Bidhan Chandra Krishi ViswavidyalayaWest Bengal

Pabitra Kr. Mani, Tarik Mitran, D. Mazumdar and M.Ray

Effects of organic and inorganic inputs on Effects of organic and inorganic inputs on phosphorus and potassium transformation phosphorus and potassium transformation in long-term rice-wheat cropping system in long-term rice-wheat cropping system

Rice-Wheat rotation is the most important production system in the Indo-Gangetic plains (IGP) of South Asia, in general and India in particular. In India, the system occupies about 10.0 million ha in the IGP and provides food security for 400 million of people (Ladha et al., 2000).

During recent past signs of stagnation or decline in yield trends have been observed (Bhandari et al., 2002) in several long-term experiments (LTE) with rice-wheat system. This has been attributed to changes in soil properties and climate conditions (Cassman et al., 1997). The trends observed in this system may be early warning indicators of what could happen in the future in farmers’ field (Dobermann et al., 2000) at particular agroecological systems (Johnston, 1997).

Several researchers have studied long-term rice–wheat experiments in India but their studies were restricted to simple yield trend analysis (Nambiar,1994; Dawe et al., 2000). In depth study of such system may help to increase and /or curb the declining yield trend of the system.

Objectives:

1)To examine the yield trends of rice under long-term fertility experiment with organic and inorganic sources of nutrients

2)To estimate apparent input-output balances of P and K

3)To study the distribution of different inorganic fractions of phosphorus and different forms of potassium in soil

Experimental sites

Rice- N:P:K:: 80:40:40Wheat- N:P:K:: 100: 60:40

Fertilizer dose

Rice-IET 4094 (IET 1444, upto1997)Wheat-UP-262 (Sonalika, upto1994)

Crop variety used7.0m X 7.0mPlot sizeIrrigatedAgro-ecosystemRice-WheatCropping SystemAeric Haplaquept, ClayeySoil12No. of TreatmentsRBD with 4 replicationsDesign of the Expt.Wet season, 1986Year of start

Mohanpur, West Bengal, India,(IGP 5)(22058/20″ N, 88030/11″E, 9.75m),

Geographical Location

Rice- N:P:K:: 80:40:40Wheat- N:P:K:: 100: 60:40

Fertilizer dose

Rice-IET 4094 (IET 1444, upto1997)Wheat-UP-262 (Sonalika, upto1994)

Crop variety used7.0m X 7.0mPlot sizeIrrigatedAgro-ecosystemRice-WheatCropping SystemAeric Haplaquept, ClayeySoil12No. of TreatmentsRBD with 4 replicationsDesign of the Expt.Wet season, 1986Year of start

Mohanpur, West Bengal, India,(IGP 5)(22058/20″ N, 88030/11″E, 9.75m),

Geographical Location

Rice WheatT1 Control (N0P0K0) Control (N0P0K0)T2 50% NPK 50% NPKT3 50% NPK 100% NPKT4 75% NPK 75% NPKT5 100% RDF (80:40:40) 100% RDF (100:60:40)

T6 50% NPK+ 50% N by FYM 100% NPK

T7 75% NPK.+ 25% N by FYM 75% NPK

T8 50% NPK+ 50% N by rice straw 100% NPK

T9 75% NPK + 25% N by rice straw 75% NPK

T10 50% NPK + 50% N by Dhaincha GLM 100% NPK

T11 75% NPK + 25% N by Dhaincha GLM 75% NPK

T12 Farmers’ practice (50:30:20) F.P ( 60:20:20)

Rice WheatT1 Control (N0P0K0) Control (N0P0K0)T2 50% NPK 50% NPKT3 50% NPK 100% NPKT4 75% NPK 75% NPKT5 100% RDF (80:40:40) 100% RDF (100:60:40)

T6 50% NPK+ 50% N by FYM 100% NPK

T7 75% NPK.+ 25% N by FYM 75% NPK

T8 50% NPK+ 50% N by rice straw 100% NPK

T9 75% NPK + 25% N by rice straw 75% NPK

T10 50% NPK + 50% N by Dhaincha GLM 100% NPK

T11 75% NPK + 25% N by Dhaincha GLM 75% NPK

T12 Farmers’ practice (50:30:20) F.P ( 60:20:20)

RiceRice WheatWheatT1T1 Control (N0P0K0)Control (N0P0K0) Control (N0P0K0)Control (N0P0K0)T2T2 50% NPK50% NPK 50% NPK50% NPKT3T3 50% NPK50% NPK 100% NPK100% NPKT4T4 75% NPK75% NPK 75% NPK75% NPKT5T5 100% RDF (80:40:40)100% RDF (80:40:40) 100% RDF (100:60:40)100% RDF (100:60:40)

T6T6 50% NPK+ 50% N by FYM50% NPK+ 50% N by FYM 100% NPK100% NPK

T7T7 75% NPK.+ 25% N by FYM75% NPK.+ 25% N by FYM 75% NPK75% NPK

T8T8 50% NPK+ 50% N by rice straw50% NPK+ 50% N by rice straw 100% NPK100% NPK

T9T9 75% NPK + 25% N by rice straw75% NPK + 25% N by rice straw 75% NPK75% NPK

T10T10 50% NPK + 50% N by Dhaincha GLM50% NPK + 50% N by Dhaincha GLM 100% NPK100% NPK

T11T11 75% NPK + 25% N by Dhaincha GLM75% NPK + 25% N by Dhaincha GLM 75% NPK75% NPK

T12T12 Farmers’ practice (50:30:20)Farmers’ practice (50:30:20) F.P ( 60:20:20)F.P ( 60:20:20)

Treatment Details

Organics N(%)

P(%)

K(%)

Farm Yard Manures 0.58 0.36 0.3

Paddy Straw 0.81 0.22 0.52

GLM 2.65 0.16 0.46

Nutrient content of the organics used

K balance= Σ (fertilizer K, manure K, rain K, irrigation water K, K in seedlings/ seeds) - Σ (plant K, losses of fertilizer K)

P balance= Σ (fertilizer P, manure P, rain P, irrigation water P, P in seedlings/ seeds) - Σ (plant P, losses of fertilizer P)

Nutrient Budgets

Regmi et al., 2002

Treatments

Yield of Paddy(Mg ha -1) Harvest

Index (HI)

Mean grain yield of rice over the

years

Sustainable Yield Index

(SYI)

Grain Straw (Mg ha -1)

T1 1.42g 2.07f 0.40 1.34g 0.56

T2 2.39f 3.49e 0.40 2.68f 0.68

T3 2.62e 3.59e 0.42 2.90e 0.54

T4 2.78e 3.80d 0.42 3.23d 0.63

T5 3.70bc 5.07c 0.42 3.57c 0.69

T6 4.08a 5.36ab 0.43 3.99a 0.73T7 3.72bc 5.28b 0.41 3.77b 0.70

T8 3.75bc 5.33ab 0.41 3.76b 0.66

T9 3.56c 5.03c 0.41 3.70bc 0.64

T10 3.87ab 5.50a 0.41 3.79b 0.72

T11 3.82b 5.44ab 0.41 3.74b 0.72

T12 3.22d 4.72c 0.40 3.02e 0.53

LSD (P=0.05)

0.215 0.187 ------ 0.164 --------

Yield values, in a column, followed by a common letter are not significantly different at P≤0.05 based on DMRT

Yield of rice as influenced by INM after 22 cycles (2008)

Rice yield trend over the years

y = -0.0026x + 6.6277R2 = 0.0058

y = 0.0334x - 62.814R2 = 0.1815

y = 0.0307x - 57.693R2 = 0.1857

y = 0.0389x - 73.837R2 = 0.2426

y = 0.048x - 92.086R2 = 0.2934

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Experimental years

Gra

in Y

ield

(mg/

ha)

T1 T5 T6 T8 T10

Magnitude of yield change (Mg ha -1year-1) in rice

y = 0.0116x - 0.0034 R2 = 0.2371

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Initial yield (Mg ha-1 )

Mag

nitu

de o

f Yie

ld c

hang

e (M

gha

-1yr

-1)

Treatment pHOC

(g kg-1)Avail-N(kg ha-1)

Avail-P (kg ha-1)

Avail-K(kg ha-1)

Initial 7.5 8.8 150.0 18.0 140.0T1 7.0 5.2 134.0 15.2 130.0T2 7.0 5.5 215.6 48.8 398.7T3 7.0 5.7 215.6 47.4 396.0T4 7.0 5.8 225.9 50.3 398.7T5 7.0 6.3 246.6 63.3 450.3T6 7.2 7.8 308.0 81.9 494.3T7 7.2 7.2 287.5 66.2 458.0T8 7.3 7.8 287.5 69.5 479.0T9 7.4 6.8 256.7 58.5 442.7T10 7.2 7.2 297.7 71.4 486.0T11 7.5 6.4 266.9 64.7 450.0T12 7.2 5.4 215.6 46.5 391.3

LSD (0.05) 0.12 0.42 51.6 8.41 75.85

Effect of different fertiliser treatments on nutrient status of soil after 22 cycles of rice- wheat cropping sequences

Phosphorus Transformation

Treatment Saloid-P Fe-P Al-P Occl-P Red-P Ca-P Total-PT1 6.20 105.6 37.4 59.73 101.2 23.54 458.3

T2 6.76 139.9 46.5 63.83 116.7 24.63 630.2

T3 6.76 138.8 47.2 63.75 123.3 25.78 640.6

T4 7.32 156.4 46.2 69.72 141.0 37.00 677.0

T5 8.48 166.3 48.2 73.71 146.5 49.33 734.4

T6 9.96 194.9 63.0 86.65 167.4 54.93 850.4

T7 9.31 180.6 54.1 74.70 155.3 33.63 792.1

T8 9.35 183.9 58.0 83.67 165.2 49.33 807.3

T9 8.69 172.9 49.2 69.58 149.8 35.87 770.3

T10 9.81 186.1 61.0 85.66 166.3 49.33 845.6

T11 9.10 175.1 55.1 71.71 150.9 42.60 787.4

T12 7.21 144.3 44.2 69.72 132.1 28.03 688.8

LSD(0.05) 1.43 27.72 3.59 3.24 3.48 2.05 37.73

Effect of organic and inorganic inputs on soil Inorganic P fractions and Total phosphorus (mg/kg)

Treatments

Saloid-P Fe-P Al-P Occl-

P Red-P Ca-PT1 1.4 23.0 8.2 13.0 22.0 5.1T2 1.1 22.2 7.4 10.1 18.5 3.9T3 1.1 21.6 7.4 10.0 19.2 4.0T4 1.1 23.1 6.8 10.3 20.8 5.5T5 1.2 22.6 6.6 10.0 19.9 6.7T6 1.2 22.9 7.4 10.1 19.6 6.5T7 1.2 22.8 6.8 9.4 19.6 4.3T8 1.2 22.7 7.2 10.3 20.4 6.1T9 1.1 22.4 6.4 9.0 19.4 4.7T10 1.2 22.0 7.2 10.1 19.6 5.8T11 1.2 22.2 7.0 9.1 19.1 5.4T12 1.1 20.9 6.4 10.1 19.1 4.1

Mean 1.1 22.4 7.1 10.1 19.8 5.2

Percent (%) contribution of different forms of inorganic-P to total- P in soil under various

treatments

Relationship between Avail-P and Al-P

y = 0.78x - 10.58R2 = 0.78

10

20

30

40

50

35 45 55 65Al-P (mg kg-1)

Ava

il-P(

mg

kg-1

)

Relationship between Avail-P and Saloid-P

y = 3.75x - 1.66R2 = 0.69

10

20

30

40

50

0 3 6 9 12 15Saloid-P (mg kg-1)

Ava

il- P

(mg

kg-1

)

Relationship between Avail- P and Fe-P

y = 0.18x - 0.68R2 = 0.61

10

20

30

40

50

90 110 130 150 170 190 210 230Fe-P (mg kg-1)

Ava

il- P

(mg

kg-1

)

Relationship between Total P and Avail-P

y = 14.69x + 290.81R2 = 0.78

200

400

600

800

1000

10 20 30 40Avail-P (mg kg-1)

Tota

l P(m

g kg

-1)

Relationship between various forms of inorganic P fractions and available P

T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12

-4.8

10.9

7.3

17.8

24.7

19.119.2

7.9

19.7

13.8

24.821.6

-5.0

0.0

5.0

10.0

15.0

20.0

25.0P

bala

nce

(kg/

ha)

Treatment

Annual apparent P balances after 22 years of rice cultivation

Potassium Transformation

33.60.393.081.560.210.18N75P40K30N60P30K30 + 25% GMT11

34.30.383.121.520.190.16N100P60K40N40P20K20 + 50% GMT10

40.60.323.371.480.180.19N75P40K30N60P30K30 + 25% StrawT9

42.10.323.571.500.200.19N100P60K40N40P20K20 + 50% StrawT8

25.70.383.21.550.210.13N75P40K30N60P30K30 + 25% FYMT7

27.30.363.181.540.200.14N100P60K40N40P20K20 + 50% FYMT6

41.20.353.371.510.220.15N100P60K40N80P40K40T5

46.70.392.931.440.200.14N0P0K0N0P0K0T1

0.342.901.420.190.09Initial

Wheat(rabi

season)

Rice(wet season)

Code

Total-K

CR-KStep K

NEK

cmol(p+) kg-1

EXCH-K

WS-K

Treatment details

33.60.393.081.560.210.18N75P40K30N60P30K30 + 25% GMT11

34.30.383.121.520.190.16N100P60K40N40P20K20 + 50% GMT10

40.60.323.371.480.180.19N75P40K30N60P30K30 + 25% StrawT9

42.10.323.571.500.200.19N100P60K40N40P20K20 + 50% StrawT8

25.70.383.21.550.210.13N75P40K30N60P30K30 + 25% FYMT7

27.30.363.181.540.200.14N100P60K40N40P20K20 + 50% FYMT6

41.20.353.371.510.220.15N100P60K40N80P40K40T5

46.70.392.931.440.200.14N0P0K0N0P0K0T1

0.342.901.420.190.09Initial

Wheat(rabi

season)

Rice(wet season)

Code

Total-K

CR-KStep K

NEK

cmol(p+) kg-1

EXCH-K

WS-K

Treatment details

Effect of different organic and inorganic inputs on different forms of potassium in soil after 22 cycles of rice-wheat cropping sequences

y = 4.0373x - 0.6188R2 = 0.7571

0.00

0.15

0.30

0.45

0.60

0.0 0.1 0.2 0.3

Exch-K (cmol(p+)kg-1)

WS-

K(cm

ol(p

+ )kg-1

)

y = 0.2028x - 0.1322R2 = 0.63

0.0

0.1

0.2

0.3

0.0 1.0 2.0 3.0NEK (cmol(p+)kg-1)

Exch

-K(c

mol

(p+ )k

g-1)

A dynamic equilibrium exists between the WS-K, Exch-K and NEK

Apparent K balance showed net losses of K ranging from –11.6 to –100.0 kg-1ha-1 yr-1 (except T8) . In spite of heavy with drawl of K yield trend of rice was maintained due to build up of P from various organic inputs. The lower ratio of NEK to Step K (1:2) (next slide) is indicative for future decline in crop yield.

-49.3

-100 -93.2 -90.1

63.6

-11.6

-53.7-70.4

-120

-90

-60

-30

0

30

60

90

K b

alan

ce(k

g ha

-1yr

-1)

T1 T5 T6 T7 T8 T9 T10 T11

Combination of organics (FYM, PS, GLM) with inorganic fertilizers maintained yield level in the order of FYM > PS = GLM

Yield trend of rice was maintained due tobuild up of Pbuild up of P from various organic inputs.

Conclusion

To offset the negative balance and maintain an adequate supply of K in soils, a revision in the existing K fertilizer recommendation towards the higher side is essential for sustaining crop productivity.

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