Weed Management Techniques for ... - Issue Popular Kheti fileetc. which negatively affect the crop...

Popular Kheti ISSN:2321-0001 146

Weed Weed Weed Weed ManagementManagementManagementManagement Techniques Techniques Techniques Techniques for Organic Farmersfor Organic Farmersfor Organic Farmersfor Organic Farmers

Rajkumar DhakarRajkumar DhakarRajkumar DhakarRajkumar Dhakar1111****, Shivani Nagar, Shivani Nagar, Shivani Nagar, Shivani Nagar2222, Chandana Behera, Chandana Behera, Chandana Behera, Chandana Behera2222

1Scientist, Central Research Institute for Dryland Agriculture, Hyderabad-500 059 2Ph.D Research Scholar, Indian Agricultural Research Institute, New Delhi - 110 012

*Email of c*Email of c*Email of c*Email of corresponding authororresponding authororresponding authororresponding author:::: [email protected]@[email protected]@crida.in

IntroductionIntroductionIntroductionIntroduction

Weed is considered to be most problematic in organic production. Farmers and researchers

trying to develop effective and economic management practices for organic farming as organic

farming prohibits the use of synthetic agrochemicals. Use of herbicide reduces the labour

requirement and increases the yield. However, it has serious implication on environment and

leads to health problems in human being, weed develops resistance to herbicide and causes

potential decrease in biodiversity of farms. Weeds increase the cost of crop cultivation of a

farmer. Hence, effective weed management can reduce the cost of weed control. Weeds are

highly competitive pest with cultivated crops for resources such as light, nutrient and water

etc. which negatively affect the crop production.

Weed management in organic farm is based on combination of various methods which

manage the weed, but not eliminate, below the economic threshold level. For selection of the

best method, farmer should familiarize with the weeds prevail on his farm and their growth

habit.

This article aims at to discuss various methods of weed management in organic farms.

In principle it includes cultural practices (crop rotations, cover crops, mulching), solarization,

stale seed bed preparation, proper sanitation and composting, tactics to increase crop

competitiveness and physical methods for minimizing the weed on organic farms.

Crop Crop Crop Crop RotationsRotationsRotationsRotations

Traditionally since long time, farmers are using crop rotations as well as extensive research

has shown that crop rotation inhibits the dominance of particular weed species through

creation of changing environment. When farmer design a crop rotation plan, the potential

Popular Kheti Volume -1, Issue-4 (October-December), 2013

Available online at www.popularkheti.info © 2013 popularkheti.info

ISSN:2321-0001 1(4) 2013

Special on

Organic Farming

Issue

Weeds are utmost problem for organic farmers. Integrated weed management is only

possible solution for weed control on organic farms in present context. In future,

extensive research is required to find out the economic ways to minimize the weeds

for organic farming.

Dhakar et al (2013), Pop. Kheti, 1(4):146-151


weed problem should consider in his mind. Some following points which farmer may

consider-

• If less dense and more dense crop to be grown in succession, it is advised to be grown

prior more dense crop which reduces the proliferation of weeds.

• If farm is affected with crop associated weed such as Phalaris minor in wheat should be

rotated with non-cereals crops (preferably legume crops).

• If late germinating weeds are a problem, an early crop followed by tillage and summer

annual crop can be taken.

• If perennial weeds are a problem, the commercial crop can be rotated with perennial

fodder crops.

Cover Cover Cover Cover CropsCropsCropsCrops

Cover crops in organic farms can suppress weeds in many ways. It also protects soil from

erosion, improve soil structure and augment soil fertility. Cover crops can be used as a live

mulch or dead mulch (as a cover crop residue). Cover crop residue as a mulch modify the soil

moisture, temperature and light and restrict the germination and growth of weed plants.

Cover crop as a live mulch act as an intercrop. However, cover crop should not

compete with main crop for resources. Otherwise, it will result in lower yield of main crop.

The crop geography, seed rate and planting time of cover crop must be design in such a way

that it should create favourable environment for main crop. It is best to confine the living

mulch between row species.

The cover crop can also suppress weeds by the means of allelopathy - a chemical secreted by

one species inhibit the growth of another. It is generally advantageous to include allelopathic

cover crops in crop rotation to suppress the weed in organic fields. Some cover crops which

produces allelochemicals is presented in Table 1.

Table 1. Cover crops that produce allelochemicalsTable 1. Cover crops that produce allelochemicalsTable 1. Cover crops that produce allelochemicalsTable 1. Cover crops that produce allelochemicals

Scientific Name Scientific Name Scientific Name Scientific Name Common Name Common Name Common Name Common Name

Triticum aestivum Wheat

Avena sativa Oats

Brassica ssp. Mustard, radish

Fagopyrum esculentum Buckwheat

Hordeum vulgare Barley

Melilotus spp. Sweet clover

Secale cereale Cereal or winter rye

Sorghum bicolor Sorghum

Sorghum bicolor x S. sudanense Sorghum-sudangrass hybrids

Sorghum sudanense Sudangrass

Trifolium spp. Clover: red, white, and

subterranean



Farmer should take care of following points when grow the allelopathic cover crops-

• Residues of cover crops which exhibit allelopathy, can significantly reduce crop

seedling establishment (Weston, 1990).

• Large-seeded and rapidly germinating crops are less likely to be adversely effected by

allelopathic cover crops than are small-seeded, slow germinating crops.

• Inhibition of transplant growth by allelopathic cover crops, though not extensively

documented, has been observed in woody seedlings grown in a living sorghum-

sudangrass cover crop (Geneve and Weston, 1988).

Farmers should select cover crops that can be easily managed and that do not negatively affect

seedling establishment to reduce the risk of poor crop germination.

Stale Seed Bed PreparationStale Seed Bed PreparationStale Seed Bed PreparationStale Seed Bed Preparation

This technique comprise of allowing weed to germinate (either after rainfall or

through light irrigation) on a prepared fine seed bed, then removing weed seedling via tillage

or flame weeding. It provides an opportunity for germination and growth of crop before the

next flush of weeds.

Soil Soil Soil Soil SolarizationSolarizationSolarizationSolarization

In this technique, soil is covered with clear or black polyethylene plastic for six-seven

weeks or longer in summer which kills the weed seedling, pathogen, insect-pests etc. via

heating effect. In general, solarization is more effective against annual weeds than perennial

weeds. Farmer should consider following point for successful solarization-

• Solarization must be performed during the summer months, due to the temperatures

required for effective soil treatment.

• Soil must be finely tilled, and the plastic tarp must fit tightly over the soil.

• Plastic should be from 0.03 to 0.08 inches (0.75 to 2 mm) thick, and it should have an

ultraviolet inhibitor added to prevent degradation.

• The recommended soil temperatures for solarization are 140°F at a depth of 2 inches

and 102°F at a depth of 18 inches (Peet, 1996).

Preventive Measures for Weed Preventive Measures for Weed Preventive Measures for Weed Preventive Measures for Weed MinimizationMinimizationMinimizationMinimization

Some preventive measures to be adopted by farmer can minimize the introduction and

movement of weeds.

• Clean farm equipment regularly to avoid transfer of weed from one farm to other.

• Limit the amount of off-farm traffic visiting production areas, either by vehicle or foot.



• Apply mulch and compost that is free of weed seeds

• Animal manure should be composted properly to ensure killing of weed seeds. To kill

the majority of weed seeds in cattle manure, compost materials at a temperature of at

least 180°F (82°C) for no less than three days (Wiese et al., 1998). This temperature is

relatively easy to reach in most composting systems.

• Seeds and transplants before planting should not be contaminated with weed seeds.

Production Practices forProduction Practices forProduction Practices forProduction Practices for Increasing Crop CompetitivenessIncreasing Crop CompetitivenessIncreasing Crop CompetitivenessIncreasing Crop Competitiveness

Organic farmers can adopt the following strategies to provide competitive advantage to

commercial crops over weeds-

• Organic farmers select crop varieties that compete well with weeds. Quick canopy-

forming varieties assist the crop competitiveness over weeds within and between rows.

• Planting at the maximum adapted population will provide the crop an in increased

competitive edge over weeds.

• Closer row spacing generally leads to greater crop competition with weeds in row

middles.

• High germination rates are critical for a rapid canopy.

• To provide a competitive advantage, warm season crops (e.g., corn, soybeans, and dry

beans) are planted when the soil is adequately warmed (usually later than May 10) to

facilitate rapid germination. Warmer soils allow quicker emergence and a more

competitive crop without major losses in yield.

Physical Physical Physical Physical TechniquesTechniquesTechniquesTechniques

Physical methods of control include mechanical weed management, thermal weed control

and mulching.

Mechanical weed managementMechanical weed managementMechanical weed managementMechanical weed management: This is the most effective method but labour intensive and

time consuming.

Thermal methodThermal methodThermal methodThermal method: In this method, propane flame burning is used for weed control. It is used

during high moisture is available in field and when tillage with large machinery with not

feasible. But, it should use with caution that should not harm the crop.

MulchingMulchingMulchingMulching: : : : Mulches modify moisture and thermal regime of soil as well as limit the light

penetration by which reduces the weed growth. Different type of mulches viz., organic mulch

and inorganic mulch can be used for weed suppression on organic farms. Organic mulch adds

an organic matter to soil which improve soil structure, enhance water infiltration and

promote microbial activity. As it is biodegradable does not contribute to landfill problems.

Inorganic mulches should be used with caution because organic certification could be

jeopardised if synthetic chemicals are introduces through mulch materials.

Dhakar et al (

Popular Kheti

Tools and Implements for Weed ManagementTools and Implements for Weed ManagementTools and Implements for Weed ManagementTools and Implements for Weed Management

Some of the weeding tools with their purpose and approximate cost are listed in

Table 2: Some tools for weed managementTable 2: Some tools for weed managementTable 2: Some tools for weed managementTable 2: Some tools for weed management

Tools/implementsTools/implementsTools/implementsTools/implements PurposePurposePurposePurpose

CRIDA Manual weeder For weeding in upland crops

Self propelled power

weeder

For weeding and intercultural operation in upland crops

viz., groundnut, soybean, maize and pigeonpea etc.

TNAU improved

dryland weeder

For weeding in row crops for removing shallow rooted

weeds. It has been designed ergonomically for easy

operation. Us

ideal at a soil moisture content of 8 to 10 per cent.

Power rotary weeder For mechanical control of weeds in crops such as

sugarcane, tapioca, cotton and orchards

Useful for weeding between rows of crops

cotton, sugarcane, maize, tomato and pulses whose rows

spacing is more than 45 cm

Tractor Drawn

Weeding cum

Earthingup Equipment

For

row crops

Tractor Operated Multi

Row Rotary Weeder

For

row crops like sugarcane, cotton, maize, etc.

Cono Weeder For weeding between rows of paddy crop

Two Row Finger Type

Paddy Rotary Weeder

For weeding in paddy row crops

Battery operated

portable wetland

weeder

For weeding in SRI field

(Source: CRIDA, CIAE, TNAU)

Dhakar et al (2013), Pop. Kheti, 1(4):146

Popular Kheti ISSN:2321-0001

Tools and Implements for Weed ManagementTools and Implements for Weed ManagementTools and Implements for Weed ManagementTools and Implements for Weed Management

ools with their purpose and approximate cost are listed in

Table 2: Some tools for weed managementTable 2: Some tools for weed managementTable 2: Some tools for weed managementTable 2: Some tools for weed management

PurposePurposePurposePurpose

For weeding in upland crops


viz., groundnut, soybean, maize and pigeonpea etc.



operation. Useful in dryland and gardenland crops and is

ideal at a soil moisture content of 8 to 10 per cent.

For mechanical control of weeds in crops such as

sugarcane, tapioca, cotton and orchards

Useful for weeding between rows of crops like tapioca,


spacing is more than 45 cm

weeding and intercultural operations in between

row crops

weeding and intercultural operations in between

row crops like sugarcane, cotton, maize, etc.

For weeding between rows of paddy crop

For weeding in paddy row crops

For weeding in SRI field

146-151

0001 150

ools with their purpose and approximate cost are listed in Table 2.

Approx. cost Approx. cost Approx. cost Approx. cost

(in INR)(in INR)(in INR)(in INR)

950


-



eful in dryland and gardenland crops and is

600

like tapioca,


100,000

weeding and intercultural operations in between 15,000

weeding and intercultural operations in between 100,000

1500

900

8000



Future Future Future Future ProspectsProspectsProspectsProspects

Weed management in organic farming with conservation agriculture should be research

priority in future. More research is needed on potential impact of climate change on weed

management as new weeds may emerge out in organic farms in the wake of climate change.

The simulation model should be develop which takes account of weed species and predict

optimum timing for weeding. Additional research is required to develop such comprehensive

models.

ConclusionConclusionConclusionConclusion

In present, farms are equilibrium with conventional system, if it is disrupted by transition

from conventional to organic may lead to short term weed competition but over the period of

time a new equilibrium is established by well managed organic system. Holistic approach for

weed management on organic farm requires proper strategy, learning and extensive research

for realising the optimum benefits.

ReferencesReferencesReferencesReferences

Geneve RL and Weston LA, 1988. Growth reduction of eastern redbud (Cercis canadensis L.)

seedlings caused by interaction with a sorghum-sudangrass hybrid (sudex). Journal of

Environmental Horticulture. 6:24-26.

Peet M, 1996. Sustainable vegetable production practices for the South. Newburyport, MA:

Focus Publishing.

Weston LA, 1990. Cover crop and herbicide influence on row crop seedling establishment in

no-tillage culture. Weed Science. 38:166-171.

Wiese AF, Sweeten JM, Bean BW, Salisbury CD, and Chenault EW. 1998. High temperature

composting of cattle feedlot manure kills weed seed. Applied Engineering in Agriculture.

14(4):377-380.

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