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2. REVIEW OF LITERATURE

The literature pertinent to the present investigation entitled, “Long-term effect of

integrated nutrient management on dynamics of nitrogen, phosphorus and potassium in

rice-wheat system” have been reviewed in this chapter under the following heads:

2.1 Effect of continuous application of organics and chemical fertilizers on nutrient

transformation

2.2 Effect of continuous application of organics and chemical fertilizers on soil

properties

2.3 Effect of continuous application of organics and chemical fertilizers on yield and

nutrient uptake

2.4 Relationship of different nutrient fractions with soil properties, crop yield and

nutrient uptake

2.1 Effect of continuous application of organics and chemical fertilizers on

nutrient transformation

2.1.1 Nitrogen fractions

The nitrogen found in soil can generally be classified into inorganic and organic

forms. The larger amount (95 to 99%) occurs in the organic forms as a part of the soil

organic matter complex which is not immediately available to crop plants. It is only the

inorganic form viz. NH4-N and NO3-N which is commonly taken up by plants. The

organic forms of soil nitrogen occur as consolidated amino acids or proteins, free amino

acids, amino sugars and other complexes, generally unidentified compounds.

Prasad et al. (1983) and Prasad et al. (1986) concluded that available nitrogen

significantly increased over control in all the treatments, where higher levels of NPK

were applied while application of 50% NPK showed depletion in nitrogen availability as

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compared to initial status (295 kg N ha-1

). Kaistha (1984) reported that the contents of

non hydrolysable N varied from 45 µg N/g whereas, non hydrolysable N varied from 521

to 1260 µg N/g in zone V to 1260 µg N/g in zone II. He further reported that organic N

fractions tended to decrease with depth.

Dhillon and Dev (1984) noted an appreciable buildup of hydrolysable NH4-N,

hexosamine N in soils of Ludhiana with the incorporation of N through straw into soil

whereas burning of rice straw resulted in decline of these fractions. Kaul (1985) reported

that the NO3-N and NH4-N increased significantly with the application of N and P

supplied at higher rate.

Rabindra and Gowda (1986) found significant increase in organic carbon and total

nitrogen content in soil with balanced use of chemical fertilizers continuously for 12

years. While Prasad et al. (1986) reported that water soluble, exchangeable, fixed,

ammonical, nitrate and available form of N increased with increasing doses of

nitrogenous fertilizers. They further reported that application of FYM and lime increased

significantly water soluble and fixed ammonical nitrogen in acid soil.

From a green house experiment, Pal et al. (1987) revealed that the addition of

nitrapyrin improved inorganic and organic forms of N viz. NH4-N and NO3-N,

hydrolysable NH4-N, serine+threonine N, amino acid N and unidentified N. A significant

improvement in ammonium and nitrate N was observed with the combined use of organic

and inorganic sources (Gupta and Narwal 1988).

Chakraborty et al. (1988) conducted a field experiment with various combinations

of urea and organic nitrogen sources on rice under waterlogged conditions and observed

that release of hydrolysable and non hydrolysable N was highest in Sesbania+urea

combination while the release of NH4-N from the urea-FYM combination proved to be

superior over other treatments.

Kher (1991) also noted an increase in available N, P and K under NPK treated

plots over control after 13 years of study. Prasad and Rokima (1991a) observed that all

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fractions of N except NO3 and hexoseamine N increased with the increasing doses of

NPK with or without organic manures.

Mahapatra et al. (1991) found that incorporation of Dhaincha, Azolla and FYM

along with prilled urea increased total hydrolysable N in soils of Pant Nagar. The

increase in total hydrolysable N due to the application of organic manures was attributed

to the presence of organic N in them and slight increase in non hydrolysable N was

attributed to non acid soluble organic N added through different bio organic sources.

Sharma et al. (1992) observed that application of bioslurry at the rate of 13 t ha-1

increased amino acid N, hexosamine N, hydrolysable NH4-N and NO3-N. They further

observed that fertilizer N application encouraged buildup of amino acid N, hydrolysable

NH4-N and unidentified N fractions. Application of 100% NPK through fertilizers

resulted in highest increase of all organic fractions of N while 100% NPK+FYM

increased amino acid N and hexosamine N (Thakur et al. 1992).

Kher and Minhas (1992) concluded that application of nitrogen maintained a

better status of all hydrolysable N fractions over control while a combined application of

nitrogen and phosphorus resulted in significant increase in amino acid bound N. They

further reported that graded NPK levels increased the contents of hydrolysable

ammonical, amino acid and hexosamine N as compared to control. Application of FYM

in conjunction with NPK increased the hydrolysable NH4-N, amino acid, hexosamine and

unidentified N fractions. Crop residue incorporation markedly increased organic carbon

and total N contents in soils under a rice-wheat cropping system (Beri et al. 1992).

Bandyopadhyay and Maji (1993) reported that application of phosphorus to soil

resulted in better build up of available and total N. Bhardwaj and Omanwar (1994) also

reported that increasing doses of NPK (50 to 150%) increased the available NPK content

of the soil. The nitrogen availability increased to a greater extent, when nitrogen was

applied along with phosphorus and potassium fertilizers at higher levels.

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Verma and Bhagat (1994) showed that NH4-N content of the soils decreased

while NO3-N increased gradually with an increase in soil depth up to feeding zone of

wheat roots under straw incorporation and straw mulch treatment. Singh et al. (1994)

observed appreciable increase in total hydrolysable N in FYM and green manure

treatment alone or in combination with N.

While studying the changes in the fractions of N, P and K of soil, Bhardwaj et al.

(1994) observed that application of FYM along with 100% NPK increased amino sugar

N, hydrolysable NH4-N, amide N, amino acid N and acid insoluble N but inorganic

fractions of N like NH4-N and NO3-N decreased with combined use of manures and

fertilizers.

In sandy loam soil of Delhi, Das and Jain (1994) found that addition of

urea+wheat straw and urea+FYM enhanced buildup of amino sugar N and amino acid N

appreciably. Meelu et al. (1994) reported that green manuring did not increase organic

carbon content significantly over fertilizer N but it increased the total N content of the

coarse textured soil. While Clement et al. (1995) reported that incorporation of crop

residues into soil increased microbial biomass ninhydrin-reactive N over control at the

tillering stage.

After four years of continuous cropping at Kharagpur, Hegde (1996) stated higher

available nitrogen in fertilized plots than unfertilized plots. He further reported that

application of 100% NPK through fertilizers in both the seasons resulted in higher

available nitrogen.

Jana and Ghosh (1996) concluded that application of 100% recommended dose of

NPK through inorganic source increased the uptake of NPK by the plants in rice-rice

sequence over 50% and 75% NPK. This higher uptake of NPK was due to greater release

of nutrients and their ready availability in soil. Sharma (1996) reported that amino acid-

N, hexosamine-N and NH4-N were the major fractions contributing towards available N

pool in soil.

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Prasad et al. (1996) indicated a decline of 23, 44 and 16% in available N, P and

K, respectively, after six years where neither manures nor inorganic fertilizers were

applied. Application of graded doses of fertilizers (50, 100 and 150% NPK) either in

presence or absence of FYM showed on an average increase of about 10 per cent in

available nitrogen after 21 years of continuous cropping. Ladha et al. (1996) reported that

nitrate-N was dominant in 30 cm top soil and was higher under legumes compared with

weedy fallow. Whereas, Tripathi et al. (1997) found that NH4-N in the 100 cm layer was

20-40 kg ha-1

in the wet season and <10 kg ha-1

in the dry season. Medhi and DeDatta

(1997) reported that both prilled urea and green manure increased the N status of the rice

plants and enhanced the uptake of some other nutrients. The highest apparent N recovery

was obtained with prilled urea followed by green manure.

From a long-term field experiment conducted at experimental farm of

CSKHPKV, Palampur, Shashikanta (1997) reported that the available N status of the soil

declined in control plots from its initial value of 540.50 kg/ha to 532 kg/ha and 475.75

kg/ha after rabi (1995-96) and kharif (1996), respectively. She further reported a buildup

of available N in 100% NPK alone or in 50% NPK along with 50% N through FYM

treated plots over control due to better crop growth and mineralization of N in soil in

these treatments.

Mishra and Sharma (1997) from a long-term experiment noted that available N, P

and K status of soil was significantly increased with application of fertilizers, FYM and

blue green algae either separately or in combination over the unfertilized and unmanured

plots. However, in a pot study, Rao and Sitaramayya (1997) found that neither the green

manures nor other organic manures had any influence on total N content at any crop

growth stages. Wilson et al. (1998) reported that by increasing the preflood N rate

significantly increased mid season fertilizer N use efficiency, total N uptake, total dry

matter accumulation and grain yield of rice.

Basumatary and Talukdar (1998) showed that integrated use of chemical

fertilizers and manures or biofertilizers increased the NH4-N, NO3-N, total N and organic

N fractions over plots treated with chemical fertilizers alone. Lakpale et al. (1999)

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reported that the application of N increased available N in soil over native N at harvest of

rice.

From a field experiment at Bhopal, Singh et al. (1999a) did not find any

significant decrease in the content of organic N fractions, except amino acid N when no

fertilizer N was applied. The alone application of fertilizer N even up to its highest level

did not show any improvement in non hydrolysable N content in soil. However, Gupta et

al. (2000) reported an increase in organic carbon and available N status of soil with

increased dose of urea N in the rice-wheat sequence at Ludhiana.

Aulakh et al. (2000) found that application of recommended rate of fertilizer

nitrogen (120 kg ha-1

) to both rice and wheat in split doses for four years resulted in a

significant increase of 35 kg ha-1

NO3-N over control, 74% of this increase occurred in

the 90 to 150 cm soil depth. Organic manure amended soils continued to produce higher

concentration of NH4-N in soil upto 70 DAT (Dey and Jain 2000).

Sarawad et al. (2001) reported that all the fertilizer treatments significantly

increased hydrolysable N, amino acid N, amino sugar N, exchangeable NH4-N and

mineralizable N in soil. From a long-term field experiment on rice-wheat system, Singh

et al. (2001) reported a decline in organic matter and total hydrolysable N with

application of fertilizer N alone while the content of both of these increased with

conjunctive use of fertilizer N and organic manure. Muneshwar et al. (2001) also reported

reduction in total hydrolysable N with the application of fertilizer N which increased with

conjunctive use of fertilizer N and organic manure.

In another study Yaduvanshi (2001) also reported that organic carbon and

available N content of the soil significantly increased with continuous use of NPK along

with green manuring and FYM. Available N, P, K and S were also found to increase

significantly with organic sources over their initial status (Sharma et al. 2001).

Sharma and Verma (2001) concluded that out of the total N added through

Lantana over a period of six years, maximum was transformed to amino acid N (27.1 to

35.0%), followed by hydrolysable NH4-N (25.6 to 32.9%) and unidentified N (2.2 to

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2.9%). Increased levels of N application were found to increase all the N fractions except

unidentified N.

Sharma and Sharma (2002) reported that application of different combinations of

N, P and K did not show any significant effect on available N content of soil, whereas,

application of NPK+FYM significantly increased available N content of soil over all

combinations of FYM.

Kumar (2003) found an increase in amino acid N, hexoseamine N and non

hydrolysable N with increasing doses of fertilizers and these fractions further increased

with incorporation of green manures. Chemical fertilizers and green manuring

significantly increased exchangeable NH4-N, hydrolysable N and total hydrolysable N.

Munoz et al. (2003) observed that the manure increased NO3-N in 0 to 30 cm soil layer

more than fertilizer N whereas the opposite was true in 30 to 60 cm and 60 to 90 cm

layers and there was buildup of NO3-N with repeated manure treatments in a

continuously corn cropped experiments.

Sharma (2004) reported that Lantana incorporation resulted in highest (9 to 37%)

increase in total amino acid N (serine+threonine N+amino acid N), followed by

hexosamine N (4-16%) and minimum in hydrolysable NH4-N. Application of FYM alone

recorded higher NH4-N and NO3-N content in soil throughout the incubation period

(Duhan et al. 2005).

While studying the distribution of mineral N in soil profile at different growth

stages of wheat Gupta et al. (2005) reported that nitrate contents in different soil layers

was more than that of NH4-N at each growth stage of wheat and total mineral N content

at different depths was influenced by the total quantity of N applied irrespective of the

source. Sihag et al. (2005) documented that application of chemical fertilizers alone or

their combined use with organic manures significantly increased all the forms of nitrogen

except unidentified hydrolysable N, over control. Talashilkar et al. (2006) found that all

the fractions of nitrogen decreased with increase in soil pH. Begum et al. (2007) reported

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that the available N increased with increased application of fertilizer during all the

sampling stages of maize.

Datt et al. (2007) also observed highest buildup of available N with the

application of neem coated urea over prilled urea. Neem coated urea also maintained

higher concentration of NH4-N over prilled urea. Kumar and Prasad (2008) found that

green manure and residue incorporation enhanced the available nitrogen content by 16.9

and 8.2%, respectively, after harvest of rice. Integrated use of inorganic fertilizer with

organic manures increased the organic carbon and NPK status of the soil (Sharma et al.

2009).

Guldekar and Ingle (2009) reported improved status of N fractions with the

application of N in combination with FYM, Zn and S. The relative abundance of N

fractions in soil followed the order insoluble humin-N > hydrolysable NH4-N + amino

sugar-N > amino acid-N > acid soluble humin-N > fixed NH4-N >NO3-N > exchangeable

NH4-N.

Dhanika (2009) observed that inorganic N and organic N contributed 4.32 and

95.68 per cent, respectively towards total soil nitrogen. She further reported that non

hydrolysable and amino acid N were dominant organic fractions. Similarly Babita (2010)

found that continuous use of chemical fertilizers and amendments for 36 years in an acid

Alfisol brought out marked increase in the organic and inorganic fractions of N, total N

and available N compared to the untreated plots. She further found that among all the

fractions, hydrolysable NH4-N was found to play a major role in the supply of nitrogen

while NH4-N was the most important fraction bearing the highest correlation with crop

yields and total nitrogen uptake.

2.1.2 Phosphorus fractions

The distribution of various inorganic P fractions and their relative change under

continuous fertilization are reported to differ according to soil and crop conditions

(Agrawal et al. 1987 and Vig et al. 2000). The relative solubility of inorganic P fractions

governs the replenishment of the labile pool when it is depleted by removal of P by the

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plant (Bahl and Singh 1997). The availability and forms of P in the soil are influenced to

a great extent by the application of organic manures.

In a long-term experiment on pearl millet-wheat rotation, Antil et al. (1985) also

found that addition of FYM increased available P and Al-P but Ca-P and Fe-P were not

affected. Kaul (1985)

reported that total inorganic-P increased with P application.

Application of mineral P along with 30 tonnes of FYM increased the soil available P

(Wenglikowska 1987).

Long-term manure application increased microbial activity, potential for

mineralization of soil organic matter (N’dayegamiye and Angers 1990) and,

consequently, may induce the transformation of soil P organic fractions to P inorganic

fractions.

A marked increase in phosphorus availability was reported with increase in the

rate of applied fertilizer P (Singh and Sarkar 1992). In incubation study in two calcareous

soils Patel et al. (1992) found that saloid-P and Al-P decreased with time while Fe-P and

Ca-P increased. They concluded that organic matter significantly increased the content of

occluded-P, organic-P and Olsen-P.

The available P content of soil decreased in treatments, which were cropped

without P fertilizer (Bandyopadhyay and Maji 1993). Dhillon et al. (1993), while

working on a sandy loam soil, stated that most of the added P was converted to saloid-P

and Al-P and it changed to Ca-P with time. On a field trial conducted on an alkaline clay

loam soil, Singaram and Kothandaraman (1993) reported that P fertilization increased

saloid-P, Al-P, reductant soluble P and Ca-P, but had no significant effect on Fe-P.

Bhardwaj et al. (1994) stated that cropping without fertilization depleted all the forms of

P, however, P treated plots and those of P untreated plots showed no significant

difference in Ca-P contents.

From a long-term fertilizer experiment on a sandy soil in Germany, Harenz

(1994) reported that total P and equilibrium concentration of the soil solution increased

with increasing fertilizer levels. Beck and Sanchez (1994) from 18 years of

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experimentation in Peru found that inorganic P extracted with NaOH was a major sink for

added P in fertilized soil and organic P was a major source of labile P. The P content of

all cultivated soils was significantly higher over uncultivated soils, because of phosphate

fertilization and accumulation of P (Tiwari et al. 1995b).

While studying changes in the forms of soil P under long-term corn cultivation on

three different soils, Richards et al. (1995) found that fertilizer P increased Olsen-P

concentrations in all the soils and on an average 16 kg ha-1

P was required to increase

Olsen-P concentration by 1 mg l-1

. After 10 years of broadcast of 90 kg P ha-1

yr-1

, labile

Pi fractions (resin-P and NaHCO3-Pi) were increased as was NaOH-Pi in all the soils. On

the most P deficient soils, where corn grain yields were increased by fertilizer P,

phosphorus fertilization also increased HCl-P, residual-P and labile-Po (NaHCO3-Po) and

NaOH-Po.

In a long-term fertilizer experiment on an acid Alfisol of Palampur, Sharma et al.

(1995) reported that application of phosphatic fertilizers for 18 years has resulted in build

up of Al-P quite markedly in 100 % NP and 150 % NPK treatments due to under

utilization and over application of P, respectively in these treatments. They further

reported that Fe-P was lower in comparison to its initial value except in 150 % NPK

while Ca-P increased due to continuous manuring and cropping in almost all the

treatments except control and 100 % N only.

While studying the long-term effect of fertilizer and manure application on the

forms and availability of soil phosphorus, Tran and N’dayegamiye (1995) reported that

on an average, labile P extracted by resin and NaHCO3 represented 17 % of the total P

(Pt), moderately labile NaOH-Pi and -Po more than 40 % and stable P 36 %. Application

of manure and fertilizers increased significantly resin-P, NaHCO3-P, NaOH-Pi and Pt.

However, NaOH-Po was decreased by fertilizer application in NPK and NPK+Mg

treatments, while long-term manure application maintained this Po pool in the soil. Stable

P fractions were not affected by fertilization or by manuring. Use of FYM with 100 %

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NPK resulted in 19 % reduction in Al-P over 100 % NPK in an acid Alfisol (Sharma et

al. 1995).

Singh and Gupta (1995) conducted a field experiment to study the effect of

sewage sludge on phosphorus transformations under wheat cultivation. They found that

availability of P in soil increased with increasing P levels but, the maximum availability

of P was found with the use of sewage sludge + DAP at the rate of 75 kg ha-1

. Inorganic

fractions (saloid-P, Al-P, Fe-P, Ca-P, red-P and occluded-P) in soil increased with

increasing P levels in wheat. The maximum increase was in the plots receiving sewage

sludge + DAP at the rate of 75 kg ha-1

. However, Ismail et al. (1996) observed that higher

application of Zn might lead to P deficiency in wheat in calcareous sandy loam soils.

Schmidt et al. (1996) studied soil P dynamics in a long-term experiment on

Norfolk loamy sand and Davidson clay loam. They found that resin P increased in the

Norfolk soil with annual P applications those were in excess of crop removal and

decreased with annual P applications that were less than its removal. In clay loam soil, it

decreased regardless of P application or removal rate. Inorganic soil P extracted with

NaHCO3 and NaOH increased with excess P additions and decreased with deficient P

additions for both soils. Long-term fertilization significantly influenced both the contents

of soil available P and range of its changes. The increase and decrease of soil available P

depended on the addition/omission of chemical P to the soil (Yao et al. 1997).

From a long term experiment with the organic amendments such as FYM, green

manure and sewage sludge Otabbong et al. (1997) reported a significant build up of total

P and levels of all P forms viz. NaHCO3-P, NaOH-P, HCl-P, residual-P increased

significantly with maximum increase in case of sewage sludge. Zhang and Mackenzie

(1997a) revealed from a long-term field experiment on Typic Hapludalf that with an

annual rate of 60 kg ha-1

manure P plus 44 kg ha-1

inorganic P; labile inorganic P

(NaHCO3-Pi) increased and moderately labile Pi (NaOH-Pi) decreased. A higher annual P

rate of 132 kg ha-1

plus manure P increased soil Pi through NaHCO3-Pi, NaOH-Pi and

stable Ca-bound Pi (HCl-Pi). Inorganic P at either rate combined with manure P

decreased labile NaHCO3-Po fractions and increased moderately labile NaOH-Po, with

the result that total extractable soil organic P (Po) increased.

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On a sandy loam soil, Mathur (1997) observed a significant increase in the

available P status of soil in the plots receiving fertilizer P and FYM in a long-term

experiment. Prasad et al. (1997) reported that application of FYM increased Al-P, Ca-P

and residual-P by 0.3, 1.7 and 0.7 %, respectively over 100% NPK alone, but Fe-P

decreased by 1.3% showing thereby an increase in Ca-P at the expense of Fe-P. Bahl and

Singh (1997) conducted laboratory and green house experiments on both alkaline and

acid soils and found that in alkaline soils added P transformed more into saloid-P and Ca-

P, while in acid soils, higher amount of Al-P and saloid-P were found.

While studying the changes of P fractions under continuous corn cultivation with

and without P fertilization Zhang and Mackenzie (1997b) noticed a marked difference in

P fractions between fertilized and non-fertilized plots. In fertilized plots, Po was not

depleted and Pi fractions increased. While, Po was a major source of plant available P

when Pi was limiting. Inadequate fertilizer P may deplete Po more than Pi. Phosphorus

addition increased predominantly NaHCO3-Pi and secondly NaOH-Pi. Only a small

portion of added P was transformed into the most stable P form of P i.e. residual-P.

The integration of organic materials with inorganic sources of nutrients has an

added benefit compared to the application of inorganic nutrients alone (Nziguheba et al.

1998). Singh et al. (1998) studied P removal and available P balance in a typic

Ustochrept under intensive cultivation and long-term fertilizer use. They reported that

chemical NPK + FYM treatment proved more effective with respect to total P uptake

than the other fertilizer treatments in maize.

In another study, Reddy et al. (1999) observed that the level of Olsen-P increased

significantly and linearly through the years in both manured and unmanured plots. The

relative sizes of labile (NaHCO3-Pi and Po), moderately labile (NaOH-Pi and Po) and

stable (HCl-P and residual-P) P pools were in the ratio of 1: 2.9: 7.6. Application of

manure significantly increased all the P fractions except HCl-P and residual-P.

On Inceptisol soil, Sharma et al. (2001) reported that continuous addition of

organics through farmyard manure, green manure and crop residues resulted significantly

higher available phosphorus than the rest of the treatments and initial status of soil.

Continuous fertilization caused build up in residual P (Zhang et al. 2001).

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Parmar and Sharma (2002) in a long-term fertilizer experiment on sandy soils

found that available P status of soil decreased in the plots receiving only nitrogen and

potash as compared to plots where FYM and P fertilizers were applied. Tiwari et al.

(2002) from a long-term fertilizer experiment reported that the plots receiving 100 and

150% NPK increased available P content (30.57 and 40.37 kg ha-1

respectively) as

compared to 10.20 and 7.6 kg ha-1

in control and initial status of soil, respectively.

While studying the effects of chemical fertilizers and amendments on phosphorus

dynamics in a long term fertilizer experiment, Verma (2002) reported that available P

status increased in plots receiving P fertilizers and other amendments like lime over

control and plots receiving only N fertilization. He found that there was a significant

increase in Al-P, Fe-P, Ca-P and residual P forms with the application of inorganic

fertilizers along with amendments like FYM and Zn application. He further reported that

after continuous cropping and fertilization for 29 years there was 44 and 11% increase in

available P in 150% NPK and 100% NPK + FYM, respectively over 100% NPK alone

treatment.

Tiwari et al. (2002) observed a significant increase in the available P status of soil

in the plots receiving fertilizer P and FYM in a long-term experiment. Sharpley et al.

(2004) suggested that addition of manure to the soils shifted P from Al-P and Fe-P to Ca-

P reaction products, accounting for the relatively greater Mehlich-3 but lower water

extractable soil P. Sharma (2004) reported that the NaHCO3-P is the most important

chemical pool of P contributing to the nutrition of rice and wheat grown in sequence.

Verma et al. (2005) reported that compared to the imbalanced mineral fertilizer

application, the balanced as well as integrated application of nutrients resulted in

significantly lower P adsorption capacity of soils. At the beginning of experiment the

various pools could be quantitatively ranked in the following order: residual-P> NaOH-

Po> NaOH-Pi> NaHCO3-P0> NaHCO3-Pi> HCl-P>H2O-P. As a result of continued P

fertilization and cropping, the order changed as follows: residual-P> NaOH-Pi> NaOH-

Po> NaHCO3-Pi> NaHCO3-P0> HCl-P> H2O-P.

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While studying the integrated use of chemical fertilizers and organics, Sihag et al.

(2005) reported that amount of P recovered as saloid-P, Al-P and Ca-P increased

significantly and the magnitude of increase with inorganic fertilizer treatments was more

in the presence than in the absence of organic material. Among organic amendments, the

highest amount of all the forms of P was recorded under FYM followed by green

manuring and press mud treatments.

Sharma et al. (2005) from a long-term fertilizer experiment reported that there

was a substantial build up of available P with continuous addition of phosphatic

fertilizers. Application of 150% NPK resulted in highest available P content of 169.7 kg

ha-1

followed by 155.5 kg ha-1

under 100% NPK + FYM treatment as compared to 12 kg

ha-1

at the start of the experiment. They further reported that after continuous cropping

and fertilization there was increase in different fractions of phosphorus compared to the

initial value. The status of NaHCO3-Pi, NaOH-Po, HCl-P and residual-P increased with

increasing the NPK fertilizer levels along with amendments.

Saavedra and Delgado (2005) revealed that ratio of the P fraction, which includes

more labile P forms to combined non-organic P fractions, was negatively correlated with

soil pH and positively correlated with the portion of combined Fe fractions related to

poorly crystalline oxides.

Bajpai et al. (2006) reported that use of fertilizer resulted in 40 per cent increase

in available P status of the soil. Incorporation of 50% N through manure and 100% NPK

recorded significantly higher available P over control. From a long-term fertilizer

experiment on sandy loam soil Reddy et al. (2006) reported that available phosphorus

increased in all the treatments compared to initial value. There was a 15 to 20 kg increase

in available P in treatments that received organic and chemical nutrition over initial status

of 24.4 kg/ha. Talashilkar et al. (2006) found that Fe-P and Al-P exhibited reduction in

slightly acidic soils than in very strongly acidic soils, whereas all other P fractions were

increased with rise in soil pH.

A field experiment conducted for three consecutive kharif seasons on a typic

Hapludult Laxminarayana (2006) reported that available P status of soil increased

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remarkably with the integrated application of NPK and organic manures over the initial

value of 9.61 kg ha-1

. Sharma et al. (2007) reported that there was significant increase in

available phosphorus content of soil in the plot receiving 100% NPK and FYM over the

plot receiving 100% NPK which may be attributed to the continuous addition of nutrients

through FYM.

In a sandy loam Typic Haplustept, Setia and Sharma (2007) reported that

application of P increased all the P forms, whereas, N and K application caused decrease

in P fractions. The relative abundance of inorganic P fractions was in the order of saloid-

P < Fe-P < Al-P < Ca-P. The various inorganic P fractions tended to decline with the crop

age. A significant build up of available P in soil receiving NPK alone or in combination

with FYM was reported every year over control (Mishra et al. 2008).

Kumar et al. (2008) studied the soil fertility changes due to long-term application

of organic manures and crop residues in rice-wheat system and reported that available P

content of the soil increased over the initial status and increase was higher in treatments

where FYM or green manure (GM) was applied along with chemical fertilizers.

2.1.2 Potassium fractions

Kaul (1985) reported that both the available K and non-exchangeable K increased

significantly over control with the application of 40 kg ha-1

K2O. Highest value of

potassium was observed in organic manured plots or with their integrated use with

inorganic fertilizers (Ganai and Singh 1988). While studying the transformation of

potassium into different chemical pools, Udayasoorian et al. (1989) reported that

different forms of potassium viz., water soluble, exchangeable and non-exchangeable

potassium increased with increasing amount of organic manure and inorganic fertilizers.

Subramanian and Kumaraswamy (1989) reported that available K depleted in the

plots receiving K fertilization under continuous cropping. Lal et al. (1990) while studying

the effect of FYM, fertilizers and lime for 28 years observed that all the forms of K

decreased in absence of potassium fertilizer and manure.

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19

Sud et al. (1990) reported that soil exchangeable potassium increased by 23.8 per

cent with the application of FYM. In another study Kher and Minhas (1991) observed

that integrated use of NPK fertilizers and FYM increased water soluble and exchangeable

potassium but decreased non-exchangeable form.

While studying the transformation of applied potassium in combination with

organic manures and BGA, Prasad and Rokima (1991b) observed that the increase in

water soluble, exchangeable and non-exchangeable K with the application of FYM, BGA

or FYM plus BGA over chemical fertilizers was in the range of 2 to 3, 2.5 to 5.3 and 3 to

33 ppm, respectively. They further reported that these fractions increased with increasing

doses of fertilizers. Similarly, Prasad (1992) also reported an increase in various K

fractions with addition of K fertilizers.

On an acid Inceptisol of Sikkim, Patiram and Singh (1993) found that the amount

of exchangeable K in the soil remained almost same in all the plots without manure

application. While Chatterjee and Mandal (1996) found that any reduction in the

recommended dose, without compensation through organic manure, depleted soil

available K at 0-15 cm soil depth.

Dhanorkar et al. (1994) found that FYM application improved water soluble K

status of soil but reduced fixed K by about 50 per cent. They further reported that the soil

available K increased by 1.3 to 5.4 folds by continuous use of FYM. Combined

application of chemical fertilizers and FYM increased the exchangeable K content in soil

over NPK treatment as well as over initial status. Singh et al. (1995) found that the

available K in soil was maintained to its initial status in the plots receiving fertilizer

potassium with increasing rates of N with or without P.

Water soluble, exchangeable and non-exchangeable K increased with the

application of graded doses of NPK (Basumatary and Talukdar 1998). They further

reported that use of Azolla, FYM and rice straw along with fertilizer showed further

increase in these forms over fertilizer treatments. They observed significantly highest

values of all these forms in treatment where 50 per cent N was substituted through

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20

Azolla. In another study Santhy et al. (1998) revealed that continuous cropping and

fertilization had a deleterious effect on total K level of soil. They further reported that

application of K at 150 per cent of optimal level could maintain the initial status of total

K.

In long-term fertilizer experiment at Pantnagar, Singh et al. (1999b) observed that

the application of FYM at the rate of 5 t ha-1

over and above the 40 kg ha-1

K2O

maintained the available K status of soil. Nikitisen et al. (2000) reported that there is K2O

only a weak response to K fertilizer as the soils are naturally well supplied with

exchangeable and non-exchangeable forms of K and the crops shall have adequate K

nutrition if 41 to 48 kg K2O is applied per hectare. Joseph et al. (2000) found that

fertilizer application significantly changed the total, exchangeable and mineral K in

surface soil, but non-significantly in subsurface soil.

At Bangalore, Thippeswamy et al. (2000) while studying the influence of

different doses of K fertilizers applied at various growth stages of rice found that

different forms of K viz., water soluble K, hot water soluble K, available K, 1 N HNO3

extractable K and 0.1 N HNO3 extractable K increased with increase in potassium dose

up to 80 kg ha-1

and decreased with growth stages from tillering to harvest.

While studying the effect of long-term Lantana addition, Sharma and Verma

(2000b) reported that addition of Lantana from 10 to 30 tones per hectare continuously

for 6 years increased all the fractions of potassium significantly and maximum increase

was found in exchangeable K followed by water soluble K over control.

Singh et al. (2000b) revealed an increase in NH4OAc extractable and 0.01 M

CaCl2 extractable K after 7 crop cycles with increased levels of FYM. They further

reported that non-exchangeable K decreased with the application of FYM and fertilizer

N. From a long-term fertilizer experiment conducted at Akola, Maharashtra Ravankar et

al. (2001) found that all the fractions of K improved with application of FYM, Zn and

sulphur in combination with NPK. Jeegadeeswari et al. (2001) reported significant

depletion of soil K under control.

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Pannu et al. (2001) reported that K content was higher in the surface layer (0-7.5

cm) and decreased with depth up to 30 cm. The treatments receiving wheat straw plus

GM plus rice straw maintained the maximum level of non-exchangeable K followed by

FYM plus GM and rice straw. They further reported that non-exchangeable K increased

with soil depth and incorporation of rice straw continuously for five years increased all

the K fractions compared to its removal. Muneshwar et al. (2001) reported that the use of

FYM and green manure increased K availability in soil but a net negative balance in total

K was noticed.

In one of the studies Xiong et al. (2001) reported that non-exchangeable and

mineral K declined in all fertilizer treatments in 0-20 and 20-40 cm soil depth. They

further reported that soil receiving no K continuously for four years, became K deficient.

While Santhy et al. (2003) reported significant increase with the application of K. The

combined application of rice straw and chemical K fertilizers is recommended to keep the

balance of potassium in purple soil (Xiong et al. 2003). While Sharma (2004) reported

that the exchangeable-K is the most important chemical pool contributing to the nutrition

of rice and wheat grown in sequence. Setia and Sharma (2004) noticed that the

accumulation of potassium in all the forms was higher in the plots receiving K dressing

than those in NP treated plots. The cumulative effect of continuous cropping and fertilizer

application markedly influenced K availability in soil. Talashilkar et al. (2006) found that

none of the K fraction showed any definite trend with changes in pH.

Sood (2005) reported that exchangeable, water soluble and 0.5 N HCl extractable

K were the most important K fractions contributing significantly towards K uptake by

maize. Sood et al. (2008) found that continuous application of fertilizers and amendments

improved all the potassium fractions in soil over control and K uptake was higher when

FYM or lime was applied with 100 % NPK.

2.2 Effect of continuous application of organics and chemical fertilizers on soil

properties

2.2.1 Physical properties

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A decline in bulk density due to the application of organic matter has been

reported by Pandey et al. (1985). Studies conducted by Sharma and Sharma (1993) also

revealed that there was a reduction in soil bulk density from the initial value due to

increased fertilizer levels or FYM application, but in un manured plots bulk density

remained stable around initial value.

Thakur et al. (1995) reported significant decrease in bulk density of silty clay

loam soil of Palampur due to incorporation of Dhaincha and French bean biomass after a

period of 3 years. In clay loam soil at Kaul (Haryana), Gupta et al. (1995) found that

incorporation of Dhaincha at the rate of 33 t ha-1

decreased the bulk density by 8.1 per

cent at 0-15 cm and 2.3 per cent at 15-30 cm depth over control.

Tripathi and Chaubey (1996) reported that FYM in conjunction with chemical

fertilizers decreased the bulk density of paddy soils. Saxena and Yadav (1998) recorded

lower values of bulk density in soils in rice-wheat cropping system owing to green

manuring with green gram. While increase in bulk density and available water with

increase in NPK levels was reported by Sarkar (1998).

In a sandy clay soil under rice-wheat cropping system Mandal et al. (1999)

observed reduced bulk density with Sesbania green manuring and green gram residue

incorporation. Decrease in bulk density with the addition of organic manures/green

manuring has also been reported by many workers (Sharma et al., 1987; Singh et al.,

2000a; Ray and Gupta, 2001; Phogat et al. 2004).

Findings of Sharma et al. (2001) in rice-wheat cropping system revealed a marked

increase in water holding capacity with integrated use of organics and fertilizers. Premi

(2003) and Mandal et al. (2003) reported that combined use of organic and inorganic

sources of N decreased the bulk density of soil. Chaudhary and Thakur (2007) revealed

that FYM along with fertilizers had a positive response on penetration resistance and bulk

density of soil.

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2.2.2 Chemical properties

Khind et al. (1987) reported an increased value of soil pH with the application of

Sesbania as green manure. While green manuring brought about considerable

improvement in available nutrients (N, P and K) after the rice harvest, as buried green

manure might act as a slow release fertilizer and conserve nutrients, especially, nitrogen

for longer periods, thus ensuring its availability to subsequent crops (Sharma and Mittra,

1988). Grewal et al. (1990), however, reported that different levels of P and K did not

have any influence on the cation exchange capacity of soil.

While studying the effect of cowpea as green manure and residue incorporation,

John et al. (1989) reported significantly higher amount of ammonical and nitrate nitrogen

in cowpea green manured and residue incorporated plots than fallow under both upland

and lowland rice. Mahapatra et al.(1991) and Mitra et al. (1992) revealed that green

manuring resulted in significant and gradual increase in availability of nitrogen in soils as

compared to no green manuring. Sharma and Sharma (1993) also found higher total

nitrogen and organic carbon content due to increased fertilizer level or FYM application,

however, organic carbon was stable around its original level in unmanured plots.

Application of P, K, NPK and FYM in acidic soils did not alter the initial soil pH except

nitrogenous fertilizer (Singh and Yadav 1994).

Long-term studies on rice-wheat system (Kumar and Yadav 1995) revealed that

integrated use of organic manures and chemical fertilizers significantly improved

available N and P contents of soil.

Under Palampur conditions, Thakur et al. (1995) found that incorporation of

Dhaincha as green manure rice resulted an increase in organic carbon content, available

N, P and K contents in the silty clay loam soil with increased fertilizer levels in rice-

wheat cropping system. Increase in soil available nitrogen by Sesbania green manuring

was also reported by Tiwari et al. (1995b). Similarly with the addition of FYM in maize-

wheat cropping system an increase in available N, P and K status was reported by Kumar

(1996). An increase in organic carbon, available P and K status of soil with increase in

fertilizer level was also reported (Brar et al. 1995). Kumar and Yadav (1995) revealed

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24

that integrated use of organic manures and chemical fertilizers significantly improved the

soil organic matter.

In a pot study, Sriramachandrasekharan et al. (1996) found that organic manures

increased the soil N, P and K contents as compared to control with maximum increase

resulting from Sesbania aculeata. On the other hand, Bellakki and Badanur (1997)

reported that continuous application of organics increased the cation exchange capacity

of soil. In a long-term fertilizer experiment on rice-wheat cropping system conducted at

various locations in India, Hegde (1998) also reported an increase in available N, P and K

contents in soil with increase in fertilizer levels along with organics. Dubey and Verma

(1999) also reported an increase in organic carbon and available N, P and K in soil over

the initial status under 50% NPK through fertilizers + 50% N through poultry manure or

through FYM compared to 100% NPK.

Kumar et al. (1999) found that application of green manure significantly

improved organic carbon, available N, P and K status of soil. They also reported that soil

fertility was further improved when organics were combined with inorganic fertilizers.

Application of green manure at the rate of 1.5 t ha-1

contributed considerable amounts of

nutrients to soil.

In rice-wheat cropping system, Saxena and Yadav (1998) noted decrease in soil

pH owing to green manuring with green gram. Ghosh et al. (2001) reported decline in

soil pH in NPK treated plots as compared to FYM over a long period of time. In another

study, Hemalatha et al. (2000) reported higher availability of N, P, and K by the in situ

incorporation of Dhaincha (12 t ha-1

) and Sunnhemp (11 t ha-1

) and application of FYM

(12.5 t ha-1

).

Kumar et al. (2000) observed an increase in organic carbon content with increase

in fertilizer levels over control in a long-term experiment on rice-wheat cropping system.

Sharma et al. (2001) also reported significant improvement in the organic carbon content,

CEC, available N, P, K and S with integrated use of inorganic fertilizers and organics

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25

through FYM, crop residues of wheat and green manuring of Dhaincha in a rice-wheat

cropping system. While Jena et al. (2000) documented that application of farmyard

manure (FYM) and Gliricidia leaves increased the organic carbon, whether applied alone

or in combination with fertilizers.

Sharma and Sharma (2002) reported that a combination of NPK + farmyard

manure increased the available N, P and K by 6-14, 7-8 and 7-32 kg ha-1

, respectively

over N alone. Ghosh and Singh (2003) also evaluated the effect of conjoint use of

farmyard manure and nitrogen on rice-wheat system in Uttaranchal mid-hill soils. They

reported that conjoint use of high levels of FYM and N fertilizer showed increased total

N and available P at the end of the experiment, while available K decreased. Phogat et al.

(2004) studied the residual effect of green manuring and farm yard manure for sustained

productivity of rice-wheat cropping sequence under shallow groundwater table

conditions. They found that the pH was lower in the FYM and GM treated plots than in

the control plots.

Yaduvanshi and Swarup (2005) found that phosphorus applied at the rate of 26 kg

ha-1

P each to rice and wheat significantly improved the yields and led to a considerable

build up of available P. Chaudhary and Thakur (2007) revealed that all the plots which

received FYM along with fertilizers had a positive response on chemical properties of

soil.

Urkurkar et al. (2010) reported that in-situ application of green manure along with

50% of recommended dose of fertilizer resulted in highest available N in surface soil.

The results also revealed that available P and K content of soil increased significantly

with FYM while pH and EC remained constant irrespective of the treatments. In rice-

wheat system, Kharub and Chander (2010) found that nitrogen and phosphorus had a

positive balance while potassium had highly negative balance where organic source of

nutrient was applied.

2.2.3 Microbiological properties

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26

Microbial biomass is among the most labile pools of organic matter and it serves

as an important reservoir of plant nutrients and can therefore, have important implication

for nutrient bioavailability.

Kukreja et al. (1991) revealed that total microbial biomass significantly increased

in plots receiving 90 t/ha FYM annually for 20 years. They further found that the basal

respiration level of population at higher levels of carbon was less than that of the

population at lower levels of carbon in soil during the period when soil respiratory

activity had stabilized.

After 45 years of cropping, Naumova and Barsukov (1991) found that NPK plots

contained 10 to 30 per cent and manured treatments 1.5 times higher microbial biomass

as compared to control. Soil biomass carbon increased with the application of organic

manures and decreased with the application of ammonium sulphate (Shen et al. 1997).

Rochette and Gregorich (1998) revealed that manure amendments increased the microbial

carbon by 2 to 3 folds compared to control. Yan et al. (1998) found that soil microbial

biomass carbon increased greatly with the application of organic manures. Dinesh et al.

(2000) also reported that soils amended with organic manures consistently registered

significantly greater microbial biomass compared to unmanured soil.

Manjaiah et al. (2000) observed that inclusion of legume in the system improved

the soil biomass. Santhy et al. (2002) found that soil biomass carbon was higher in 100%

NPK + FYM treated plots over 150% NPK alone. Mljat et al. (2004) carried out a field

experiment on sandy loam soil of Modipuram and reported that microfloral population

was higher under all the residue management practices compared to in situ burning.

There was a gradual increase in biomass C and N content of soil for the graded levels of

NPK from 50 to 150% and application of 100% NPK along with FYM recorded

significantly highest biomass C and N (Selvi et al. 2004).

Wang et al. (2006) reported that soil microbial biomass increased faster where

organic fertilizers were added as compared to alone application of inorganic fertilizers.

Masto et al. (2006) reported that application of NPK along with FYM significantly

increased the soil microbial biomass. Yangchun et al. (2007) indicated increase in

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27

microbial biomass carbon after organic manure application. They further found that

application of organic manures with a reduced amount of fertilizers increased the

microbial biomass carbon compared to application of inorganic fertilizer alone.

2.3 Effect of continuous application of organics and chemical fertilizers on yield

and nutrient uptake

2.3.1 Yield

Application of 100% NPK to wheat crop produced highest grain yield and further

increase in fertilizer levels failed to exhibit any significant effect on yield of the crop

(Dixit et al. 1984). Singhania and Singh (1986) recorded significantly higher rice yield

when 40 kg N ha-1

was applied through FYM and 40 kg N ha-1

through urea.

Kundu and Pillai (1992) reported that the annual use of 10-15 t ha-1

FYM in

combination with recommended dose of chemical fertilizers considerably increased the

production of rice based cropping system without any marked change in nutrient balance.

Wheat yield increased with increase in fertilizer dose that also showed residual effects on

succeeding rice crop in terms of grain yield (Gurung and Sherchan 1993). Pooled analysis

of four years data from an experiment carried out by Jayakarishankumar et al. (1994)

revealed that green manuring did not increase the grain yield of rice significantly as

compared to 100 per cent NPK through chemical fertilizers, but application of FYM or

green manure had significant residual effect on wheat.

Gill et al. (1994) obtained significantly higher grain yield of rice and succeeding

wheat with the application of 6 t ha-1

FYM and Dhaincha green manure supplemented

with 100 per cent NPK through fertilizers over 100 per cent NPK applied through

chemical fertilizers alone. It was further concluded that addition of organic manure with

recommended dose of chemical fertilizers produced the grain yield equal to the

application of 150 per cent of NPK through chemical fertilizers; hence a net

economization of 33 per cent NPK could be achieved in rice-wheat system.

Kumar and Yadav (1995) from a long-term field experiment found that 25-50%

nitrogen through FYM or Sesbania rostrata green manure along with 50-75 per cent of

recommended fertilizer to rice gave either equal or more yield in comparison to 100 per

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28

cent NPK through fertilizers. After three years of experiment, positive residual effect of

FYM and green manure was observed regularly on succeeding wheat. However, Rajput

(1995) observed that green manuring through Dhaincha with 50 per cent or more of NPK

gave higher grain yield of rice than the addition of organic matter alone, but there was no

residual effect on succeeding wheat. Green manuring with Sesbania rostrata or Sesbania

rostrata along with 40 kg ha-1

N gave rice yield at par with 120 kg ha-1

N, wheat yield

increased significantly owing to the carry over effect of green manures as well as N-

fertilization to rice crop (Tiwari et al. 1995a).

Gupta et al. (1995) reported that application of organic manures like FYM, rice

husk, saw dust and green manures in rice increased grain yield of rice-wheat cropping

system. An increase in the productivity of rice-wheat sequence was reported from 4.35 to

8.40 t ha-1

in control and with green manuring with Dhaincha, respectively (Mahapatra

and Sharma 1995).

Application of FYM to rice increased the grain yield of both rice and wheat over

control showing marked residual effect on soil fertility (Brar et al. 1995). A significant

increase in grain and straw yields of rice over control by 5.90 and 6.36 per cent and of

wheat by 13.73 and 14.06 per cent was obtained with the application of 10 t ha-1

FYM to

rice crop (Singh et al. (1996). While Dubey et al. (1997) reported that 25-50% of

chemical fertilizers can be substituted by FYM or Sunnhemp green manure without

scarifying grain yield in rice-wheat sequence.

Findings of long-term fertilizer experiments conducted at various locations in

India, indicated that 25 to 50% nitrogen needs of rice can be substituted through FYM or

green manure without any detrimental effect on the productivity of rice-wheat cropping

system (Hegde 1998).

Singh et al. (1999b) concluded that if 50% NPK is applied through chemical

fertilizers along with 50% N through FYM, the productivity of both cotton-wheat and

paddy-wheat cropping systems can be maintained higher in comparison to 100% NPK

applied through chemical fertilizers only. Application of 10 t ha-1

FYM coupled with

50% of recommended dose of nitrogen, resulted in maximum grain and straw yields

which were more than those under 100% NPK through chemical fertilizers (Singh and

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29

Verma 1999). Increase in productivity of rice-wheat cropping system has also been

reported by Nair and Gupta (1999) with the use of green manures in rice. Tiwari et al.

(2001) reported a linear increase in yield of rice grains with the increasing levels of FYM

up to 10 t ha-1

which also recorded a significant residual effect on wheat.

Yaduvanshi (2001) reported that mean rice and wheat yields obtained from

combined application of 100% NPK through inorganic fertilizers + organic manures

(FYM or Sesbania green manure) were significantly higher than those obtained from the

application of 100% NPK through chemical fertilizers alone.

Singh et al. (2001) found that addition of 5 t ha-1

FYM or rice straw or green

manure in rice along with 100% NPK through fertilizers increased the grain yield

significantly over variable doses of NPK applied through inorganic fertilizers. It was

further mentioned that FYM maintained its superiority over other organics with respect to

grain yield of succeeding wheat. Combination of 100% NPK + FYM increased the grain

yield of rice-wheat system by 1.2 to 1.3 t ha-1

and straw yield by 0.7 to 2.3 t ha-1

over N

alone (Sharma and Sharma, 2002).

In rice-wheat cropping sequence Yaduvanshi (2003) recorded mean grain yield

with Sesbania green manure or 10 t ha-1

FYM along with 50% of recommended NPK

similar to that obtained from the application of 100% of recommended NPK. He also

reported that the residual effect of green manures combined with the full recommended

inorganic fertilizers gave significantly higher wheat grain yield than that from the full

recommended inorganic fertilizers alone. Application of 100% NPK + FYM resulted in

significant increase in grain yield of wheat over 100 or 150% NPK alone (Singh and

Singh 2003).

Ghosh and Singh (2003) evaluated the effect of conjoint use of farmyard manure

and nitrogen on rice-wheat system in Uttaranchal mid-hill soils. They observed that grain

and straw yields increased with increasing rates of FYM and N fertilizer for both the

crops, and the highest yields were obtained with 15 t ha-1

FYM + 60 or 80 kg ha-1

N.

Phogat et al. (2004) found that the total productivity of rice-wheat system increased

significantly with green manure and FYM compared to control, and with FYM over

green manure in all the years. Mljat et al. (2004) carried out a field experiment on sandy

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30

loam soil of Modipuram and reported that In situ burning of rice residue + N enriched

phosphocompost resulted in maximum grain yield during both the years. Debtanu and

Das (2005) obtained highest grain yield of rice and wheat (4.25 and 4.78 t ha-1

) with NPK

+ Zn + FYM treatment.

On a sandy loam soil in Kanpur, Niranjan and Singh (2005) observed that the

application of various organic sources and inorganic fertilizers significantly increased the

grain yield of rice and wheat. The highest grain yield was recorded with green manure,

followed by FYM. Yaduvanshi and Swarup (2005) found that continuous use of fertilizer

N alone (120 kg ha-1

) or in combination with P and K significantly improved rice and

wheat yields over control (no fertilizer).

Chaudhary and Thakur (2007) have documented that the application of FYM in

conjunction with chemical fertilizers had stimulatory effect on yield irrespective of crops

and season; however, quantum of yield was much higher when applied in kharif. Over 16

years of the study, highest rice and wheat yield was registered when 50% N was supplied

through green manure in conjunction with 50% NPK through inorganic fertilizers

(Urkurkar et al. 2010). Kharub and Chander (2010) reported that growth and yield

attributes of rice were statistically similar under inorganic, organic and integrated plant

nutrient supply in rice-wheat system.

2.3.2 Nutrient uptake

Ganai (1983) observed a consistent and significant increase in N, P and K uptake

by grains and straw of rice and wheat with increase in fertilizer from 50 to 100 per cent

NPK. Dixit et al. (1984) found that initial increase in fertilizer levels in wheat did not

exhibit any effect on N, P and K contents in grains and P content of straw; however,

higher levels increased the N and K contents of straw. Swarup (1987) also reported that

green manuring significantly increased uptake of N, P, K, Mg, S, Fe, Mn and Zn by the

rice crop.

Mahapatra et al. (1987) revealed that application of 45 kg N through urea and 45

kg N through Dhaincha green manure or Azolla resulted in higher nitrogen uptake in rice

crop. The residual effect of these treatments on nitrogen content of grain and total

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31

nitrogen uptake was also found spectacular in succeeding wheat. Increase in nitrogen

concentration and uptake by wheat due to the residual effect of green manuring was also

reported by Goswami et al. (1988). While Jadhav (1990) reported that N, P and K uptake

by wheat increased significantly with increasing fertilizers levels which was ascribed to

higher grain and straw yields along with higher nutrient contents.

Narang et al. (1990) reported an increase in uptake of N, P, K, Zn, Fe and Mn

with increase in fertility levels. Increasing levels of fertilizer from 50 to 150 per cent

NPK in rice-wheat cropping system resulted in an increase in N, P and K contents as well

as their uptakes in grains and straw of rice and wheat crops under Palampur conditions

(Sharma, 1992). Paikaray et al. (2001) found that Sesbania green manuring in rice

resulted in removal of 199.8, 36.5 and 241.9 kg ha-1

N, P and K, respectively in rice-

wheat sequence which was significantly higher than control where no green manure was

applied. Similar findings were reported by Kumaresan (2001).

Sharma and Sharma (2002) reported that NPK + farmyard manure increased 38 to

45, 7-10 and 25 to 42 kg ha-1

N, P and K uptake, respectively over N alone. While

working at Bahraich, Uttar Pradesh, Singh et al. (2006) found that 25% N through

pressmud + 75% NPK through recommended inorganic fertilizers resulted in the highest,

total nutrient (N, P and K) uptake by rice and wheat.

2.4 Relationship of different nutrient fractions with soil properties, crop yield

and nutrient uptake

2.4.1 Nitrogen fractions

A good supply of nitrogen not only stimulates root growth and development, but

also augment uptake of other plant nutrients.

Kaul (1985) from a field study at experimental station Bhadiarkhar, CSKHPKV

Palampur, Himachal Pradesh found that the influence of increasing doses of N and P on

the buildup of total N was statistically significant in both surface and sub surface soils.

From a long-term experiment Prasad et al. (1986) found positive and significant

correlations between NO3-N and water soluble, exchangeable and fixed NH4-N. Total

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32

nitrogen uptake by 5 crops was also significantly related to water soluble, exchangeable

and fixed ammonium N, NO3-N and available N.

On the soils of Tamil Nadu, Perumal et al. (1986) found that hydrolysable NH4-N,

amino acid N and to a lesser degree hexosamine N and exchangeable NH4-N showed

significant and positive relationship with yield and N uptake by rice. Zucker and Zech

(1987) observed that amino acid N, amino sugar N and amide N decreased from organic

to mineral horizons which indicated that organic matter contributes significantly to

organic forms of N.

Aggarwal et al. (1990) studied amount and nature of nitrogen in different soil

profiles in Rajasthan and observed a positive relationship of amino acid N and amino

sugar N with nitrate N indicating the contribution of these two fractions to available N

pool.

Similarly, from a four year study on integrated nutrient management in a rice-

wheat system, Bhandari et al. (1992) found that both rice and wheat yields continued to

increase significantly with increasing NPK levels up to 100% of recommended dose.

Among the different organic sources of N for rice, green manure proved significantly

superior over both FYM and wheat cut straw in respect of crop yield and nutrient uptake.

The N uptake by rice increased significantly due to application of N over control while

nitrogen use efficiency decreased with increasing level of N application (Upadhyay and

Patel 1992).

Pandian and Perumal (1994) reported that incorporation of green manure alone

(12.5 t ha-1

) without mineral nitrogen recorded 11.9% more grain yield over control. Gill

et al. (1994) also found that the yield of rice obtained with 150% NPK was similar to

green manuring + 100% NPK treated plots which was significantly superior over all other

treatments. Amino acid N, hexosamine acid N, hexosamine N and NH4-N were found to

be the major fractions contributing towards available N pool in soil (Sharma 1996).

While studying five soil profiles representing five major soil series in Bangladesh,

Khan et al. (1997) reported that total nitrogen content in soil ranges from 0.26 to 2.0 g

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33

kg-1

and in all the pedons there was a regular decrease of total nitrogen from the surface

downwards. Rao and Sitaramayya (1997) indicated a significant correlation of nitrogen

uptake with total and available nitrogen forms at 45 and 60 DAT. Both prilled urea and

green manure increased the N status of rice and also enhanced the uptake of other

nutrients and the highest apparent N recovery was obtained with prilled urea followed by

green manure (Medhi and DeDatta 1997).

While studying four soil pedons of Himachal Pradesh, Kaistha and Dubey (1998)

found that total N (980-2856 mg kg-1

) in different soil depths was significantly correlated

with all the fractions of organic N except amino sugar N. Increasing preflood N rate

significantly increased midseason fertilizer N uptake efficiency, total N uptake, total dry

matter accumulation and grain yield of rice (Wilson et al. 1998).

Singh et al. (1999a) observed positive relationship among the N fractions after

rice and wheat crops except of amino sugar which is probably due to production of amino

sugar nitrogen from sources other than through mineralization of organic nitrogen. They

also found a significant relationship between grain yield and hydrolysable ammonical N,

amino acid N and amino sugar N. Application of N increased its availability over native

status at harvest of rice and besides increased uptake, the availability of native N in soil

also increased (Lakpale et al. 1999).

Hattab et al. (2000) studied the effect of inorganic fertilizer with locally available

organic manures on rice yield and recorded highest N uptake with the addition of 50%

organic and 50% inorganic N with Sesbania rostrata. Dey and Jain (2000) from a green

house experiment on urea enriched green manures reported that nitrogen application

irrespective of sources and levels produced higher grain yield of rice than control and

maximum yield was produced by guar enriched with 3% urea.

Sarawad et al. (2001) observed that all the fractions of N, except acid insoluble

and hydrolysable unknown N, were highly correlated among themselves and with

mineralizable soil N and uptake of N by maize, wheat and cowpea and the cropping

sequence as a whole.

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Duraisami et al. (2002) reported that NH4-N and NO3-N significantly contributed

towards the grain and straw yields of sorghum while the same fractions with hexosamine

and amino acid N enhanced N uptake at different growth stages. They also reported that

most of the fractions improved at flowering stage and reduced at harvest while the

unidentified hydrolysable N and non hydrolysable N showed a consistent decrease with

crop growth.

Duhan and Singh (2002) found that yield and nutrient uptake of rice increased

significantly with increasing N levels while application of N along with green manure

showed additive effect on these parameters.

Kumar (2003) found that exchangeable NH4-N significantly correlated with N

uptake by rice and wheat. Its indirect contribution via non hydrolysable N towards N

uptake by rice (0.596) and wheat (0.354) was fairly high over other N fractions on N

uptake. Maiti and Das (2005) also concluded that both rice and wheat yield was

significantly higher in the treatment where organic manure was applied along with

chemical fertilizers containing N, P, K and Zn.

Gupta et al. (2005) studied distribution of mineral N in soil profile at different

growth stages of wheat and reported that NO3-N contents in different soil layers was

higher than that of NH4-N at each growth stage of wheat and total mineral N content was

influenced by the total quantity of N applied irrespective of the source. They also found a

positive relationship of N uptake with both the forms, the magnitude of relationship being

higher with NO3-N. Total N is the main pool for all N fractions and hence all the

extraction methods showed significant correlations with it (Laxminarayana 2006).

Bhattacharya et al. (2006) found that there was no accumulation of NO3-N in the

soil but NH4-N remained sufficiently high up to 55 DAT. Gupta et al. (2006) also

reported that total N uptake by rice wheat system was lowest under control and increased

by applying fertilizers with or without manures. Integration of 75% recommended

nitrogen through fertilizer and 25% nitrogen through karanj leaf in rice followed by

100% recommended dose of NPK in wheat recorded maximum nitrogen uptake (Barla

and Upasani 2008).

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2.4.2 Phosphorus fractions

Tandon (1987) reported that Al-P and Fe-P were more abundant in acid soils

while Ca-P dominated in alkaline soils. Significant relationship of P uptake by wheat was

reported with saloid P, Al-P and Fe-P (Jaggi 1987).

Kumaraswamy and Sreeramulu (1991) studied the relationship between P

fractions and P uptake by rice crop in different soil series of Tamil Nadu. They reported

that in Koduveri and Vyalogam soil series Fe-P and Al-P accounted for 82-89 % of P

uptake by rice, with greater contribution from Fe-P. While in Kalathru and Maddukkar

soil series, Al-P accounted for 77 to 84 per cent of the P uptake by crop.

Sharma (1991) reported that Al-P and Fe-P fractions contributed towards dry

matter yield and P uptake by wheat to a greater extent while the contribution of Ca-P was

comparatively less. Rokima and Prasad (1991) found that all the forms of P were

significantly correlated with grain and straw yields and P uptake by rice and wheat. The

contribution of all the P forms was found towards grain and straw yields (Sood and

Bhardwaj 1992).

Inspite of preponderance of reductant soluble and Fe bound phosphate, the Al-P

showed the highest correlation coefficient (r), regression (b value) and multiple

determination coefficient (R2) with P extracted with all the methods except North

Carolina which implied that Al-P is the major source of labile P in laterite soils (Dongale

and Kadrekar 1992).

Patiram et al. (1993) studied the relationship among the different forms of soil P

and available P indices by chemical extractants and showed that Al-P and Fe-P were the

main sources of available P. Ca-P did not have any significant positive relationship while

reductant soluble P was positively and significantly related to available P in the Entisols.

Stepwise regression analysis gave the indication that Al-P was the dominant inorganic

form of P which contributed to available P.

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While studying P nutrition of rice-wheat cropping sequence in a sandy loam soil

Dhillon et al. (1993) found that saloid P and Al-P correlated significantly with grain and

P uptake by rice and wheat. Singaram and Kothandaraman (1993) reported similar results

in case of finger-millet in an alkaline clay loam soil. Rao and Chakraborty (1994) showed

from stepwise regression analysis that Al-P and Ca-P are the predominant fractions

contributing towards availability of P.

On an acid Alfisol, Sharma et al. (1995) observed that Al-P and Fe-P were the

main sources of available P. They further observed that only Fe-P had significant

relationship with grain and straw yield of wheat and total P uptake. Tran and

N’dayegamiye (1995) found that labile P pools (Resin Pi and NaHCO3-Pi), moderately

labile Pi (NaOH-Pi) and total P were strongly correlated with P uptake in silage corn.

Giridhara Krishna and Satyanarayana (1996) studied the relationship of available

P with different inorganic fractions in Vertisols. They observed that Al-P, Fe-P and

occluded P were the major contributors to available P. The amount of Ca-P, though

significantly and positively correlated with available P as estimated by different methods,

contributed very little to the P extracted. The correlation of available P was not

significant with saloid P.

In a long-term field experiment on typic Hapludalf, Zhang and Mackenzie

(1997b) found that in the manure-inorganic-P system, 86 per cent of the bicarbonate-Pi

(labile-P) was supplied from added inorganic P, indicating reduced P fixation compared

to inorganic-P system. The NaOH-Pi and residual-P were soil P sinks, with residual P

being supplied from both the NaOH-Po and HCl-Pi fractions. In contrast, NaOH-Pi in the

inorganic P system was the major source for NaHCO3-Pi.

Bahl and Singh (1997) observed significant correlation between dry matter yield

and saloid P plus Al-P. The fall in levels of Fe-P and Al-P indicated the contribution of

these fractions towards P nutrition of maize. Gupta and Srivastava (1998) indicated that

available P was significantly and positively correlated with total P and all inorganic-P

fractions except occluded Al-P. Path coefficient analysis showed that Al-P and organic P

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directly influenced available soil P while other soil inorganic P fractions showed their

effect indirectly through Al-P.

Reddy et al. (1999) reported that the changes in NaHCO3-Pi, NaOH-Pi and

NaOH-Po fractions were significantly correlated with the apparent P balance and were

thought to represent biologically dynamic soil P and act as major sources and sinks of

plant available P.

Guo et al. (2000) found that in slightly weathered soils, HCl-P and residual P

acted as a buffering pool for the NaHCO3-Pi. Residual P in these soils was plant available

for a relative short time scale. In highly weathered soils, the accumulation of residual P

indicates its unavailability to plants. Organic P (NaHCO3 and NaOH) fractions were not

significant contributor to available P in soils that received high levels of inorganic P.

Sharma and Verma (2000a) observed that among different P fractions, Fe-P and

Al-P were the most important P fractions with respect to grain and straw yield and P

uptake by rice and wheat grown in a sequence, under a field trial on an Alfisol.

Desorbable P was more closely correlated with Al-P than Fe-P, indicating that Al-P is

probably the most important source of desorbable independent of biosolid amendments

(Maguire et al. 2000).

Verma (2002) reported from a long-term fertilizer experiment that Olsen-P was

correlated positively and significantly with all the fractions except H2O-P. The highest

value of coefficient of correlation was with NaHCO3-Pi indicating maximum correlation

of available P with this fraction. Step-wise regression analysis also showed that NaHCO3-

Pi was the most important variable contributing about 86 per cent of the total variation in

available P in surface layer. He also reported that P uptake was correlated positively and

significantly to NaHCO3-Pi, NaOH-Po and Olsen-P of both the depths as in case of grain

and stover yields.

Saavedra and Delgado (2005) revealed that the ratio of P fractions, which

includes the more labile P forms to combined non-organic P fractions, was negatively

correlated with the soil pH and positively correlated with the portion of combined Fe

fractions related to poorly crystalline oxides.

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Setia and Sharma (2007) studied the relationship between inorganic fractions and

uptake of P by wheat at different crop stages. They reported that total P content at

tillering was significantly associated with P concentration and its uptake. The Ca-P at ear

initiation stage was significantly related with P uptake by wheat grain and straw. A

significant relationship between saloid-P and its uptake by straw was also observed at

harvesting.

2.4.3 Potassium fractions

Lal et al. (1990) reported that exchangeable and non exchangeable K significantly

affected the K uptake by field crops. Correlation studies indicated that the most important

form which influenced the yield was water soluble K (r=0.81) followed by exchangeable

K (r=0.72) and non exchangeable K (r=0.70).

Singh and Upadhyay (1990) studied K release behaviors of some soils of North

Western Himalayas and found that non exchangeable K contributed 52.4, 59.0, 75.2 and

78.4 per cent of total K uptake by four successive crops of wheat and maize.

Prasad and Rokima (1991b) found that contribution of different fractions of

potassium to K nutrition varied with the type of crop and reported that exchangeable and

non exchangeable fractions of potassium were important in predicting the K uptake in

wheat, while exchangeable and available K were the most significant fractions in rice.

However, Bhardwaj et al. (1994) could not find this type of variation with the type of

crop and reported that different forms of potassium influenced K uptake in a same

manner in different crops.

In the soils of Tarai Singh et al. (1993) observed that water soluble and

exchangeable K contributed 35.1 and 80 per cent, respectively, to available K. Reddy et

al. (1993) recorded that NH4OAc-K was positively and significantly correlated with the

dry matter yield and K uptake. From multiple regression equations, Dixit et al. (1993)

reported that exchangeable K alone contributed 93.3 per cent variation in available K

while inclusion of water soluble K increased it to 99.9 per cent.

From a long-term manurial trial under sorghum-wheat sequence Dhanorkar et al.

(1994) found that available K was significantly correlated with exchangeable, lattice,

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total and water soluble K. Available K had significant and positive correlation with water

soluble, exchangeable and total K and values of coefficient of correlation (r) were 0.71,

0.99, 0.73 and 0.80, respectively (Sharma 1996).

Chaudhary and Prasad (1997) found that available K had significant and positive

correlation with water soluble and exchangeable K. While Ahmed and Walia (1999)

reported that available K was positively correlated with non exchangeable K (r=0.69) and

Lattice K (r=0.53) indicating their contribution towards labile pool of soil K. Simons and

Setatou (1996) found that the total amount of potentially available K in rye grass was on

an average 3 per cent of total K.

From a field experiment carried out at T. Begur in Bangalore, Thippeswamy et al.

(2000) reported that available K is positively and significantly related with 0.1 N HNO3

extractable K. They further reported that 1 N HNO3 extractable K was positively and

significantly related to K content and grain and straw yield of rice.

In soils of Rajasthan, Chand and Swami (2000) found that both exchangeable and

non exchangeable K was significantly correlated with available K. The step wise

regression data showed exchangeable K to be the most important potassium fraction

contributing in the regression of available K.

Sharma and Verma (2000b) found that non exchangeable K contributed 10 per

cent towards available K. They further found that among different K fractions, non

exchangeable and exchangeable K were the most important forms contributing towards

potassium nutrition of rice-wheat system in acid alfisols of Palampur. Ravankar et al.

(2001) from a long-term fertilizer experiment at Akola, Maharashtra observed that all the

forms of K showed significant correlation with yield of sorghum and wheat crop.

From a long-term fertilizer experiment with grassland at Rothamsted Johnston et

al. (2001) found hardly any change in exchangeable K after 6 years with K fertilization.

Rupa et al. (2001) studied the effect of 27 years of continuous cropping, fertilization and

mannuring on potassium uptake and found that in soils without K fertilization about 100

per cent of total K uptake by the crops was from non-exchangeable reserve as compared

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to 49.5 and 32.5 per cent when annually 84 kg ha-1

K alone and 84 kg ha-1

K with 15 t ha-

1 FYM were applied, respectively. Positive but weak correlation of Lattice K was

observed with available K, however, the non exchangeable K had significant relationship

with available K (Kartar et al. 2001).

Brady and well (2002) reported that readily available K constitutes only about 1

to 2 per cent of total K while in another study Prakash et al. (2002) found that non

exchangeable K contributed 96.25 and 49.02 per cent to total potassium removal under

NP and NPK treatments, respectively.

From a field experiment conducted at Bijapur, Karnataka Patil et al. (2003)

reported that K availability in top (0-15 cm) and sub soil (15-30 cm) at harvest was

positively and significantly correlated with grain yield of winter sorghum. In another

study Subehia et al. (2003) observed that potassium dynamics equilibrium following K

fertilization shifted towards non exchangeable K with the advancement of crop growth.

While studying the vertical distribution of chemical pools of potassium and their

relationship with potassium nutrition of wheat, Setia and Sharma (2004) observed that the

coefficient of determination (R2) between K uptake by grain and all forms of K except

exchangeable improved when K status of subsoil (15-30 cm) was also taken into

consideration.