).Quality of commercial samples oforganically grown wheat. AspectsAppl. Boil., 36 : 205 – 209.

Stockdale, E.A., Lampkin, N.H., Hovi,M., Keatinge, R., Lennartsson,E.K.M., Macdonald, D.W., Padel,S., Tattersall, F.H., Wolfe, M.S.and Watson, C.A. (2000).Agronomic and environmentalimplications of organic farmingsystems. Adv. Agron. 70 : 261-327.

Tandon, H.L.S. (1995) Sustainableagriculture for productivity andresource quality- A model forIndia. Fert. News, 40 (10) ; 39-45

Thakur, R.B., Choudhary, S.K. and Jha,G. (1999). Effect of combined useof green manure crop andnitrogen on productivity of rice-wheat under lowland rice. IndianJ. Agron., 44 (4): 664-668



Impact of continuous cropping with fertilizer and manure applicationon soil fertility and crop productivity

A.K. Dwivedi

Principal ScientistDepartment of Soil Science & Agricultural Chemistry, JNKVV, Jabalpur

Soil fertility is one of the keycomponents to determine productivity.Proper management of soil fertilitydemands careful identification ofconstraints of current nutrient statuswith monitoring the changes in soilfertility so as to sustain food productionat a reasonable level to ensurecontinued high productivity in thefuture. Thus, maintenance of optimumfertility vis-à-vis nutrient managementat optimum level is one of the keyfactors in activating high andsustainable productivity. (Dwivedi et al ,2005). With the advent of sustainableagriculture concept the sustainability ofsoil productivity has now looked intomore in areas where dependence onagrochemicals and fertilizers havesharply increased for crop production.So the current concept of soil healthmonitoring is a subject of vital concernfor not only the soil fertility andproductivity factors but also otheraspects responsible for the soils welfare(Tomar and Dwivedi, 2007). On theother hand, stagnation to productivityhas been observed due to long termcultivation and imbalance use of plantnutrients, which deteriorate the qualityof soil (Tomar and Dwivedi 2008). Amajor component of sustainable landuse is to sustain the productivity andimprove the soil quality. Assessing thesoil health indicators (soil properties) isusually linked to soil factors. Severalindicators have been suggestedreflecting changes over various spatialand temporal scales. Improved soilquality often is indicated byimprovement on physical, chemical andmicrobiological soil environment (Singh,et al, 2012).Agricultural production becomesimperative for establishment of therelationships between crop productivity,use of plant nutrients and soilcharacteristics. What farmers need?

to know is how much and which plantnutrients they should supply to providethe optimum economic increase in yieldwithout damaging the soil environment(Thakur et al 2011b). The answerdepends on the soil test basedrecommendation for the specific farmingsystem. Increased attention is now beingpaid to developing such a PlantNutrition Systems that maintain orenhance soil productivity through abalanced use of mineral fertilizerscombined with organic sources of plantnutrients, including biological nitrogenfixation (Singh et al, 2012). Integratednutrient management is only option tomotivate the farming community whichmay consequently improve both soilproductivity and crop yields. The worksof AICRP on LTFE is repertory for theparameters concern to soil productivityand crop yields.

The challenges for plant nutritionmanagement are aimed to maintainsustainable crop productivity to enhancethe quality of soil and water resources.Crops inevitably remove plant nutrientsfrom the soil. Consequently, if acropping system is to be sustainable,these nutrients have to be replaced bywhatever sources are available. The lossof soil fertility from continual nutrientmining by crop removal withoutadequate replenishment, combined withimbalanced plant nutrition practices,poses a serious threat to soil fertility andagricultural production. Hence,, the useof external sources such as mineralfertilizers and organic manures etc isessential to meet crop requirements andto increase crop production in farmingsystems (Singh, et al, 2012).

Crop Productivity: Continuouscropping without adequate restorativepractices may endanger thesustainability of Agriculture. Nutrientdepletion is a major form of soil



degradation. A quantitative knowledgeon the depletion of plant nutrients fromsoils helps to understand the state ofsoil degradation and may be helpful indevising nutrient managementstrategies. Nutrient-balance exercisesmay serve as instruments to provideindicators for the sustainability ofagricultural systems. Studies havebeen undertaken suggested that a widespread occurrence of nutrient miningand soil fertility decline has beenreported. Most nutrient-balance studiesalso provide rapid findings, based on ashort time-frame exercise, andnecessarily depend on a number ofassumptions relating to systemdynamics. In this regards the findingson impact of four decades ofcontinuous use of fertilizer on cropproductivity and soil fertility of black soilis monitored under AICRP on LTFE atJabalpur. The lowest crop productivityof Soybean ( Fig- 1) and wheat ( Fig -2)was recorded in control (T10) and it wasfound to be increased by around 30%due to use of N alone (T7) thusapplication of optimal dose of N alonemay not be an economic preposition forobtaining high crop productivity.However, when P was also included in

fertilizer schedule (i.e. 100% NP) thecrop productivity increased by 127 %over control and 75 % over 100 % Nalone. These findings indicated theimportance of Pin crop productivity inSoybean-Wheat cropping sequencefollowed in this region as both the cropsare heavy feeder of P. Responses to Papplication by Soybean and Wheat havealso been recorded by Bhatnagar et, al.(2011). Further inclusion of K in thetreatment (100 % NPK v/s 100 % NP)

caused an increase in crop productivityindicating the importance of K assuggested by Chouhan et al 2011Thakur et al (2011 a). Increasing levelsof NPK application had resulted inincreased crop productivity as 12 %, 15%A and 197% increased was observedover control due to the application of50% NPK, 100 % NPK and 150 % NPKapplication respectively. The differencebetween 100% and 150 % NPKtreatment were very marginal whichcould be due to the fact that higher levelof fertilizer application could haveresulted in higher demand of othernutrients (micro nutrients) which mighthave remained un fulfilled causing aconstraint on crop productivity. Datashows at the optimal dose of fertilizers isused in conjunction with FYM increasesthe crop productivity indicating thebeneficial effect of organic manure,which not only contribute plantnutrients but also help in creatingfavorable soil environment for cropgrowth due to its effect on soil physicalproperties. Deletion of S in the fertilizeschedule had resulted in 11% decreasein crop productivity over its inclusion(T2) this clearly brings about theimportance of S in plant nutrition andalso crop productivity similar resultshave been reported by Dwivedi et al2002.

Soil Fertility: The date on available NPKcontents in soil (table-1) clearly indicatethat cultivation of crops withoutaddition of fertilizers and manureresulted in marginal increased inavailable N and P content of soil but hadcaused substantial lowering of availableK and S contents, which indicatesdeterioration in soil health. Similarfindings of fertilizer addition on soilhealth have been reported by Dwivedi et

Fig 1 : Impact of continuous use offertilizer on crop productivity of Soybean

Fig 2 : Impact of continuous use of fertilizeron crop productivity of Wheat



al, (2005) , Thakur et al, (2010) andThakur et al, (2011b). However,balanced use of fertilizers either alone orin combination with manure had helpedin strengthening the N and P status ofsoil. Since removal of K by crops washigher resulted in substantial loweringin available status of K. the magnitudeof lowering was however low ascompared other treatments. Thesefindings indicate that use of balancedfertilizer either alone or in combinationwith organic manure is conductive formaintaining soil health as reported byDwivedi and Dixit, 2002 Thakur et al,Thakur et al, 2010, 2011a Thakur et al,2011 b. The data clearly indicate thatthere is need for upward revision of thedoses of K that is being applied to thecrop Sawarker et al (2013). On the otherhand lowering in available S status ofsoil in N P K without S treatmentindicates that use of sulphur freefertilizer will have deleterious effect onsoil health especially of sulphur fertility(Dwivedi et al, 2009).

Management of fertility of the soilRestoring, maintaining and increasingthe fertility of the soil are majoragricultural priorities, particularly in themany parts of the country where soilsare inherently poor in plant nutrients,and the demand for food production isincreasing rapidly. In such areas, thereis a need to intensify the cropproduction to meet demand for foodwithout using former land fallowpractices. A fertile soil provides a soundbasis for flexible food productionsystems that, within the constraints ofsoil and climate, can grow a wide rangeof crops to meet changing needs. IPNS isused to maintain or adjust soil fertilityand plant nutrient supply to achieve agiven level of crop production byadopting the following measures:

Promote the balanced use of fertilizerscombined with organic and biologicalsources of plant nutrients in improvingthe efficiency of fertilizer, thus limitinglosses to the soil environment Identify a better understanding of therole of plant nutrients for maintainingsoil productivity in securing thesustainability of agriculture.

Formulate recommendations forfertilizers based on soil test, productiongoals and strategies within specific agroecological management ,

References:

Bhatnagar,R.K. Dwivedi,A. K.Schidanand , B. and Pahalwan, D.K. (2011) Impact of integratedapplication of organic manure andchemical fertilizers on productivityof soybean, wheat and chickpeagrown on vertisols of MadhyaPradesh. JNKVV Res. J. 45(2) 190-193

Chauhan S. S., V Kumar, Bhadauria,UPS, and Dwivedi A.K, (2011) Effectof conjoint use of organic andinorganic fertilization on SoilFertility and Productivity ofSoybean - Wheat crop sequence.Ann. Pl. Soil Res. 13(1) : 47-50

Dwivedi A. K, Chauhan, S.S. andDikshit, P. R. (2005). Productivitysustenance in soybean wheatcropping system in Typic HaplustertInternational ConferenceSustainable crop production instress environment: Managementand genetic options held at JNKVV,Jabalpur during Feb. 9-12, 2005.Abst No. 1503: 54 pp.

Dwivedi A.K ,Bhatnagar, R.K. ChauhanS. S. and Vaishya U.K (2009)Longterm Influence of Organic &Inorganic manuring on Soil Fertilityand Productivity of Soybean -Wheat System in a Vertisol . JNKVVRes. J. 42:132-35

Dwivedi, A. K. & Dikshit, P. R. (2002).Influence of long term fertilizer useon productivity and nutrition ofsoybean (Glycine max) – wheat(Triticum aestimum). 2nd

International Agronomy Congresson Balancing food andEnvironmental Security – Acontinuing challenge Nov. 26-30,2002, Vol. 1: pp 354-56.

Sawarkar, S.D., Khamparia, N.K., Thakur,Risikesh, Dewda, M.S. and Singh,Muneshwar (2013). Distribution ofpotassium fractions as influenced bylong term continuous application ofinorganic fertilizers and organic manurein Vertisol. Journal of the Indian Societyof Soil Science,61 ( 2) :



Singh ,Muneshwar , Wanjare, R H Dwivedi, A K and Ram Dalal ( 2012) Yieldresponse to applied nutrients andestimates of N2 fixation in 33years old Soybean – Wheatexperiment on a vertisol . Expt Agric.Cambridge University Press .12:: 1–15

Tembhare, B. R. Dwivedi, A. K. & Tiwari,A. (1998). Effect of continuouscropping and fertilizer use on cropyields and fertility of TypicHaplustert. Proc. Long Term soilfertility management throughintegrated plant nutrient supply. Edt.Swarup, A. Raddy, D. D. and Prasad,R. N. IISS, Bhopal. pp. 221-228.

Thakur Risikesh, Kauraw D.L. and SinghMuneshwar (2011 a). ProfileDistribution of Micronutrient Cationsin a Vertisol as Influenced by LongTerm Application of Manure andFertilizers. Journal of the IndianSociety of Soil Science 59 (3): 239-244.

Thakur Risikesh, Sawarkar S.D., VaishyaU.K. and Singh Muneshwar (2011b).Impact of Continuous Use ofInorganic Fertilizers and OrganicManure on Soil Properties andProductivity under Soybean-WheatIntensive Cropping of a Vertisol.Journal of the Indian Society of SoilScience, 59 (1): 74-81.

Thakur, Risikesh and Sawarkar, S.D.(2009). Influence of Long TermContinuous Application of Nutrientsand Spatial Distribution of Sulphuron Soybean-Wheat CroppingSequence. Journal of Soils and Crops,19 (2): 225 – 228.

Thakur, Risikesh, Sawarkar, S.D.,Kauraw, D.L. and Singh, Muneshwar(2010). Effect of Inorganic andOrganic Sources on NutrientsAvailability in a Vertisol.Agropedology, 20 (1): 53-59.

Tiwari, K. N. (2002) Nutrient managementfor sustainable agriculture J. IndianSoc. Soil Sci., 50: 374-397.

Tomar V.S. and Dwivedi, A.K. (2007 )Potassium nutrient and crop healthJNKVV, Res J 41 (1).

Tomar V.S. and Dwivedi, A.K. (2008) SoilQuality as a Measure of sustainableManagement Proc.“Soil, Plant andWater Testing for Efficient Use ofInput Resources for an Eco-FriendlyProduction System” CAS Deptt. of SoilSci. Agri. Chem., JNKVV, Jabalpur

Table 1 : Impact of continuous use of fertilizer on changes in status of soil fertilityAv. N Av. P Av. K Av. S

Treatment pH EC(dSm-1)

OC(g kg-1)

(kg ha-1)

Av. Zn(mg kg-1)

50% NPK 7.52 0.14 5.58 222 23.1 251 22.5 0.51

100% NPK 7.57 0.17 7.67 289 34.2 278 35.5 0.56

150% NPK 7.60 0.20 8.76 325 42.2 304 42.2 0.59

100% NPK + HW 7.55 0.17 7.62 265 32.7 257 32.1 0.54

100% NPK + Zn 7.61 0.17 7.66 278 33.1 261 34.1 1.29

100% NP 7.57 0.19 6.72 261 29.7 232 31.1 0.52

100% N 7.48 0.15 5.26 206 11.5 196 13.1 0.42

100% NPK+FYM 7.57 0.19 9.90 351 44.6 349 45.9 0.93

100% NPK - S 7.59 0.17 7.27 260 30.7 254 13.7 0.46

Control 7.56 0.14 4.20 180 9.6 183 12.8 0.27

CD (P=0.05) NS NS 0.65 7.23 7.78 7.42 7.29 0.06

Initial (1972) 7.6 0.18 5.7 193 7.6 370 15.6 0.33



Soil Pollution, its causes and remidial measures forsustaining soil health

B.L.Sharma and G.D.SharmaDepartment of Soil Science and Agricultural Chemistry

J.N.Krishi vishwavidyalaya, Jabalpur-482004 (M.P.)

Over the last three decades there has beenincreasing global concern over thepublic health impacts attributed toenvironmental pollution, in particular,the global burden of disease. The WorldHealth Organization (WHO) estimatesthat about a quarter of the diseasesfacing mankind today occur due toprolonged exposure to environmentalpollution. Most of these environment-related diseases are however not easilydetected and may be acquired duringchildhood and manifested later inadulthood.

Improper management of solidwaste is one of the main causes ofenvironmental pollution and degradationin many cities, especially in developingcountries. Many of these cities lack solidwaste regulations and proper disposalfacilities, including for harmful waste.Such waste may be infectious, toxic orradioactive.

Municipal waste dumping sitesare designated places set aside for wastedisposal. Depending on a city’s level ofwaste management, such waste may bedumped in an uncontrolled manner,segregated for recycling purposes, orsimply burnt. Poor waste managementposes a great challenge to the well-beingof city residents, particularly those livingadjacent the dumpsites due to thepotential of the waste to pollute water,food sources, land, air and vegetation.The poor disposal and handling of wastethus leads to environmentaldegradation, destruction of theecosystem and poses great risks topublic health.

Soil is one of the important andvaluable resources of the nature. Lifeand living on the earth would beimpossible without healthy soil. 95% ofhuman food is derived from the earth.Making plan for having healthy andproductive soil is essential to human

survival. Entrance of materials,biological organisms or energy into thesoil will cause changes in soil quality.This problem causes soil to remove fromits natural state.

Human and ecological systemsrely on soil for the provision of waterand nutrients for plant growth, theregulation of the water cycle and thestorage of carbon. Climate change andits impacts — increases in temperature,changing precipitation patterns, floods,droughts — will not only affect us butmay also affect how soil provides theseservices. Importantly soil is a majorfactor in our response to tacklingclimate change as it is the secondlargest carbon pool after the oceans.

Climate change is expected tohave an impact on soil. However, theinterrelations between climate changeand changes in soil quality are complexand still under study. As a consequencepredictions, which are based onhypothetical scenarios and dataobtained under controlled conditions,are still more qualitative thanquantitative. But, it is clear that tacklingclimate change cannot be done withouta better understanding andmanagement of our soils.

What is pollution?The word pollution is derived from Latinword “POLLUTIONEM” which means tomake dirty. The pollution is defined asthe harmful changes in naturalenvironment of air, water and soilcaused by anthropogenic activities.Different Types of Pollution Soil Pollution Air pollution Water pollution Noise pollution Industrial pollution Environmental pollution



Environmental PollutionEnvironmental pollution is a phenomenawhere natural ingredients are replacedor damaged by the presence of harmfulunnatural ingredients which havepotentiality to cause imbalance to thesystem and to create number of healthhazards to animals and human beings.One of the greatest problems that theworld isfacing today is thatof environmental pollution, increasingwith every passing year and causinggrave and irreparable damage to theearth.Environmental pollution consistsof five basictypes of pollution, namely,air, water, soil, noise and light.Air pollution is by far the most harmfulform of pollution in our environment. Airpollution is cause by the injurioussmoke emitted by cars, buses, trucks,trains, and factories, namely sulphurdioxide, carbon monoxide and nitrogenoxides. Even smoke from burning leavesand cigarettes are harmful to theenvironment causing a lot of damage toman and the atmosphere. Evidence ofincreasing air pollution is seen in lungcancer, asthma, allergies, and variousbreathing problems along with severeand irreparable damage to flora andfauna. Even the most naturalphenomenon of migratory birds hasbeen hampered, with severe airpollution preventing them from reachingtheir seasonal metropolitan destinationsof centuries.Chlorofluorocarbons (CFC), releasedfrom refrigerators, air-conditioners,deodorants and insect repellents causesevere damage to the Earth’senvironment. This gas has slowlydamaged the atmosphere and depletedthe ozone layer leading to globalwarming.

Water pollution caused industrial wasteproducts released into lakes, rivers, andother water bodies, has made marine lifeno longer hospitable. Humans pollutewater with large scale disposal ofgarbage, flowers, ashes and otherhousehold waste. In many rural areasone can still find people bathing andcooking in the same water, making itincredibly filthy. Acid rain further addsto water pollution in the water. Inaddition to these, thermal pollution and

the depletion of dissolved oxygenaggravate the already worsenedcondition of the water bodies. Waterpollution can also indirectly occur as anoffshoot of soil pollution – throughsurface runoff and leaching togroundwater.

Noise pollution, soil pollution and lightpollution too are the damaging theenvironment at an alarming rate. Noisepollution include aircraft noise, noise ofcars, buses, and trucks, vehicle horns,loudspeakers, and industry noise, aswell as high-intensity sonar effectswhich are extremely harmful for theenvironment.

Acid Rain"Acid rain" means the deposition ofacidiccomponents such as sulphurdioxide (SO2) and nitrogen oxides, thatis, sulphuric acid (H2SO4), ammoniumnitrate (NH4NO3) and nitric acid (HNO3)in rain, snow, fog, dew, or dryparticles. Acid rain was first reported inManchester, England.

Soil PollutionThe soil pollution is defined as thedeterioration of physical, chemical andbiological properties of soil which haveadverse effect on crop production,human and animal health [2].Causes of Soil Pollution

1. Industrial Activity: Industrialactivity has been the biggest contributorto the problem in the last century,especially since the amount of miningand manufacturing has increased. Mostindustries are dependent on extractingminerals from the Earth. Whether it isiron ore or coal, the by products arecontaminated and they are not disposedoff in a manner that can be consideredsafe. As a result, the industrialwaste lingers in the soil surface for along time and makes it unsuitable foruse.2. Agricultural Activities: Chemicalutilization has gone up tremendouslysince technology provided us withmodern pesticides and fertilizers. Theyare full of chemicals that are notproduced in nature and cannot bebroken down by it. As a result, they seep



into the ground after they mix withwater and slowly reduce the fertility ofthe soil. Other chemicals damage thecomposition of the soil and make iteasier to erode by water and air. Plantsabsorb many of these pesticides andwhen they decompose, they cause soilpollution since they become a part of theland.3. Waste Disposal: Finally, a growingcause for concern is how we dispose ofour waste. While industrial waste is sureto cause contamination, there is anotherway in which we are adding to thepollution. Every human produces acertain amount of personal wasteproducts by way or urine and feces.While much of it moves into the sewerthe system, there is also a large amountthat is dumped directly into landfills inthe form of diapers. Even the sewersystem ends at the landfill, wherethe biological waste pollutes the soil andwater. This is because our bodies arefull of toxins and chemicals which arenow seeping into the land and causingpollution of soil.4. Accidental Oil Spills: Oil leaks canhappen during storage and transport ofchemicals. This can be seen at most ofthe fuel stations. The chemicals presentin the fuel deteriorates the quality of soiland make them unsuitable forcultivation. These chemicals can enterinto the groundwater through soil andmake the water undrinkable[5, 11].

Use of PesticidePesticide use in India (year wise)Year Pesticide use g ha-1

1960-61 151965-66 941973-74 2971978-79 3431981 3441990 4042004 570Source : Gupta A. (2006)Pesticide use is forty fold during 2004 incomparision to year 1960-61 which may15 g ha-1..

Relative proportion of different kindsof pesticide uses globally and in India(%)Name ofpesticide

Global India

Insecticide 29 61

Herbicide 44 17

Fungicide 21 19

Others 6 3Source : Gupta A. (2006)Nitrate content (mgL-1) in tube welland hand pump water in PunjabBlock Tube

wellwater

Hand pumpwater

High fertiliser

Jagraon 6.49 12.6

Samrala 4.06 12.4

Low fertiliser

Pakhowal 2.82 6.75

DehlonSource :Singh B 2002

4.29 8.67

Nitrate Content in Water Samplesfrom Madhya Pradesh

Tube well water Hand pumpwater

District

Range Mean

Range

Mean

Overallmean

Jabalpur

2.3 -118.3

10.3 13.6-450

95.2 35.7

Morena

2.2-31.9

12.2 4.6-555.2

129.7

65.3

Source: Singh et. al. (2008)The nitrate content in hand pump waterwas found more in comparision to tubewellwater in both places ie two blocks ofPunjab and one district of Morena



Water quality standards for humanand livestock consumptionElement(mgL-1) Human Livestock

Lead <0.10 <0.10

Arsenic <0.05 <0.05

Selenium <0.01 <0.01

Zinc <15.0 <20.0

Cadmium <0.01 <0.01

Mercury <0.01 <0.002

Nitrate <10.0 <40.0

Chlorides <400 <1000

Source : Tisdale et al (2007)Heavy Metal Contamination in Soil

Mining, manufacturing, and theuse of synthetic products (e.g.pesticides, paints, batteries, industrialwaste, and land application of industrialor domestic sludge) can result in heavymetal contamination of urban andagricultural soils. Heavy metals alsooccur naturally, but rarely at toxiclevels. Potentially contaminated soilsmay occur at old landfill sites(particularly those that acceptedindustrial wastes), old orchards thatused insecticides containing arsenic asan active ngredient, fields that hadpast applications of waste water ormunicipal sludge, areas in or aroundmining waste piles and tailings,industrial areas where chemicals mayhave been dumped on the ground, or inareas downwind from industrialsites[10].

Excess heavy metalaccumulation in soils is toxic to humansand other animals. Exposure to heavymetals is normally chronic (exposureover a longer period of time), due to foodchain transfer. Acute (immediate)poisoning from heavy metals is rarethrough ingestion or dermal contact, butis possible. Chronic problemsassociated with long-term heavy metalexposures are:

Lead – mental lapse.Cadmium – affects kidney, liver,

and GI tract.Arsenic – skin poisoning, affects

kidneys and central nervous system. The most common problem causingcationic metals (metallic elements whoseforms in soil are positively chargedcations e.g., Pb2+) are mercury,cadmium, lead, nickel, copper, zinc,chromium, and manganese. The mostcommon anionic compounds (elementswhose forms in soil are combined withoxygen and are negatively charged e.g.,MoO4 2-) are arsenic, molybdenum,selenium, and boron[3].

Soil Pollution Control TechniquesSoils are considered as

purification of the nature. Moreoversupplying food, soils have alsopurification property. This soil propertyis caused by their physical properties(water permeability operation frompores), their chemical properties (surfaceabsorption and evaporation) and theirbiological properties (decomposition andcorruption of organic matters) .1. Controlling Oil Pollutions in Soil

Oil materials and theirderivatives may cause soil pollution as aresult of transport or storage. If more oilmaterials are penetrated into the moredepth of soil, removing its pollution willbe more difficult. Some bacteria andmicroorganisms in soil can causedecomposition of oil materials which willbe explained in the topic entitled"Elimination of Pollution Biologically".Hereunder are regarded as the ways tocontrol effects of oil pollution:1. Preventing oil from spreading widely,2. Improve the soil ventilation throughplowing and mixing,3. Increasing food nutrients to the soillike nitrogen and phosphor,4. Combining soil with microorganismswhich decompose oil materials .2. Controlling Pollutions Caused byWaste in soil

Waste is one of the mostimportant sources of soil contamination.Waste can penetrates into the groundand pollute the water resources as well.Methods of waste disposal include: 1-dumping, incinerating and recyclingIn dumping method, areas are createdas “Land field” and garbage or waste isdumped there. In this method, waste isdumped below the ground level, aimedat not to be observed from groundsurface but the said method creates



subsequent problems. These problemsinclude: pollution of water resources,producing bad odor and poisonousmethane gas which provides fire danger,accumulation of harmful insects andorganisms .To control soil pollution caused by thewaste, the following techniques arerecommended:1. Application of effective technology fordumping waste like compressing andcovering of openings and holes,2. Dumping waste higher than thehighest underground water levels,3. Creating impenetrable layers inbuilding of land fields4. Creating drainage system for thecollection of leachates5. Using the gases produced in landfields.

In incineration method, allwastes are collected at a place awayfrom residing place and then, they areput on fire. Incineration method is oneof the worst methods of waste disposal,because, incineration will produce verypoisonous gases which will pollute theair and incur irreparable loss to theenvironment as well. After incineration,ash of waste is remained and will createvisual pollution.

Recycling is the best method ofwaste disposal. With storing some wasteand reusing them, human can greatlycontribute reduction of waste. In thismethod, not only creation of more wasteis prevented, but also, more cost willalso be saved remarkably [13].

3. Controlling Pollution Caused byIndustrial Activities in SoilThis method includes all the pollutantswhich are entered the soil by thefactories. These wastes include asfollows:Wastes produced by steel industries andpower plants, wastes of chemicalindustries, wastes of steel mfg.industries, wastes of metalworkingindustries, wastes of oil industries(extraction and refining), wastes of wood,cellulose and paper mfg. industries,wastes of leather production industriesas well as waste of food industries.Accumulation of heavy metals in soil isthe major discussion of the industrialpollutions. These metals include lead,cadmium, silver and mercury which

their harmful effects have been provenon the living organisms and haverepeatedly caused environmentaldisasters .Some of these effects are as follows:- Disturbance of biological activities ofsoil,- Toxic effects on plants,- Harmful effects on human being as aresult of entrance of materials to thefood chainThere are three main methods for soildecontamination from industrial wastesas follows:1. Soil can be excavated up to thespecified depth and the excavated soilcan be taken away from the region andthen, it can be restored.2. The soil can be restored at the samearea.3. Keeping soil in the area is the othermethod. Under such circumstances,auxiliaries are added to the soil toprevent spread of infection to the plants,animals and human.

Usually, a large plastic is drawn on thesoil to prevent spread of soil pollution, toprevent water from penetrating into thesoil and to prevent spread of pollution tothe other regions[13, 14].Role of Plants in Controlling andDecreasing Soil Pollution(Phytoremediation)Pollution caused by the exhaust of cars&homes and departments’ heatingdevices and appliances will incurirreparable damages to the health ofhuman beings, animals, water, soil andair.Increase of diseases in human beings,eradication of many plants andendangerment of many generations ofanimals are a solid evidence of the saidclaim.For this purpose, biological scientistsand environmentalists forced to think ofnatural ways (biologic) for fighting withpollutions. The use of plants is thesimplest biological way, because, usingplants is a non-technical andcosteffective method in terms oftechnology[2].Soil Pollution Control TechniqueCaused by Lead Existing in ItFungi are used to fight lead existing insoil, because, satisfactory and goodreports have been received both in



coexistence among plants and fungi likeARBASCULAR – MYCORRIZA FUNGI(AMF) in absorption of the lead. Creatingcolony of this fungus on the root ofplants will cause increase of root levelfor absorption of the lead which resultsin more absorption of the lead elementto the host plant. These reports indicatethat these fungi help plants survive andtolerate pollution better. The researchersconsider this tolerance as a result ofprotection of their roots by the fungi insoil[1, 7].

Phytoremediation Technique toControl Soil PollutionPhytoremediation is a cost-effective,environmental and scientific techniquewhich is suitable for developingcountries and is considered as avaluable business. Unfortunately,despite this potential, the technique, asa technology, has not yet commerciallyused in some countries like our country.Through the use of Green PlantsEngineering like herbaceous and woodyspecies, phytoremediation is used forremoving pollutants from water and soilor decreasing risks of environmentalpollutants like heavy metals, rareelements, organic compounds andradioactive materials .Heavy metals are the most importantmineral pollutants and soilmicroorganisms are able to decomposeorganic pollutants. But for microbialdecomposition of metals, there is a needfor organic or metal changes, in which,plants are presently used for this part.Although way of using the plants, whichare polluted in this form, is the majorconcern of the experts, strategy ofgenerating energy opened anotherchapter for the scientists as one of themost essential aspects of today’s life[9].From a global perspective, soil crust isconsidered as the third majorcomponent of the human environmentafter water and air. In addition to thebase of terrestrial living organismespecially human communities, soil isconsidered as a unique environment forliving of different life especially plants.Unlike the weather, soil pollution cannotbe measured easily in chemicalcompound terms. In other words, aclean or pure soil is indefinable. Then,we have to study potential issues of the

soil pollution within the framework ofanticipated probable damages andhazards in performance of soil. With thedevelopment of manmade projects andcontamination of soils by the heavymetals, the structure of soil will bedangerous and poisonous for the growthand development of plants and willentangle biodiversity of the soil as well .The studies show that application ofphysicochemical techniques will causeeradication of soil usefulmicroorganisms like microriza nitrogenstabilizers and consequently, it willweaken biological activities of the soilwhich will cost dearly in comparisonwith the phytoremediation technique .Soil and water plants are used in rizo-filtration method that pollutants ofcontaminated water resources aredeposited or condensed with littledensity in their roots. This method isapplied especially for industrialwastewater treatment plants,agricultural runoff and/or wastewater ofacid mines and is suitable for the metalslike lead, cadmium, copper, nickel, zincand chrome. The plants like Indianmustard, sunflower, tobacco, rye andcorn enjoy this capability. These plantsenjoy high capability of absorbing leadfrom the sewage system, based onwhich, sunflower has the highestcapability of absorbing lead from thesewage than other plants [8].In another method, restricting mobilityand availability of pollutants is carriedout in soil through using power of theroot. This method is usually used in soil,sediment and sludge to reduce thepollution and is carried out throughabsorption, deposition, complex and/orreduction of the capacity .In plant evaporation method, plantsabsorb pollutants from the soil and thenconvert them into the steam andtransfer with the transpiration andatmosphere operation. This method isused in growing trees to absorb organicand inorganic pollutants. In anothermethod which is known as "ReducedPlan", the plant helps removal ofpollution from soil and undergroundwaters with its metabolism throughtransferring, decomposition,stabilization and sublimation of thepollutant compounds. In this method,organic compounds are broken into



simpler molecules and can be enteredinside the plant tissue. The studies haveshown that plants enjoy the enzymesthat can decompose waste of chlorinatedsolvents like tri-chlorine, ethylene andother insecticides .Future of PhytoremediationTechnique in Controlling SoilPollutionAlthough this science is developing veryrapidly, the studies show thatcommercial phytoremediation should beable to compete with the othertechnologies in terms of time. Morephytoremediation tests have beencarried out in hydroponics environmentin laboratory scale and heavy metalshave been given to them, while soilenvironment is completely different. Inreal soil, there are many metals ininsoluble forms and their availability islow. The said issue is the greatestproblem. Many plants have not yet beenknown that should be identified andmore should be known about theirphysiology .

Although 10 years have passedfrom the initial application of thephytoremediation technology in theworld, this science has been developedvery rapidly and today,phytoremediation has vast applicationon organic, inorganic and radioactivematerials. This process is sustainable,affordable and is suitable for thedeveloping countries. Generally, thismethod is cost effective as well. Thestudies show that efficiency of thismethod is increased with the applicationof fast-grown plants with high biomassand high absorption power of the heavymetals. In most contaminated places,appropriate species have been identifiedfor the removal of pollution. Twomethods of composting and condensingcan be regarded as preliminary stagesfor reducing production volume of theseplants but it should be considered thatleachate of condensation should becollected completely. The researchersbelieve that incinerating consumes theleast possible time among the methodswhich reduce the pollutants' biomassand is more suitable in comparison with

the direct incineration in environmentalterms[6].However, it is observed that today worldcan devise improvements withinspiration of the nature and its virginnondiminishable system for what thehuman being has destroyed with hishand which undoubtedly is not easierthan preventing pollution of resourcesespecially soil resources.

REFERENCES

[1] Bavandi, Bijan, Ecosystem,Publications of the Department of theEnvironment (DoE), 1975.[2] Bahram Soltani, Kambiz, AnIntroduction on Identification ofEnvironment, Publications of theDepartment of the Environment (DoE),1986.[3] Erfan-Manesh, Majid & Afyouni,Majid, Environment, Water, Soil and AirPollution, Publications of Arkan Danesh,2008.[4] Commoner, Bari, Human andEnvironment (Translated by BehrouzDehzad), Moj-e Sabz Publications, 2003.[5] Kordovani, Parviz, NaturalEcosystems, Ghoms Publications, 1996.[6] Miller, J. T., Living in Environment(Traslated by Majid Makhdoum), TehranUniversity Printing andPublications Institute, 2003.[7] Beeton, A.M., Changes in theEnvironment and Biota of the GreatLakes, In Eutrophication: Causes,Consequences, Corrective, Symposium,National Academy of Science,Washington, D.C., 1969.[8] Jordan, Gil., The SovietEnvironment, Clear Creek, 1971.[9] Goldman, Marshall I., EnvironmentalDisruption in the Soviet Union, NewYork, McGraw-Hill, 1971.[10] Hazardous Waste “Soil Treatment”Reference Library Peroxide Application,1998.[11] Pfife, Daniel. Killing the Goose,Environment, 13, 3, 1971.[12] http://www.Bioweb.Pasteur[13] http://www.Coneord.org[14] http://www.ebi.ac



Seed Priming: A Tool in Sustainable AgricultureF.C. Amule and N.G. Mitra

I. Sustainable agriculture (GordonMcClymont proposed in 1950’s) is theact of farming using principlesof ecology, the study of relationshipsbetween organisms and theirenvironment. It has been defined as "anintegrated system of plant and animalproduction practices having a site-specific application that will last over thelong term". Thematically, sustainableagriculture is an approach that satisfieshuman food and fiber needs, enhancingenvironmental quality and the naturalresource, using most efficiently the non-renewable resources and integrating on-farm resources, it has economic viabilityand enhances quality of life for farmersand society as a whole. The NationalResearch Council (1989) of the USNational Academy of Sciences advocatedthat soil quality is the "key" to asustainable agriculture. The alternative agriculture was definedas a system of food and fiber productionthat applies management skills andinformation to reduce costs, improveefficiency of input resources, andmaintain production levels throughpractices like crop rotations, properintegration of crops and livestock,nitrogen fixing legumes, integrated pestmanagement, conservation tillage, andrecycling of on-farm wastes as soilconditioner and biofertilizers. In short,improving the efficiency of inputresources is one of the prime factors insustainable agriculture. Input like seedsof only good quality does not directlyensure for its uniform germination,establishment and growth of crops freefrom seed and soil pathogen and lack ofproper soil management. Seed primingbefore sowing is one of the mostimportant solutions to these problems.

II. Seed Priming

Priming could be defined as controllingthe hydration level within seeds so thatthe metabolic activity necessary forgermination can occur but radicleemergence is prevented. Different

physiological activities within the seedoccur at different moisture levels. Thelast physiological activity in thegermination process is radicleemergence. The initiation of radicleemergence requires a high seed watercontent. By limiting seed water content,all the metabolic steps necessary forgermination can occur without theirreversible act of radicle emergence.Prior to radicle emergence, the seed isconsidered desiccation tolerant, thus theprimed seed moisture content can bedecreased by drying. After drying,primed seeds can be stored untill time ofsowing.

Different priming methods have beenreported to be used commercially.Among them, liquid or osmotic primingand solid matrix priming appear to havethe greatest acceptance. However, theactual techniques and procedurescommercially used in seed priming areproprietary.

Primed seeds are just like the pre-fabricated house, seed germination inthe field takes less time, because part ofthe germination process is alreadycomplete.

Germination of tomato seeds

III. Importance of Prime Seed

Primed seed usually emerges from thesoil faster, and more uniformly than nonprimed seed of the same seed lot. Thesedifferences are greatest under adverseenvironmental conditions in the field,such as cold or hot soils. There may belittle or no differences between primedand non primed seed if the field



conditions are closer to ideal. Somegrowers use seed priming during theearlier plantings in cold soil, and notlater in the season when conditions arewarmer.

Better seedling establishment under lessthan optimal conditions can beachieved. Priming alone does notimprove percent useable plants; removalof weak, dead seeds is also needed.

IV. The subcellular basis of seedpriming

Seed priming is a technique whichinvolves uptake of water by the seedfollowed by drying to initiate the earlyevents of germination up to the point ofradicle emergence. Its benefits includerapid, uniform and increasedgermination, improved seedling vigourand growth under a broad range ofenvironments resulting in better standestablishment and alleviation ofphytochrome-induced dormancy in somecrops. The common feature in thesepriming techniques is that they allinvolve controlled uptake of water. Themetabolic processes associated withpriming are slightly different, withrespect to their dynamics from thosewhich occur during germination, wherethe water uptake is not controlled. Also,the salts used during priming elicitspecific subcellular responses.

i. Stages of water uptake duringgermination where priming isrelevantWhen a dry seed is kept in water, theuptake of water occurs in three stages.Stage I is imbibition where there is arapid initial water uptake due to theseed’s low water potential. During thisphase, proteins are synthesized usingexisting mRNA and DNA, andmitochondria are repaired. In stage II,there is a slow increase in seed watercontent, but physiological activitiesassociated with germination areinitiated, including synthesis of proteinsby translation of new mRNAs andsynthesis of new mitochondria. There isa rapid uptake of water in stage III

where the process of germination iscompleted culminating in radicleemergence.Stages I and II are the foundations ofsuccessful seed priming where the seedis brought to a seed moisture contentthat is just short of radicle protrusion.The pattern of water uptake duringpriming is similar to that duringgermination but the rate of uptake isslower and controlled.

ii. Synthesis of proteins and enzymesduring primingA proteome analysis of seed germinationduring priming in the model plantArabidopsis thaliana by MALDI-TOFspectrometry identified those proteinswhich appear specifically during seedhydropriming and osmopriming. Amongthese are the degradation products ofthe storage protein 12S-cruciferin-subunits. It has been reported that theaccumulation of the degradation productof the β-subunit of 11-S globulin duringseed priming by an endoproteolyticattack on the A-subunit. This suggeststhat enzymes involved in mobilization ofstorage proteins are either synthesizedor activated during seed priming. Otherreserve mobilization enzymes such asthose for carbohydrates (α and βamylases) and lipids mobilization(isocitrate lyase) are also activatedduring priming. These results indicatethat priming induces the synthesis andinitiates activation of enzymes catalysingthe breakdown and mobilization ofstorage reserves, though most of thenutrient breakdown and utilizationoccur post-germinative after the radicalemergence.The proteomic analysis also reveals thatα and β tubulin subunits, which areinvolved in the maintenance of thecellular cytoskeleton and areconstituents of microtubules involved incell division, are abundant duringpriming. Accumulation of β-tubulinsduring priming has been observed inmany species in relation withreactivation of cell cycle activity and isdiscussed later.Another protein detected by theproteomic analysis, whose abundancespecifically increases duringhydropriming is a catalase isoform.



Catalase is a free-radical scavengingenzyme. It is presumed thathydropriming initiates an oxidativestress, which generates reactive oxygenspecies, and catalase is synthesized inresponse to this stress to minimize celldamage. In addition to catalase, levels ofsuperoxide dismutase, another keyenzyme quenching free radicals alsoincreases during priming. Increasedlevels of these free radical scavengingenzymes due to the oxidative stressduring priming could also protect thecell against membrane damage due tolipid peroxidation occurring naturally.Shinde19 reported synthesis of a 29 kDpolypeptide after 2–6 h of priming incotton seeds.The abundance of low molecular weightheat shock proteins (LMW HSPs) of 17.4and 17.7 kD specifically increased inosmoprimed seeds in the MALDI-TOFspectrometry analysis10,11. LMW HSPsare reported to have molecularchaperone activity, these data suggestedthat LMW HSPs may act by maintainingthe proper folding of other proteinsduring osmopriming, preventingaggregation and binding to damagedproteins to aid entry into proteolyticpathways. In osmopriming, seeds aresoaked in osmotica, viz. polyethyleneglycol (PEG) and mannitol, which resultin incomplete hydration and an osmoticstress situation is created. This explainsthe abundance of heat shock proteins,which are known to accumulate in highamounts during any kind of stress.These HSPs synthesized duringosmopriming in response to stress couldalso protect the proteins damaged bynatural ageing. Similarly, the enzyme L-isoaspartyl protein methyltransferase,which repairs age-induced damage tocellular proteins, is reported to increasein response to priming. Thus, it appearsthat one of the ways in which priming iseffective at the subcellular level is byconferring protection to the cellularproteins damaged through naturalageing.

iii. Gene expression and synthesis ofnew mRNA during primingI has been reported that priming-induced synthesis of RNA in cottonseeds, corresponding to the actin gene,following a reverse transcriptase

polymerase chain reaction (PCR)analysis. Studies on gene expression inosmoprimed seeds of Brassica oleraceaon a cDNA microarray revealed that inprimed seeds many genes involved incellular metabolism are expressed (andsynthesize mRNA) at a level intermediarybetween those in dry seeds andgerminating seeds imbibed in water.These genes mostly code for proteinsinvolved in energy production andchemical defence mechanisms. A fewgenes are expressed to the same extentin osmoprimed seeds as in germinatingseeds. These include genes for serinecarboxypeptidase (involved in reserveprotein mobilization and transacylation)and cytochrome B (involved in themitochondrial electron transport).This microarray analysis in combinationwith Northern analysis gives some ideaof transcripts synthesized duringpriming. To obtain direct evidence forthe synthesis of new mRNA, techniqueswhich involve detection of prematureRNA species before intron splicingshould be integrated with the othermethods.iv. Effect of priming on proteinsynthesizing machineryPriming improves the integrity of theribosomes by enhancing rRNA synthesis.The microarray gene expression studiesin B. oleracea seeds, reveal that RNAlevels of genes encoding components ofthe translation machinery, such asribosomal subunits and translationinitiation and elongation factors,increase during osmopriming. Thus, oneof the ways in which priming enhancesprotein synthesis is by improving thefunctioning of the protein synthesismachinery.

v. DNA repair during primingMaintenance of the integrity of DNA byrepairing the damages incurrednaturally is important for generatingerror-free template for transcription andreplication with fidelity. It has beenreported that the damage to DNA whichaccumulates during the seed ageing isrepaired by aerated hydrationtreatments as also during early hours ofgermination. DNA synthesis measuredby the incorporation of 3H thymidine inartificially aged seeds of B. oleracea L.



was advanced by this treatment(compared to that in the untreated agedseeds) along with an improvement ingermination. This recovery in DNAsynthesis is attributed to pre-replicativerepair of DNA damaged during ageing bythe hydration treatment since treatmentwith hydroxyurea, which is an inhibitorof replicative DNA synthesis does notinhibit the synthesis. The exactmechanism of this repair is not yetknown and needs to be investigated.vi. Association between priming andthe cell cycleTo achieve maximum benefits frompriming, the process is stopped justbefore the seed loses desiccationtolerance, i.e. before the radicleemergence or stage III of water uptake.Radicle emergence involves cellexpansion and is facilitated by anincreased turgor pressure in thehydrated seed, whereas active celldivision starts after radical emergence.So, it is expected that priming does notexert any major effect on cell division perse. However, priming advances the cellcycle up to the stage of mitosis.Flow cytometric analyses of osmoprimedtomato seeds reveal that theimprovement of germination associatedwith priming is accompanied by increasein 4C nuclear DNA indicating thatpriming enhances DNA replicationallowing the advancement of the cellcycle from G1 to the G2 phase. It hasbeen confirmed that an increase in theproportion of nuclear DNA present as 4CDNA in high vigour cauliflower seedssubjected to aerated hydrationtreatment. It has also been reported as atwo-fold increase in total genomic DNAcontent in hydro-primed corn seed.Immunohistochemical labelling of DNAwith bromodeoxyuridine (BrdU) duringseed osmoconditioning in tomatoconfirms the presence of cells in the S-phase of the cell cycle synthesizing DNA.The actively replicating DNA is tolerantto drying as incorporation of BrdU isdetected in embryo nuclei before andafter osmoconditioned seeds are re-dried. Although the frequency of 4Cnuclei after the osmoconditioningtreatment is higher than that ofuntreated seeds imbibed in water for 24h, lower numbers of BrdU-labelled

nuclei are detected in osmoconditionedembryos. This is because of the fact thatthough priming enhances DNAreplication to some extent and facilitatesthe synchronization of DNA replicationin all the cells of the embryo, DNAreplication per se is lesser duringpriming under controlled hydration thanduring direct imbibition in water.Following western analysis it has beenobserved that the level of β-tubulin,which is a cytoskeletal protein and isrelated to the formation of corticalmicrotubules increases in response toaerated hydropriming. It has also beenobserved that accumulation of β-tubulinin all tissues of the tomato seed embryoduring osmopriming. After redrying β-tubulin appeared as granules orclusters. This is because microtubulesare sensitive to dehydration and arepartly depolymerized after drying. Theamount of soluble β-tubulin detectedafter re-drying is relatively high becausemicrotubules are dynamic structuresand exist in an equilibrium betweensoluble tubulin subunits and thepolymerized microtubules. Duringpriming, the cell cycle is arrested at theG2 phase allowing the synchronization ofcells. Mitotic events and cell divisionoccur earlier and to a greater extent inembryos of primed seeds uponsubsequent imbibition in water than inthe control seeds. Thus, the pre-activation of the cell cycle is one of themechanisms by which priming inducesbetter germination performance relativeto untreated seeds. The regulation of thecell cycle by priming could be throughthe regulation of the activity of the cellcycle proteins such as cyclins, cyclindependent protein kinases andproliferating-cell nuclear antigens(PCNA). Imbibition of maize seed in thepresence of benzyladenine increases theamount of PCNA over control, which isassociated with the acceleration of thepassage of cells from G1 to G2. There isno information on the effect of primingon the cell cycle proteins and researchneeds to be initiated in this area.vii. Effect of priming on energymetabolism and respirationIt has been observed that imbibition oftomato seeds in PEG results in sharpincreases in adenosine triphosphate(ATP), energy charge (EC) and ATP/ADP



(adenosine diphosphate) ratio. Theseremain higher in primed seeds even afterdrying than in unprimed seeds. Duringsubsequent imbibition in water, theenergy metabolism of the primed anddried seed is much more than that of theunprimed seed making the primed seedmore vigorous. The high ATP content ofthe re-dried primed seed is maintainedfor at least 4–6 months when stored at20oC. Maximum benefit of osmoprimingis obtained when performed inatmospheres containing more than 10%oxygen. Priming treatment is totallyineffective in the presence of therespiratory inhibitor (NaN3) at highconcentration, suggesting thatrespiration is essential for priming to beeffective. The beneficial effect of primingis optimal for values higher than 0.75for EC and 1.7 for the ATP/ADP ratio.Hydropriming improves the integrity ofthe outer membrane of mitochondriaafter 12 h of imbibition (estimated by thecytochrome C permeation assay), butthere is no concomitant increase in theability of the mitochondria to oxidizesubstrates. Significant increase in thenumber of mitochondria in response topriming has also been reported inosmoprimed leek cells, although thesehave not been correlated to respirationlevels. The association betweenimprovement in the mitochondrialintegrity by priming and mitochondrialperformance needs to be elucidated.

viii. Priming and seed dormancyPriming also releases seed dormancy insome crops. In thermosensitive varietiesof lettuce, germination is reduced orcompletely inhibited at hightemperatures such as 35oC. The embryoin lettuce seed is enclosed within a twoto four cell layer endosperm, whose cellwalls mainly comprise galactomannanpolysaccharides and hence theweakening of endosperm layer is aprerequisite to radicle protrusion,particularly at high temperatures. Endo-β-mannase is the key regulatory enzymein endosperm weakening, whichrequires ethylene for activation. Hightemperatures reduce germinationprimarily through their inhibitory effecton ethylene production by seeds, whichin turn reduces the activity of endo-β-mannase. Osmopriming of seeds with

PEG (–1.2 MPa) at 15oC with constantlight could overcome the inhibitoryeffects of high temperature inthermosensitive lettuce seeds in theabsence of exogenous ethylene supply.Imbibition of seeds of lettuce in1-aminocyclopropane-1-carboxylic acid(ACC, a precursor of ethylene) improvedtheir germination at 35oC and alsoincreases the activity of endo-β-mannase. Osmopriming of lettuce seedshad a similar effect as imbibitions inACC, improving both germination andthe activity of endo-β-mannase. Thissuggests that osmopriming is able tosubstitute the effect of ACC for breakingthermodormancy. Osmopriming in thepresence of aminoethoxyvinylglycine(AVG), an inhibitor of ethylene synthesis(it inhibits ACC synthase) does not affectthe enhancement of germination. Thus,osmopriming is able to overcome thedormancy even when ethylene synthesisis interrupted. A possible explanation forthis is that osmopriming helps inreleasing the ethylene within theembryonic tissues encased by theendosperm and seed coat and thiswould be sufficient to allow seedgermination. Priming in the presence ofsilver thiosulphate (STS), a putativespecific inhibitor of ethylene action,which interacts with the binding site ofethylene, inhibits germination,suggesting that ethylene activity isindispensable for the release ofdormancy. There are several studies thatshow an increased ability for primedseeds to produce ethylene. However, it isnot clear whether ethylene production isintegral to obtaining a priming effect inseeds or whether it is simply the resultof high vigour displayed by primedseeds. In other species also such astomato, carrot and cucumber which donot require ethylene, priming enhancesthe loosening of the endosperm/testaregion that permits germination atsuboptimal temperatures.

ix. Priming and seed longevityIn general, priming improves thelongevity of low vigour seeds, butreduces that of high vigour seeds. Thehigh vigour seed is at a more advancedphysiological stage after priming nearlyat stage III, and thus more prone todeterioration. When a low vigour seed is



primed, it requires more time to repairthe metabolic lesions incurred by theseed before any advancement ingermination can occur, thus preventingfurther deterioration.It has been observed that aeratedhydration treatments improve storagepotential of low vigour seeds anddecrease the longevity of high vigourseeds. The improved longevity of lowvigour seeds is associated withincreased Ki (initial seed viability) afterpriming and a reduced rate ofdeterioration.The most frequently cited cause of seeddeterioration is damage to cellularmembranes and other subcellularcomponents by harmful free radicalsgenerated by peroxidation ofunsaturated and polyunsaturatedmembrane fatty acids. These freeradicals are quenched or converted toless harmful products (hydrogenperoxide and subsequently water) byfree radical scavenging enzymes andantioxidants. Hydropriming andascorbic acid priming of cotton seed isreported to maintain germination andsimultaneously the activities of anumber of antioxidant enzymes such asperoxidase, catalase, ascorbateperoxidase, glutathione reductase andsuperoxide dismutase against theprocess of ageing. Also the accumulationof by-products of lipid peroxidation,such as peroxides, malonaldehyde andhexanals is decreased by osmopriming,which is correlated with decreased lossin viability of soybean seeds understorage. Solid matrix priming inmoistened vermiculite reduces lipidperoxidation, enhances antioxidativeactivities and improves seed vigour ofshrunken sweet corn seed stored at coolor subzero temperatures. Treatment ofshrunken sweet corn seeds with 2,2′-azobis 2-aminopropane hydrochloride(AAPH), a water-soluble chemicalcapable of generating free radicals,damages the seeds by increasing lipidperoxidation. This damage is partiallyreversed by solid matrix priming whichincreases free radical and peroxidescavenging enzyme activity andsubsequent reduction in peroxideaccumulation.As stated earlier, when high vigour seedlots are primed, their longevity gets

adversely affected. Attempts have beenmade by several workers to developmethods to restore seed longevity afterseed priming. Slow drying at 30oC whichreduces the moisture of osmoprimed B.oleracea to 25% in the first 72 h ofdrying, followed by fast drying at 20oC tobring the moisture level down to 7%improved the performance of theosmoprimed seed in a controlleddeterioration test compared to that ofthe osmoprimed seed subjected to fastdrying. Concomitant with the improvedlongevity of slow dried-seeds is theenhanced expression of two stresstolerant genes during slow drying. Thesetwo genes namely Em6 and RAB 18,which belong to the late embryogenesisabundant (LEA) protein groups, are alsoexpressed to a large extent in matureseeds and are responsible for conferringdesiccation tolerance during seedmaturation. Em6 belongs to group 1bLEA proteins and shares features withDNA gyrases or molecular chaperoneswhich suggest a role for Em6 inprotecting DNA integrity duringcontrolled deterioration treatments. RAB18 belongs to group 2 LEA proteins andencodes an abscisic acid (ABA)-inducibledehydrin. It accumulates in plants inresponse to drought stress and certainlyhas a protective role in stress tolerancebut the exact mechanism is not known.These genes are expressed to a lesserextent in the fast dried seeds becausethe moisture content drops much toorapidly.A post-priming treatment including areduction in seed water content followedby incubation at 37oC or 40oC for 2–4 hrestores potential longevity in tomatoseeds. This treatment is accompanied bythe increase in the levels of theimmunoglobulin binding protein (BiP) anER resident homolog of the cytoplasmichsp 70. BiP is known to be involved inrestoring the function of proteinsdamaged by any kind of stress and mayfunction as a chaperone in thereactivation of proteins damaged due tothe imbibition and drying processesinvolved in seed priming.

V. Seed priming – an overviewA broad term in seed technology,describing methods of physiologicalenhancement of seed performance



through presowing controlled-hydrationmethodologies. Seed priming alsodescribes the biological processes thatoccur during these treatments.Improvements in germination speedand/or uniformity common with primedseed lots

Seed priming – hydration statusIn primed seeds, Phase II is extendedand maintained until interrupted bydehydration, storage. Phase III wateruptake is achieved upon subsequentsowing and rehydration

Fig. Phases during seed priming: PhaseII is extended and maintained withinterruption by dehydration and

storage- In seed priming. Phase III isrehydration upon subsequent sowing

Seed priming – seedling establishmentPrimed seed contributes to betterseedling establishment especially undersub-optimal conditions at sowing (e.g.temperature extremes, excess moisture).Primed seed can also improve thepercent useable seedlings in greenhouseproduction systems (e.g. plugs,transplants)

Fig. Shift in germination time due toseed priming

Seed primingCurrently used commercially in high-value crops where reliably uniformemergence is important: Field seeding/plug production of

tomato, pepper, onion, carrots, leeks

Potted/bedding plants like begonia,pansy (Viola spp.), cyclamen,primrose and many culinary herbs

Large scale field crops (e.g. sugarbeet) and some turfgrass species

Also valuable in circumventinginduced thermodormancy (e.g. somelettuce, celery, pansy cvs.) - primingcan raise upper temperature limit forgermination

Physiological mechanisms of seedprimingKey processes involved include:1. Hydrotime concept2. DNA replication, preparation for celldivision (cell cycle studies)3. Endosperm weakening for specieswith mechanical restraint

Fig. Relationship between effectivenessof priming to hydrotime

4. Hydrotime accumulated duringpriming Priming treatment effectiveness is

linked to accumulated hydrotime Highest germination rate for broccoli

seeds ‘Brigalier’ occurred after 218and 252 MPa hrs

Fig. Relation between germination andhydrotime

When priming occurs at sub-optimaltemps, thermal time can also beadded to the equation.

Goal is to provide a predictive tool foridentifying optimal priming trts. for aseed lot without extensive empiricaltests.



General validity ofhydrotime/hydrothermal models hasspurred research on temps, H2Opotential thresholds and seedgermination dynamics.

Priming-physiology and eventsassociated with germination

Fig. Priming physiological eventsassociated with germination and post-

germinationPriming - technologiesThree basic systems used todeliver/restrict H2O and supply airto seeds, biopriming is the inclusionof beneficial organisms in addition toother basic priming. All can beconducted as batch processes.Commercial systems can handlequantities from tens of grams toseveral tons at a time.

1. osmopriming2. matrix-priming3. hydropriming4. biopriming

After completion of priming seeds arere-dried. Slow drying at moderatetemps is generally, but not alwayspreferable. Controlled moisture-losstreatments (e.g. slow drying, or useof an osmoticum) can extend seedlongevity by 10% or more inhydroprimed tomato, for example.Heat-shock is also used; keepingprimed seeds under a mild H2Oand/or temp stress for several hrs(tomato) or days (Impatiens) beforedrying can increase longevity.

Osmopriming (Osmoconditioning)

Seeds are kept in contact withaerated solutions of low waterpotential, and rinsed uponcompletion of priming.

Mannitol, inorganic salts [KNO3,KCL, Ca(NO3)2, etc] are usedextensively; small molecule size,possible uptake and toxicity adrawback.

Polyethylene glycol (PEG; 6,000-8,000mol. wt.) is now preferred; largemolecule size prevents movement intoliving cells.

For small amounts, seeds are placedon surface of paper moistened withsolutions, or immersed in columns ofsolution.

Continuous aeration is usuallyneeded for adequate gas exchangewith submerged seeds.

Matrix-priming (matriconditioning) Seeds in layers or mixes kept in

contact of water and solid of insolublematrix particles (vermiculte,diatomaceous earth, clay pellets, etc.)in predetermined proportions.

Seeds are slowly imbibe reaching anequilibrium hydration level.

After incubation/priming, the moistmatrix material is removed by sievingor screening, or can be partiallyincorporated into a coating.

Mimic the natural uptake of water bythe seed from soil, or greenhouse mixparticles.

Seeds are generally mixed into carrierat matric potentials from -0.4 to -1.5MPa at 15-20oC for 1-14 days.

Technique is successful in enhancedseed performance of many smallerand large seeded species.

Hydropriming (steeping) Currently, this method is used for

both in the sense of steeping(imbibition in H2O for a short period),and in the sense of ‘continuous orstaged addition of a limited amount ofwater’.

Hydropriming methods have practicaladvantages of minimal wastage ofmaterial (vs. osmo-, matripriming).

Slow imbibition is the basis of thepatented ‘drum priming’ and relatedtechniques.

Water availability is not limited here;some seeds will eventually complete



germinate, unless the process isinterrupted prior to the onset ofphase III water uptake.

At its simplest, steeping is anagricultural practice used over manycenturies; ‘chitting’ of rice seeds, on-farm steeping advocated in manyparts of the world as a pragmatic, lowcost/low risk method for improvedcrop establishment

Steeping can also remove residualamounts of water soluble germinationinhibitors from seed coats (e.g.Apiaceae, sugar beets).

Can also be used to infiltrate cropprotection chemicals for the control ofdeep-seated seed borne disease, etc.

Treatment usually involvesimmersion or percolation (up to 30oCfor several hrs.), followed by drainingand drying back to near originalSMC.

Short ‘hot-water steeps’(thermotherapy), typically ~ 50 oC for10 to 30 min, are used to disinfect oreradicate certain seed borne fungal,bacterial, or viral pathogens; extremecare and precision are needed toavoid loss of seed quality.

Drum priming (Rowse, 1996) – evenlyand slowly hydrates seeds to apredetermined MC (typically ~ 25-30% dry wt. basis) by misting,condensation, or dribbling.

Seed lots are tumbled in a rotatingcylindrical drum for even hydration,aeration and temperature controlled.

Fig. Machineries for Hydropriming

Biopriming (e.g. Bacillus,Trichoderma, Gliocladium)

Beneficial microbes are included inthe priming process, either as atechnique for colonizing seeds and/orto control pathogen proliferationduring priming.

Compatibility with existing cropprotection seed treatments and otherbiologicals can vary.

Priming – promotive & retardantsubstances Combination of priming with PGR’s or

hormones (GA’s, ethylene, cytokinins)that may affect germination

Transplant height control and seedpriming with growth retardants (e.g.paclobutrazol) also effective.

Other promoting agents, plantextracts can be included in futurepriming treatments.

Drying seeds after priming Method and rate of drying seeds

after priming is important tosubsequent performance.

Slow drying at moderate temps isgenerally, but not always preferable.

Controlled moisture-loss treatments(e.g. slow drying, or use of anosmoticum) can extend seedlongevity by 10% or more inhydroprimed tomato, for example.

Heat-shock is also used; keepingprimed seeds under a mild H2Oand/or temp stress for several hrs(tomato) or days (Impatiens) beforedrying can increase longevity.

Priming and development of freespace in seeds Hydropriming and osmopriming

showed tomato seed free spacedevelopment (8-11%), almost all atthe cost of endosperm area

When seeds are osmoprimed directlyafter harvest do not show free spacechange; dehydration prior to primingrequired.

Facilitates water uptake, speeds upgermination ?



Seed priming and ‘repair’ of damage – a modelFig. A model of seed deterioration and its physiological consequences during seed storage

and imbibition

Seed priming - conclusions Clear benefits, especially for seedling

establishment under less thanoptimal conditions.

Seed longevity of primed lots isnegatively affected (% RH oF = 80 orless, rather than 100%)

Priming alone does not improvepercent useable plants; removal ofweak, dead seeds also needed.

VI. Seed priming- The pragmatictechnology

Priming could be defined as controllingthe hydration level within seeds so thatthe metabolic activity necessary forgermination can occur but radicleemergence is prevented. Differentphysiological activities within the seedoccur at different moisture levels. Thelast physiological activity in thegermination process is radicleemergence. The initiation of radicleemergence requires a high seed watercontent. By limiting seed water content,all the metabolic steps necessary forgermination can occur without theirreversible act of radicle emergence.Prior to radicle emergence, the seed isconsidered desiccation tolerant, thus theprimed seed moisture content can bedecreased by drying. After drying,primed seeds can be stored untill time ofsowing.

Different priming methods have beenreported to be used commercially.

Among them, liquid or osmotic primingand solid matrix priming appear to havethe greatest following. However, theactual techniques and procedurescommercially used in seed priming areproprietary.

A. Types of seed priming commonly

used:

1. Osmopriming (osmoconditioning)This is the standard priming technique.Seeds are incubated in well aeratedsolutions with a low water potential, andafterwards washes and dried. The lowwater potential of the solutions can beachieved by adding osmotica likemannitol, polyethyleneglycol (PEG) orsalts like KCl.

Seeds in contact with aerated solutionsof low water potential is performed, andthen rinsed upon completion of priming.Mannitol, inorganic salts [KNO3, KCL,Ca(NO3)2, etc] are used extensively.However, salts of small molecule sizemay pose for possible uptake andtoxicity as drawback. Polyethylene glycol(PEG; 6,000-8,000 mol. wt.) is nowpreferred; it is large molecular size thatprevents movement into living cells.Seed Priming: Seeds of a sub-samplewere soaked in distilled water.Another sub-sample is pretrearedwith Polyethylene glycol 6000 (PEG)at a concentration of 253 g/kg watergiving an osmotic potential of -1.2MPa for 12 hours. Priming



treatments were performed in anincubator adjusted on 20 ± 1oCunder dark conditions. Afterpriming, samples of seeds wereremoved and rinsed three times indistilled water and then dried to theoriginal moisture level about 9.5%(tested by high-temperature ovenmethod at 130±2°C for 4 hours).Laboratory germination test: Fourreplicates of 50 seeds weregerminated between double layeredrolled germination papers. The rolledpaper with seeds was put into plasticbags to avoid moisture loss. Seedswere allowed to germinate at 10±1oCin the dark for 21 days. Germinationis considered to have occurred whenthe radicles are 2 mm long.Germinated seeds were recordedevery 24 h for 21 days. Rate ofseed germination (R) is calculatedaccording to Ellis and Roberts.(1980).2. Hydropriming (drum priming /Steeping)This is achieved by continuous orsuccessive addition of a limited amountof water to the seeds. A drum is used forthis purpose and the water can also beapplied by humid air. 'On-farm steeping'is the cheep and useful technique that ispractised by incubating seeds (cereals,legumes) for a limited time in warmwater.Hydropriming can also be practised toinfiltrate crop protection chemicals forthe control of deep-seated seed bornedisease, etc. Treatment usually involvesimmersion or percolation (up to 30oC forseveral hrs.), followed by draining anddrying back to near original SMC (seedmoisture content). Short ‘hot-watersteeps’ (thermotherapy), typically ~ 50oCfor 10 to 30 min, are used to disinfect oreradicated certain seed borne fungal,bacterial, or viral pathogens. Hereextreme care and precision are neededto avoid loss of seed quality.

3. Matrixpriming (matriconditioning)Matrixpriming is the incubation of seedsin a solid of insoluble matrix(vermiculite, diatomaceous earth, cross-linked highly water-absorbent polymers)

with a limited amount of water. Thismethod confers a slow imbibition.Adoption of Pregerminated seeds isonly possible with a few species. Incontrast to normal priming, seeds areallowed to perform radicle protrusion.This is followed by sorting for specificstages, a treatment that re-inducesdesiccation tolerance, and drying. Theuse of pre-germinated seedscauses rapid and uniform seedlingdevelopment.

In matriconditioning the use of sawdust(passed through a 0.5 mm screen) onseeds can be adopted to improve seedviability and vigour. The ratio of seeds tocarrier to water used was 1: 0.4: 0.5 (byweight in grams). The seeds areconditioned for 18 h at roomtemperature, and air-dried afterwardsfor 5 h. The treatment significantlyincreases pod yield 1.5 times as muchas the untreated.

Matriconditioning using eithermoist sawdust or vermiculite (210μm) at 15

oC for 2 days in the light

showed improvement in uniformityand speed of germination ascompared to the untreated seeds.The ratio of seed to carrier to waterused was 1: 0.3: 0.5 (by weight ingram) for sawdust, and 1: 0.7: 0.5for vermiculite. However, there wasno significant difference between thesawdust and vermiculite treatments.Uniformity increased from 42% inthe untreated to 61.7% in thesawdust- and 60.3% in thevermiculite-matriconditioned seeds.Speed of germination increased from17.3% to 20.0% (sawdust) or 19.7%(vermiculite). Even though therewere no significant differences ingermination and electricalconductivity betweenmatriconditioned seeds and theuntreated ones, matriconditioningtreatments increased percent ofgermination and reduced seedleakage as shown by reduction in theelectrical conductivity values of thesoaked water, thus improvement inmembrane integrity has occurred.



Study with hot pepper seed indicatedthat improvement in seed quality bysawdust-matriconditioning plus GA3treatment was related with increasein total protein content of the seed.The seeds were conditioned for 6days at 15oC, and the ratio of seedsto carrier to water was 1: 2: 5.Observations on blight disease incidenceat 45, 60 and 75 days after sowing wererecorded by scoring five plants in eachtreatment on a 0 to 9 scale of Mayee andDatar (1986) and percent disease index(PDI) was calculated using a formulagiven by Wheeler (1969)

Sum of numerical disease ratings 100PDI =xNo. of plants/leaves observedMaximum disease rating value

Head diameter, test weight (100-seedweight) and yield (quintal/ha) were alsorecorded.

4. Bio-priming or Biological SeedTreatmentBio-priming is a process of biologicalseed treatment that referscombination of seed hydration(physiological aspect of diseasecontrol) and inoculation (biologicalaspect of disease control) of seedwith beneficial organism to protectseed. It is an ecological approachusing selected fungal antagonistsagainst the soil and seed-bornepathogens. Biological seedtreatments may provide analternative to chemical control andbalanced nutrient supplement.Procedure Pre-soak the seeds in water for 12

hours. Mix the formulated product of

bioagent (Trichoderma harzianumand/or Pseudomonas fluorescens)with the pre-soaked seeds at therate of 10 g per kg seed.

Put the treated seeds as a heap. Cover the heap with a moist jute

sack to maintain high humidity.

Incubate the seeds under highhumidity for about 48 h at approx.25 to 32 oC.

Bioagent adhered to the seed growson the seed surface under moistcondition to form a protective layerall around the seed coat.

Sow the seeds in nursery bed. The seeds thus bioprimed with the

bioagent provide protection againstseed and soil borne plantpathogens, improved germinationand seedling growth (Figure)

Rice seed biopriming with Trichodermaharzianum strain PBAT-43

B. Priming – promotive & retardantsubstancesMany reports are available oncombination of priming with PGR’s orhormones (GA’s, ethylene, cytokinins)that may affect germination. Transplantheight control and seed priming withgrowth retardants (e.g. paclobutrazol)are also effective. Other promotingagents, plant extracts can be included infuture priming treatments.C. Drying seeds after primingMethod and rate of drying seeds afterpriming is important to subsequentperformance. Slow drying at moderatetemps is generally, but not alwayspreferable. Controlled moisture-losstreatments (e.g. slow drying, or use of anosmoticum) can extend seed longevity by10% or more in hydroprimed tomato, forexample. Heat-shock is also used;keeping primed seeds under a mild H2Oand/or temp stress for several hrs(tomato) or days (Impatiens) beforedrying can increase longevity.

VI. Discussion and conclusionsPre-sowing priming improves seedperformance as the seed is brought to a



stage where the metabolic processes arealready initiated giving it a head start overthe unprimed seed. Upon further imbibition,the primed seed can take off from where ithas left completing the remaining steps ofgermination (stage III) quicker than theunprimed seed. Priming also repairs anymetabolic damage incurred by the dry seed,including that of the nucleic acids, thusfortifying the metabolic machinery of theseed. Another beneficial effect of priming isthe synchronization of the metabolism of allthe seeds in a seed lot, thus ensuringuniform emergence and growth in the field.The different ways in which priming couldpossibly be effective at the subcellular levelin improving seed performance is depicted inFigure 1. This figure is an adaptation of thefigure suggested by Bewley et al.7 toillustrate the metabolic events in the seedupon imbibition in water. Since hydration isalso the key process in priming, albeit in acontrolled fashion, and conforms to thetriphasic pattern of water uptake, theoriginal figure has been superimposed withthe present one to describe the subcellularevents specifically associated with priming.The figure also incorporates other aspects ofpriming discussed in the earlier sectionssuch as its effect on dormancy release andseed longevity.The most important ameliorative effect ofpriming should be the repair of damagedDNA to ensure the availability of error freetemplate for replication and transcription.Since the water uptake is slower duringpriming than germination, the seed getsmore time for completion of the process ofrepair. Unfortunately, there is no directexperimental evidence to support orcorroborate this. One strategy (there could beother possible approaches) to specificallydetect repair synthesis differentiating it fromreplicative synthesis is to artificially inducedamage to DNA of the seed by UV irradiation.The damaged seeds can then be primed, theDNA labelled with BrdU, and ssDNAtransients generated during repair inresponse to priming can be detected using ananti- BrdU antibody.It is evident that priming advances themetabolism of the seed. Many proteins andenzymes involved in cell metabolism aresynthesized to a level intermediary betweenthe dry seed and the seed imbibed directly inwater, while a few of these are synthesized tothe same extent as the germinating seed.Some proteins are synthesized only duringpriming and not during germination. Forexample, the degradation products of certainstorage proteins (such as globulins andcruciferin) are detected only during primingand not when imbibed in water. A possibleexplanation is that the slight water stress

situation created during priming (particularlyosmopriming) can induce the breakdown ofthese proteins thus initiating the process ofreserve protein mobilization earlier than inthe unprimed seed. Similarly, low molecularweight HSPs are specifically synthesizedduring osmopriming and not duringimbibition in water. These proteins functionas molecular chaperones and are synthesizedto protect the cell from moisture stressoccurring during the process of osmoprimingbut they could very well be effective inprotecting those proteins also which aredamaged naturally. Free radical scavengingenzymes such as catalase and superoxidedismutase are synthesized duringhydropriming to protect the cell from damagedue to lipid peroxidation, which occurs dueto the oxidative stress induced byhydropriming. These enzymes could also beeffective in quenching the free radicalsgenerated by lipid peroxidation occurringnaturally.Priming synchronizes all the cells of thegerminating embryo in the G2 phase of thecell cycle so that upon further imbibition,cell division proceeds uniformly in all thecells ensuring uniform development of allparts of the seedling. Priming also preparesthe cell for division by enhancing thesynthesis of β -tubulin which is a componentof microtubules. These effects of priming areretained even after drying the primed seed.The exact mechanism by which primingregulates the cell cycle needs to beinvestigated. There is enhanced ATPproduction during priming, which is retainedeven after drying making the primed seedmore vigorous than an untreated seed.When a primed seed is stored underconducive conditions (low temperature andlow moisture) most of the beneficial effects ofpriming are retained. However, the storabilityof the primed seed per se is either improvedor adversely affected, depending upon theinitial physiologicalstatus of the seed. Priming improves thestorability of low vigour seeds, but reducesthat of high vigour seeds. The longevity ofseeds after priming can be extended bygiving post-priming treatments involvingsubjecting the seed to slight moisture andtemperature stress before drying the seedcompletely. These treatments areaccompanied by the synthesis of stressrelated proteins (similar to those which areabundant when the seed undergoesdesiccation during maturation) which protectthe cellular proteins from damage and thus,in turn, extend the seed longevity.While we know that all the beneficialsubcellular responses induced by seedpriming occur between stages I and II ofwater uptake, we are not able to give the



exact sequence of their occurrence at thispoint in time. Similarly, for optimization ofpriming technology, no suitable marker isreported, which can indicate the completionof stage II. This can be of immense practicaluse. More in-depth research on thephysiology of seed priming would help us torefine the technique and develop betterpriming protocols to achieve maximumbenefits.VII. Biofertilizer Delivery Systems

In seed biopriming, plant growthpromoting rhizobacteria are deliveredthrough several means based onsurvival nature and mode of infection ofthe pathogen. It is delivered through1. Seed treatment2. Bio-priming

3. Seedling dip

4. Soil application5. Foliar spray6. Fruit spray7. Hive insert8. Sucker treatment9. Sett treatment10. Multiple delivery systems

Various delivery systems of biofertilizers(Pseudomonas fluorescens, 108 cfu/gtalc based powder formulation) incontrolling phytopathogens enteringthrough different vulnerable sites

Delivery system Technique Purpose ModeSoaking of seeds in culturesuspension 10 g/lit for 24 h

Sheath blight of rice Establishment ofrhizobacteria on chickpearhizosphere

Seed treatment

Seed coating 4 g/kg seed Chickpea wilt Establishment ofrhizobacteria on chickpearhizosphere

Biopriming Incubation of seeds with culturesuspension at 25oC for 20 h

Increase germination andimprove seedlingestablishment

Proliferation andestablishment ofbacterial antagonist

Seedling deeping Root deeping in culturesuspension (20 g/ltr) for 2 h

Rice sheath blight byRhizoctonia solani

Prevents host-parasiterelationships

Soil application Braodcast culture 2.5 kg mixedwith 25 kg FYM or 50 kg soil

Chickpea wilt byFusarium oxysporum

Increases rhizospherecolonization of Pf

Foliarapplication

Foliar spay of culture 1 kg/ha onground nut at 15 days intervalssince 30 DAS

Leaf spot and rust ofgroundnut

Actively competes foramino acids on the leafsurface and inhibitsspore germination

Fruit spray Spray of 10% WP 10 g/lit overapple fruits

Blue and grey mold ofapple

Population of antagonistPs increased in wounds>10 fold during 3 monthsin storage (post harvestdisease management)

Hive insert Dispenser dusting over bee hiveand nectar sucking bees aredusted / coated with powderformulation

Erwinia amylovoracausing fire blight ofapple infects throughflower and developsextensively on stigma

Colonisation byantagonist at the criticaljuncture is necessary toprevent flower infection

Suckertreatment

Banana suckers were dipped insuspension (500 g/50 lit) for 10min after pairing and pralinageand followed by capsuleapplication (50 mg Ps/capsule) onthird and fifth month afterplanting

Panama wilt of banana Management of soilborne diseases ofvegetatively propagatedcrops

Sett treatment Setts are soaked in suspension(20g/l) for 1 h and incubated for18 h prior to planting

Red rot of sugarcane Acts as a predominantprokaryote in therhizosphere

Multiple deliverysystems

1. Seed treatment-4 g/kg of seed;followed by soil application-2.5kg/ha at 0, 30, and 60 DAS2. Seed treatment followed by 3foliar application

1. Pigeonpea wilt

2. Rice blast

Colonisation byantagonist in rhizosphereand phyllosphere

VIII. Benefits of seed primingFor practical purposes, seeds are primed



for the following reasons:1. Reasons of priming

to overcome or alleviatephytochrome-induced dormancy inlettuce and celery,

to decrease the time necessary forgermination and for subsequentemergence to occur,

to improve the stand uniformity inorder to facilitate productionmanagement and enhanceuniformity at harvest.

2. Extension of the temperaturerange at which a seed cangerminate

priming enables seeds to emergeat supra-optimal temperatures

alleviates secondary dormancymechanisms particularly inphoto-sensitive varieties

One of the primary benefits of priminghas been the extension of thetemperature range at which a seed cangerminate. The mechanisms associatedwith priming have not yet been fullydelineated. From a practical standpoint,priming enables seeds of several speciesto germinate and emerge at supra-optimal temperatures. Priming alsoalleviates secondary dormancymechanisms that can be imposed ifexposure to supra-optimal temperatureslasts too long or in photo-sensitivelettuce varieties.

3. Increases the rate of germination atany particular temperature

emergence occurs before soilcrusting becomes fully detrimental,

crops can compete more effectivelywith weeds, and

increased control can be exercisedover water usage and scheduling.

The other benefit of priming has been toincrease the rate of germination at anyparticular temperature. On a practicallevel, primed seeds emerge from the soilfaster and often more uniformly thannon-primed seeds because of limitedadverse environmental exposure.Priming accomplishes this importantdevelopment by shortening the lag ormetabolic phase (or phase II in thetriphasic water uptake pattern in thegermination process. The metabolic

phase occurs just after seeds are fullyimbibed and just prior to radicleemergence. Since seeds have alreadygone through this phase during priming,germination times in the field can bereduced by approximately 50% uponsubsequent rehydration. The increase inemergence speed and field uniformitydemonstrated with primed seeds havemany practical benefits:

4. eliminates or greatly reduces theamount of seed-borne fungi andbacteria

Lastly, priming has been commerciallyused to eliminate or greatly reduce theamount of seed-borne fungi andbacteria. Organisms such asXanthomonas campestris in Brassicaseeds and Septoria in celery have beenshown to be eliminated within seed lotsas a by-product of priming. Themechanisms responsible for eradicationmay be linked to the water potentialsthat seeds are exposed to duringpriming, differential sensitivity topriming salts, and/or differentialsensitivity to oxygen concentrations.

IX. Seed Priming Risks

The number one risk when using primedseed is reduced seed shelf life.Depending on the species, seed lot vigor,and the temperature and humidity thatthe seed is being stored, a primed seedshould remain viable for up to a year. Ifthe primed seed is stored in hot humidconditions, it will lose viability muchmore quickly. In most of the caseshowever, primed seed has shorter shelflife than the non primed seed of thesame seed lot. For this reason, it’s bestnot to carry primed seed over to the nextgrowing season.



Integrated Nutrient management: way to for sustainable cropproduction

P.S. Kulhare

Principal ScientistDepartment of Soil Science & Agril. Chemistry

College of Agriculture, JNKVV, Jabalpur

India has a total area of 328.8 millionha and land area of 316.6 m ha.Agricultural land area has beenrelatively stable since 1960at 180 M ha.Oh this, the crop land area is about 158M ha. The arable land area peaked at163 M ha in 1980 and has sincedeclined by 3 %, and additional declinedmay occur because of numerouscompeting uses ( urbanization,infrastructure development andindustrial installation) and losses todegradation by accelerated erosion, andsecondary salinization.

Whereas the availableagricultural and arable lands aredecreasing, the population is increasing.Therefore, there as an exponentialdecline in the per capita land area foragriculture and arable uses. The percapita land area has declined from0.34ha in 1961 to 0.18 ha in 2010 and theprojected to 0.10 ha by 2050.Thus, allbasic necessities for human wellbeing(food, feed, fiber and fuel)and otherecosystem services must be met fromper capita agricultural land are of < 0.1ha.

The production of major foodgrain increase drastically between 1961and 2010.The increase was by a factorof about 3 for rice, 9 for wheat, 5 formaize, and 3.4 for total grain production.The soybean production increased frommerely 5000Mg in 1960 to 12 million by2012, and it has a potential toquadruple within the coming decade. Yetthe production stagnated or declined forbarley and sorghum and increased bymarginally for for beans and lentils.Furthermore, most of the observedincreases in crop production forprincipal cereals (wheat, rice and maize)have occurred under irrigated conditionsand with increasing use of fertilizers andpesticides. Crop yields have stagnated

under rainfed conditions and low inputuse systems. Thus, there exists a largepotential to enhance food productionunder rain fed conditions.

In accord with the increase in theproduction, the net per capitaproduction index has progressivelyincreased between between 1965 and2011 from 73 to 122 for agriculture, 75to 111 for total cereals, 79 to 123 forcrops, 73 to 120 for total food and 81 to144 for non-food production. Whereasthe trends in agricultural and foodcomplacency because even greaterchallenges lie ahead Thus, there is astrong need to identify and implementintegrated nutrient managementpractices to enhance food productionfrom decreasing soil and waterresources, under changing anduncertain climate.

Reason of low crop production –(1) Inadequate imbalance use of

chemical fertilizer created a 8-10 M tnegative nutrient balance

(2) Only use of organic manure systemcannot sustain the crop productiondue to less availability.

(3) Deteriorating soil health / qualityresulting multi nutrient deficiencies.

(4) Decreasing nutrient response.

Integrated Nutrient management (INM)

INM is an integrated approach ofeffective and efficient utilization of allnutrient resources, organic includingmicrobial as well as inorganic which arelocally available economically viable, sociallyacceptable and ecofriendly for sustaining andincreasing crop production. INM technologyenvisaging conjuctive use of inorganic ,organic sources , hold great promise inmaintenance of soil quality , enhancingnutrient use efficiency and realizing optimumand sustainable yield of crops.



The effects of organic and inorganicfertilizers are complementary to eachother in terms of soil fertilityimprovement and sustainableagriculture

INM helps in restoring andsustain soil fertility and cropproductivity. It also helps in arrestingthe emerging deficiencies of macro,secondary and micronutrients favorablyby optimizing the physical, chemical andbiological environment of soil andachieving economy and efficiency infertilizer use. In view of shrinkage ofland resources for cultivation in, shortsupply and escalating cost of chemicalfertilizers, environmental pollution andill effects on soil animal, and humanhealth there is a need to adopt INMconcept for achieving the objective ofenvironmentally and economicallysustainable agriculture. Inclusion oflegume crops in cereal based croppingsequence, regularly or intermittently isof great help owing to their soilamelioration benefits. Prasad (1996) alsoreported that N fixed by legume cropsnot only meets their own requirementsbut also a sizable quantity (30-90 kg Nha-1) is left for succeeding crop. Thebeneficial effect of green manure in rice-wheat cropping system has beenrecorded to be 18% in terms of rice yield(Hegde and Dwivedi 1992).

Chemical fertilizers or organicmanure alone cannot sustains thedesired levels of crop production.Integration of chemical and organicsources and their efficient managementhave shown promising results not onlyin sustaining the production but also inmaintaining soil health (Au lakh 2011).

Advantages of INM

(1) Combined use of organic andinorganic have been well established.

(2) INM is helpful in arresting thenutrients deficiencies and favorablyoptimizing physical, chemical andbiological environment of soil andbringing economy and efficiency offertilizer.

(3) INM concept is economicallyfavorable, environmental friendlyand sustaining productivity andenhancing quality of soil.

Components of INM.1. Chemical fertilizers-

With the use of high yieldingvariety and increase of total irrigatedarea, chemical fertilizers played themost significant role in increasing theproduction of crop. The imbalanced andskewed application of NPK has not onlystagnated/reduced crop yield but alsoimproved nutrient use efficiency andcrop yield (Tiwari et al 2006).

Cost of fertilizer is increasing constantly,besides these, only use of inorganicfertilizer is adversely affecting the soilproductivity (Sutaria et al 2011).Adaption of the continuous use of NPKfertilizer has remarkably increasedproduction but simultaneously broughtabout problems related to secondaryand micronutrients deficiency,particularly those of S and Zn in soils.Decline in the crop response to appliedfertilizer nutrients, but a large part ofthis decrease could be as cribed togradual decline in the supply of soilnutrients to crops leading to macro andmicronutrients imbalances due to inappropriate fertilizer application andlittle recycling of organic sources(Aalakh and Malhi 2005).

2. Organic sources

Organic manure induceimprovements in soil quality andsustainable crop production. Theintegrated nutrient supply including useof chemical fertilizers with FYM,compost green manure, biofertilizers etchelps not only is bridging the existingwide gap between the nutrient removaland also in ensuring balance nutrientproportion , in enhancing nutrientresponse, efficiency and maximizingcrop productivity of desired quality.

The inclusion of legumes as aninter crop or otherwise in the croppingsequence contribute considerable Nthrough biological N – fixation andhaving residual effect on succeedingcereal crops. Long term fertilizerexperiments in different agro ecologicalzone of India clealy demonstrated thatover full application of recommendeddoses of NPK fails to sustain the soilquality and crop productivity, butcombined use of chemical fertilizers and



FYM could obtain higher crop yieldbeside improvement of soil fertility(Swarup,1998). The positive influence ofregular additions of organic manures onsoil quality was envident inimprovements in values of differentphysical , chemical and biologicalattributes of soil OC, mean weight

diameter, water retention , infiltration ,microbial biomass- C and microbialcount increased and bulk density andexchange acidity decreased with theapplication of recommended NPK+FYMcompared to NPK alone in long termexperiments (Table- 1 and 5, Chhibba,2010).

Table 1. Effect of organic materials on soil physical properties of soil under Rice-wheat production system

Post wheat harvest soil propertiesTreatment Bulk density

(Mg m-3)Infiltration rate

(x 10-2 cm min-1)Mean weight

diameterUrea to rice 1.72 2.30 0.35

GM (Sesbania) + urea to rice 1.68 3.00 0.40

FYM + urea to rice 1.70 2.75 0.41

FYM+GM to rice 1.64 4.64 0.49

Wheat straw + GM 1.67 4.19 0.44

Wheat straw + GM + urea 1.62 3.92 0.52

Wheat straw + urea + RS 1.65 3.45 0.46

Wheat straw + GM+ urea + RS 1.58 7.30 0.56

LSD (P =0.05) 0.03 - 0.03

FYM- Farmyard manure; GM – Sesbaniagreen manure; RS- Rice straw

Table 2. Effect of rice straw management on soil properties. Post - rice harvest soil properties

Straw management Bulk density(mg m-3)

Infiltration rate(cm h-1)

Mean weightdiameter (mm)

Aggregatestability (%)

Removal 1.69 0.34 0.26 8.0

Burning 1.67 0.34 0.32 10.0

Incorporation 1.59 0.41 0.37 15.0

LSD (P=0.05) 0.03 - 0.067 2.4

Table 3: Effect of green manuring on crop yield and soil nutrient status.Yield (t ha-1) Change over initial Apparent

nutrient balanceSequence

Rice Wheat O.C.(%)

P(kg ha-1)

K(kg ha-1)

N P K

Rice wheat 5.73 5.65 +1.1 +15.5 -7.8 +141 +28 -63

Rice–wheat-greengram GM 6.80 5.71 +19.1 +32.2 +2.1 +210 +76 -04

Rice-wheat-Sesbania GM 6.58 5.69 +14.6 +36.8 +2.5 +166 +70 -10

Table 4: Crop residue management and soil biological fertilityResidue managementParameter

Removal Burning IncorporationBacteria (x 106) 15.3 2.8 30.7Fungi (x 103) 60 10 109Phosphatase activity (mg p-NP g-1h-1) 125 135 175Dehydrogenase activity (mg TPFg-1 24 h-1) 36 33 52



Table 5: Effect of burning and incorporation of straw on soil nutrient status.

Sandy loam Silt loamTreatmentO.C.

(g kg-1)Available P(kg acre-1)

Available K(kg acre-1)

O.C.(g kg-1)

Available P(kg acre-1)

Available K(kg acre-1)

Burning 0.35 3.7 30 0.59 9.4 68Incorporation 0.42 4.6 33 0.66 10.4 73

Source: (Chhibba, 2010)The integrated nutrient supply has to bebased on need based application of fertilizernutrient and other amendments which mayrequired for correcting any fertilizer inducedimbalance in soil environment and health (Gos wami and Rattan, 2000).

3. Biofertilizers

Biofertilizers are the productscontaining living cells of different types asmicro organisms that have an ability tomobilize nutrients from non usable to usableform through biological process. Thesebroadly include N fixers, P solubulizercapable of mobilizing nonlabile nutrients andtransporting metals to and across the plantroots. On global basis biological fixed Npotential has been estimated at 139 M t/ha/yr as against 70 M t N fixed chemically(Brady and Weil, 1998). In India, BNFpotential is 20 mt/ annum for 1997-97against 10.08 mt fertilize N produced(Fertilizer statistics 1997-98). Conjointapplication of biofertilizers, chemicalfertilizers and organic manures, in additionto include of legumes in cropping systemand incorporation of on and off farmgenerated crop residues constitutes areefficient nutrient management strategy.

4. Legumes as green manuring.

Usefulness of legumes as soil fertilitybuilding practice in multiples croppingsystems is well established. Symbioticassociation of the legumes with differentspecies of Rhizobium has proved useful insequestering significant amounts ofatmospheric N in the soil plant system tothe extent of 25-50% of

the chemical fixed N requirement of thesucceeding cereal crop can be met byatmospheric N fixed by legume (Table-6).

Table 6: contribution of green manure forN fixation

Biomass (tha-1)

N harvest(kg ha-1 )

Dhaincha SesbaniaAculeta

22.5 125

Dhaincha Sesbaniarostrata

20.06 146

Sunhemp CrotolariaJuncea

18.4 113

Green gram Vigna radiata 6.5 60.2Black gram Vigna mungo 5.1 51.0Cowpea Vigna

unguiculata7.17 63.3

Sources: Pathak and Ram , 20045. Urban waste

Large quantity of city and urbanwaste is available that can be used as sourceof plant nutrients after proper treatment.Urban sludge improve soil structure containsecondary and micro nutrients as well aNPK.6. Recycling of Agriculture waste

Composting is the best method ofrecycling. Enriching of the nutrient value ofcompost is possible with gypsum. Rockphosphate , microbial inoculants andpressmud resources production from sugarfactories is a good sourced amendment foracid and sodic soils. For quick decompositionof agricultural waste application of efficientstrategies of micro-organics is a practical.(Table -7)

Table 7: Nutrient potentiality of various organic resourcesTypes of organic resource Total nutrients (Mt yr-1)

Availability(Mt yr-1)

N P2O5 K2O Total (N+P2O5+K2O)

Crop residues 273 1.28 1.97 3.91 7.16Cattle manure 280 2.81 2.00 2.07 6.88Rural compost 285 1.43 0.86 1.42 3.71Forest litter 19 0.10 0.04 0.10 0.24City garbage 15 0.23 0.15 0.23 0.61Press mud 3 0.03 0.079 0.055 0.164Sewage water (millioncubic meters)

6351 0.32 0.14 0.19 0.65

Industrial waste water(million cubic meters)

66 0.003 0.001 0.001 0.005

Total 6.203 5.20 7.976 19.419



Conclusion

The integrated managementshould we based on the need offertilizers nutrients and amendments foroptimum supply of nutrients to the cropusing all the possible nutrient sourcesfor sustainable crop production.

References

Aulakh, M.S. (2011) Integrated soiltillage and nutrient management;the way to sustain cropproduction, soil plant-animal-human health and environment.Journal of Indian society of soilscience. 59 (Supplement) 523-534.

Aulakh, M.S. and Malhi, S.S. (2005)Interactions of N with othernutrients and water-Effect oncrop yield and quality, nutrientuse efficiency, carbonsequestration and environmentalpollution. Advances in agronomy86, 341-409.

Brady , N.C. and weil, R.K. (1998) Thenature and properties of soils,M.C. Millan Pub. New York.

Goswami, N.N. and Rattan R.K. (2002)Ecofriendly and efficientintergrated nutrient managementin sustainable agriculture.

Hedge, D.M. nad Dwivedi, B.S. (1992)Nutrient management in rice-wheat cropping system in India.Fertilizer News 39,19-26.

Prasad, R. (1996) cropping andsustainability of agriculture.Indian farming 46, 39-40.

Sutaria G.S. Akbari, K.N., Vora, V.D.Padmani, D.R. (2011) Residualeffect of nutrient management onsoil fertility and yield of blackgram under rainfed condition.Legume Reseaarch 34, 59-60.

Swarup, A. (1998) Emerging soilfertilizer management issues andsustainable crop production inhigher system in long termfingermillet maize cropping inAlfisol. AICRP - LTFE IndianInstitute of Soil Science,Nabibagh, Bhopal, P.P. 1-1

Tiwari K.N. Sharma, S.K. Singh, V.K.Dwivedi, B.S. and Shukla, A.K.(2006) site specific nutrientmanagement for increasing cropproductivity in India. Resultswith rice-wheat system. PDCSRModipuram and PPIC IndiaProgramme Gurgaon. ResearchBulletin 1/2006, PP 1-92.



Screening and evaluation of plants for high water-use efficiencyR.S. Shukla and Niharika Shukla

Department of Plant Breeding and GeneticsJawaharlal Nehru KrishiVishwavidyalaya, Jabalpur - 482004 (MP)

[email protected]

Introduction:To meet the rising worldwide

demand for food, there are someoptions, such as further exploration ofplanting in dry seasons, that often leadsto lower yields, increased productivity,and the expansion of cultivation areas,an alternative that ensures greater foodproduction and is still viable in someemerging countries. When wateravailability and soil nutrients arelimiting to plant growth anddevelopment, there is a reduction ofmetabolism, biomass, and the surfaceareas of various plant organs, thusaffecting the productivity (Sultenfussand Doyle 1999). Considering this fact,several plant breeding programs haveemerged, and other lines of researchhave been directed at improvingconditions for abiotic stresses. Thus, twobreeding strategies can be considered:tolerance to a low availability of waterand nutrients and resource-useefficiency.

is an urgent imperative (Hamdyet al., 2003). Of the world’s allocablewater resource, 80% iscurrentlyconsumed by irrigated agriculture. Thislevel ofconsumption by agriculture is notsustainable into the future. Projectedpopulation growth (another 2 billionpeople within 2–3 decades) will requirethat more of the available water resourcebe used for domestic, municipal,industrial, and environmental needs.The most realisticsolution to theincreased demand for water will bereallocation to these other purposes ofsome of the water currently used byagriculture. Even a modest reallocation,reducing agriculture’s share to 70%,would increase the amount of wateravailable for other purposes by up to50%. However, the expandedpopulations will not only need morewater to satisfy these other purposes; itwill also need to be fed and clothed. Thiswill require substantially more efficient

production from a smaller irrigationwater resource. It will also requiresubstantially higher water-use efficiencyfrom rain-fed agriculture, which remainsthe primary means of food production inmost countries and for most farmers.Several strategies will be required toimprove the productivity of water use inirrigated and rain-fed agriculture (Wanget al., 2002).Breeding crop varieties thatare more efficient in theirwater use isone such strategy. Others includemanagement of the water resource andchanges in crop management. None ofthese strategies should be seen asoperating in isolation. Rather, it is likelythat the greatest gains will be obtainedthrough complementary approachesinvolving each of them.In this article,recent progress in breeding for highwateruseefficiency will be reviewed andsome possible avenues for makingfurther advances will be outlined. As astarting point, the article will firstestablish a conceptual framework forconsidering ways by which crop water-use efficiencymight be improved throughbreeding. The prospects forimprovingcrop water-use efficiency by changingthe wateruseefficiency of leaf gasexchange will be considered insomedetail. Other likely avenues will also beconsideredbriefly where substantialgains in crop water-use efficiencycouldbe made. The review willsconcentrate oncereals andparticularly on wheat, adominant food crop which is growninirrigated and rain-fed productionsystems over a widerange of latitudes.Wheat is also a crop that has beenthefocus of a long-standing breedingeffort for higher wateruseefficiency.

The definition and concept of water useefficiency (WUE) at different scales:WUE is a complex trait that is controlledby many genes that are related tophysiological drought-resistancetraits.In agronomic terms, WUE is equalto biomass yield, oreconomic yield, or



economic value/amount of waterused(Condon et al., 2002,). There arethree requirements:the first is that WUEis related to droughtresistanceanddrought tolerance, and utilization ofwater with high efficiencybut littlebiomass and yield under seriouswaterstress; the second is that WUE isrelated to water-savingand the highlyefficient use of water, mediumdroughtresistance (tolerance), andmedium or medium-highyield undermoderate water stress. The third is thatWUEis related to the highly efficient useof water and maximumpotential yield.These three kinds of descriptionfor WUEbasically reflect the nature of traditionalcrop. WUE although they emphasizecorrespondingly differentaspects (Zhanget al., 2007; Shao et al.,2010).In terms of physiology, WUE is equal tothe accumulationof assimilationproducts/amount of waterused(transpiration, T), which reflects theenergy conversionefficiency per unit ofwater used in the plant. WUE couldbedefined as encompassing three concepts:one is thatleaf WUE (WUEl) ortranspiration efficiency (TEl) isphotosynthesis rate (Pn) /transpirationrate (T), where Pnand T are measuredwith suitable apparatus. The secondisthat WUE for the whole plant (WUEp) isthe weight ofbiomass or economic weight/amount of water used (ET, T).Water-use efficiency as a breedingtarget:Breeding to address a specific objectiveimplies first, thatthe objective has beenwell defined and, second, that heritabletraits have been identified that can comesomeway towards achieving the breedingobjective. ‘Water-use efficiency’ as abreeding target could be defined in manyways, depending on the scale ofmeasurement and the unitsof exchangebeing considered. All potentialdefinitions will have some measure ofwater being exchanged for some unitofproduction. For physiologists, the basicunit of reductioncould be moles ofcarbon gained in photosynthesis(A) inexchange for water used in transpiration(T). Thusa physiological definition mightequate, at its most basiclevel, to theinstantaneous water-use efficiency ofleaf gas exchange (A/T). For farmers andagronomists, the unit of production is

much more likely to be the yield ofharvestedproduct achieved from thewater made available to the cropthrough precipitation and/or irrigation,i.e. a farmer’s definition is one ofagronomic water-use efficiency. Whileagronomic water-use efficiency will betaken to bethe ultimate breeding target,a major thrust of this article willbe toplace the physiological definition ofwater-use efficiencyin the context of thefarmer’s definition. To do this it isusefulto consider crop yield as beingconstructed froma framework ofrelatively simple components (equation1).Yield=ET3T=ET3W3HI ð1ÞIn this framework, grain yield isdescribed as beinga function of theamount of water used by thecrop(evapotranspiration, ET), theproportion of that wateractuallytranspired by the crop (T/ET), thetranspirationefficiency of biomassproduction (W), i.e. how muchbiomass isproduced per millimeter of watertranspired,and, lastly, how effectivelythe achieved biomass is partitionedintothe harvested product, i.e. the ratio ofgrain yieldto standing biomass termedthe harvest index (HI). Thisframework isnot based on the notion of ‘droughtresistance’,but rather on the broadprocesses by whichcrops actuallyachieve yield in water-limitedenvironments(Richardset al., 2002).None of the components of this yieldframeworkis truly independent of theothers, but each can be considered atarget forgenetic improvement. Leaf-levelwater-use efficiency, A/T,is directlyrelated to only one of these components,W, thetranspiration efficiency of biomassproduction. However, aswill bediscussed in following sections, A/T alsohas thepotential to influence each of theother three components in the yieldframework.Varietal Differences in WUE:Crop breeders interested in developingcultivars that can perform well underwaterlimitedconditions would like toincrease wholecropWUE. Over the lastfew decades, evidence hasaccumulatedthat there is substantial variability forWUE within species, suggesting thatWUE isa factor that can be improvedthrough selection.However, recall thatmaximum single leaf WUE tends to



occur at very low stomatal conductance,where photosynthetic CO2 assimilationis also very low; Obviously, this is notanideal characteristic for a commercialcultivar. Thus, selecting for maximumWUE per se is not apromising strategyfor breeders. Instead, they must selectfor both high WUE and high cropgrowthrates. Such a combination would arisefrom: Appropriate stomatal regulation

(no "luxury" water consumption,but enough

conductance to support highrates of photosynthesis)

High leaf photosyntheticresponse to CO2 (thusmaintaining low ci)

Low rates of maintenancerespiration

The next figure shows the differencesin WUE recorded in Israel for a numberof upland cotton(Gossypium hirsutum),and Pima cotton (Gossypiumbarbadense) lines, as well as a hirsutumx barbadense interspecific cross. In thisfield experiment, differences in WUEbetween the lineswere similar, whetherWUE was measured on the basis of totalabove ground DM, or yield ofseedcotton.The final figure shows thefrequency distribution for WUE amongF4derivedlines from a crossbetween thesoybean variety "Young" (high WUE) andan exotic plant introduction (lowWUE).The approximately normaldistribution of WUE among these linessuggests that WUE is a quantitativelyinherited (multi gene) trait.Breeding for greater leaf-level water-useefficiency:The prospect of improving agronomicwater-use efficiencyby breeding forgreater leaf-level water-use efficiencyhaslong been an attractive one. To assistinidentifying ways this might beachieved, leaf-level wateruseefficiency,A/T, can be described mathematicallybynoting that, first, A is the product ofstomatal conductance toCO2 (Gc) andthe gradient in concentration of CO2between the outside (Ca) and inside (Ci)of the leaf (equation 2)A=GcðCa_CiÞð2Þand, second, that T is the product ofstomatal conductance to water vapour(Gw) and the gradient in concentrationofwater vapour from the inside (Wi) to

the outside (Wa) of the leaf (equation3)T=GwðWi_WaÞ ð3ÞFor CO2, theconcentration is greater in the airoutside theleaf, while the reverse is truefor water vapour. The ratio A/Tthenbecomes (equation4)A=T=½GcðCa_CiÞ_=½GwðWi_WaÞ_ð4Þwhich can be simplified even further(equation 5) by notingthat the ratio ofthe diffusivities of CO2 and watervapour inair has a value of c. 0.6.Thus,A=T_0:6Cað1_Ci=CaÞ=ðWi_WaÞð5ÞEquation (5) indicates two possibleroutes for improvingleaf-level water-useefficiency. One is to lower the value ofCi/Ca, thereby increasing the value of(1_Ci/Ca). The otheris to make (Wi_Wa)smaller, i.e. to make the gradient drivingtranspirational water loss smaller.

Whole Crop WUE:As we have seen, crop physiologists havea strong theoretical understanding ofthe factors thatdetermine WUE at thesingle leaf level. However, it is quitedifficult to apply these concepts inaquantitative manner at thewholecanopylevel.First, there is theobvious complexity of trying to modelthe activity of all leaves in the canopysimultaneously, when each leaf has itsown distinct light environment, and itsown distinctphotosynthetic response tolight and CO2.Additional complicationsarise from the fact that whole crop WUEis measured in terms of drymatteraccumulation, over relatively longperiods of time. This means that WUE,measured on awholecropbasis, will beaffected by any factor that affects finaldry matter. For example, allother thingsbeing equal, a higher rate ofmaintenance respiration will decreasecrop WUE.Similarly, crops that producelarge amounts of energyrichcompounds,such as lipids, will WUE.Whereas it issometimes difficult to pinpoint thephysiological basis of differences inwholecropWUE, there is no doubt thatsuch differences exist. For instance, ithas been known for over 70years thatcommon crop species differ in WUE.Based on the theorydescribed above, canyou speculate as to why C4 plants wouldtend to have higher WUE than C3plants? Also, why do you think sugarbeet has such a high WUE?



Lowering the gradient in water vapourconcentration: The simplest and most influentialmeans by which breedinghas improvedthe transpiration efficiency of biomassproductionvia greater A/T has been tochange crop characteristicsso as tolower the average evaporative gradientduringthe crop growth cycle. Reflectingprocesses at the leaf level, cropwaterloss is driven by the gradient inwater vapour concentration between thecrop canopy and the atmosphere. Thisgradientis least in cool, humid regionsand, in most regions, duringthe coolestmonths of the year. During the pastcenturybreeders of many crop specieshave exploited geneticvariationassociated with intrinsicearliness, response to photoperiod, andvernalization requirement to generateenormousvariation in crop phenology.This phenological variation has allowedcrops to be grown successfully inregions and attimes of the year thatlower the prevailing evaporativedemand,thus raising A/T and boostingcrop yield. As opportunitiesarise, everyeffort should be taken to exploitthissimple route to improved crop water-use efficiency further. Even seeminglyunrelated objectives, such as eliminatingdisease susceptibility so that crops canbe grown reliably incooler, more humidconditions may present opportunitiestoadjust sowing time and cropphenology for improved A/Tand cropyield. A good example of what is possibleis thedoubling of yield achieved byimproving the disease resistanceofchickpea, transforming it from a spring-sown toan autumn-sown crop innorthern Syria.

Changing the value of Ci/Ca:Referring back to equation (5), anotherway that breedingcould improve A/T,and thereby improve thetranspirationefficiency of biomassproduction, is to raise the value of thenumerator (1_Ci/Ca), i.e. to selectgenotypes for which the ratio Ci/Ca issmall. A small value of Ci/Ca will reflecteither relatively low value of G, arelatively high photosyntheticcapacity(amount and activity of photosyntheticmachineryper unit leaf area) or acombination of these two. The

interrelationships between Ci/Ca,photosynthetic capacity, and stomatalconductance are perhapsbestappreciated in the context of the ‘A/Ci’plot (Long and Bernacchi, 2003). In sucha plot (Fig. 1), curved lines rising fromnear the origin describe the dependenceof A on Cias external CO2 concentrationis varied experimentally. Variation in theinitial slope of these curves equates tovariationin photosynthetic capacity. InFig. 1, the two curved lines areintersected by two straight linesoriginating at theambient CO2concentration, Ca. Variation in the slopeofthese straight lines equates tovariation in stomatal conductance. Theintersections indicated by numeralsrepresentthe operating values of Ci (andthus Ci/Ca, A, and G) forthreegenotypes of a C3 species. As shown inFig. 1, lower operating values of Ci/Ca(say 0.6 compared with 0.7) may beachieved through higher photosyntheticcapacity (genotype‘2’ compared withgenotype ‘1’), lower stomatalconductance (genotype ‘3’ comparedwith genotype ‘1’), or acombination ofthese two.The relationship between carbonisotopediscrimination and Ci/Ca:Despite the advent of reliable, relatively-portable leaf gasexchangesystems, it ispertinent to note that G, photosyntheticcapacity, and A/T are still tedious tomeasure in large breeding populations.It is now accepted that relativedifferences in Ci/Ca, at least within C3species,may be evaluated indirectly bymeasuring the carbon isotopecomposition of plant dry matter. Thestable isotope of carbon, 13C, makes upvery close to 1% of the carbon inatmospheric CO2. The proportion of 13Cin the dry matter ofC3 plants isfractionally less than in the atmosphere,primarily becauseC3 speciesdiscriminate against13Cduringphotosynthesis. Carbonisotope discrimination (D13C) isameasure of the 13C/12C ratio in plantmaterial relative tothe value of the sameratio in the air on which plants feed, andhas been defined asfollows:D13C=½ðRa=RpÞ_1_31000ð6Þwhere Ra is the value of the13C/12C ratio in the atmosphere andRp is the value of 13C/12C in plant



material. Forconvenience, units of D13Care expressed as per thousand(&), i.e.the fractional difference from unity ismultipliedby 1000. The ratio Ra/Rp hasa value near 1.02 for C3 plants, givingvalues of D13C near 20&.There areseveral processes that contribute to thevalue ofD13C measured in plant drymatter of C3 speciesCarbon isotope discrimination andwater-use efficiency:The realization that D13C could providea relatively simple, indirect measure ofvariation in A/T gave renewed impetusto theprospect of exploiting variation inleaf-level water-use efficiency to improveagronomic water-use efficiency. Uptothat time, it had been considered thatthere was little variation in Ci/Ca withinor among C3 crop species, theonlysubstantial difference being thatbetween C3 and C4 species. Sincethepioneering work of Farquhar andcolleagues, it has subsequently beendemonstrated, for several C3 species,that variation in D13C closely reflectsvariation in the ratio Ci/Ca.Variation inD13C among genotypes of C3 species islarge enough to, in theory, generatesubstantial variation inA/T andpotentially, substantial variation inwater-use efficiency of dry matterproduction. This has been confirmed innumerous studies with pot-grownplants. Negative correlations betweenD13C andplant water-use efficiencyhave been demonstrated inmanyspeciesHowever, significantchallenges have arisen as attempts havebeen made to ‘scale up’ fromassociations betweenD13C and water-use efficiency of leaves and single plantsto associations between D13C andwater-use efficiency and yield of fieldstands. Some of these challenges wereanticipated, others were not. The natureof these challenges and possiblesolutions are considered in the followingsections.Relationships between grain yield andcarbonisotope discrimination inwheat and barley:The greatest challenge to using D13C inbreeding for greateragronomic water-useefficiency is the high level ofinconsistencyobserved in therelationship between D13C andyield.This inconsistency has been well-

documented in numerousstudiesinvolving the cereals bread wheat(Triticum aestivum L.), durum wheat (T.turgidum var. durum L.) andbarley(Hordeum vulgare L.). From the negativeassociationbetween D13C and leaf-levelA/T and the consistentlynegativeassociations observed between D13Cand wateruseefficiency at the singleplant level in many pot studies, itmightbe inferred that crop yield and D13Cmight also beconsistently negativelyrelated. Yet for a largenumber ofstudiesinvolving collections of cereal genotypesgrown inrain-fed and irrigatedenvironments in Australia theMediterranean region andelsewhererelationships reported betweengrain yield andD13C have onlyinfrequently been negative. Muchmoreoften these relationships have beeneither positive or‘neutral’. Many of thestudies on associationsbetweenproductivity and D13C incereals have used sets of genotypesinwhich there has been substantialvariation not onlyin D13C, but inflowering date and height as well,twocharacteristics that could stronglyinfluence yield independentof variationin D13C.Why have relationships between grainyield and D13C beenso variable in somany studies? There appear to beseveralreasons, but a critical one is thatfor cereals low-D13C (highA/T) is a‘conservative’ trait in terms of water useand,perhaps more importantly, in termsof crop growth rate. Putsimply, in theabsence of soil water deficit, low-D13Cgenotypes tend to grow slowerthan high-D13C genotypes,resulting inlower total biomass production andgrain yield. So, in cereals, higherphotosynthetic capacity maynotnecessarily be associated with fastercrop growth rate. Asimilar conclusioncan be drawn from the study by onphysiological changes in breadwheatreleased by CIMMYT from 1962 to1988. The more recentof thesewheat hadsubstantially higher grain yields underirrigation, but this was not associatedwith greater biomass production. Theyield gain, however, reflectedhigherharvest index for the more recentwheat Among this ‘historic’ collection ofCIMMYT wheat there was nochange in



total biomass production despite themore recentwheat having both higherphotosynthetic capacity andhigher G,together generating substantially highervalues ofA on a leaf area basis.Interactions between growth andwater use:Irrespective of its physiological basis,‘conservative’ cropgrowth by low-D13Ccereal genotypes hasimportantimplications for agronomicwater-use efficiency. Themostconsistently positive relationshipsbetween D13C and yieldhave been foundin environments or seasons wheresupplementalirrigation or regularrainfall events throughout the growingseason have maintained a high soilwaterstatus. In these environments thefaster growth of high-D13C genotypeshas usually translated directly intohigherfinal biomass production andgrain yield. Low-D13C genotypes haveachieved less biomass and lower yields.It is also likely that they have also leftmore waterbehind in the soil profile atmaturity. In less favorableenvironments, variation in the extentandtiming of any water limitation mayinteract with the’ conservative’ growthand water use of low-D13C genotypestogenerate complex relationships betweenyield andD13C. This complexity is alsoillustrated in. In thedrier 1992 season,high-D13C was associated withlowerbiomass production and grain yieldin the lines from onecross but for linesfrom the secondcross there were noassociationsbetween productivity andD13C. Soil water status at flowering islikely to have been higher for the secondcrossbecause lines from this crossflowered, on average, oneweek earlierthan lines from the first cross. Theresults forthese two sets of lines grownin these two seasons indicatethat theamount of rainfall is an importantvariable contributingto variation in grainyield. They also indicate that thetimingof development of soil water deficit, withrespect tothe critical flowering phase, isalso an important variable.If high-D13Cgenotypes exhaust the available soilwatertoo quickly, before flowering, thereis likely to be a yieldpenalty. However,the penalty, interms of crop water useand yield, associated with fastergrowthof high-D13C cereals is not always as

great as mightbe expected. In fact, thefaster growth of high-D13Ccerealgenotypes has often been shown tobe of benefit in seasonsor environmentsin which frequency of rainfall eventswashigh early in the season, but was notsustained during laterstages of growth,typical Mediterranean-typeenvironment(Merah et al., 2001; Royoetal., 2002;) In this sort of environment,evaporation from the soilsurface canaccount for as much as 50% of thegrowingseason rainfall. Studies wherewateruse has been carefully partitionedbetween plants and soilhave shown thatthe more ‘profligate’ transpirationassociatedwith high-D13C actuallyresulted in little differencein total wateruse to anthesis, despite substantiallymore growth by high-D13C genotypes atthis critical stage of development. Inother environments high-D13Cgenotypes have achieved greateranthesis biomass at the expense ofsubstantiallygreater soil water depletionat anthesis. Yet despite achieving verylittle growth afterflowering comparedwith low-D13C genotypes that hadbeenmore conservative in their water use, thehigh-D13Cgenotypes were still able toyield more. This was becausehigh-D13Cgenotypes achieved a larger grainnumber(associated with higher anthesisbiomass) and were thenable to fill thesegrain, probably by trans locatinglargeamounts of stored assimilate. In thesame environmentslow-D13C genotypesfailed to use stored assimilatesaseffectively. They may have had fewerreserves, due to less anthesis biomass,or the stored assimilates may nothavebeen necessary because the low-D13C genotypes had subsoilmoisture inreserve to sustain higherphotosynthesisduring grain filling. Oneoutcomeof achieving high yield, despiterelatively little post an thesis growth, isthat high-D13C genotypes tend to haveahigher harvest index (HI).Finally, therehave been a small number ofstudiesconducted in environmentswhere there was relatively littlerainfallduring the growing season and cropsrelied heavilyon soil moisture reservesfrom substantial rains beforesowing orvery early in crop development. It hasbeen in these few studies, where therewasrelatively little soil evaporation and a



strong reliance onmetering-out soil-water reserves before anthesis, thatnegative associations between yield andD13C have been mostconsistentlyobserved.

Yield response to breeding for high A/T:Experience over many growing seasonsat a range oflocations in easternAustralia, supported by the outcomesofthe simulation study, indicated thatbreeding for higher A/Tcould have alarge average benefit in the northerncroppingregion of eastern Australia. Inthis region the wheat croprelies onmoisture stored from summer rains andT makesup a large proportion of totalcrop ET. A back crossing programmewas initiated to improve A/T (i.e. lowertheD13C) of the relatively high-D13Cvariety Hartog, widely grown inAustralia’s sub-tropical northern region.Briefly, Hartog was crossed with a low-D13C donor, the lowest-D13C F3families were selected and these wereback-crossed with Hartog twice more,without selection between thesetworounds of crossing.The effect on yield ofdivergent selection at the BC2stage,based on measurements of D13C wastested bygrowing 60 BC2 lines with verysimilar height and floweringtime in ninerain-fed environments in easternAustraliaand five in Western Australia.Thirty of the BC2 lines hadhigh A/T (lowD13C) and the other 30 had low A/T(highD13C).Opportunities to improve yield bybreeding forhigh A/T in other species:Exploiting high A/T in breeding forgreater agronomicwater-use efficiency iscomplicated for cereals by anassociationbetween high A/T and slow crop growthrate.This seems not to be the case forgroundnut (Arachis hypogaea L.). Forthis species, field studies in bothwellwateredand water-limitedenvironments consistently showgreaterbiomass production to be associatedwith higher A/T(Nautiyal et al., 2002). Ingroundnut,variation in photosyntheticcapacity accounts for a largeproportionof the variation in A/T. Importantly,high photosynthetic capacity inthisspecies does not appear to beassociated with a slower rateof leaf areagrowth. Effective selection for high A/Tingroundnut is achieved via selection for

low specific leafarea (SLA), a lessexpensive alternative to D13C.However,one complication still remains,which is a tendency for lowSLA (highA/T) to be associated with low HI Theproblem is being overcome byapplyingconcurrent selection pressurefor low SLA and high HI(Nigam et al.,2001).

There may be species in additionto groundnut in whichhighphotosynthetic capacity is associatedwith faster cropgrowth and higher A/T.Likely candidates may be othergrainlegumes because they have the capacityfor symbioticnitrogen fixation. Limitedscreening of cowpea (Vigna unguiculata(L.)Walp.)and common bean (Phaseolusvulgaris L.) germplasm indicates thatvariationin stomatal conductance maybe the dominant source ofvariation inA/T for these species. More extensivescreeningis warranted in these andother legumes.Identifying species orgenotypes of species in whichhighphotosynthetic capacity isassociated with faster crop growth andhigher A/T could be done by combiningmeasurementsof D13C withmeasurements of conductance and/orphotosyntheticcapacity. There aretechniques available fordetectinggenotypic variation inconductance directly andrapidly usingviscous-flow porometers or indirectlyusing oxygen isotope composition ofdrymatter or canopy temperature.Measurements of specific leaf areaor leafchlorophyll concentrationmay beeffective means ofcharacterizingvariation inphotosynthetic capacity. Of coursetheremay also be cropping environmentsfor some crop specieswhere the slowcrop growth rate and high A/Tassociated with low stomatalconductance is desirable becausesoilwater is conserved for the criticalflowering phase. The use ofcropsimulation models may be useful inidentifying suchcircumstances.Greater early vigour to improveagronomic water-use efficiency:To this point, this review has focused onimprovingagronomic water-use efficiencyby manipulating leaf-levelwater-useefficiency, primarily through the use ofD13C.However, there are other



strategies that also offer promise.Asdiscussed earlier, animportant strategyto improve agronomic water-useefficiencyin cropping environmentswhere the soil surface isfrequentlyrewetted is to restrict water lost byevaporationfrom the soil surface. Thismaximizes crop transpirationandimproves the ratio T/ET. For cereals,indeed any crop,a reduction in soilevaporation is most easilyachievedthrough the rapid developmentof leaf area to shade the soilsurface fromdirect solar radiation. Good standestablishmentand vigorous early plantgrowth will both contributeto rapid leafarea development.Good standestablishment is best achieved by plantsthatreach the soil surface quicker if seedis sown relativelyshallow, and that reachthe soil surface much moreconsistentlyif seed is sown deep, such as whenfarmersare seeding into moisture belowa dry topsoil. In wheat, thewidely-usedGA-insensitive dwarfing genes Rht-B1b(Rht1) and Rht-D1b (Rht2) have hada major impact onagronomic water-useefficiency by improving HI andcropstandability. The latter feature hasbeen most important inirrigatedcropping systems, but the same genesstronglyinhibit the expression of longcoleoptiles that may be animportantattribute for rain-fed systems (Ellis etal., 2004).Alternative, GA-sensitivedwarfing genes exist in wheatthat allowthe expression of much longercoleoptiles (fromtall wheat) in plantswith semi-dwarf stature and highHI.Early vigor (fast leaf areadevelopment) is an importantadaptationof barley and durum wheat to terminaldrought inMediterranean environmentsbecause it improves the ratio T/ET andencouragesgrowth when evaporativedemand is low, giving higher A/T.Traitsimportant for vigorous early growth incereals wereidentified by comparingbarley with bread wheat Thiscomparison showed that largeembryosize, high SLA, and growth of a largecoleoptile tillerwere important attributesof barley, which is characterizedby veryhigh early vigor, but these traits werelacking insemi-dwarf wheat. Extensivescreening of a collection oftall wheatrevealed excellent sources of each ofthese traits (Richards and Lukacs,

2002). In a targeted breedingprogramme, these were combined toproduce a new parentalline with earlyleaf area growth double that ofcurrentAustralian semi-dwarfvarieties.High-vigor backcross lines withthis parent as the vigordonor out-yieldedlow-vigor lines from the samepopulationby up to 13% in favorableMediterranean-type environments(c.280–450 mm in-season rainfall), butthere wasno difference in yield in drierenvironments with less than250 mm in-season rainfall.Conclusion:

There are now growing evidencethat targeting specific traits in a breedingprogramme may lead to higheragronomicwater-use efficiency. It is alsoclear that the effects of anyone trait mustbe considered in the context of theenvironmentin which the crop is to begrown. A particular trait,such as high A/T,may be associated with higher yield inonetype of environment but may have noeffect or even bedetrimental in otherenvironments. Breeding for high A/Tusinglow-D13C measured in the leaves ofunstressed wheatplants has resulted inthe release of new, higher-yieldingvarietiesfor eastern Australia. The new varietiesresult from a backcrossing programmetargeting environments where stored soilmoisture needs to be metered out fromrelativelyearly in the cropping season so asto maximize seed setand sustain seedgrowth. By contrast, for cereals growinginMediterranean-type cropping regions andirrigated environments,higher yieldappears to be associated withhigh-D13C ofgrain. For Mediterranean-type regionsthisassociation may, in part, be a result ofan associationbetween high-D13C and fastcrop growth rate. Fast cropgrowth rate isreflected in the vigorous development ofleafarea to shade the soil surface, a keytrait for croppingenvironments where thesoil surface is frequently rewettedand largegains in T/ET can be made. Effectiveselectionprotocols for faster leaf areagrowth have been devisedand shown to besuccessful for yield improvementinMediterranean-type environments. It ispossible that evengreater yield gains maybe achievable in these and otherrain-fedenvironments if fast crop growth rate canbe combinedwith high A/T. Breeding hasbeen initiated to combinethese two traitsin bread and durum wheat, but thismayprove difficult if an a strategy that sets



out deliberately to target a combinationofhigh early vigor and high A/T in wheatmay notbe necessary in other species. Itwill depend strongly on theextent andtiming of any water limitation in relationtodevelopmental phases critical for yielddetermination, andwhether there is anassociation between high A/T andslowcrop growth rate. Such an associationis likely to depend on whether variation inA/T is due to variation in stomatalconductance or photosynthetic capacityand the effects ofthese two components oncrop growth rate. Relativelysimpletechniques are now available forcharacterizing variation in stomatalconductance and photosyntheticcapacity.Other interactions may also comeinto play. Ingroundnut, A/T is positivelyassociated with crop biomassproduction,but negatively associated with HI.Breedingprogress is being made in thisspecies by applying concurrentselectionpressure for high A/T and high HI.Progressmay be more rapid if the reasonsfor the associationbetween A/T and HIwere better understood.References:Condon AG, Richards RA, Rebetzke GJ,

Farquhar GD. (2002). Improvingintrinsic water-use efficiency and cropyield. Crop Science 42, 122–131.

Ellis MH, Rebetzke GJ, Chandler P,Bonnett D, Spielmeyer W, RichardsRA. (2004). The effect of differentheight reducing genes on the earlygrowth characteristics of wheat.Functional Plant Biology 31, 583–589.

Hamdy A, Ragab R, Scarascia-MugnozzaE. (2003). Coping with water scarcity:water saving and increasing waterproductivity. Irrigation and Drainage52, 3–20

Long SP, Bernacchi CJ. (2003). Gasexchange measurements, what canthey tell us about the Underlyinglimitations to photosynthesis?Procedures and sources of error.Journal of Experimental Botany 54,2393–2401.

Merah O, Deleens E, Souyris I, Nachit M,Monneveux P. (2001). Stability ofcarbon isotope discrimination andgrain yield in durum wheat. CropScience 41, 677–681.

Nautiyal PC, NageswaraRao RC, Joshi YC.(2002). Moisture deficit- inducedchanges in leaf-water content, leafcarbon exchange rate and biomassproduction in groundnut cultivars

differing in specific leaf area. FieldCrops Research 74, 67–79.

Nigam SN, Upadhyaya HD, Chandra S,Rao RCN, Wright GC, ReddyAGS.(2001). Gene effects for specificleaf area and harvest index for threecrosses of groundnut (Arachishypogaea). Annals of Applied Biology139, 301–306.

Richards RA, Lukacs Z. (2002). Seedlingvigour in wheat—sources of variationfor genetic and agronomicimprovement. Australian Journal ofAgricultural Research 53, 41–50.

Richards RA, Rebetzke GJ, Condon AG,van Herwaarden AFV. (2002). Breedingopportunities for increasing theefficiency of water use and crop yieldin temperate cereals. Crop Sci 42,111–121.

Royo C, Villegas D, Garcia del Moral LF,Elhani S, Aparicio N, Rharrabti Y,Araus JL. (2002) Comparativeperformance of carbon isotopediscrimination and canopytemperature depression as predictorsof genotype differences in durumwheat yield in Spain. AustralianJournal of Agricultural Research 53,561–569 .

Shao HB, Chu LY, Ruan CJ, Li H, GuoDG, Li WX. (2010). Understandingmolecular mechanisms for improvingphytoremediation of heavy metal-contaminated soils. Crit Rev Biotech30, 23–30.

Sultenfuss JH, Doyle WJ (1999)Phosphorus for agriculture. BetterCrops Plant Food 83:1–40

Wang HX, Liu CM, Zhang L. (2002). Water-saving agriculture in China: anoverview. Advances in Agronomy 75,135–171.

Zhang ZB, Shao HB, Xu P, Chu LY, Lu ZH,Tian JY. (2007). On evolution andperspectives of Bio-water saving.Colloids and Surfaces B: Biointer1, 1–9.



Role of Potassium in Sustainable Agricultural ProductionA.K. Dwivedi

Principal ScientistDepartment of Soil Science

J.N. Krishi Vishwa Vidhyalaya, Jabalpur-482004 (M.P.)

AbstractThis review intends to focus on

the role of potassium in sustainableagricultural production. Moisture deficitcreated by drought or withholdingirrigation results in a significantreduction in plant water potential,osmotic potential, relative water content,photosynthetic rate, respiration, etc.Moreover, a marked reduction in variousgrowth characters like, leaf area, weightor yield has been reported under abioticand biotic stresses incidence of insect-pest and diseases. The application ofpotassium in general, mitigates theadverse effect of such stresses, whichfacilitate the conditions, that favoursmore or higher growth and yield levels ofcrop.Introduction

Potassium is an alkali metal thatoccurs naturally in most of the soils.The total K content of the earth crust isabout 2.3 to 2.5 per cent, but only avery small proportion of it becomesavailable to plants (Leigh and Jones,1984). It is one of 18 elements that areessential for both plant and animal life(Brady and Weil, 2002). Plants require Kproportionately in large quantities,hence, it is regarded as one of the threemajor plant food elements (Golakiya andPatel, 1988; Leigh and Jones, 1994;Dev, 1995). Higher yields of betterquality depend greatly on the capacityand capability of the crop to resist ortolerate moisture and temperatureabnormalities, diseases and otherstresses during growing periods(Amtmann et al., 2004; Dev, 1995).Potassium is involved in manyphysiological processes such asphotosynthesis (Vyas et al., 2001),photosynthetic translocation (Umar,1997; Tiwari et al., 1998), protein andstarch synthesis, water and energyrelations (Rao and Rao, 2004),translocation of assimilates (Tomar,1998) and activation of number of

enzymes (Vyas et al., 2001; Sharma andAgrawal, 2002). Potassium alsoimproves the water use efficiency (Singhet al., 1997; 1998) through its influenceon maintenance of turgor potential(William, 1999). As most of the kharifand rabi crops are grown under rainfedconditions, crops experience water andtemperature stresses of varying degreesand duration at various growth stages,thus, relevance of K nutrition undersuch stress conditions may assumegreat importance.Potassium in Plant System

Potassium, an importantmacronutrient for plants, carries outvital functions in metabolism, growthand stress adaptations (Krauss, 2001;Krauss and Johnston, 2002). Thesefunctions can be classified into thosethat rely on high and relatively stableconcentrations of K+ in certain cellularcompartments and those that rely on K+

movement between differentcompartments, cells or tissues (Vyas etal., 2001). The first class of functionsincludes enzyme activation, stabilizationof protein synthesis and neutralizationof negative charges on proteins(Marschner, 1996). The second class,linked to its high mobility, is particularlyevident where K+ movement is thedriving force for osmotic changes as, forexample, in stomatal movement, light-driven and seismonastic movements oforgans, or phloem transport (Amtmannet al., 2004). In other cases, K+

movement provides a charge-balancingcounter-flux i.e. essential for sustainingthe movement of other ions (Singh andSingh, 1999). Thus, energy productionthrough H+ ATPases relies on overallH+/K+ exchange (Tester and Blatt,1989). Accumulation of K+ (togetherwith an anion) in plant vacuoles createsthe necessary osmotic potential for rapidcell extension (Singh and Singh, 1999;Warwick and Halloran, 1991).



Potassium deficiency leads to (i)growth arrest due to the lack of themajor osmoticum (Singh et al., 1997 ;Warwick and Halloran,1991) , (ii)impaired nitrogen and sugar balancedue to inhibition of protein synthesis,photosynthesis (William,1999) and long-distance transport (Bhaskar, et al.,2001)and (iii) increased susceptibility topathogen probably due to increasedlevels of low molecular weight nitrogenand sugar compounds (Tiwari et al.,2001). In a natural environment, low-Kconditions are often transient therefore,plants have developed mechanisms toadapt to short-term shortage of Ksupply.

Potassium is involved innumerous functions in the plant, suchas in enzyme activation, cation/anionbalance, stomatal movement, phloemloading, assimilate translocation andturgor regulation, etc. (Golakiya andPatel, 1988; Singh et al., 1999; Umar,1997). Stomatal resistance decreasesand photosynthesis increases withincreasing K content of leaves (Peoplesand Koch, 1979). In tobacco plants wellsupplied with K, 32% of the total N15

taken up within 5 hrs was incorporatedinto protein whereas, by 11% in Kdeficient plants (Koch and Mengel,1974). Potassium deficient leaf cellsaccumulate substantial quantities of lowmolecular weight organic compounds(Noguchi and Sagawara, 1966; Baruahand Saikia, 1989) because they act asan osmoticum in the absence ofsufficient potassium.Potassium and Stress Tolerance

Abiotic and biotic stressesnegatively influence survival (Agrawal etal., 2006) biomass production and cropyield (Amtmann et al., 2004; Dev, 1995;Tomar, 1998). Climatic extremes andunfavorable soil conditions are twomajor determinants affecting cropproduction (Singh et al., 2004).Potassium supply up to certain extent,can lessen their adverse effects on cropgrowth. The word abiotic means non-living and the components are thosethat do not have life, such as soil andclimate / weather parameters. The bioticmeans living and components are thosethat have life, for example, plants,animals, microorganisms as well assome decomposers.

Abiotic StressesSoil moisture

The transport of K ion in soilmedium towards plant roots takes placeby mass flow and diffusion. On anaverage 10 per cent of total K+

requirement of crops is transported bymass flow. In general diffusion is themain process of K+ transport. Accordingto Nye (1979) the diffusion of K+ in thesoil solution increases with soilmoisture. Tortuousity i.e. the soilimpedance increases with drying of soil.The diffusion coefficient for K+ of about1x10-7 cm-2 sec-1 at a soil water contentof 23% decreases to 5x10-8 cm-2 sec-1 at10% moisture content which is about1.5x10-5 cm2 sec-1 in pure water (Mengeland Kirkby, 1980). As water stressdevelops, K+ helps in reducing the extentof crop growth loss through maintaininghigher activity of enzyme nitratereductase, which normally decreasesunder stress condition (Saxena, 1985).Potassium is also involved in thebiosynthesis of proline and cropvarieties with higher proline content arereported to have high yield stability aswell as high productivity under moisturestress (Krishnasastry, 1985).

With variations in wet and dryconditions, the added K fertilizer mayyield large responses in K responsivesoils. Barber (1963; 1971) reported thatlesser the rainfall for 12 weeks afterplanting, the greater the per cent yieldincrease of soybean from K additions(Fig.1). However, with low rainfall theroots tend to function more in the sub-soils and much lower in low K status(Nelson, 1978).

To provide 5 kg K/ha to theroots, the required K concentration inthe soil solution in moist and dry soilsvaried. The drier the soil, the higher isthe needed K concentration (Johnston etal., 1998). The K flux improves with the

Percent yield

increase from K

addition



soil moisture (Fig. 2). On the other hand,a generous K supply can, to certainextend, compensate less diffusive K fluxin drier soils.

With high rainfall and/or inwaterlogged conditions the pore spacesin the soil get filled with water andoxygen content declines. This lowersrespiration in plant roots and thusdecline in nutrient absorption. However,by adding high amounts of K, the K needof the plant can be met even when rootrespiration is restricted (Skogley, 1976).Working on barley crop the adequate Khad a reduced transpiration rate duringstress (rate relative to 1.0 under non-stress) 5 minute after exposure to hotwindy conditions. On the other hand,under severe K deficiency, thetranspiration rate greatly increased.Greater water loss, thus, could limit thecrop yield. Hot and dry winds arecommon occurrence in the plains andmay be disastrous to crops.

Potassium fertilization canpartially overcome the adverseconditions of poor aeration caused bywaterlogging or compaction (Nye, 1979).The uptake of K is a process thatrequires energy provided by rootrespiration. If oxygen is lacking, rootrespiration is impaired and so is Kuptake. As early as in 1963, Brownreported that poorly drained soils withlow K resulted in poor yield as comparedto the well drained soils. However, whenK was increased to 150 kg/ha the yieldincreased even in poorly drained fields(Table 1).Table 1. Yield of lucerne (ton/ha)under varying pH and drainageconditions

pH 5.8 pH 6.5Soil

drainage37kgK/ha

150kg

K/ha

37 kgK/ha

150kg

K/ha

Poorlydrained

7.4 10.7 8.10 12.3

Welldrained

9.2 10.7 9.8 11.9

Source: Brown, 1963A number of physiological

disorders are related to K levels in poorlyaerated paddy soils. In such soilsexcessive ferrous (Fe2+) or the presenceof respiration inhibitors like hydrogensulphide may inhibit K uptake and

cause Fe toxicity, a disorder commonlyknown as “bronzing” (Dev,1995 ;Hardter,1997).Soil salinity

Plant adaptations to salineconditions can depend on an increase inspecific inorganic and organic soluteswithin the cell, which may contributeosmoregulation or to the ability toprevent the accumulation of salts withinthe cytoplasm (Warwick and Halloran,1991; Singh and Singh, 1999) . Theoperation of either mechanism isimportant for tolerance and adaptationsto salinity. Analysis of plant tissues forNa and K contents under salt stresscondition has been suggested as one ofthe useful parameter to measure thevarietal salt tolerance (Warwick andHalloran, 1991; Singh and Tiwari,2006). In this regard, Singh and Singh(1999) tested four chickpea varietiesincluding tolerant and susceptible for Naand K contents with increasing saltstress (Singh et al., 2004). It wasobserved that the values of K content intolerant genotypes were significantlyhigher than those of susceptiblegenotypes (Singh et al., 2006).

Fig. 2. K diffusive fluxes asaffected by soil water contentand K status of the soil(Source: Gath, 1992)

TemperaturePotassium can help plants to

tolerate to both very high and very lowtemperatures (Grewal and Singh, 1980).The relationship between K nutritionand temperature is complicated by theinteraction of soil and plant factor(Johnston et al., 1998). Frost damagehas been reduced by maintaining ofgood level of K in the tissues of bothannual and perennial crops (Grewal andSingh 1980; Shrinivasa Rao and Khera,1995). The results from the findings of



Grewal and Singh (1980) demonstratedthat frost damage of the foliage of potatois inversely related to the K content ofleaves.

Similarly, the pattern of K uptakeincreases with increasing temperatureup to a maximum and very hightemperature can be detrimental if theloss of energy through respirationbecomes excessive. Alterations in theamount of shade influences the effect offactors, such as temperature andmoisture condition on growth and yieldand thereby, K requirements (Nelson,1978; Dev, 1995; Rao, 2004).Biophysical properties

The biophysical role ofpotassium, in turgor maintenance andexpansive growth, particularly its role instomatal regulation and its effects onwater use and carbon dioxideassimilation processes are affected by Kdeficiency (Rao, 1999). However,moisture stress undoubtedly is knownto reduce the turgidity of cells (Umar,1997) and thereby, decreases stomatalconductance and photosynthesis (Singhet al., 1998). Potassium applicationhelps in drought tolerance andenhanced maturity as well as juicequality in sugarcane. The application ofpotash @ 80kg K2O/ha resulted in anincrease in leaf area, diffusion resistanceof stomata and thereby, reducedtranspiration rate over withoutapplication (Tiwari et al., 1998). Thiscould be due to adequate supply of thepotassium. However, the stomata closerapidly under drought and minimize thetranspiration rate (Umar, 1997). Role ofK in stomatal regulation in Brassicaunder moisture stress had also beenreported (Sharma et al., 1992).

It has also been observed thatmost of the tropical legumes experiencefrequent droughts of varying degree anddurations during their growth periods.Potassium influences the water economyand crop growth through its effect onwater utilization, by root growthreflecting maintenance of turgor,transpiration and stomatal behavior(Nelson, 1978) and consequentlyinfluencing dry matter production togreater extent (Cadisch et al., 1993).Singh et al. (1997) also observedrelatively lower values of leaf osmoticpotential under water stress. While,

these increased upon watering,indicating the change in osmoregulation.Under stress condition, the decline inosmotic potential is mainly due to theaccumulation of solute like K+, prolineand soluble carbohydrates. Moreover,the osmotic adjustment enables plantsto deplete the soil water to a lower soilwater potential level. Thus, facilitates agreater exploration of available soilmoisture by roots (Singh et al., 1997;Tiwari et al., 1998; Willium, 1999).

Golakiya and Patel (1988)studied the effect of cyclic dry spells andpotassium treatments on the yield andleaf diffusive resistance of groundnut.The repeated occurrence of stressconditions caused considerablereduction (up to 75%) in pod yield andthe shortfall in production was stillhigher in the case of consecutive dryspells. Potassium application of 60 kgK2O/ha enhanced the level of productionover control (no water stress) and couldalso restore the loss in pod yield to anoticeable extent. A marked increase inthe diffusive resistance of leaves with Kfertilization supports the contention thatpotassium plays an importantphysiological role in counteractingadverse conditions caused by drought.

Photosynthesis is the processthrough which the energy of solarradiation is directly converted in tosugar, starch and other organiccomponents (William, 1999). Though, Kis not an integral part of chlorophyllmolecule, but it influencesphotosynthesis to a greater extent.Photosynthesis rate drasticallydecreases under water deficit because ofboth stomatal and non-stomatal factors(Umar, 1997; Singh et al., 2004). Thereduction in photosynthetic rate is alsodue to decreased leaf water potentialand RWC under water stress, whichleads to decrease in stomatalconductance. The rate of photosynthesisis enhanced with supply of K in rootingmedium because K helps in maintainingthe rate by improving RWC and leafwater potential through osmoticadjustment under stress (Singh et al.,1997). It has also been reported thataccumulation of optimum K in guardcells provides the adequate amounts ofsolute necessary in developing properleaf water potential gradient required for



movement into guard cells for stomatalopening necessary for photosynthesis.The amount of solar energy transformedinto dry matter production, thus will begreater even in moisture stress conditionunder adequate K supply (Cadisch et al.,1993).

Effect of K levels (25, 50,100 and200 ppm) on water relations, CO2

assimilation, enzyme activation andplant performance under soil moisturedeficit in cluster bean (Vyas et al., 2001)have shown that the plant waterpotential and RWC declined due to waterstress at all K levels . However, thedecline was less in plants growth at 200ppm K level as compared to plantsgrown at low K levels. Wyrwa et al.(1998) observed that in K depleted soilsunder drought condition, the triticaleyield got decreased by more than 50%whereas, application of 100 kg K2O/haincreased the yield to a level which wasonly about 17% less than the yield ofplants well supplied with water (Fig. 3).

Fig. 3. Effect of potassium supply onyield of triticale as affected bydrought

(Source: Wyrwa et al., 1998)The yield improvement due to K

application in number of crops suggeststhat under low moisture K applicationmay result in yield improvement onlywhen K availability is limiting. Theevidences indicate that application of Kmitigates the adverse effect of waterstress by favorably influencing internaltissue moisture, photosynthetic ratesand nitrogen metabolism.Biotic StressesInsect, pest and disease incidence

Crops are constantly subjected toseveral fungal, bacterial and viraldeceases. It has been observed thatdisease incidence, in general increases

with the increase in Nitrogen level(susceptibility) that results in anincrease in reducing and non-reducingsugar contents, but invariably decreaseswith potassium applications(Velazhahan and Ramabadran, 1992).Amongst fungal diseases especially thesheath rot caused by Sarocladiumoryzae in rice has assumed muchimportance in recent years by causingheavy yield losses (Bhaskar et al., 2001).They reported that the sheath rotdisease incident in rice increases withincrease in N levels from 0 to 300 kgN/ha while, the phenol content in leafsheath was found to increase with Kapplication as compare to N levels.Further, it was observed that higher thephenol content, lower was the sheath rotincident probably due to growth ofinhibiting pathogens.

Potassium has been shown toreduce the severity of several plantdiseases. For example, Baruah andSaikia, (1989) reported that at low levelsof potash the stem rot diseaseinfestation in rice was relatively muchgreater ranging from 38.5 to 42.5 percent, in comparison to optimum Klevels. Potassium inhibits theaccumulation of soluble carbohydratesas well as nitrogenous compounds in thetissues, thus helping to counteract asituation that favours fungal growthwhen K level is deficient. Similarly,lignifications of vascular bundles couldbe responsible for greater susceptibilityin plant for pathogen attack andsurvivals (Jayraman andBalasubramanian, 1988). Potassium,more than any other element, is knownto reduce plant susceptibility to diseasesby influencing biochemical processesand tissue structures. Due to theinteraction of factors, such asenvironmental conditions, susceptibilityof the plant or variety to disease, diseaseincidence and level of other nutrients,the effects of K can be variable. In arecent review it has been reported thathigh levels of K nutrition reduced theseverity of more than 20 bacterialdiseases, more than 100 fungal diseasesand 10 diseases caused by viruses andnematodes (Marschner, 1995;Marschner et al., 1996). Potassiumdeficiency usually results in theaccumulation of soluble N compounds



and sugars in plants, which are asuitable food source for parasites.Whereas adequate K results in strongertissue and thicker cell walls which aremore resistant to disease penetration,while N has the opposite effect.

The concentration of solubleassimilates in a plant cell is animportant factor for the development ofinvading pathogens especially forobligate parasites such as mildew orrust. This group of pathogens requiresliving plant cells to complete their lifecycle. Thus, the host cell must survivethe invasion by the parasite if the latteris to survive. Ample N supply helps inlongevity of cells, high turnover ofassimilates and high content of lowmolecular weight compounds.Facultative parasites, in contrast,require weak plants to be infested andkilled to survive. Vigorous plant growthstimulated by ample N would suppressinfestation by this group of pathogens.This may explain differences in theexpression of plant diseases in relationto the nutrition of the host (Krauss,2000) summarizes (Fig. 4) the effects ofN and K on the severity of the infestationby both obligate and facultativeparasites.

Fig. 4: Effect of N and K on expression ofdiseases caused by obligate and facultativeparasites (Source: Marschner, 1995)

As a general observation, plantsexcessively supplied with N have softtissue with little resistance to penetrationby fungal hyphae or sucking and chewinginsects (Krauss, 2000). On-farm trials inIndia with soybean showed considerableless incidences with girdle beetle,semilooper and aphids when supplied withadequate potash (Fig. 5).

Fig.5: Pest incidence in soybean asaffected by potash supply (Source:Krauss, 2000)

Similarly, excessive growth due toan unbalanced N supply can also createmicroclimatic conditions favorable forfungal diseases. Lodging of cereals ascommonly observed at over supply withnitrogen and inadequate potash is a goodexample, humidity remains longer inlodged crops giving ideal conditions forgermination of fungi spores.

Insufficient K also causes a paleleaf colour that is particularly attractive toaphids, which not only compete forassimilate but transmit viruses at thesame time. Wilting, commonly observedwith K deficiency, is another attraction toinsects. Cracks, fissures and lesions thatdevelop at K deficiency on the surface ofleaves and fruits provide easy access,especially for facultative parasites.

The ratio between nitrogen andpotassium plays obviously a particular rolein the host/pathogen relationship.Perrenoud (1990) reviewed almost 2450literature references on this subject andconcluded that the use of potassium (K)decreased the incidence of fungal diseasesin 70% of the cases. The correspondingdecrease of other pests was bacteria 69%,insects and mites 63% and viruses 41%.Simultaneously, K increased the yield ofplants infested with fungal diseases by42%, with bacteria by 57%, with insectsand mites by 36%, and with viruses by78% (Fig. 6).

Fig.6: Effect of potassium on yield increaseand pest incidences(Source: Perrenoud, 1990)



The effect of K on crop specifichost/pathogen relationships for rice inAsia has recently been summarized byHardter (1997). For example, stem rot,Helminthosporium sigmoideum, generallyoccurs at high nitrogen supply in soilspoor in K. With improved K supply, theincidence decreases and yields increase.A similar inverse relationship betweendisease incidence and plant nutritionwith K has been reported for brown leafspot in rice (Helminthosporium oryzae),rice blast (Piricularia oryzae) or sheathblight of rice (Thanatephorus cucumeris).A curative effect from applying K is alsoseen for bacterial diseases in rice likebacterial leaf blight, Xanthomonasoryzae, although highly susceptiblevarieties hardly responded to K incontrast to varieties with a moderatedegree of resistance. The number ofwhitebacked plant hopper, Sogatellafurcifera, could be substantially reducedwith K in the resistant rice variety IR2035 but K had almost no effect withthe susceptible variety TN-1.

The enhanced rates of Kapplication can induce or improve insectresistance by the following mechanisms.Accumulation of defensive phenoliccompounds and their derivatives foundto be toxic to insects. Thus, making theplants less palatable to insects andthereby causing non-preference(Perrenoud, 1990; Hardter, 1997).

Probable explanations for thebeneficial effect of K on the hostpathogen relationship focus on thefollowing mechanisms. At insufficient Kand/or excessive nitrogen, lowmolecular soluble assimilates like aminoacids, amide and sugars accumulate inthe plant cells. Correspondingly,Noguchi and Sugawara (1966) found inleaf sheaths of rice that the content ofsoluble N increased from 0.18 atadequate K to 0.45% at NP only.Similarly, soluble sugar increased from1.52% to 2.43% at NP. Theconcentration of soluble assimilates in aplant cell is an important factor for thedevelopment of invading pathogens suchas obligate parasites to complete theirlife cycle.Conclusion

In India, moisture andtemperature stresses are the mostimportant abiotic stresses for crop

productivity and yield potentials. Soilmoisture alters physiological processes;root elongation, turgidity and rate ofregeneration; stomatal conductance;photosynthesis and rate of cropdevelopment and maturity. It has beenobserved that crop responses to fertilizerK additions are often the greatest whenwater is either deficient or excessive.Potassium stimulates the degree andextent of root proliferation, rootbranching, etc. The greater rootproliferation usually gives plants betteraccess to sub soil moisture. Adequate Kdecreases the rate of transpirationthrough affecting the stomatalconductance.

Potassium usually speeds therate of development and maturity,altering the deleterious effects of stressat critical growth stages. Underconditions where rainfall patterns arehighly cyclical, drought effects can bereduced by advancing the date ofpollination when most crops are highlysensitive to moisture stress.

Pulses especially chickpeaexperiences temperature stress underrainfed condition as this crop is takenafter kharif crops. The crop experienceslow temperature at initial stage ofgrowth, results in poor and slowvegetative growth while, hightemperature at the end of croppingsequence leads to forced maturityresulting low crop production.Potassium application helps plants totolerate both the high and lowtemperatures.

Amongst abiotic stresses, soilsalinity is a major constraint that affectsplant growth and yield. Extraexpenditure of energy for osmoticadjustments or in repair mechanismunder salinity stress causes growthreduction. Potassium content in salttolerant genotypes has been reported tobe significantly higher than those ofsusceptible genotypes. Addition of K insalt-affected soils improves crop yieldsincluding vegetable crops.

Potassium application inhibitsthe accumulation pf solublecarbohydrates as well as nitrogenouscompounds in the tissues. This helps tocounteract a situation that favoursfungal growth when K levels aredeficient. Similarly lignifications of



vascular bundles could be responsiblefor greater susceptibility in plant forpathogen attack and survivals.Insufficient K also causes pale yellowcolour to leaves that attracts aphids,wilting in crops, commonly observed inK deficient soils. Cracks, fissures andlesions that develop under K deficiencyon surface of leaves and fruits provideeasy access for facultative parasites.

Available literature on K showsthat K application decreases incidence offungal diseases by 70 % of the cases,bacteria by 69%, insect and mites 63%and viruses 41%. Simultaneously,increase the yield of plants infested withfungal diseases by 42% with bacteria57% with insect and mites by 36%andwith viruses by 78%. It has established that phenol contentin leaves increases with increase in Kapplication resulting in low diseaseincidence (leaf sheath rot and stem rotin rice). Potassium content in shoots oftolerant genotypes of various crops hasbeen reported to be significantly higherthan those of susceptible genotypes.Plants under moisture stress have lowphotosynthetic rate. The decrease insolar energy harvest efficiency due tomoisture could be enhanced with KapplicationReferencesAgrawal, P, Agrawal, P., Reddy, M. and

Sopory, S. 2006. Role of DREBtranscription factors in abioticand biotic stress tolerance inplants. Plant cell reports 25 (12):1263-1274.

Amtmann, A, Armengaud, P. andVolkov, V. 2004. Potassiumnutrition and salt stress. In M.R.Blatt, ed, Membrane Transport inPlants. Blackwell Publishing,Oxford.

Barber, S.A. 1963. Rainfall andresponses. Better Crops withPlant Food 47 (1): 6-9.

Barber, S.A. 1971. Soybean responds tofertilizer and rotation. . BetterCrops with Plant Food 55(2): 9.

Baruah, B.P. and Saikia, L. 1989.Potassium nutrition in relation tostem rot incidence in rice.Journal of Potassium Research 5:121-124.

Bhasker, C.V. Ramarao, G. and Reddi,K.B.2001. Effect of nitrogen and

potassium nutrition on sheathrot incidence and phenol contentin rice. Indian Journal of PlantPhysiology 6: 254 – 257.

Brady, N.C. and Weil, R.R. 2002. TheNature and Properties of Soils.Pearson Education, inc. pp.6.

Brown, C.S. 1963. Alfalfa adoption withfertilizers. Better Crops with PlantFood 47 (7): 4 - 13.

Cadisch, G., Bradley, R.S., Boller, B.C.and Nosberger, J. 1993. Effect ofP and K on N2 fixation of fieldgrown Centrosema acutifoliumand C. macrocarpum. Field CropResearch. 31:329-340

Dev, G. 1995. Potassium – An essentialelement. Proc. Use of potassiumin Punjab agriculture. PAU,Ludhiana, July 5, 1994. pp.17-23.

Gäth, S. 1992. Dynamik derKaliumanlieferung im Boden.Report of the Institut fürLandeskultur, Justus-Liebig-University Giessen, Germany.

Golakiya, B.A. and Patel, M. S. 1988.Role of potassium incounteracting the effect of cyclicdrought on groundnut. Journal ofPotassium Research 4: 163-167.

Grewal, J.S. and Singh, S.N. 1980.Effect of potassium nutrition onfrost damage and yield of potatoplants on alluvial soils of thePunjab (India). Plant Soil 57:105-110.

Härdter, R. 1997. Crop nutrition andplant health of rice basedcropping systems in Asia. Agro-Chemicals News in Brief 20(4):29-39.

Jayraman, S. and Balasubramniam, R.1988. Role of potassium on yieldand incidence of pest anddiseases in chilli. J. PotassiumRes. 4(2): 67-70.

Johnston, A.E., Barraclough, P.B.,Poulton, P.R. and Dawson, C.J.1998. Assessment of somespatially variable soil factorslimiting crop yield. Proc. TheInternational Fertilizer Society,York, UK: 419.

Koch, K. and Mengel, K. 1974. Theinfluence of the level ofpotassium supply to youngtobacco plants (Nicotiana



tabacum L.) on short term uptakeand utilization of nitratenitrogen. Journal of Science andFood Agriculture 25: 465-471.

Krauss, A. 2001. Potassium and bioticstress. Ist FAUBA – Fertilizer –IPIWorkshop Potassium inArgentina Agricultural SystemsNov. 20 – 21, 2001 Buenos AiresArgentina.

Krauss, A and Johnston A.E. (2002)Assessing soil potassium, can wedo better? Proc. 9th Int. Cong.Soil Sci. Faisalabad, Pakistan.

Krauss. A. 2000. Potassium, integralpart for sustained soil fertilityProc Regional IPI Workshop onPotassium and PhosphorusFertilization effect on soil andcrops, 23-24 October, 2000Dotnuva - Akademija, Lithuania.

Krishnasastry, K.S. 1985. Influence ofpotassium on prolineaccumulation under stress PRIIRes. Review Series 2: 39-45.

Leigh, R.A., Jones, R.G.W.1984. Ahypothesis relating criticalpotassium concentrations forgrowth, distribution andfunctions of this ion in the plant-cell. New Phytol. 97: 12-13.

Marschner, H. 1995. Mineral nutritionof Higher Plants. 2nd ed.,Academic Press, pp. 436-460.

Marschner, H., Kirkby, E.A. andCakmak, I. 1996. Effect ofmineral nutritional status onshoot-root partitioning of photoassimilates and cycling ofmineral nutrients. Journal Exp.Botany 47: 1255-1263.

Mengel, K. and Kirkby, E.A. 1980.Potassium in crop production.Adv. Agronomy 33: 59-110.

Nelson, W.L.1978. Influence of K ontolerance to stress. Potassium inSoil and Crops Potash Researchinstitute of India, New Delhi pub.pp. 203-221.

Noguchi, Y. and Sugawara, T. 1966.Potassium and japonica rice.Intern. Potash Inst., Basel,Switzerland: 102.

Nye, P.H.1979. Diffusion coefficient anduncharged solute in soil and soilclays. Advances in Agronomy31:225-272 .

Peoples, T.R. and Koch, D.W. 1979. Role

of potassium in carbon dioxideassimilation in Medicago sativaL. Plant Physiology 63: 878-881.

Perrenoud, S. 1990. Potassium andplant health. IPI Res. Topic 3,Intern. Potash Institute, Basel,Switzerland.

Rao, N.K. and Kameshwarrao, B.V. (2004) Effect of potash levels andtopping on leaf potassium , yieldand quality in flue cured tobacco.Indian Journal of Plant Physiology9: 288-293.

Saxena, N.P. 1985. The role ofpotassium in drought tolerance.Potash Review 16: 102.

Sharma, G.L. and Agrawal, R.M. 2002.Potassium induced changes innitrate reductive activity in Cicerarietinum L. Indian Journal ofPlant Physiology 7 (3): 221-226.

Sharma, K.D. Kuhad, M.S. andSandwal, A. S. 1992. Possiblerole of potassium on droughttolerance in Brassica. Journal ofPotassium Research 8: 320-327.

Singh, A.K. and Singh, R.A. 1999. Effectof salinity on sodium andpotassium and proline content ofchickpea genotypes. IndianJournal of Plant Physiology4:111-113.

Singh, N., Chhonkar, V., Sharma, K.D.and Kuhad, M.S. 1997. Effect ofpotassium on water relations,CO2 exchange and plant growthunder quantified water stress inchickpea. Indian Journal of PlantPhysiology 2 : 202 - 206.

Singh, R.A. Roy, N.K. and Haque, M.S.2004. Effect of nitrogen andpotassium on sheath rotincidence and nutrient content inrice. Indian Journal of PlantPhysiology 9 : 90-93.

Singh, S.N. and Tiwari, U.S. 2006.Sodium and potassium ratio asan index to sodicity tolerance oftomato. Indian Journal of PlantPhysiology 11: 329 – 332.

Singh, S. Tiwari, T.N. Shrivastava, R.P.and Singh, G.P. 1998. Effect ofPotassium on stomatal behavior,yield and juice quality ofsugarcane under moisture stressconditions Indian Journal of PlantPhysiology 3: 303 – 305.



Singh, T., Deshmukh, P.S. andKushwaha, S.R. 2004.Physiological studies ontemperature tolerance inchickpea (Cicer arietinum L )genotypes. Indian Journal ofPlant Physiology 9: 294-301.

Skogley, E.O. 1976. Potassium inMontana soils and croprequirements. Montana Agr.Ext.Stn. Res. Report 18.

Shrinivasa Rao, Ch. and Khera, M.S.1995. Consequences ofpotassium depletion underintensive cropping. Better crops79: 24 -27.

Tester, M, Blatt, M.R. 1989. Directmeasurement of K channels inthylakoid membranes byincorporation of vesicles intoplanar lipid bilayers. PlantPhysiology 91: 249-252.

Tiwari, H.S., Agrawal, R.M. and Bhatt,R.K. 1998. Photosynthesis,stomatal resistance, and relatedcharacteristics as influenced bypotassium under normal watersupply and water stressconditions in rice (Oryza sativaL). Indian Journal of PlantPhysiology 3: 314 -316.

Tomar, V.S. 1998. Role of potassium inwater stress management insoybean . Farmer and Parliament33: 15-26.

Umar, S. 1997. Influence of potassiumon solar energy harvestingefficiency of groundnut underdifferent soil moisture stress.Indian Journal of Plant Physiology2 : 315-317.

Velazhahan, R. and Ramabadran, R.1992. Influence of potassiumfertilization on sheath rot andphenol content of rice. MadrasAgricutural Journal 70:294-298.

Vyas, S.P., Garg, B. K., Kathju, S. andLahiri, A.N. 2001. Influence ofpotassium on water relations,photosynthesis, nitrogenmetabolism and yield of Clusterbean under soil moisture stress.Indian Journal of Plant Physiology6: 30 – 37.

Warwick, W. N. and Halloran, G.M.(1991) Variation in salinitytolerance and ion uptake inaccessions of beetle grass(Diplachne fusca L). New Phytol.119: 161-168.

William, T.P. 1999. Potassium deficiencyincreases specific leaf weightsand leaf glucose levels in fieldgrown cotton. Agronomy Journal91: 962-968.

Wyrwa, P., Diatta, J.B. and Grzebisz, W.1998. Spring triticale reaction tosimulated drought andpotassium fertilization. Proc.11th Int. Symposium on Codes ofgood fertilizer practice andbalanced fertilization, September,27-29, 1998, Pulawy, Poland:255-259.



Microbial Indicators of Soil HealthR.K. Thakur, F.C. Amule and N.G. Mitra

Department of Soil Science & Agril. Chemistry, JNKVV, Jabalpur

Part I1. Preamble

According to USDA, soil qualityindicators are classified into fourcategories that include visual, physical,chemical, and biological indicators.Visual indicators can be obtainedthrough field visits, perception offarmers, and local knowledge. These areidentified through observation orphotographic interpretation, subsoilexposure, erosion, presence of weeds,color, type of coverage, and throughcomparison between systems operatedwith the unaudited interimanthropogenic, which gives a clear ideawhether the soil quality has beenaffected positively or negatively. Theintegration between scientist´s andfarmer´s evaluation shows how the localknowledge used as indicators as validfor consistent classification of soilquality.

The physical indicators arerelated to the organization of theparticles and pores, reflecting effects onroot growth, speed of plant emergenceand water infiltration; they includedepth, bulk density, porosity, aggregatestability, texture and compaction.Chemical indicators include pH, salinity,organic matter content, phosphorusavailability, cation exchange capacity,nutrient cycling, and the presence ofcontaminants such as heavy metals,organic compounds, radioactivesubstances, etc. These indicatorsdetermine the presence of soil-plant-related organisms, nutrient availability,water for plants and other organisms,and mobility of contaminants.

Finally, biological indicatorsinclude measurements of micro- andmacro-organisms, their activities orfunctions. Concentration or populationof earthworms, nematodes, termites,ants, as well as microbial biomass,fungi, actinomycetes, or lichens can beused as indicators, because of their rolein soil development and conservation;nutrient cycling and specific soil fertility.

Biological indicators also includemetabolic processes such as respiration,used to measure microbial activityrelated to decomposition of organicmatter in soil, and a commonly usedindex: the metabolic quotient (qCO2),defined as the respiration to microbialbiomass ratio, which is associated tomineralization of organic substrate perunit of microbial biomass.

Other biological indicators thathave been widely studied are thechemical compounds or metabolicproducts of organisms, particularlyenzymes such as cellulases,arylsulfatase, phosphatases, related tospecific functions of substratedegradation or mineralization of organicN, S or P. Soil enzymatic activity assaysact as potential indicators of ecosystemquality being operationally practical,sensitive, integrative, described as"biological fingerprints" of past soilmanagement, and relate to soil tillageand structure. Determination of rates ofdecomposition of plant debris in bags ormeasurements of the numbers of weedseeds, or the presence andquantification of the population ofpathogenic organisms can also serve asbiological indicators of soil quality.

Intensification of agriculture isone of the major impacts to the Danishsoil environment, as griculture accountsfor two-third of the land use[Organisation for Economic Cooperationand Development, Paris (OECD, 1999)].Adverse impacts of agriculture includeloss of biodiversity, nitrogen dischargesinto surface water, eutrophication ofsurface water, contamination ofgroundwater from pesticides and nitrate,and ammonia volatilisation due to over-fertilisation with manure. These impactsare exacerbated by infrastructuredevelopment, increasing urbanisation,waste disposal and forestry practices(Ministry of the Environment, 2000).Healthy soils are essential for theintegrity of terrestrial ecosystems toremain intact or to recover from



disturbances, such as drought, climatechange, pest infestation, pollution, andhuman exploitation includingagriculture. Protection of soil is therefore

of high priority and a thoroughunderstanding of ecosystem processes isa critical factor in assuring that soilremains healthy.

Table 1 : Relationships between soil functions and ecological services

Soil functions Ecological services Examples of related soil biotaC-cycling Microbial biomass,

methanogensDecomposition of orgnaicmatter

Microarthropods, saprotrophicfungi

N-cycling Nitrifiers, denitrifiersP-cycling Phosphatase, mycorrhizaS-cycling S- reducing bacteriaN fixation RhizobiaPrimary (microbial) activity Microbial community

structure and activitySoil food web transfers Microbial community and food

web structureDisease & pesttransmission / suppression

Predators, pathogens

Nutrient supply fromsymbioses

Mycorrhiza, N-fixers

Redistribution bybioturbation

Earthworms, ants

Food and fibreproduction

Bio-aggregation of soil Fungi, wormsDegradation /immobilization ofpollutants

Fungi, worms

C retention / release Microbial biomass,methanogens

N retention / release Nitrifiers, denitrifiersP retention / release Microbial activity, mycorrhizaS retention / release S-reducing bacteriaTolerance / resistance(toxins)

Soil community structure andactivity

Redistribution bybioturbation

Earthworms, ants

Environmentalinteractions

Bioaggregation of soil Fungi, wormsHabitat for rare soil species Wax cap fungi, Southern Wood

AntGermination zone of plants Plant roots, mycorrhizaNutrient supply fromsymbioses

Mycorrhiza

Food source (above ground) Fungi, insectsReservoir for soilbiodiversity (taxonomic)

Soil species and diversity

Reservoir for soibiodiversity (genetic)

Community DNA and RNA

Supportingecologicalhabitats andbiodiversity

Reservoir for soilbiodiversity (functional)

Nitrifiers, trophic structure,worms



Objective of terrestrial monitoring:Long-term terrestrial monitoring

programme with the objective to followthe state of the terrestrial environmentin the country has been proposed. It isproposed to include monitoring ofimportant natural areas, biodiversity,and the impact of xenobiotics andclimate changes. Monitoring activitieswill, according to present plans,primarily concentrate on vegetation,fauna and abiotic properties. Monitoringof soil is not explicitly mentioned, but assoil supports all life forms in theterrestrial environment, terrestrialmonitoring without soil monitoring isincomplete. The monitoring strategy willconsist of both extensive monitoring ofmany small areas and intensivemonitoring of a few large areas with highpriority. The monitoring activities will bedesigned to discriminate betweennatural variations and human inducedchanges, including impacts of policymanagement.

2. Soil healthTo manage and maintain soil in a

sustainable fashion, the definition of soilhealth must be broad enough toencompass the many functions of soil,e.g. environmental filter, plant growthand water regulation. Soil health is thenet result of on-going conservation anddegradation processes, depending highlyon the biological component of the soilecosystem, and influences plant health,environmental health, food safety andquality.

Definition of soil healthSeveral definitions of soil health havebeen proposed during the last decades.Historically, the term soil qualitydescribed the status of soil as related toagricultural productivity or fertility. Soilhealth are attributes chiefly associatedwith biodiversity, food web structure,and functional measures proposed thefollowing definition of soil health: The continued capacity of soil to

function as a vital living system,within ecosystem and land-useboundaries, to sustain biologicalproductivity, promote the quality of airand water environments, andmaintain plant, animal and humanhealth

The definition encompasses a timecomponent, reflecting the importance ofcontinuous functions over time and thedynamic nature of soil. Soil health thusfocuses on the continued capacity of asoil to sustain plant growth andmaintain its functions regardless of thefitness for any certain purposes.Examples of dynamic soil propertiescould be organic matter content, thenumber or diversity of organisms, andmicrobial constituents or products.

Microorganisms have key functionsin soilThe biological activity in soil is largelyconcentrated in the topsoil, the depth ofwhich may vary from a few to 30 cm. Intopsoil, the biological componentsoccupy a tiny fraction (<0.5%) of thetotal soil volume and make up less than10% of the total organic matter in soil.These biological components consistmainly of soil organisms, especiallymicroorganisms. Despite their smallvolume in soil, microorganisms are keyplayers in the cycling of nitrogen,sulphur, and phosphorus, and thedecomposition of organic residues.Thereby they affect nutrient and carboncycling on a global scale. That is, theenergy input into the soil ecosystems isderived from the microbialdecomposition of dead plant and animalorganic matter. The organic residuesare, in this way, converted to biomass ormineralised to CO2, H2O, mineralnitrogen, phosphorus, and othernutrients. Mineral nutrients immobilisedin microbial biomass are subsequentlyreleased when microbes are grazed bymicrobivores such as protozoa andnematodes. Microorganisms are furtherassociated with the transformation anddegradation of waste materials andsynthetic organic compounds.In addition to the effect on nutrientcycling, microorganisms also affect thephysical properties of soil. Production ofextra-cellular polysaccharides and othercellular debris by microorganisms helpin maintaining soil structure, as thesematerials function as cementing agentsthat stabilise soil aggregates. Thereby,they also affect water holding capacity,infiltration rate, crusting, erodibility,and susceptibility to compaction.



Microorganisms as indicators of soilhealth

Microorganisms possess theability to give an integrated measure ofsoil health, an aspect that cannot beobtained with physical/chemicalmeasures and/or analyses of diversity ofhigher organisms. Microorganismsrespond quickly to changes, hence theyrapidly adapt to environmentalconditions. The microorganisms that arebest adapted will be the ones thatflourish. This adaptation potentiallyallows microbial analyses to bediscriminating in soil healthassessment, and changes in microbialpopulations and activities may thereforefunction as an excellent indicator ofchange in soil health.Microorganisms also respond quickly toenvironmental stress compared tohigher organisms, as they have intimaterelations with their surroundings due totheir high surface to volume ratio. Insome instances, changes in microbialpopulations or activity can precededetectable changes in soil physical andchemical properties, thereby providingan early sign of soil improvement or anearly warning of soil degradation. Anexample is the turnover rate of themicrobial biomass. This is much faster,e.g. 1-5 years, than the turnover of totalsoil organic matter. Observations in theSoil Monitoring Programme have shownthat most microbial indicators indeedhave discriminating power relative todifferent soil treatments. This has alsobeen shown for microbial biomass andbasal respiration at a regional scale. Thebioavailability of chemicals, e.g. heavymetals or pesticides, is also animportant issue of soil health because ofits connection with microbial activities.The impact of such chemicals on soilhealth is dependent on microbialactivities. For example, theconcentration of heavy metals in soil willnot change over small time periods, buttheir bioavailability may. It has thusbeen shown that the bioavailability ofpoly-aromatic hydrocarbons was lowerin summer or fallow period compared to

cropping seasons due to a highermicrobial activity after the growingseason. Therefore, the total content ofchemicals in soil is not a reliableindicator of its bioavailability andthereby soil health. Instead,bioavailability has to be measured inrelation to bioassays and specificmicrobial processes. In context of this,microbial responses also integrate theeffect of chemical mixtures, aninformation not obtained by studyingthe chemical mixtures themselves.

Definition of microbial indicatorIndicators of soil health have furtherbeen defined as measurable surrogatesfor environmental processes thatcollectively tell us whether the soil isfunctioning normally. In the context ofmicrobial indicators, thesemeasurements will cover soil microbialprocesses and related parameters. Amicrobial indicator is thus:

A microbial parameter that representsproperties of the environment (statevariables) or impacts to theenvironment, which can be interpretedbeyond the information that themeasured or observed parameterrepresents by itself.

3. Framework for evaluating soilhealthEvaluation of soil health should beconsidered relative to the many differentland uses, e.g. agriculture, forestry,urbanisation, recreation, andpreservation. The objective forevaluating soil health in an agriculturalecosystem may, consequently, bedifferent from objectives used forassessing urban or natural ecosystems.Thus, in agriculture, soil may bemanaged to maximise productionwithout adverse environmental effects,whereas in a natural ecosystem, soilmay be managed by a set of baselinevalues against which future changes inthe system may be compared.



Figure 1. Policy-relevant end points of soil health monitoring, several examples ofpressures on soil health are presented (shaded box) and this may impactseveral end points of soil health (elliptical boxes).

A framework for soil health evaluation iscritical for the development of a usefulmonitoring programme covering thedifferent functions and land-uses and itmust identify priorities and relevantindicators relating to policy-relevant endpoints. The main objective of this is toprovide policy-makers with relevantenvironmental parameters based onreliable and comparable data related tosoil and to facilitate comprehensivereporting on the state of soils. It alsoprovides consistent measuring andassessment at any site, from handling ofsoil samples to the evaluation andstorage of data.

Integrated environmental assessmentRelevant indicators of specific end pointscan be identified using the IntegratedEnvironmental Assessment method,which is based on the Driving force-Pressure-State-Impact-Response(DPSIR) assessment framework, that has

been developed primarily forenvironmental issues (OECD, 1993). TheDPSIR framework analyses the complexrelationships between the environmentand the impact of economic activitiesand societal behaviour. The driving force(D) lead to pressures (P) on theenvironment, affecting the state (S) andleading to impacts (I), which finallyresults in response (R) by the society.The DPSIR framework has recently beenadopted by EEA (European EnvironmentAgency, Copenhagen, Denmark)specifically for soil issues (Figure 2) andis recommended for the terrestrialmonitoring programme. A prerequisitefor the use of the DPSIR framework is aclear definition of the problems and ascientific understanding of the causalmechanisms. Further, the developmentof indicators for each of the PSI-elements is necessary. These indicatorsshould relate to the policy-relevant endpoints of soil health.



Figure 2. The DPSIR assessment framework applied to soil, examples of differentelements for agriculture are given

Requirements of indicatorsAccording to OECD (1993),environmental indicators must fulfil thefollowing three basic criteria. Theyshould have: policy relevance and utility for users analytical soundness measurabilityCriteria specific for soil health indicatorshave further been listed. They should be: linked and/or correlated with

ecosystem processes integrated with soil physical,

chemical, and biological properties selected relative to ease of

performance and cost effectiveness responsive to variations in

management and climate at anappropriate time scale

compatible with existing soil databases when possible

Because of the multi-functionality ofsoil, it is difficult to identify one singleproperty as a general indicator of soilhealth. Instead, end points can becharacterised by several soil ecosystemparameters (Table 1), which again canbe characterised by several microbialindicators (Table 2):

End point soil ecosystemparameters microbial indicators

A list of microbial indicators relating toend points of soil health is shortlypresented in the next chapter, while amore detailed description of these ispresented in Part II.

Table 2 : End points of terrestrial monitoring and corresponding soil ecosystem parameters.

End point Soil ecosystem parameterAtmospheric balance C-cyclingSoil ecosystem health Biodiversity

C-cyclingN-cyclingMicrobial biomassMicrobial activityKey species

Soil microbial community health BiodiversityC-cyclingMicrobial biomassMicrobial activityBioavailability

Leaching to underground water or surfacerun-off

N-cyclingBioavailability

Plant health N-cyclingKey species

Animal health Microbial biomassBioavailability

Human health Key speciesBioavailability



4. Microbial indicators of soil healthMicrobial indicators of soil health covera diverse set of microbial measurementsdue to the multi-functional properties ofmicrobial communities in the soilecosystem (Table 2). In this part of thetopic, microbial indicators coverbacteria, fungi and protozoa. Theindicators are grouped according to thedifferent soil ecosystem parameters. It isnot a complete list of all possiblemicrobial indicators, but it includes avast number of available and futuremethods. Both traditional methods andmodern, often suitable molecular-basedmethods are included.

4.1. Guidelines for selection ofmicrobial indicatorsMinimum data set (MDS)Inclusion of all the microbial indicatorslisted in Table 3 in a monitoringprogramme is not feasible. Instead, aminimum data set (MDS) consisting ofthe smallest number of indicatorsneeded to address the specific end pointshould be defined. Besides microbialindicators, a MDS for soil healthmonitoring should also include physical,chemical and biological indicators.A MDS is based on the objective of themonitoring programme and may verywell be different for different end points.Furthermore, the optimal MDS vary fordifferent soil types and regions, sinceindicators vary due to climate,topography, parent material, vegetationand land use practices. Representativesof both inherent and dynamic soilcomponents should be included in aMDS. Inherent soil properties aredetermined by the basic soil formingfactors, including the geologicalmaterial, climate, time, topography andvegetation. Dynamic soil properties arebased on biological activity and includemicrobial indicators. In the following,only microbial indicators will be dealtwith as a part of a MDS.Generally, indicators of a MDS shouldbe selected on the basis of their ease ofmeasurements, reproducibility, andtheir sensitivity towards key variablescontrolling soil health. Each microbialindicator, however, represents slightlydifferent aspects of soil health and hasits advantages and disadvantages. Some

kind of guiding of this selection istherefore needed and several ways toselect are presented below.

Broad or detailed measurementsThe selection of indicators should bebroad enough to give policymakersand/or the general public an overview ofthe state of the environment, whiledetailed indicators are needed to betterunderstand underlying trends. Formicrobial indicators, the overview will beaccomplished by measurements at theecosystem level (e.g. processes), whichhave been proposed to offer the bestpossibilities for rapidly assessingchanges in soil health. Resulting datawill allow decisions to be made at thecommunity (e.g. biomass andbiodiversity) or population (e.g. speciesor functions) levels and allow thesedetailed studies to be planned moreprecisely.

Ranking of the indicatorsRanking of the indicators according toapplicability, economy, ease ofinterpretation, development needs,sensitivity etc. has also been proposedas a way to select the optimal indicatorof soil health. It is the experience thatmakes ranking very subjective. Rankingof applicability and development needsto be straightforward, while ranking ofthe interpretation, sensitivity, andeconomy is more complicated. In Table3, a ranking with respect to applicabilityand needed development of themicrobial indicators is attempted.

Methodological requirementsMethodological requirements areincluded in the selection of indicators inthe Soil Monitoring Programme. Themethods thus should (i) have a highdegree of standardisation, (ii) have ahigh practicability and be labourextensive, (iii) have a highreproducibility, (iv) be statisticallyevaluated, (v) have a satisfactoryexperience so far, and (vi) be broadlyaccepted internationally.



Table 3.List of microbial indicators for soil health monitoring (see Part II for moredetails of the specific indicators)

Soil ecosystemparameter

Microbial indicator Ready-to-use methods Future methods

Genetic diversity PCR-DGGE T-RFLPFunctional diversity BIOLOG Enzyme patterns

Diversity of mRNAOligo-/copio-trophs

Biodiversity

Marker lipids PLFASoil respiration CO2-production or

O2-consumptionMetabolic quotient (qCO2) Cresp/Cbiomass

Decomposition of organicmatter

Litter bags Wood sticks

Soil enzyme activity Enzyme assaysMethane oxidation

C-cycling

Methanotrphs MPNPLFA

FISH

N-mineralization NH4+ -accumulationNitrification NH4+ -oxidation assayDenitrification Acetylene inhibition

assayN-fixation: Rhizobium Pot test Molecular methods

N-cycling

N-fixation: Cyanobacteria MPNNitroginase activity

Microbial biomass: Directmethods

MicroscopyPLFA

Microbial biomass:Indirect methods

CFI, CFE, Ergosterol

Microbial quotient Cmicro/Corg

Fungi PLFA, ErgosterolFungi-bacterial ratio PLFA

Microbialbiomass

Protozoa MPN MPN-PCRBacterial DNA synthesis Thymidine

incorporationBacterial proteinsynthesis

Leucine incorporation

RNA measurements RT-PRCFISH

Community growthphysiology

CO2-production orO2-consumption

Microbialactivity

Bacteriophages Host specificplaque assay

Mycorrhiza Microscopy, Pot test Molecular methodsHuman pathogens Selective plating Molecular/immuno

logical methods

Key species

Suppresive soil Pot testBiosensor bacteria Remedios, Microtox New genetic

constructionsPlasmid containingbacteria

Gel electrophoresis

Antibiotic resistantbacteria

Selective growth Molecular methods

Bioavailability

Incidence and expressionof catabolic genes

Selective growth ActivityMolecular methodsRNA measurements



Laboratory versus fieldmeasurementsIndicators can also be selected on basisof whether they are laboratory (in vitro)or field (in situ) measurements. In vitromeasurements may involve incubationof a soil sample in the laboratory understandardised conditions and thusprovide an estimate of the potential ofthe soil. Interpretation of in vitromeasurements in relation to soil healthcan be difficult, since the results dependon the incubation conditions, which maynot be comparable to field conditions.Examples of in vitro measurements aresoil respiration, CFI/CFE, SIR, N-mineralisation, nitrification,denitrification, MPN and other growth-based methods (Table 3). In situmeasurements are based either on directmeasurements in the field or fixedsamples analysed in the laboratory.They give a “snap-shot” measurement ofthe conditions in the soil. In situmeasurements, however, are often verysensitive to spatial and temporalvariation (see 5.1) and this may over-ride the variability in soil health status.Examples of in situ measurements aregas emissions, PLFA, organic matterdecomposition, thymidine and leucineincorporation, short-term enzyme assaysand most molecular methods (Table 3).Integrated measurementsIntegration of more indicators into onesingle method may be a way to reducethe number of indicators. At present,only few methods provide suchintegrated information. Thephospholipid fatty acid (PLFA) analysisprovides information about soilmicrobial biomass, fungal-bacterialratio, biodiversity and occurrence of keyspecies (see Part II for more details) inone analysis. Substrate inducedrespiration (SIR) provides measurementof basal respiration and soil biomass.Finally, the carbon utilisation pattern(BIOLOG) provides a profile of themicrobial community and informationon potential metabolic capacity, whichtogether comprise functional diversity.

Microbial indicator MDS in soilmonitoring programmesIt has recently been noted thatmeasurements relating to early changes

in organic matter and biological andmicrobial attributes are particularlyunderrepresented in existing soilmonitoring networks world-wide,although these are emerging areas ofinterest to the scientific community.Experience with the use of microbialindicators in soil monitoring is availablein some European countries, where themost commonly used indicators aremicrobial biomass and soil respiration.A recent report on new molecular toolsfor soil monitoring activitiesrecommends BIOLOG and PLFA analysisas future methods for biodiversitymeasurements in ecotoxicologicalanalysis. In the United States,comprehensive investigations onmicrobial indicators are implemented atmany monitoring sites that are part ofThe International Long-Term EcologicalResearch (ILTER) network.5.2. Sampling strategiesA sampling strategy includes plans forsite selection, sampling methods,sampling frequency, and pre-treatmentof samples and is intimately connectedto the purpose of the programme.Generally, the biggest challenge in soilsampling strategies is to reduce thenumber of samples to an acceptablelevel based on scientific output andanalytical costs.5.2.1. Site selectionThere are two main approaches for siteselection in a soil monitoringprogramme: the regional and the plotapproach. The regional approachinvolves hundreds or thousands of sitesand generates large amounts of data ondifferent land-use types, therebyoverriding inter-site variability. The plotapproach is more site specific andinvolves a smaller number of sites. Thedata generated is generally moreintensive and of greater scientific value,especially for understanding ecologicalrelationships between the soil attributes.The plot approach is therefore useful forbasic research studies, while theregional approach is useful formonitoring purposes.5.2.2. Sampling methodsDifferent sampling methods are availableand basically the selection is a matter ofprecision level compared to costs.



Composite samplingComposite sampling is a way to reduce thecost of analysing samples in thelaboratory, since individual samples,obtained from the area, are bulkedtogether and mixed. The method requiresthat the sampling units are the same andthat no significant interactions existamong the individual sampling units. Theuse of field-scale composite samples hasbeen claimed to be an insensitive strategyfor the purpose of monitoring undisturbedsites, since it does not say anything aboutthe distribution of variation. Compositesampling should be avoided, since itgreatly reduces the variability.Systematic samplingBy systematic sampling, samples areobtained at predetermined points, usuallyalong sets of parallel lines (transects) or ina grid. This method ensures that the entiresite being sampled is well represented bythe individual samples. The approach iseffective in characterising contaminatedsoil and advantageous for geostatisticalmethods (see below) and for identifyinghigh and low values of the indicator.Random samplingRandom sampling uses random samplepoints within a grid and is completelyunbiased. The method provides limitedinformation on the spatial distribution ofthe soil property being measured anddeviating sub-areas are generallyunderrepresented by this samplingmethod. Random sampling is unsuitablefor a monitoring programme, as the aim offully categorising the site is of a higherpriority than that of having a completelyunbiased site selection.Stratified random samplingStratified random sampling takes deviatingsub-areas into account, because the areato be sampled is divided into smaller sub-areas according to specific habitats and/orland use patterns. Each sub-area issampled following the random samplingprocedure. This sampling method isprobably the most suitable for soilmonitoring and is consistent with theecosystem and land use boundary conceptused in the definition of soil health (seeChapter 2).Geostatistical analysisGeostatistic is a modern statistical tooldesigned to determine spatial patterns andpredict values of non-sampled locations.The analysis is based on the assumption

that points situated close to one anotherin space share more similarities thanthose farther apart. The first step is todevelop a mathematical model, avariogram, which describes the spatialrelationship of sampling points. Thesecond step is kriging, which uses themodel to estimate each value in the non-sampled area and use these to producedetailed interpolation maps of specificparameters. Geostatistical analysis is alsoa tool for estimating number of samplesfor a given precision and has improved thesensitivity of forest soil monitoring. Thepractical use of this method for a national-scale monitoring programme has, however,been questioned, because a minimum of200 sample points may be required toestimate a variogram.The required sampling frequency dependson the degree of variation within thesampling area and financial limitations.Sampling frequencies in several Europeansoil monitoring programmes vary from oneto ten years depending on the microbialindicator. This frequency fits well with theidentification of microbial properties asdynamic ndicators, which is recommendedto be analysed within these time intervals.Due to their dynamic nature, microbialindicators are highly variable and it isrecommended to measure at a time of theyear when the climate is stable and whenthere has been no recent soil disturbance.Time of sampling is usually before plantgrowth and when the soil is not too wet(50-60% WHC).5.2.3. Pre-treatment of soil samplesPre-treatment of soil samples for analysisin the laboratory includes packing in thefield, transporting, and possibly sieving,storage and incubation before analysis. Itis generally recommended that soilsamples for microbial analyses are packedin plastic bags and placed on ice fortransport to the laboratory andsubsequent use. The microbial analysesshould be carried out, as quickly aspossible. International standards for pre-treatment of soil samples formicrobiological analyses do exist (seebelow).SievingSieving is used to obtain homogenous soilsamples free of plant residues and soilanimals. A mesh size of 2 to 4 mm isrecommended, the larger mesh size formoist clay soil. A mesh size of 5 mm isused in some monitoring programmes. Ifthe soil is too wet, careful drying is



necessary before sieving to avoid smearingof aggregates. It is recommended to sievebefore freezing of the samples.StorageStorage of soil samples for microbialanalysis is performed differently in thereviewed soil monitoring programmes(Table 5). Storage time varies between oneand six months, depending on storagetemperature and microbial indicator. It isgenerally recommended to store soilsamples for microbial analysis at 2-4 oCExperiments have shown that soil samplesfor microbial biomass determination canbe stored up to six months at 2-4 oC,however, analysis of some soil enzymeactivities allows only a very short storageperiod, because of rapidly decreasingactivity with time. Storage of moist soil at–20oC for up to one year was found to bethe best method for determination ofmicrobial biomass and several microbialprocesses. Fast thawing and asubsequently short pre-incubation periodhave further been shown to be important,especially for studies on N-mineralisationand basal respiration.

Pre-incubationPre-incubation of soil samples for in vitroanalyses is often used to condition thesamples before analysis. Applied pre-incubation conditions may vary. The timeof pre-incubation varies from 3 to 28 days,the temperature from 12 oC to 22 oC orroom temperature and the soil moisturefrom 40 to 60% WHC.5.3. Standardisation of methodsSampling method standardisationInternational standards for samplingprocedures (collection, handling andstorage) and pre-treatment of soil samplesexist within the ICP-IM network.Analytical method standardisationISO standards (International Organisationfor Standardisation, 1994, ISO standardscompendium. Environment - Soil quality,Geneva, Switzerland) exist however fordetermination of microbial biomass by SIR(ISO 14240:1:1997) and CFE (ISO 14240-2:1997) and for N-mineralisation andnitrification (14238:1997).

Table 4. Recommended microbial indicators in a terrestrial monitoring programme

End point of soil health Soil ecosystem parameter Proposed microbial indicatorIncluded in a MDS for a specificend point

Atmospheric balance C-cycling Methane oxidationBiomass Microbial biomass (direct

method)C-cycling Decomposition of organic matterN-cycling N-mineralizationBiodiversity Genetic diversity

Functional diversityStructural diversity

Soil ecosystem health

Key species MycorrhizaC-cycling Decomposition of organic matterMicrobial activity Bacterial DNA / protein

synthesisBiodiversity Genetic diversity

Functional diversityStructural diversity

Soil microbial communityhealth

Bioavailability Biosensor bacteriaN-cycling N-mineralizationLeaching to underground

wateror surface run-off

Bioavailability Sensor bacteria

N-cycling N-mineralizationPlant healthKey species MycorrhizaBiomass Protozoa biomassAnimal healthBioavailability Antibiotic-resistant bacteria

Human health Bioavailability Antibiotic-resistant bacteriaKey species Human pathogens



Part IICatalogue of microbial indicators ofsoil healthMicrobial indicators of soil healthencompass a diverse set of microbialmeasurements due to the multi-functional properties of microbialcommunities in the soil ecosystem. Inthe present catalogue, bacteria, fungiand protozoa indicators are considered.They are grouped according to the

different soil health parameters of theecosystem that is biodiversity, carboncycling, nitrogen cycling, biomass,microbial activity, key species andbioavailability. The indicators relate tothe ecosystem (e.g. processes),community (e.g. biomass andbiodiversity) or population (e.g. speciesor functions) levels and this relationshipis noted together with relations to policy-relevant end point (see Part I Chapter 3).

1. Indicators of biodiversity

End points Soil ecosystem parameter Microbial indicatorsSoil ecosystem healthSoil microbial communityhealth

Biodiversity Genetic diversityFunctional diversityStructural diversity

Information about microbial communitystructure and diversity has been notedas important for understanding therelationship between environmentalfactors and ecosystem functions. Thediversity of a community is expressed asthe species richness and the relativecontribution each species makes to thetotal number of organisms present. Thenumber of species has traditionally beendetermined by taxonomic classificationstudies, but as these are sub-optimal formicroorganisms, molecular andbiochemical techniques of estimatingabundance and number of each speciesmust be applied. The benefit of a highgenetic diversity is currently underdebate because it is not alwayscorrelated to functional diversity.Furthermore, the correlation betweensoil health and biodiversity is notcompletely understood, although amedium to high diversity is generallyconsidered to indicate a good soil health.1.1. Microbial genetic diversityThe genetic resources present in theenvironment are the basis of all actualand potential functions. The geneticdiversity of soil microorganisms is anindicator of the genetic resource.Methods for determination of the geneticmicrobial diversity include severalmolecular methods of which a few maybe implemented into a soil monitoringprogramme.Bacterial genetic diversityGenetic diversity of bacteria is mostcommonly studied by diversity of the16S rDNA genes, which occur in all

bacteria and which show variation inbase composition among species. 16SrDNA genes are thus used forphylogenetic affiliation of Eubacteria andArchaea and large databases exist onsequences of 16S rDNA. Two methodshave been developed to examine thediversity of 16S rDNA sequences in totalDNA extracted from soil microbialcommunities, namely PCR-DGGE and T-RFLP. Denaturing Gradient GelElectrophoresis (PCR-DGGE) andTemperature Gradient GelElectrophoresis (PCR-TGGE) are basedon variation in base composition andsecondary structure of fragments of the16S rDNA molecule. By PCR withprimers principally targeting alleukaryotes or selected subgroups, afragment of 16S rDNA of known size canbe amplified. Following PCR, theproducts are separated by gelelectrophoresis. By PCR-DGGE the gelitself contains a chemical-denaturinggradient, making the fragmentsdenature along the gradient according totheir base composition. By PCR-TGGE atemperature gradient is created acrossthe gel, resulting in the same type ofdenaturation. The number and positionof fragments reflect the dominatingbacteria in the community.For the PCR-DGGE and PCR-TGGEmethods, the low resolution of gelelectrophoresis compared to the highdiversity of bacterial communities canbe a problem. Soil communities mayeasily contain several hundred bacterialstrains, while the resolution of morethan 20-50 bands on a gel is difficult.



Terminal Restriction FragmentLength Polymorphism (T-RFLP) is analternative method for examiningdiversity of 16S rDNA sequences ofmicrobial communities. It is also basedon PCR amplification of 16S rDNA withspecific primers. The primers arelabelled with a fluorescent tag at theterminus resulting in labelled PCR-products. The products are cut withseveral restriction enzymes, one at atime, which result in labelled fragmentsthat can be separated according to theirsize on agarose gels. As the PCRproducts are labelled at the terminus,only restriction enzyme fragmentscontaining either of the terminal ends ofthe PCR product will be detected. Thedigested PCR products are subsequentlyloaded on a sequencer. The outputincludes fragment size and quantity.Recently, the potential of the T-T-RLFPmethod to discriminate soil bacterialcommunities in cultivated and non-cultivated soils has been demonstrated.The method allows comparison betweendifferent soils analysed in different labs.The method, however, requires delicateand expensive instruments along withvery pure DNA.

Fungal genetic diversityThe classical method for estimating thefungal diversity of soil has been numberand morphology of fruiting bodies.However, the majority of fungi in soil arepresent either as resting stages (spores)or mycelium. Both spores and myceliumcan be isolated from soil, but if a fruitingbody is not formed, identification of theorganisms is difficult at best, andgenerally impossible. Further, theisolation step may be selective to specificfungal groups, e.g. the fast growingones. Molecular methods based on 18SrDNA provide tools that can overcomethese problems. However, a majorlimitation is the limited number offungal nucleic acid sequences presentlyavailable in databases. Diversitymeasurements within the fungalcommunity in soil can also be measuredby PCR-DGGE and PCRTGGE(methodologies similar to bacterialgenetic diversity).Protozoan genetic diversityProtozoa is a phylum of single cell

eukaryotic organisms and as such mayresemble and better represent higherorganisms than prokaryotes. Protozoaare a paraphyletic group primarilyconsisting of naked amoebae, testateamoebae, ciliates and heterotrophicflagellates. Protozoa are very abundantin soil, like bacteria, and exist in verydiverse and harsh environments. Theyalso resemble bacteria in that they areimportant for soil health and fertility,react quickly to environmental changes,are ubiquitous and do not easily movearound in soil. Protozoa form anessential part of all soil ecosystems andhave been proposed as early warningindicators. Protozoan bioassays, forexample, have been used as adiscriminating indicator of heavy metalcontamination in soil amended withsewage sludge.Determination of the diversity ofprotozoa is normally carried out bytaxonomic affiliation to species, groupsor families based on morphologicalfeatures. This method is very timeconsuming, requires specialists and isfurther complicated by the incompletetaxonomic description of protozoa.Alternatively, protozoan diversity can bedetermined by molecular methods. Thediversity of protozoa has beencharacterised by PCR-DGGE targetingan 18S rDNA fragment (method similarto bacterial genetic diversity).

1.2. Microbial functional diversityThe diversity of functions within amicrobial population is important for themultiple functions of a soil. Thefunctional diversity of microbialcommunities has been found to be verysensitive to environmental changes.However, the methods used mainlyindicate the potential in vitrofunctionality. Functional diversity ofmicrobial populations in soil may bedetermined by either expression ofdifferent enzymes (carbon utilisationpatterns, extra-cellular enzyme patterns)or diversity of nucleic acids (mRNA,rRNA) within cells, the latter alsoreflecting the specific enzymaticprocesses operating in the cells.Indicators of functional diversity are alsoindicators of microbial activity andthereby integrate diversity and function.



Carbon utilisation patterns (BIOLOGassay)Carbon utilisation patterns can bemeasured by the BIOLOG assay. In thisassay, a soil extract is incubated withup to 95 different carbon sources in amicrotiter plate and a redox-dye is usedto indicate microbial activity. Sets ofspecific carbon sources have beenselected specifically for studies of soilmicrobial communities. The result of theassay is a qualitative physiologicalprofile of the potential functions withinthe microbial community.

The BIOLOG assay has beenshown to be more sensitive thanmicrobial biomass and respirationmeasurements to impacts of soilmanagement practices and of sewagesludge amendments to soil.

Enzyme patternThe enzymatic activity in soil is

mainly of microbial origin, being derivedfrom intracellular, cell-associated or freeenzymes. Only enzymatic activity ofecto-enzymes and free enzymes is usedfor determination of the diversity ofenzyme patterns in soil extracts.Discrimination between free and cell-associated enzyme activity can beobtained by a simple filtration step toseparate microbial cells from the soilextract. The enzyme activity is quantifiedby incubation of the soil extract withcommercial fluorogenic enzymesubstrates (4-methylumbelliferin (MUF)and 4-methylcoumarinyl-7-amide (MC)or colometric substrates (remazolbrilliant blue, p-nitrophenol ortetrazolium salt) coupled with specificcompounds of interest (e.g. cellulose orphosphate).

Diversity of mRNAmRNA molecules are gene copies

used for synthesis of specific proteins bythe cell. The nucleotide sequences ofmRNA molecules reflect the type ofenzymes synthesised. Concentration ofmRNA is correlated with the proteinsynthesis rate and as such with theactivity of the microorganism. Therefore,the content and diversity of mRNAmolecules will give very accuratepictures of the in situ function andactivity of the microbial community.

Detection and quantification of a specificmRNA molecule can be done by reversetranscription PCR (RT-PCR), which is avery sensitive method. A prerequisite ofthis technique is knowledge of thenucleic acid sequence of the mRNA for aspecific gene. For certain genes, thisinformation is available. However, thetechnique of quantifying mRNA is still inits developmental stage. Sensitivity ofthe method has though been improvedby associating a magnetic capturesystem.

1.3. Structural diversityPhospholipid fatty acids (PLFAs)

are stable components of the cell wall ofmost microorganisms. They are polarlipids specific for subgroups ofmicroorganisms, e.g. gram-negative orgram-positive bacteria, methanotrophicbacteria, fungi, mycorrhiza, andactinomycetes. Individual PLFAs canthus be related to microbial communitystructure. The method gives afingerprint of the relative PLFAcomposition of the resident microbialcommunity.PLFAs are extracted from soil samplesand subsequently analysed by gaschromatography. Specific PLFAs aresubsequently identified and/orquantified and the result is evaluated bymultivariate statistics.

PLFA profiles of soil samples offersensitive reproducible measurements forcharacterising the numerically dominantportion of soil microbial communitieswithout cultivating the organisms. Thetechnique gives estimates of bothmicrobial community composition andbiomass size (see chap. 4.1), and theresults represent the in situ conditionsin soil. The method is, however, timeconsuming, although the extractionprocedure may be automated. PLFAanalysis has been used to detect apollution gradient in soil.

Ratio of oligo- and copio-trophicbacteria

The ratio of oligotrophs (bacteriathat require a low nutrient input) tocopiotrophs (bacteria that require a highnutrient input) has been proposed toreflect the nutrient stress tolerance ofthe species present in soil. A high ratio,e.g. dominance of oligotrophs, may



indicate stable environmental conditionswith low substrate availability. A lowratio, e.g. dominance of copiotrophs,may, in contrast, indicate anenvironment regularly receiving input oforganic rich substrate, e.g. addition ofsewage sludge or pesticides.

The ratio of oligotrophs tocopiotrophs can be determined by eithercolony appearance on agar substrates,the rRNA-gene copy number in isolatedbacteria or rRNA-expression in bacterialmicrocolonies. The appearance ofcolonies on agar substrates may simplybe determined by counting colonyforming units (CFUs) at specific timeintervals. The counts are complementedby calculation of mean lag-phases andabsolute numbers of bacterialsubpopulations. Early appearing CFUsrepresent copiotrophic bacteria, whilelate appearing CFUs representoligotrophic bacteria. The number ofrRNA copies in isolated bacteria,determined by molecular techniques,

has recently been shown to correlatewith the expression of the rRNA gene.The rRNA gene expression can bedetermined during growth in bacterialmicrocolonies (mCFUs) by measuringthe 16S rRNA concentration byfluorogenic in situ hybridisation. A lowrRNA-copy number or a low rRNAexpression during growth indicatedominance of oligotrohic bacteria andhence a high ratio.

The CFU method is a simple andinexpensive method and is ready to useupon standardisation of incubation andcounting procedures. The molecularmethods are more comprehensive andtime consuming and still needconsiderable testing beforeimplementation into a monitoringprogramme. However, they have thepotential for specifying the interactinggroups of organisms depending on thespecificity of the hybridisation probes inuse.

2. Indicators of carbon cycling

End points Soil ecosystem parameter Microbial indicatorsSoil ecosystem healthSoil microbial communityhealthAtmospheric balance

C-cycling Soil respirationOrganic matter decompositionSoil enzymesMethane oxidation

A major activity of soil microorganismsis decomposition of organic matter. Soilmicroorganisms are in generalheterotrophic and rely on input ofcarbon energy from outside themicrobial community. Organic matter insoil is largely derived from higher plantsconsisting of cellulose (15-60%),hemicellulose (10-30%) and lignin (5-30%). Indicators of carbon cyclingrepresent measurements at theecosystem level.

2.1. Soil respirationSoil respiration, which is the biologicaloxidation of organic matter to CO2 byaerobic organisms, notablymicroorganisms, occupies a key positionin the C cycle of all terrestrialecosystems. It provides the principalmeans by which photosynthetically fixedcarbon is returned to the atmosphere.The metabolic activities of soilmicroorganisms can be quantified by

measuring CO2 production and/or O2

consumption.Measurement of soil respiration is one ofthe oldest, but still most frequently usedtechniques for quantification ofmicrobial activities in soil. Soilrespiration is positively correlated withsoil organic matter content, and oftenwith microbial biomass and microbialactivity. Soil respiration measurementsare included in most soil monitoringprogrammes.Soil respiration can be determined byeither CO2 production or O2

consumption. Measurement of CO2

concentration is more sensitive, becausethe atmospheric concentration of CO2 isonly 0.033% versus 20% for O2.Determination of CO2 production fromsoil samples can be made in thelaboratory by simple and inexpensivetechniques based on alkaline CO2 trapsfollowed by chemical titration or by moresophisticated automated instruments



based on electrical conductivity, gaschromatography or infraredspectroscopy. Combined with automatedsampling from test soil samples,automated instruments make it possibleto determine CO2 production as afunction of time for several days.Respiration is highly influenced bytemperature, soil moisture, nutrientavailability and soil structure. Pre-conditioning and standardisation of thesoil before measuring respiration isnecessary to minimise the effect of thesevariables. Field measurements of soilrespiration are less often used due tothe high sensitivity to environmentalconditions, although suchmeasurements have been shown todiscriminate between different soilmanagement practices. Finally, soilrespiration measurements have beenused as an indicator of pesticide andheavy metal toxicity.Metabolic quotientThe metabolic quotient (qCO2), alsocalled the specific respiratory rate, isdefined as the microbial respiration rate(measured as evolution of CO2) per unitmicrobial biomass. Microbial biomassfor this purpose is often determined bysubstrate induced respiration (see chap4.1), and the respiratory activity isdetermined concomitantly using thesame instruments.The qCO2 has been used to study soilover time and, generally, the quotientdecreases as the soil ages. Furthermore,the qCO2 has been used in effect studiesof environmental conditions, such astemperature and pH, soil management,soil texture and compaction and heavymetals. Generally, the qCO2 is found tobe highest when ecosystem stress levelis high. Caution, however, should betaken when interpreting qCO2, since ahigh quotient may infer stress, animmature ecosystem or a morerespirable substrate.2.2. Organic matter decompositionAny disturbance in microbial activity willresult in a change of the organic matter(OM) decomposition rate and hence theavailability and cycling of the mostimportant organic bound nutrientswithin the ecosystem, such as carbon,nitrogen, sulphur and phosphorus.Knowledge about rates of OM

decomposition is thus a prerequisite forunderstanding the availability andrecycling of all these nutrients.Field incubation of different types ofplant litter or more standardised piecessuch as cotton strips and wood sticks,are the most commonly used methodsfor studying OM decomposition rates.

Litter bagsThe advantage of using plant litter forstudying decomposition rates is thenatural origin of the litter, whichprovides a direct correlation to naturallyoccurring processes within the soilecosystem. The disadvantage of themethod is the difficulties in obtaininguniform litter from year to year. Changesin cellulolytic and ligninolytic enzymeactivities in litter bags have recentlybeen shown to explain changes in litterdecomposition upon nitrogen deposition.A protocol for litter bag decompositionstudies is included in the ICP-IMmanual.Cotton strips and wood sticksDecomposition of cotton strips and woodsticks can be measured by directplacement into the soil. Decompositionrate of the cotton strips is determined asreduction in tensile strength per timeinterval, while the rate for the sticks isdetermined as simple weight loss. Theadvantage of using cotton strips andwood sticks is the ease of obtainingstandardised material. The disadvantageis the fact that both substrates aresurrogates for the natural occurringprocesses and hence, results that maybe difficult to interpret. Thedecomposition rate of cotton, whichconsists of pure cellulose, is much fasterthan the rate of wood sticks. The cottonstrip method is however dependent onspecialised equipment for tensilestrength measurements. Wood sticksinserted into the soil have recently beenrecommended for decomposition studiesin the Environmental Change Networkin UK, 1999.All three types of OM tests make itpossible to determine and compare thedecomposition rates between differentsites, ecosystems, and time. Verticalposition in the soil horizon and the timeintervals between samplings must bestandardised.



2.3. Soil enzymes and metabolitesEnzymes are the direct mediators forbiological catabolism of soil organic andmineral components. Thus, thesecatalysts provide a meaningfulassessment of reaction rates forimportant soil processes. Soil enzymeactivities (i) are often closely related tosoil organic matter, soil physicalproperties and microbial activity orbiomass, (ii) change much sooner thanother parameters, thus providing earlyindications of changes in soil health,and (iii) involve simple procedures. Inaddition, soil enzyme activities can beused as measures of microbial activity,soil productivity, and inhibiting effects ofpollutants. Disturbance of the soilmicrobial activity, as shown by changesin levels of metabolic enzymes, can serveas an estimate of ecosystemdisturbance. This relationship has been

clearly shown when soil is polluted withheavy metals.Easy, well-documented assays areavailable for a large number of soilenzyme activities. These includedehydrogenase, β-glucosidases, urease,amidases, phosphatases,arylsulphatase, cellulases and phenoloxidases (Table 7). A standard methodfor determination of acid phosphataseactivity exists within the ICP-IM soilmonitoring network. Hydrolysis of thefluorescent fluorescein diacetate isthought to broadly represent soil enzymeactivity, because it is hydrolysed by anumber of different enzymes, such asproteases, lipases and esterases. Theseenzymatic activities are widelydistributed in soil, where they mainlyoriginate from microorganisms, but alsofrom plants or animals.

Table 5. Soil enzymes as indicators of soil health

Soil enzyme Enzyme reaction Indicator of

Dehydrogenase Electron transport system Microbial activity

Beta-glucosidase Cellobiose hydrolysis C-cycling

Cellulase Cellulose hydrolysis C-cycling

Phenol oxidase Lignin hydrolysis C-cycling

Urease Urea hydrolysis N-cycling

Amidase N-mineralization N-cycling

Phosphatase Release of PO4 P-cycling

Arylsulphatase Release of SO4 S-cycling

Soil enzymes Hydrolysis General OM degradative enzymeactivities

Enzyme activities can be measured as insitu substrate transformation rates or aspotential rates if the focus is morequalitative. An important parameter iswhether decisions are made relative to insitu or to maximum enzyme activities.For comparisons of soil enzymeactivities, the natural choice is themaximum activities. Measurements ofsoil enzyme reaction are usually based

on the addition of an artificial, solublesubstrate at a concentration sufficient tomaintain zero-order kinetics, thusachieving a reaction rate proportional toenzyme concentration. Long incubationperiods have to be omitted to avoidsubstrate depletion and microbialgrowth. Enzyme activities are usuallydetermined by a dye reaction followed bya spectrophotometric measurement.



Table 6. Examples of specific soil enzyme activities to assess functional diversitybetween and within nutrient cycles

Nutrient Form Compound EnzymeEndo-cellulaseCelluloseβ-Glucosidase

β (1-3) glucan β (1-3) glucanaseHemicellulose Xylanase

Endo-chitinaseChitinN-acetyl glucosaminidase

Polysaccharide

Starch AmylasePhenol oxidasePeroxidase

Aromatic Lignin

Mn-peroxidase

Carbon

Aliphatic Fatty acid esters LipaseProtein Endo-protease

Amino peptidasePeptide

PeptideCarboxy peptidaseAmidaseUreaseAdinosine deaminase

Nitrogen

Non-peptide Primary amine

Aryl deaminasePhospho diesteraseDiesterDNAase, RNAasePhospho mono esterase

Phosphorus

MonoesterPhytase

- Enzyme activitiesEnzyme activities have been associatedwith indicators of biogeochemical cycles,degradation of organic matter and soilremediation processes, so they candetermine, together with other physicalor chemical properties, the quality of asoil. Enzymes are as good indicatorsbecause: a) they are closely related toorganic matter, physical characteristics,microbial activity and biomass in thesoil, b) provide early information aboutchanges in quality, and are more rapidlyassessed. Nevertheless, due to enzymeorigin (from bacteria, fungi, plants, anda range of macro-invertebrates), differentenzyme locations (intra or extracellular),matrix association (alive or dead cells,clays or / and humic molecules) andassay laboratory conditions, it has beendemonstrated that it is of greatimportance to optimize the proceduresfor enzymatic activity determination inorder to obtain the best values andindices according to intrinsic soilproperties. Because enzymes aredifficult to extract from soils andregularly loose their integrity, enzymeactivity determination must be made

under strict laboratory conditionspaying particular attention totemperature control, incubation time,pH buffer, ionic strength of the solution,and substrate concentration.

o β-GlucosidaseIt is widely distributed in theenvironment, and its activity has beendetected in soil, fungi and plants. It hasbeen used as a key soil quality indicatordue to its importance in catalyticreactions on cellulose degradation,releasing glucose as a source of energyto maintain metabolically activemicrobial biomass in soil. At the sametime, it plays an important role in energyavailability in the soil which is directlyrelated to labile C content and with theability to stabilize soil organic matter,showing low seasonal variability. On theother hand, it has been reported thatenzyme activity could be inhibited by thepresence of heavy metals like Cu andCd.As a free enzyme in soil solution, itnormally has a short-lived activity,because they can be rapidly degraded,denatured or irreversibly inhibited.



However, a certain proportion of thesefree enzymes may lose stabilizationbecause of adsorption on soil mineralsor incorporation into humic material,which, despite affecting their catalyticpotential it may enable enzyme activityto persist in soil.

o PhosphatasePhosphorus is an essential nutrient forplant growth and crop yields; however alarge portion is immobilized because ofintrinsic characteristics of soils such aspH that affects the availability ofnutrients and the activity of enzymes,altering the equilibrium of the soil solidphase. Soil microorganisms play a keyrole on phosphate solubilization with therelease of low molecular weight organicacids and production of extracellularenzymes as phosphatases.Phosphatases are a group of enzymesthat catalyze hydrolysis of esters andanhydrides of phosphoric acid. Itsactivity depends on extracellularenzymes, which can be free in the soilwater phase or stabilized in the humicfraction or clay soil content. In soil,phosphomonoesterases have been themost studied enzymes probably becausethey have activity both under acidic andalkaline conditions, according to itsoptimal pH, and because they act on lowmolecular P-compounds includingnucleotides, sugar phosphates andpolyphosphates; thus they can be usedas soil quality indicators. Phosphataseactivity in soils can be correlatedbetween the enzyme activity and soilproperties such as pH, total N, organic Pand clay content.

o DehydrogenaseDehydrogenase enzyme activitydetermination is attractive due to thefact they are an integral part ofmicroorganisms and are involved inorganic matter oxidation; nevertheless,this activity is not consistentlycorrelated with other properties ofbiological systems such as O2

consumption, CO2 production ormicrobial biomass. However, it has beenconsidered as a soil quality indicator,because it is involved in electrontransport systems of oxygen metabolismand requires an intracellular

environment (viable cells) to express itsactivity.Consistently, the activity of this enzymeis not present in extracellular form ashydrolases (β - Glucosidase, urease,phosphatase), which suggests that it isnot an enzyme that can be used toevaluate the processes of soildegradation, since its activity fluctuatesas microbial activity does, in response tomanagement practices and/or climaticeffects.Nevertheless, dehydrogenase activity isbound to living and active cells, but itdepends on the presence of interferenceslike heavy metals (eg., Cu), catalyticassay procedure and other alternativeelectron acceptors (eg., nitrate andhumic substances).

o UreaseThese enzymes are involved on ureahydrolysis into CO2 and NH3 andconsequently with soil pH increase andN losses by NH3 volatilization. Due to therole of urea as a fertilizer, focus hasbeen placed on urease in order toevaluate N supply to plants, however,fertilization practices have been reportedas being very inefficient due to large Nlosses to the atmosphere byvolatilization mediated by theseenzymes. On the other hand, newenzymes involved in N-cycle have beensubject of study; in this aspect, there isnot a much data available aboutammonia monooxygenase (AMO) activityin soil; even though it is not included asquality indicator, this membrane-boundenzyme could be useful in determiningnitrification rates and the effect ofnitrification inhibitors. This enzyme canbe used to make some inferences aboutthe nitrification process in soil anddetermine if nitrogen losses are due tovolatilization, nitrification ordenitrification.Urease has been widely used to evaluatechanges on soil quality related tomanagement, since its activity increaseswith organic fertilization and decreaseswith soil tillage. This enzyme, mostly thecases, is an extracellular enzymerepresenting up to 63% of total activityin soil. It has been shown that itsactivity depends on microbialcommunity, physical, and chemical



properties of soil, and its stability isaffected by several factors: organo-mineral complexes and humicsubstances make them resistant todenaturing agents such as heat andproteolytic attack.Urease activity is used as a soil qualityindicator because it is influenced by soilfactors such as cropping history, organicmatter content, soil depth, managementpractices, heavy metals andenvironmental factors like temperatureand pH. The understanding of ureaseactivity should provide better ways tomanage urea fertilizer, especially inwarm high rainfall areas, flooded soilsand irrigated conditions.

- MetabolitesThere are many metabolic substancesthat can be used as soil qualityindicators; they include sterols,antibiotics, protein, etc.

- ErgosterolErgosterol, is the main endogenoussterol of fungi, actinomycetes, and somemicro-algae; its concentration is animportant indicator of fungal growth onorganic compounds and mineralizationactivity. Heavy metals (Cu 80 ppm, Zn50 ppm or Cd 10 ppm) and fungicides(Thiram 3 ppm or pentachlorophenol 1.5ppm) can reduce the metabolic activityin soil between 18% and 53% (pollutantstressed cultures), but did not affect theergosterol content. While the fungicideZineb (25 ppm) reduced significantly theergosterol content in biomass basis.Likewise, a correlation has been foundbetween fungi hiphae and ergosterolquantity and soil aggregates stability,demonstrated by electron microscopythe importance of fungi in Thixotropy, apurely physical process involvingrearrangement of the clay micelles, insoil. Ergosterol plays the most activerole in soil metabolic activity withindustrial contamination.

- GlomalinAmong these fungal components,glomalin, an insoluble and hydrophobicproteinaceous mix of substances, is ofparticular interest. Glomalin as

glomalin-related soil protein (GRSP) hasbeen proposed to improve the stability ofsoil by avoiding disaggregation by water.It is proposed that aggregates (and soils)with high glomalin-related soil protein(GRSP) concentrations may be fairly“saturated” with GRSP, perhaps becausemost pores in these macro-aggregateshave already been partially “sealed” bydeposition of this substance, slowingdown penetration of water into theaggregate.The GRSP concentration and soilaggregate stability were positivelycorrelated with mycorrhizal root volumeand weakly correlated with total rootvolume.

2.4. Methane oxidationMethane (CH4) is found extensively innature and is a greenhouse gas in theatmosphere. Methane is produced inanoxic environments by methanogenicArchaea and consumed by aerobicmethane oxidising bacteria, themethanotrophs (see below). Importantterrestrial sites for methane oxidationare wetland areas receiving a high inputof organic material. Furthermore,landfills containing high amounts oforganic wastes are a source of methaneand the habitat of many methanotrophs.Net production of methane can beconsidered as an indicator ofgreenhouse gas emission and mayfurther be linked to monitoring of theatmospheric balance. Methane oxidationis measured by spiking a soil samplewith methane and incubate the samplein a closed jar in the laboratory. Loss ofmethane is subsequently determined bygas chromatography.

Number of methanotrophsThe number of methanotrophs is anindicator of potential greenhouse gasconsumption. Methanotrophs can bequantified directly in soil by fluorescentin situ hybridisation (FISH) or standardgrowth-dependent MPN counts.Analyses of methanotrophiccommunities can be done with PCR-DGGE (see chap. 1.1) usingmethanotrophs-specific 16S rDNAprimers.



3. Indicators of nitrogen cycling

End points Soil ecosystem parameter Microbial indicatorsSoil ecosystem healthPlant healthLeaching to ground waterSurface run-offAtmospheric balance

N-cycling N-mineralizationNitrificationDenitrificationN-fixation

The mineralisation of soil organicnitrogen (N) through nitrate to gaseousN2 by soil microorganisms is a veryimportant process in global N-cycling.This cycle includes N-mineralisation,nitrification, denitrification and N2-fixation (Figure 4). Indicators of nitrogencycling represent measurements at theecosystem level.Organic N is mineralised to ammonium(NH4+) by a wide variety of soilmicroorganisms and it reflects theturnover of organic material in soil andthe available indigenous N-pools toplants. Ammonium is subsequentlyeither immobilised by soilmicroorganisms (that is, assimilated intonew biomass) or oxidised to nitrite (NO2-)and subsequently to nitrate (NO3-) by

aerobic nitrification. Chemoautotrophicbacteria, the nitrifier population, carryout this process. At this step, leaching ofN to the ground water may occur due tothe negative charge of the nitrate ion.Under normal circumstances, however,nitrate is subsequently reduced togaseous nitrogen (N2) via nitrous oxide(N2O) by anaerobic denitrification.Denitrification is represented by avariety of soil bacteria. Nitrification anddenitrification together lead to losses ofbioavailable N since nitrous oxide andgaseous N2 may be lost to theatmosphere. N2 can be re-fixed into thesoil by N2-fixing microorganisms.Nitrous oxide is a greenhouse gas whenlost to the atmosphere.

Figure 4. Global cycling of nitrogen

3.1. N-mineralisationAmmonification is actually a measure ofthe net N-mineralisation, sinceimmobilisation of NH4+ by soilmicroorganisms into new biomassoccurs simultaneously with themineralisation process. Themeasurement thus reflects the potentialN-mineralisation in soil and is measuredby the accumulation of NH4+ in soil

slurry under aerobic conditions over aperiod of several weeks. Anaerobicincubation is sometimes preferredbecause there is less microbialimmobilisation under anaerobicconditions and nitrification is inhibited.Compared to other measurements of N-cycling, the N-mineralisation is relativelyinsensitive to disturbances because awide variety of microorganisms areinvolved in the process.



3.2 NitrificationNitrification is believed to be a moresensitive parameter than Nmineralisation, because only a smallnumber of bacteria, the nitrifiers, areinvolved in the process.Nitrification measurements have,however, been reported to be no moresensitive than N-mineralisation and, asa result of this, nitrificationmeasurements have recently beenreplaced by N-mineralisationmeasurements in the Soil MonitoringProgramme. Nitrification measurementsreflect the population size of thenitrifiers since ammonium is anessential substrate for these organisms.Furthermore, these measurementstogether with denitrificationmeasurements may indicate depositionof ammonia on N-limited habitats.Nitrification is measured by theammonium oxidising assay. With thismethod, a soil slurry is incubated withexcess ammonium and chlorate, thelatter inhibiting the oxidation of nitriteto nitrate. The oxidation of ammoniumto nitrite is measured by gaschromatography.

3.3. DenitrificationThe denitrifying capacity is a widespreadfeature among soil bacteria andtherefore denitrification can be used as arepresentative for microbial biomass.Since denitrification is an anaerobicprocess the amount of denitrificationfound in soil is very dependent onabiotic factors such as precipitation andsoil compaction. Thus, soil managementpractices readily influence the amount ofdenitrification found in agriculturalfields. Denitrification measurementsmay, together with nitrificationmeasurements, indicate deposition ofammonia in N-limited habitats.Measurement of denitrification is carriedout by the acetylene inhibitiontechnique, in which the reduction of N2Oto N2 is inhibited by acetylene andaccumulated nitrous oxide is measuredby gas chromatography. Nitrate must beavailable in surplus. The method is oftenused to measure the potentialdenitrification where nitrate and carbonare added and anaerobic conditions areestablished. However, interpretation of

denitrification data is complicated,because the denitrification enzymes aresynthesised only under anaerobicconditions and the enzymes are notfunctional under aerobic conditions,even though they persist in themicrobial community. The denitrificationassay may thus reflect historicalanaerobic situations and not necessarilythe size of the actively denitrifyingbiomass.

3.4. N-fixationGaseous nitrogen (N2) is a product of theanaerobic denitrification of nitrate. N2 islost to the atmosphere or consumed byN2-fixing Rhizobium or cyanobacteriadue to their nitrogenase enzyme.

RhizobiumBacteria of the genera Rhizobium areabundant in soil, where they formsymbiotic associations with legumeroots. The bacteria reside in noduleswhere they fix N2 and provide the plantwith nitrogen for growth. In return, theplant provides the bacteria with organicsubstrates for growth. The Rhizobium-legume symbiosis is characterised byhigh host specificity. Numbers ofRhizobium has previously been proposedas an indicator of soil health based onthe organisms sensitivity to pesticidesand heavy metals. The abundance ofRhizobium has been included as amicrobial indicator of heavy metalcontamination in agricultural soils.The frequency and diversity ofRhizobium in soil can be determined bya simple pot test, where a diverse set oflegume seeds are sowed in the test soiland number of nodules formed aredetermined after a specific growthperiod. Alternatively, the bacteria maybe quantified by direct isolation from soilusing selective growth media togetherwith morphological and physiologicalcharacterisations. A number ofmolecular methods have also beenapplied for diversity measurements ofthese bacteria. These include plasmidprofiles and insertion sequencefingerprints, 16S-23S rDNA spacersequences, PCR detection of specificgenes, colony hybridisation, RFLP andRAPD.



Detection of Rhizobium by growinglegumes in the test soil and determiningroot nodule-formation is a rather simplemethod. The molecular methods, on theother hand, are more technicallydemanding. Although it relies on thedevelopment of specific probes for thedifferent Rhizobium-subgroups, thecolony hybridisation procedure isprobably the best way to detectRhizobium. A combination ofquantitative and diversity measurementswill allow a screening of the soilpotential for Rhizobium-legume mediatednitrogen fixation.

CyanobacteriaThe cyanobacteria, or blue-green algae,are photoautotrophic bacteria. Incontrast to Rhizobium, they are non-symbiotic. They form microbiotic crustsin intimate association with surface soil,which contribute significantly to thestabilisation of soil towards erosion.

Cyanobacteria have mainly been used asindicators of heavy metal contamination(e.g. from sewage sludge application) insoil. Most experiments have shown anegative correlation between the numberof cyanobacteria or nitrogenase activityand the concentration of heavy metals.Measurement of the potential N2-fixation under standard laboratoryconditions has, therefore, beensuggested as a better alternative.Nevertheless, the number ofcyanobacteria is recommended as anearly indicator of heavy metal pollutionin the soil monitoring network.The number of cyanobacteria can bedetermined either by MPN methods ordeterminations of nitrogenase activityusing light as energy source.Nitrogenase activity is measured by theacetylene reduction assay, where thereduction product, ethylene, easily canbe measured by gas chromatography.

4. Indicators of soil biomass

End points Soil ecosystem parameter Microbial indicatorsSoil ecosystem health Soil biomass Microbial biomass

Protozoan biomass

In this report, soil biomass includesbacterial, fungal and protozoan biomass.Biomass is fundamental for soilprocesses to occur and quantification ofmicrobial biomass is as such ameasurement at the ecosystem level.

4.1. Microbial biomassSoil microbial biomass represents thefraction of the soil responsible for theenergy and nutrient cycling and theregulation of organic mattertransformation. A close relationship hasbeen reported between soil microbialbiomass, decomposition rate and N-mineralisation. Microbial biomass hasalso been shown to correlate positivelywith grain yield in organic, but not inconventional farming. Finally, soilmicrobial biomass contributes to soilstructure and soil stabilisation. Soilmicrobial biomass has also beenrecommended as indicators of soilorganic carbon.Several methods have been used for theestimation of microbial biomass in soil.The methods can be divided into direct

(e.g. microscopy or determinations ofspecific membrane phospholipid fattyacids (PLFAs) and indirect (e.g.chloroform fumigation (CFE/CFI) orsubstrate induced respiration (SIR).

Direct methods (microscopy, PLFA)Determination of soil microbial biomassby direct methods (microscopy or PLFAanalysis) gives results that very closelyrepresent the in situ soil conditions.Although the methods are time-consuming, they are currently used forsoil monitoring purposes. Theautomation of PLFA extraction hasreduced analysis time to some extent.Direct counts or bio-volume estimationsusing conversion factors can estimatemicrobial biomass. Different soilpreparation methods and stainingtechniques in combination with epi-fluorescens microscopy are available.Combined with automated imageanalysis, direct counts can be usedroutinely for the determination of soilmicrobial biomass in many samples ofdifferent origin.



The total amount of PLFAs in soil is analternative method to microscopiccounting. PLFAs are found only inmembranes of bacteria and fungi.Individual PLFAs are specific for specificsubgroups of microorganisms. Usingextraction of soil samples and analysisby gas chromatography, the totalamount of PLFAs can be quantified. It isalso possible to quantify different groupsof microorganisms by this method. PLFAanalysis hereby provides information onbiodiversity (see chap. 1.3) and thefungal-bacterial biomass ratio (seebelow).

Indirect methods (CFI, CFE, SIR)Indirect methods are generally cheaper,faster and easier to use than the directmethods. Results obtained by theindirect methods have been documentedto be very close to the directmeasurements, thus providingconfidence in the utility of indirectmethods.Chloroform fumigation is the mostcommonly used indirect method. Thismethod is considered to measure mostof the soil microbial biomass, e.g. bothdead and alive, though somemicroorganisms (e.g. spores) areinsensitive to the fumigation process.Determination of microbial biomass bychloroform fumigation covers twoindirect methods: the chloroformfumigation incubation method (CFI) andthe chloroform fumigation extractionmethod (CFE). In both cases, thechloroform vapour kills themicroorganisms in the soil, andsubsequently the size of the killedbiomass is estimated either byquantification of respired CO2 over aspecified period of incubation (CFI) or bya direct extraction of the soilimmediately after the fumigationfollowed by a quantification ofextractable carbon (CFE; ISO-standard14240-2:1997). The release of CO2 afterfumigation is the result of germinatingmicrobial spores utilising the Csubstrate provided by the killedmicrobial cells.Another common indirect method issubstrate induced respiration (SIR). Thismethod measures only the metabolicallyactive portion of the microbial biomass.SIR (ISO-standard 14240:1:1997)

measures the initial change in the soilrespiration rate as a result of adding aneasily decomposable substrate (e.g.glucose). The technique has beenautomated and is used in soilmonitoring in several countries. Soilmicrobial biomass is subsequentlycalculated using a conversion factor.

Microbial quotientThe amount of microbial biomasscarbon (Cmicro) may be related to the totalcarbon (Corg) content by the microbialquotient (Cmicro/Corg). This quotientprovides a measure of soil organicmatter dynamics and can be used as anindicator of net C loss or accumulation.Using the quotient avoids the problemsof comparing trends in soils withdifferent organic matter content.

Fungal biomassLiving fungal biomass can be estimatedby quantification of fungal specificmembrane molecules such as ergosterolor specific phospholipids (PLFAs) (seeabove). The procedure for determinationof ergosterol content in soil is simplercompared to determination of PLFAs.However, an important disadvantage ofthis method is that oomycetous fungiand a number of yeasts do not produceergosterol. Additionally, it isrecommended that total hyphal length ismeasured simultaneously for preciseestimations of only living fungalbiomass, but this is a very laborious andcumbersome technique. Quantificationof enzyme activities such as fluoresceindiacetate hydrolytic activity (FDA) or N-acetyl-beta-glucosaminidase (Nag)activity have been proposed asalternative, semi-quantitative measuresof soil fungal biomass.

Fungal-bacterial biomass ratioThe fungal-bacterial biomass ratio canalso be determined directly frommeasurements of fungal-specific andbacterial-specific PLFAs. Moreinformation is thus obtained from onesingle PLFA-analysis. The ratio has beenused in soil management studies as amicrobial indicator. A higher ratio istypical of long-term unfertilised ororganic managed grasslands comparedto fertilised grasslands of the same soiltype.



4.2. Protozoan biomassProtozoan biomass is determined byextracting a soil sample and countingdirectly by use of an invertedmicroscope. This yields the number ofactive protozoa. However, the vastmajority of protozoa are encysted(inactive). An alternative method is thusto extract protozoa from the soil followedby a MPN counting based on a growthmedium that causes protozoa to excyst.Both methods are very laborious andlimited by the problems of extractionefficiency. The MPN approach furtherpossesses the problems of culturability;not all cysts will excyst and not allprotozoa grow under the laboratory

conditions in liquid culture. A newlydeveloped molecular method, MPN-PCR,has been used to quantify a specificgroup of soil flagellates directly in agnotobiotic soil system and higher butcorresponding numbers was foundcompared to traditional MPN countingbased on culturing. The application ofMPN-PCR assays for soil protozoa is,however, currently limited by thescarcity of molecular data. Bioassaysbased on a 24 h growth response ofcommon ciliates have been developedand successfully applied to heavy metaltoxicity testing.

5. Indicators of microbial activity

End points Soil ecosystem parameter Microbial indicatorsSoil ecosystem healthSoil microbial communityhealth

Microbial activity Bacterial DNA synthesisBacterial protein synthesisRNA measurementsBacteriophages

Indicators of microbial activity in soilrepresent measurements at theecosystem level (e.g. processesregulating decomposition of organicresidues and nutrient cycling, especiallynitrogen, sulphur, and phosphorus).Measurements at the community levelinclude bacterial DNA and proteinsynthesis. Frequency of bacteriophagesis a measurement at the populationlevel.5.1. Bacterial DNA synthesisSynthesis of DNA is a prerequisite forbacterial cell division and, as such, anindicator of bacterial growth. DNA isunique in the way that it onlyparticipates in cell division. DNAsynthesis can be determined byincorporation of 3H- or 14C-thymidineinto bacterial DNA as thymidine is aunique nucleoside, which onlyparticipates in DNA synthesis. Themethod has several requirements: (i)DNA synthesis has to be linearlycorrelated with the cell growth (balancedgrowth); (ii) all bacteria must take upthymidine through the cell membrane,which has been shown not to be thecase; (iii) thymidine should not bemetabolised and (iv) the radioactive label(3H) should not exchange with other

molecules, e.g. proteins. It has beenshown that only 5-20% of the 3H-thymidine incorporated into totalmacromolecules is incorporated intoDNA.A soil extract is incubated withradiolabelled thymidine for a short timeperiod and then filtered to measure theamount of radiolabel in the cells. Athorough extraction and purification ofDNA from the cells can solve theproblem with unspecific incorporation ofradiolabel. The method is extensivelyused in aquatic environments. Duringthe last decade it has been adopted tosoil, but the use is not as widespread asin aquatic environments. The method isused routinely in the Soil MonitoringProgramme and has been shown todiscriminate between different soil typesand land uses, e.g. grassland on clayand horticultural farm on sand.Bacterial growth rate (number of cellsformed per unit time) is calculated byuse of a conversion factor. Thisconversion factor is based on manyassumptions, including estimates of thenumber of cells present and the amountof radiolabelled thymidine incorporatedin relation to GC content of the totalDNA content of cells.



5.2. Bacterial protein synthesisBacterial protein synthesis is directlycorrelated to bacterial activity and canbe determined by incorporation of 3H- or14C- leucine, as this amino acid isincorporated into proteins only. Themethod for leucine incorporation is thesame as for thymidine incorporation (seeabove) and the incorporation of bothprecursors can be carried out in a singleassay if different radiolabels are used.Incorporation of 14C leucine is routinelymeasured in the Soil MonitoringProgramme in combination with 3H-thymidine incorporation and has beenshown to possess discriminative power.The advantages and drawbacks of themethod are the same as for radiolabelledthymidine incorporation, althoughbalanced growth is not a prerequisite.Furthermore, most bacteria take upleucine, although the incorporationefficiency may differ between soils.Measurements of protein synthesis aresupposed to be more accurate than thatof DNA synthesis, because of a relativelyhigher protein content in cells.5.3. RNA measurementsThe RNA molecules, ribosomal RNA(rRNA) and messenger RNA (mRNA), playkey roles in the protein synthesis. Theamount of RNA in individual cells or in acommunity may, therefore, be taken asan indicator of protein synthesis and,thus, microbial activity.The number of active cells can bedetected by fluorescent in situhybridisation (FISH). By this method,individual cells carrying highconcentrations of rRNA, situated onribosomes, are quantified byfluorescence microscopy. The amount ofrRNA in a community can also bedetected by Reverse TranscriptasePolymerase Chain Reaction (RT-PCR),where rRNA extracted from soil isdetected by creating a DNA copy andseparating by gel electrophoresis.Quantification of activity by eithermethod is still problematic andcomprehensive method development isneeded before implementation into amonitoring programme. In the futurethis will also include implementation ofmicroarrays with simultaneousmeasurements of numerous genes.mRNA molecules are gene copies used

for synthesis of specific proteins by thecell. Determination of mRNA can betaken as equivalent to the expression ofa specific gene in soil. Suchmeasurements can be done by real timequantitative RT-PCR, which detects andquantifies low amounts of mRNA inenvironmental samples including soil. Aprerequisite for using this method isknowledge of the sequence of the mRNA.At present, this method is probably tooadvanced for use as a microbialindicator in a monitoring programme,but with further method development itmay prove useful.5.4. BacteriophagesA bacteriophage is a virus, which infectsand multiplies in a specific hostbacterium. Bacteriophages areabundant in the soil environment andhave been isolated for nearly everyknown species of soil bacteria. Mostphages isolated from soil are temperatephages, e.g. phages that can lie dormantin bacterial cells after infection. Themultiplication of bacteriophages strictlydepends on the activity of the hostbacteria. As such, monitoring of thefrequency and host specificity of freebacteriophages in soil is an indicator ofthe activity of specific soil bacteria. Thisis in contrast to the other microbialactivity indicators, which measure theactivity of whole microbial communities.Determination of free bacteriophages insoil can be carried out by a standardmethod of extraction followed by aplaque-assay with specific host bacteria,e.g. Pseudomonas, Bacillus, Rhizobium.A high number of plaques are presumedto indicate a recent high activity ofsimilar host bacteria in the test soilassuming a direct correlation betweenthe number of bacteriophages andbacterial activity. Such a correlation hasindeed been shown for Azospirillumbrasilense (microcosm study), andSerratia liquefaciens (field study), buthas to be confirmed for other bacterialgroups.The selection of host bacteria should berepresentative for the soil type to beinvestigated. Furthermore, thebacteriophage sensitivity to the hostbacteria should be known. Thefrequency and persistence of thebacteriophages in different soil types



should be estimated a priori in order tostandardise the method. Generally,temperate bacteriophages survive forlong periods of time within the host

bacteria. Without host bacteria, thesurvival of bacteriophages depends onabiotic parameters, e.g. clay content, soilmoisture, temperature and pH.

6. Key species

End points Soil ecosystem parameter Microbial indicatorsSoil ecosystem healthPlant healthAnimal healthHamn health

Key species MycorrhizaSuppressive soilHuman pathogens

Microbial key species in soil are heredefined as organisms that possessimportant functions in the soilecosystem (e.g., nutrient cycling, plantpathogenesis) or are of human healthconcern (e.g. humanpathogens/zoonoses). A number ofcriteria has to be fulfilled for key speciesto be useful in a monitoring programme.For example, they should be(ecologically) relevant, preferablyabundant, and easy to enumerate andidentify. Key indicator species representmeasurements at the population level.6.1. MycorrhizaThe majority of higher plants exist innatural symbiosis with mycorrhizalfungi. The group of mycorrhizal fungiincludes ectomycorrhizal (mainly foresttrees), arbuscular mycorrhizal(terrestrial plants) and ericoidmycorrhizal (heather) fungi. Theycolonise plant roots and provide theplant with nutrients, especiallyphosphorus, due to the increasednutrient availability caused by the extra-radical mycelium. Furthermore,mycorrhizal associations can have apositive influence on plant diversity,plant stress and disease tolerance, andon soil aggregation. Only arbuscularmycorrhiza (AM) will be dealt with here.Colonisation by AM has been shown tobe highly dependent on the presence ofhost plants, on land use and on soilmanagement practices. Sporeabundance and diversity have beenshown to discriminate betweenextensively and intensively managedsoils and AM diversity has been reportedto be sensitive to heavy metalcontamination, organic pollutants andatmospheric deposition. Quantitativeanalysis of AM based on sporemorphology is implemented as a

microbial indicator in the soilmonitoring network, where it is used toindicate heavy metal contamination insoil. Colonisation of AM in soil has beenproposed as an important indicator ofplant and ecosystem health.Abundance and diversity of AM isdetermined by extraction of spores fromsoil samples and subsequent countingin a microscope. An alternative methodis to use the test soil in a plant bioassayand harvest either the spores or theroots. The determination of sporenumbers is, however, poorly correlatedto the actual colonisation potential ofthe soil and molecular tools for detectionof AM in roots are the future needswithin the Soil Monitoring Programme.Methods for direct detection andquantification of AM in soil samples orin roots have been developed. Theseinclude 18S rDNA PCR, nested PCR atthe species level and AM-specific PLFAs(see chapter 1.3).6.2. Suppressive soilMany of the proposed soil healthindicators focus on the presence ofbeneficial rather than the absence ofdetrimental organisms, although bothare important. The presence of plantpathogens (e.g. fungi) in soil mayindicate the existence of other soilhealth problems, e.g. nutrientimbalance. A suppressive soil is able tosuppress specific plant diseases byinherent biotic and abiotic factors. Thesuppressiveness of a certain soil maythus be an indicator of plant health.Several methods are available fordetermining soil suppressiveness. It canbe determined by inoculation of target-plant seeds directly into the test soil orinto a pathogen-infested test soil. Thefrequency of diseased plants and/orpathogenic propagules in soil is scored



after incubation for about 3 to 4 weeksand compared to a reference soil.The plant bioassay is a conventionaltechnique and a positive correlationbetween the plant bioassay and theactual field measurements has beenshown for suppressiveness of pea rootrot. A specific test plant system has tobe selected for a monitoring programmeand the correlation between bioassayand field measurements has to beconfirmed on a diverse set of soils. Theassay requires a relatively long time (e.g.weeks) before the results can beobtained, but it is simple and cheap.6.3. Human pathogensHuman pathogens can enter agriculturalsoils through amendment with manureand sewage sludge. The presence ofhuman pathogenic bacteria in soil is anindicator of potential human infectionand as such an indicator of humanhealth. Presence of Escherichia coli, havetraditionally been used as an indicatorof faecal contamination and hence as anindicator of the possible presence ofother more pathogenic bacteria. Sincethe ability of the pathogenic bacteria tosurvive in the environment may notnecessarily be equal to that of E. coli, itwould be advantageous if the pathogenswere enumerated directly.Enumeration of pathogenic bacteria canbe carried out either by cultivation or bymolecular / immunological techniques.

Methods relying on cultivation usegrowth media selective for specificgroups of microorganisms, i.e. XLD agarfor isolation of Salmonella and Shigellaand MacConkey agar for isolation ofcoliforms. These methods are well-established, cheap, and easy to use.Molecular techniques may give a moreaccurate estimate of the populationsizes, as they do not rely on growth ofthe bacteria. On the other hand theymay detect dead bacteria as well as freeDNA. Among the molecular methods,that would be suitable for a monitoringprogramme, are quantitative PCR andspecific fluorescent oligo-nucleotideprobes. With immunological methods,specific antibodies are used instead ofoligo-nucleotide probes and thedetection limit can further be loweredwhen combined with immune-magneticseparation.The drawback of using both themolecular and immunologicaltechniques is that they technically aremore demanding than the traditionalculturing methods. Little is known aboutthe occurrence of pathogenic bacteria inagricultural soil and investigations onthe differences between fields receivingmanure and/or sewage sludge anduntreated fields are needed prior toimplementation into a monitoringprogramme.

7. Indicators of bioavailability

End points Soil ecosystem parameter Microbial indicatorsSoil microbial communityhealthLeaching to ground waterSurface run-off

Bioavailability Biosensor bacteriaPlasmid containing bacteriaAntibiotic resistant bacteriaCatabolic genes

Chemical compounds may oftenbe adsorbed to soil particles, such asclay minerals, and made unavailable tothe biota. The bioavailable concentrationwill be equal to or lower than the totalchemically extractable concentration.From an environmental viewpoint, thebioavailable fraction of a chemicalcompound may be a more relevantparameter than the chemicallyextractable fraction. Microorganisms canmeasure the bioavailability of a chemicalcompound in soil. Indicators ofbioavailability represent measurementsat the community and population levels.

7.1. Biosensor bacteriaBiosensor bacteria are designed torespond to certain stress situations (e.g.toxicity) through the use of reportergenes. Environmental relevant bacteriacan be selected and genetically modifiedby fusing reporter genes (e.g.bioluminescence) to the genes of interestand thereby give a certain signal to aspecific response. Ultimately, fibre opticlinked membrane bound biosensorprobes may facilitate in situ eco-toxicitymonitoring of soil.



Biosensor bacteria responding tomercury or chromate or zinc arepresently available. The zinc biosensorbacteria have been used for soilmonitoring purposes, where it was themost discriminative method.Commercial biosensor bacteria productsfor overall eco-toxicological analysis areavailable (Remedios and Microtox).

7.2. Plasmid-containing bacteriaThe frequency of plasmid-containing soilbacteria has been shown to be higher inpolluted soils compared to agriculturalsoils, and to increase by addition ofheavy metals to soil. Thus,measurement of numbers of plasmid-containing bacteria or numbers ofplasmids in soil can be used as ageneral indicator of environmentalcontaminants. If numbers of plasmidsincrease at a site, an investigation toidentify the stress factor (e.g. pollutants)can subsequently be initiated.Two different approaches can be used toassess the occurrence of plasmids insoil, the endogenous and the exogenousapproach. By the endogenous approach,plasmids are extracted from soil bacteriaisolated on agar plates followed by avisualisation of the plasmids on agarosegels. By the exogenous approach,suitable plasmid free recipient bacteriaare used as “fishing rods”. The plasmidfree bacteria are mixed with a soilsample and allowed time to pick up (byconjugation) naturally occurringplasmids from the indigenous bacteria.Plasmids are extracted and visualised asin the endogenous approach.A major disadvantage of the endogenousplasmid extraction procedure is that itonly analyses the fraction of soil bacteriathat grow on cultivation media. Thisstep is eliminated in the exogenousplasmid isolation procedure. However,only conjugative and mobilisableplasmids may be isolated by thismethod. The frequency and variability inplasmid numbers in different soil typesshould be estimated in order tostandardise the method.

7.3. Antibiotic resistant bacteriaRestricted use of antibiotics (e.g.

growth promoters) in agriculture hasreduced but not eliminated antibioticresistant bacteria in livestock and food

(Anonymous 1998). Urban effluents,which also contain antibiotics, havebeen demonstrated to result in anincrease in the number of antibioticresistant bacteria in riverineenvironments. Antibiotic substanceshave been detected in outlets of sewagetreatment plants, manure andagricultural fields. Although themeasured concentrations of antibioticsubstances are generally below theminimum inhibitory concentration (MIC)to microorganisms, they maynevertheless select for the outgrowth ofresistant bacteria in the soil ecosystem.Very little, however, is known about theoccurrence of resistant microorganismsin agricultural soil. Heavy metalpollution may also indirectly select forantibiotic resistant bacteria, since acorrelation between bacterial antibioticresistance and mercury concentration inriverine sediments has been observed.Thus, monitoring antibiotic resistantbacteria in soil will not only allow anassessment of the potential risk ofantibiotic resistant bacteria to humans(human health), but can also be used asan indicator of industrial and urbanpollution (potential leaching or surfacerun-off).Enumeration of antibiotic resistantbacteria can be carried out either bycultivation and/or moleculartechniques. Methods relying oncultivation on selective growth mediacontaining antibiotics (tetracycline,kanamycin, etc.) are well established,cheap, and can easily be implemented ina monitoring programme. By use ofthese methods, not only can numbers ofresistant bacteria be estimated, but theMIC and the breakpoint value may alsobe determined. This is necessarybecause an antibiotic concentrationappropriate to distinguish betweenresistant and sensitive bacteria of onespecies, may not be applicable toanother. A well-known drawback of thecultivation methods is non-culturabilityof some bacteria. This can be overcomeby molecular techniques, which estimatethe population sizes of the resistancegenes. PCR and molecular gene probeanalysis can possibly be used to detect aspecific resistance gene in a soil sampleand to develop quantitative PCRmethods.



Since little is known about theoccurrence of antibiotic resistantbacteria in agricultural soil, somebaseline testing is required to investigatethe possible differences between treated(i.e. with manure/sludge) and untreatedfields. Monitoring of antibiotic resistantbacteria may be complemented withmeasurements of bioavailableconcentrations of antibiotics by use ofbiosensor bacteria or plasmid-containingbacteria (see above).

7.4. Incidence and expression ofcatabolic genesWhen the degradation pathway of achemical compounds (e.g. pesticides) isknown, key enzymes and catabolic genescan be identified and quantified. Thepresence of degradable chemicalcompounds in a soil is presumed toprovoke a higher incidence andexpression of corresponding catabolicgenes due to either growth of bacteria orthe spreading of the catabolic genes tothe microbial community. Catabolicgenes may, however, also be present dueto their involvement in the degradationof naturally occurring and relatedorganic compounds. The incidence ofspecific catabolic genes thus givesinformation on the ability of a soil tomodify or degrade xenobioticcompounds. An elevated expression of

the catabolic genes will, on the otherhand, indicate a partial or completedegradation of the correspondingorganic compound.Several methods have been proposed fordetermination of the incidence andexpression of specific catabolic genes.These include conventional culturing ofdegradative microorganisms, activitymeasurements of specific degradativekey enzymes, and molecular methods fordetection of catabolic genes (e.g. PCR,qPCR) and measurements of theirexpression (e.g. mRNA, rRNA, biosensorbacteria). The molecular methods aredescribed elsewhere (see chap. 1.1, 5.3,7.1 and 7.3) and only the culturingtechnique will be dealt with here.The potential for degradation of axenobiotic compound in soil can beestimated by incubation of a soil slurryspiked with the compound (radiolabelledor unlabelled) of interest andsubsequent determinations of eitherradiolabelled CO2-production, therespiration rate (see chap. 2.1) or cellgrowth. The incubation approach is alsoused for isolation of consortia or purecultures able to grow on and degradespecific xenobiotic compounds. Theassay, though, is entirely dependent onthe activity of the microorganisms andtheir culturability at the incubationconditions provided.



SOIL TAXONOMY: A NEW TREND OF SOIL CLASSIFICATIONG.P. Gupta

Retd. Professor & ADRJawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur (M.P.)

Soil Taxonomy: Soil Taxonomy is thelatest system of soil classification thathas new design and nomenclature.The word Taxonomy was derived fromthe Greek word “Taxis” which means asystematic arrangement or order orgrouping of similar soils. Soil Taxonomyis defined as it is based upon themorphometric properties which areobservable and measurable.Superiority over old soil classificationsystems1. Soil Taxonomy is based on observable

and measurable soil properties whichare easily verified by others to lessenthe controversies amongst thescientists.

2. It is not based on virgin soils.3. It has completely new nomenclature

which are clearly defined.4. Subgroup as a new category has been

included and soil type as an oldcategory has been excluded.

Requirements of Soil Taxonomy1. It should accommodate whole soils of

the world.2. It should be based on observable and

measurable properties3. It should be flexible enough to

incorporate new knowledge .4. It should not alter due to drastic

changes like fire, single ploughing oras a result of land use.

5. Properties selected should eitheraffect soil genesis or be affected by it.

6. Emphasis should be given to theproperties significant to plant growth

7. Subdivisions of classes should not bemade in common properties.

Important terms used in soiltaxonomy

Pedon It is the smallest volume of soil that

should be recognized as soilindividual.

It has three dimension. The minimalhorizontal area of a pedon isarbitrarily set as 1 m2 but may rangeto 10 m2 depending upon thevariability of soils.

Individual : It is the smallest natural body which

is complete in itself collectively.

Model individual

It defines the central concept of theclass. Model properties are typified inthe class.

Class : It is a group of individuals whichare similar in selected properties. It isdistinguished from other classes.Population : Population is like akingdom for example plant, animal ofsoil. It consists of may individuals ofvarious natures.Taxon : A class of any taxonomical levelof classification in the soil taxonomy iscalled Taxon.Nomenclature developed in SoilTaxonomy Soil Taxonomy has a unique

nomenclature which gives a definiteconnotation of their majorcharacteristics of a soil in question.

Nomenclature has been coined mainlyfrom Greek and latin words (roots anda few from Japanees, German,English and French words (roots).

Name of each taxon clearly indicatesits place and tells some of itsimportant properties.

A formative element from each ofhigher categories is successfullycarried down to family level.

It seems difficult and strange in thebeginning but with a little study andexperience several useful statementscan be drawn.

Example to show the validity of SoilTaxonomyAs an example soil classification ofKulholi soil series is given as under;“Coarse loamy, mixed, calcareous,hyperthermic, Typic, Halaquept”

The useful statements drawnfrom such classification are : There is some inception in the genetic

horizon (ept). Soil exists in waterlogged conditions

(aquic).



Exchangeable sodium is more than15% (Hal).

Soil is deep (Typic) Mean annual soil temperature is

>22oC with a difference of >5 oCbetween mean summer and meanwinter at 50 cm depth (hyperthermic).

Calcium carbonate present is >5%because there is violent effervescence(Calcareaus).

Mineralogy is mixed. It shows that noany fraction exists >40% (mixed)

Clay is less than 35% (Coarse loamy)1. Order - Inceptisol (ept)2. Suborder - aquept (aquic)3. Great Group - Halaquept4. Sub Group - Typic Halaquept5. Family - Coarse loamy,

mixed, Calcareous,hyperthermic

6. Soil series - KULHOLI(District –Morena M.P.)

Nature of soil characteristics :Soil characteristics are of three types :

a. Differentiating characteristics: Theproperties chosen as the basis todifferentiate among classes areknown as Differentiatingcharacteristics. Mean values of suchproperties within each class definethe model individual of the group.For example- TEXTURE.

b. Accessory characteristics: Propertiesassociated with the Differentiatingcharacteristics are called Accessorycharacteristics. For example- CEC,WHC, Cohesion.

c. Accidental characteristics: Propertieswhich are independent from theDifferentiating characteristics arecalled accidental characteristics. Forexample – SLOPE

SOIL TAXONOMY : A MULTIPLECATEGORY SYSTEM (MCS)

Population is so diverse that asingle/mono grouping fails to showrelationships. Hence the divisions orclasses so formed are again subdividedto show more relationships.

Importance of multiple category system

The number of statements increasefrom higher to lower category

Homogeneity of classes increases withdecrease of abstraction.

Higher category is a grouping ofclasses of the preceeding lowercategory

Soil Taxonomy : both a natural andtechnical system

Natural classification : It performsimportant function of organizing,naming and defining the classes.Objects are classified in such a way thatthe name of each class brings in mindthe fixed characteristics in relation toothers.Technical classification : It is aclassification of objects for specific,applied or practical purposes e.g.Irrigation Suitability Classes (ISC).

Principles of soil classificationPoints used as a background for

discussion of soil classification systemsare termed as principles of soilclassification. There are four importantprinciples :-

Genetic thread principle : Theories ofsoil genesis must provide the significantproperties to use as differentiatingcharacteristics.Principle of accumulatingdifferentiate : In a MCS, differentiatingcharacteristics must accumulate fromhigher to lower level of generalization.

Principle of wholeness of Taxonomiccategories : All the individuals of apopulation must be classified accordingto differentiating characteristics in eachcategory.Ceiling of independence : Adifferentiating characteristic in aparticular category must not separatesimilar individuals in lower category .Categories of soil taxonomy : Categoryis the series of array of taxa produced bydifferentiations at a given level ofabstraction or generalization. It is a setof classes defined at about the samelevel of abstraction that includes allsoils.



Table 1 Categories of Soil Taxonomy (2010)

S.N. Category No. Sub divisions are due to

1. Order (12) Presence or absence of major diagnostic horizons

developed due to soil forming processes and extremes

of soil temperature and moisture regimes.

2. Suborder (61) Associated properties like wetness, soil moisture

regimes, PM & Veg. effect and diagnostic horizons.

3. Great Group (316) Kind and arrangement of horizons, base status, soil

temperature, plinthites and pans.

4. Subgroup (2484) Inter or extra gradations to taxa in other orders.

5. Family (6600) Properties responsible for plant growth like texture

class, mineralogy, soil temperature of control section.

6. Series (18000) Kind and arrangement of horizons in respect of colour,

texture, structure, consistence, reactions etc.

I. SOIL ORDER1. Name of the ORDER ends with “sol”

(Latin word: solum).2. Formative elements of each order exit

in the end of sub order, great group,subgroup and family.

3. ORDERS differ due to the existence ofdifferent sets of diagnostic horizons

(i). Undeveloped profiles : Entisolsii). (Minimum degree of

horizondevelopment

: Inceptisols,Andisols

(iii). Dominant kind ofgenetic horizons

: Vertisols, Aridisols,Mollisols.Spodosols,Ultisols, Histosols

(iv). Kind and degree ofweathering and soilformation

: Oxisols

Table 1: Soil Orders and their derivatives

No. Soil Order Derivation Pronunciation FormativeElement

1 Gelisol Frozen soil Permafrost el

2 Histosol Gk.histos Histology ist

3 Spodosol Gk. spodos Podsol, old od

4 Andisol modified from ando Andesite and

5 Oxisol Fr. oxide, oxide Oxide ox

6 Vertisol L.verto, turn Invert ert

7 Aridisol L.aridus,dry Arid id

8 Ultisol L.ultimus, last Ultimate ult

9 Mollisol L . mollis, soft Mollify oll

10 Alfisol nonsense symbol Pedalfer alf

11 Inceptisol L. inceptum, beginning Inception ept

12 Entisol nonsense symbol Recent ent



Table 2 : Sequence of soil orders for use in Soil Taxonomy (Soil Survey Staff, 2014)

Soil Order (12 in Number)S.N.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Orders (- sols)

Gel

i-

His

to-

Spo

do-

An

di-

Oxi

-

Ver

ti-

Ari

di-

Ult

i-

Mol

li-

Alfi

-

Ince

pti-

En

ti-

First Alphabet G H S A O V A U M A I ESymbolicexpressions

A B C D E F G H I J K L

Chapters devoted 9 10 14 6 13 16 7 15 12 5 11 8Sequence of chapters 5 6 10 2 9 12 3 11 8 1 7 4

Govt. High School Appeared On Village And Upper, Middle At Interior End (for remembrance)

Table 3: Orders and their endopedons and epipedons

No. Order Soils called as Epipedon Endopedon1. Gelisol Frozen soils ochric -2. Histosol Organic, >30% organic matter

(Peat, Muck)histic -

3. Spodosol Humus and sesquioxide rich ochric spodic (Fe, Al,Humus accum.)

4. Andisol Volcanic (Slightly developed) ochric -5. Oxisol Highly weathered soil ochric oxic6. Vertisol Shrink-swell (Cracks when dry) ochric vertic7. Aridisol Dry soils ochric no/argillic

/natric8. Ultisol Low base saturated soils ochric argillic9. Mollisol Very high base saturated (dark) mollic no/argillic

/natric10. Alfisol High to medium base saturated ochric argillic /natric11. Inceptisol Embryonic soil (slightly developed) ochric

/umbriccambic

12. Entisol Recent (undeveloped) ochric -

Table 4: Major adsorbed cations (%) by soils of various soil orders

No. Order H+ & Al3+ Ca2+ Mg2+ K+ Na+

1. Gelisol - - - - -2. Histosol - - - - -3. Spodosol 80 15 3 2 Tr4. Andisol - - - - -5. Oxisol 85 10 3 2 Tr6. Vertisol 48 38 15 5 27. Aridisol - 65 20 10 58. Ultisol 65 25 6 3 19. Mollisol 30 43 18 6 310. Alfisol 45 35 13 5 211. Inceptisol - - - - -12. Entisol - - - - -



Development of different soil orders :Soil orders having different charectersicts develop different soil orders(i). Extensive mineral weathering Oxisols>Ultisols

(ii). Dominant swelling clays Vertisols

(iii). Organic soils Histosols

Table 5: Keys showing the central concept of the orders in Soil Taxonomy

S.N. Soil properties Yes Order But if no

1. Soils with permafrost or gel material Gelisol

2. Organic materials extending downwords or organic layer 40cm thick

Histosol

3. Andic properties that do not have albichorizon with an associated spodichorizon

Spodosol

4. Spodic horizon within 2m of soilsurface

Andisol

5. An oxic horizon within 2m of soilsurface

Oxisol

6. 30% or more clay to a depth of 50cmand shrink swell clays

Vertisol

7. An aridic soil moisture regime or a salichorizon

Aridisol

8. An argillic horizon or fragipan and BSP<35 at 1.25m below argillic horizon or75cm below the fragipan.

Ultisol

9. A mollic epipedon and BSP >50 to animpermeable layer or at 1.8m fromsurface

Mollisol

10. An argillic horizon or natric horizon ora fragipan

Alfisol

11. A cambic sulphuric, calcic, gypsic,petrocalcic, petrogypsic , horizon orwith a mollic, umbric or histic epipedonor with an ESP>15

Inceptisol

12. Others Entisol

II. SUBORDERS It is differentiated on the basis of

additional soil properties where thehorizons are differentiated due todifference in soil temperature , soilmoisture, chemical and texturalfeatures.

The name of the suborder has twosyllables. The last syllable is theformative element of the order. Firstsyllable represents additionaldiagnostic properties.For example

aqu ent(First) (last)

where last one is the FormativeElement of the ORDER It has about 26 FormativeElements (Soil Survey Staff, 2010)

III. GREAT GROUPIt is differentiated on the basis of

Differentiating soil horizons i.e.accumulation of clay and/or humusand pans that interfere in watermovement or root penetration .

Differentiating soil features i.e. selfmixing properties of clays, soiltemperature and major differences incontents of Ca, Mg, Na, K, Gypsumand other salts.

It has 3 to 4 syllables. Last two

syllables are the name of suborder.

First syllable connotes additionaldiagnostic propertyNatr Argid(First) (last)



In case of 4 syllables one vowel isintroduced for continuity in the greatgroup

cry o fluvent It has 56 formative elements

IV. SUBGROUP Subgroup is formed by adding one or

more adjectives before the name ofGreat group.

There are 3 kinds of subgroups :(i) Typic : It represents the central

concept of its Great Group.(ii) Intergrade : When it tends

towards other orders, subordersor great groups (i.e. different soilproperties or specific propertiesdiffering from Typic)

(iii) Extragrade : When the soilintergrades with non soil groupe.g. Hard rock, sediments etc.

Properties may not be intergradingclearly but some other propertiesprevail.

Formative elements of the subgroupare -

Most representative subgroup is Typicor Haplic meaning simple.

V. FAMILY Family within a subgroup is

differentiated on the basis of soilproperties which are important forthe plant growth and development orfrom engineering point of view

Family grouping is done on the basisof similar physic-chemical propertieswhich are responsive to managementand manipulation for use i.e.movement of air, water and plantnutrients.

Family consists a name of subgrouppreceeded by 3-5 modifiers. Thesemodifiers narrow the propertiesenough to permit general statementabout the use and management ofsoil.

Family Control Section (FCS) A part of the profile representing the

whole profile development is knownas Family Control Section. It providesweighted averages of variousproperties.

Weighted Average: The values ofvarious properties multiplied with soilthickness (cm), added and averaged

by the total soil thickness are knownas weighted averages of FCS.

Location of family control section :there are three conditions(i) When argillic horizon does not

exist: FCS extends from a depthof 25 to 100 cm.

(ii) When argillic horizon is >50cmthick, upper 50cm thick argillichorizon is considered as FCS.

(iii) When argillic horizon is <50cm,whole argillic horizon isconsidered as FCS.

Components of family differentiae

(a) The family differentia are used todistinguish families is of mineralsoils and the mineral layers ofsome organic soils within asubgroup

(b) The class names of thesecomponents are used to form thefamily name.

(c) The components are listed anddefined in the same sequence inwhich the components appear inthe family names.

Main components are :1. Particle size classes2. Mineralogy classes3. Calcareous and reaction classes4. Soil temperature classes5. Soil depth classes6. Soil slope classes7. Soil consistence classes8. Classes of coatings (on sand)9. Classes of cracks.

VI. SOIL SERIES (common category of1938)

“It is a group of soils havingsoil horizons similar in differentiatingcharacteristics and arrangement of soilpedon except for the texture of surfacesoil and developed from a particular typeof parent material”

Criteria to separate various soil seriesSoil series are differentiated on thebasis of observable and mappableproperties. Soils in the same soilseries have the followingcharecterstics :

a. Similar kind, appearance andproperties such as thickness,colour, texture, structure,consistence, calcareousness andreaction classes (pH)



b. Similar number and arrangement ofsoil horizons in the pedon.

c. Similar chemical and mineralogyproperties.

d. Different soil series have differentsets of soil properties.

Naming of soil series Naming of soil series has no

pedogenic significance. It representsprominent geographic names like ariver, town or area where it wasrecognized for the first time.

Soil Series names remain tentativeunless they are established by theSoil Correlation Authorities (SCA).

Soils within a series arehomogeneous in all the pedoncharacteristics but may vary in soilmapping units. In a soil seriessurface texture, depth, erosion,stoniness, etc may vary to a certainextent that no additionalmanagement is required. Exceedingthese limits may need extramanagement making possible tocreate other soil series.

Each series is subdivided into soilmapping units which are calledphases of soil series.

Requirement for the establishment of asoil series :

(i) The one soil series should differfrom other soil series.

(ii) It should have in area of at least800 ha.

(iii) It should have atleast 10 pedonsshowing similar characteristics.

Description of standard soil series

1. Status of soil series2. Initials of authors with date3. Name of soil series4. Introductory paragraph5. Typifying pedon6. Type location7. Range in characteristics8. Competing series and their

differentiae9. Setting10. Principal associated soil series11. Drainage and permeability12. Extent of use and vegetation13. Distribution and extent14. Soil series proposed or established15. Remarks

Soil phase (subdivision of soil series) :

(i) Soil phase is used as associationwith soil series but is not a categoryof the soil classification system.

(ii) Phase of soil series has replaced thesoil type as a soil mapping unit

(iii) Its most common use is asubdivision of a soil seriesdelineating a soil mapping unit.

(iv) It helps in delineating soil areas forpractical use such as farming,municipal and Tehsil zoning

(v) Mapping units are also called as thepolypedons

(vi) Soil phases have differences insurface soil texture, solumthickness, percentage slope,stoniness, saltiness, extent ofdamage from erosion and others

(vii) Phase may also be used as asubdivision of soil order, sub order,great group, subgroup or family inSoil Taxonomy.

CENTRE OF ADVANCED FACULTY - JNKVV · 14. Improving soil health through Green Manuring M.L.Kewat...

Documents

Transcript of CENTRE OF ADVANCED FACULTY - JNKVV · 14. Improving soil health through Green Manuring M.L.Kewat...