This document describes a long-term study on the effects of organic and inorganic inputs on phosphorus and potassium transformations in a rice-wheat cropping system in India. The study examined yield trends over 22 cycles, nutrient balances and distributions of phosphorus and potassium forms in the soil under different treatment combinations of organic and inorganic fertilizers. Key findings included higher yields and soil nutrient levels with the combined application of organic and inorganic fertilizers compared to inorganic-only or control treatments.

1. Bidhan Chandra Krishi Viswavidyalaya
West Bengal
Pabitra Kr. Mani, Tarik Mitran, D. Mazumdar and M.Ray
Effects of organic and inorganic inputs onEffects of organic and inorganic inputs on
phosphorus and potassium transformationphosphorus and potassium transformation
in long-term rice-wheat cropping systemin long-term rice-wheat cropping system

2. 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).

3.  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.

4. 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

5. Experimental sites
Rice- N:P:K:: 80:40:40
Wheat- N:P:K:: 100: 60:40
Fertilizer dose
Rice-IET 4094 (IET 1444, upto1997)
Wheat-UP-262 (Sonalika, upto1994)
Crop variety used
7.0m X 7.0mPlot size
IrrigatedAgro-ecosystem
Rice-WheatCropping System
Aeric Haplaquept, ClayeySoil
12No. of Treatments
RBD 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:: 80:40:40
Wheat- N:P:K:: 100: 60:40
Fertilizer dose
Rice-IET 4094 (IET 1444, upto1997)
Wheat-UP-262 (Sonalika, upto1994)
Crop variety used
7.0m X 7.0mPlot size
IrrigatedAgro-ecosystem
Rice-WheatCropping System
Aeric Haplaquept, ClayeySoil
12No. of Treatments
RBD 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

6. Rice Wheat
T1 Control (N0P0K0) Control (N0P0K0)
T2 50% NPK 50% NPK
T3 50% NPK 100% NPK
T4 75% NPK 75% NPK
T5 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 Wheat
T1 Control (N0P0K0) Control (N0P0K0)
T2 50% NPK 50% NPK
T3 50% NPK 100% NPK
T4 75% NPK 75% NPK
T5 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 WheatWheat
T1T1 Control (N0P0K0)Control (N0P0K0) Control (N0P0K0)Control (N0P0K0)
T2T2 50% NPK50% NPK 50% NPK50% NPK
T3T3 50% NPK50% NPK 100% NPK100% NPK
T4T4 75% NPK75% NPK 75% NPK75% NPK
T5T5 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

7. 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

8. 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

9. 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
0.73
T7
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
0.72Yield 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)

10. Rice yield trend over the years
y = -0.0026x + 6.6277
R2
= 0.0058
y = 0.0334x - 62.814
R2
= 0.1815
y = 0.0307x - 57.693
R2
= 0.1857
y = 0.0389x - 73.837
R2
= 0.2426
y = 0.048x - 92.086
R2
= 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
GrainYield(mg/ha)
T1 T5 T6 T8 T10

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

13. Phosphorus
Transformation

14. Treatment Saloid-P Fe-P Al-P Occl-P Red-P Ca-P Total-P
T1 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)

15. Treatments
Saloid-
P
Fe-P Al-P Occl-P Red-P Ca-P
T1 1.4 23.0 8.2 13.0 22.0 5.1
T2 1.1 22.2 7.4 10.1 18.5 3.9
T3 1.1 21.6 7.4 10.0 19.2 4.0
T4 1.1 23.1 6.8 10.3 20.8 5.5
T5 1.2 22.6 6.6 10.0 19.9 6.7
T6 1.2 22.9 7.4 10.1 19.6 6.5
T7 1.2 22.8 6.8 9.4 19.6 4.3
T8 1.2 22.7 7.2 10.3 20.4 6.1
T9 1.1 22.4 6.4 9.0 19.4 4.7
T10 1.2 22.0 7.2 10.1 19.6 5.8
T11 1.2 22.2 7.0 9.1 19.1 5.4
T12 1.1 20.9 6.4 10.1 19.1 4.1
Percent (%) contribution of different forms of inorganic-P
to total- P in soil under various treatments

16. Relationship between Avail-P and Al-P
y = 0.78x - 10.58
R
2
= 0.78
10
20
30
40
50
35 45 55 65
Al-P (mg kg
-1
)
Avail-P(mgkg-1
)
Relationship between Avail-P and Saloid-P
y = 3.75x - 1.66
R2
= 0.69
10
20
30
40
50
0 3 6 9 12 15
Saloid-P (mg kg-1
)
Avail-P(mgkg-1
)
Relationship between Avail- P and Fe-P
y = 0.18x - 0.68
R
2
= 0.61
10
20
30
40
50
90 110 130 150 170 190 210 230
Fe-P (mg kg-1
)
Avail-P(mgkg-1
)
Relationship between Total P and Avail-P
y = 14.69x + 290.81
R
2
= 0.78
200
400
600
800
1000
10 20 30 40
Avail-P (mg kg-1
)
TotalP(mgkg-1
)
Relationship between various forms of inorganic
P fractions and available P

17. 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
24.8
21.6
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
Pbalance(kg/ha)
Treatment
Annual apparent P balances after 22 years of rice cultivation

18. Potassium
Transformation

19. 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
EX
CH-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
EX
CH-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

20. y = 4.0373x - 0.6188
R2
= 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(cmol(p
+
)kg
-1
)
y = 0.2028x - 0.1322
R
2
= 0.63
0.0
0.1
0.2
0.3
0.0 1.0 2.0 3.0
NEK (cmol(p+)kg-1)
Exch-K(cmol(p
+
)kg
-1
)
A dynamic equilibrium exists between the
WS-K, Exch-K and NEK

21. Apparent K balance showed net losses of K ranging from –11.6
to –100.0 kg-1
ha-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
Kbalance(kgha-1
yr-1
)
T1 T5 T6 T7 T8 T9 T10 T11

22.  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 to
build 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.

23. THANK YOU