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Assessing on-farm efficiency and economics of fertilizer N, P and K in rice wheat systems of India
Field Crops Research 81 (2003) 39±51
Assessing on-farm ef®ciency and economics of fertilizer N, P and K in rice wheat systems of India R.L. Yadav* Project Directorate for Cropping Systems Research, Modipuram, Meerut 250110, India Received 8 May 2002; received in revised form 12 September 2002; accepted 4 October 2002
Abstract On-farm experiments were conducted in the Indian districts of Ludhiana (Punjab province), Karnal (Haryana province), Rampur, Faizabad, and Banda (Uttar Pradesh province), Ranchi (Jharkhand province) and Raipur (Chattisgarh province) to (i) measure grain output per unit of fertilizer-use through agronomic ef®ciency (AE) and partial factor productivity (PFP), and (ii) elucidate the economics of N, P and K applications in rice±wheat systems through marginal analysis. Five treatments of fertilizer N±P±K, i.e. un-fertilized control (0±0±0), N (N±0±0), NP (N±P±0), NK (N±0±K) and NPK (N±P±K) were tested on 81 farmers' ®elds during 1999 and 2000. The levels of N±P±K used were as per locally recommended rates. The AE of applied nutrients, in rice varied from 4.3 kg grain kg 1 in Ranchi to 14.7 kg grain kg 1 in Faizabad for N, from 12.8 kg grain kg 1 in Rampur to 51.7 kg grain kg 1 in Raipur for P, and from 7.7 kg grain kg 1 in Ludhiana to 42.6 kg grain kg 1 in Ranchi for K. In wheat, AE for N varied from 5.0 kg grain kg 1 in Banda to 13.1 kg grain kg 1 in Karnal, for P from 15.2 kg grain kg 1 in Karnal to 61.3 kg grain kg 1 in Ranchi, and for K from 4.9 kg grain kg 1 in Karnal to 22.8 kg grain kg 1 in Faizabad. The marginal pro®ts earned per rupee invested on fertilizer application varied from Rs. 1.63 in Ranchi to Rs. 8.04 in Samastipur for N alone, from Rs. 4.00 in Ranchi to Rs. 9.48 in Samastipur for NP, from Rs. 3.94 in Raipur to Rs. 7.60 in Ranchi for NK and from Rs. 4.96 in Raipur to Rs. 9.69 in Samastipur for NPK. Grain yield in control plots (i.e. Y0) exhibited a positive correlation with soil organic C (SOC) (r 0:34, 0.42 in rice and wheat, respectively), available N (r 0:53, 0.49 in rice and wheat, respectively), P (r 0:66, 0.56 in rice and wheat, respectively), and K (r 0:55, 0.50 in rice and wheat, respectively) contents. Both rice and wheat responded to applied NPK. However, the magnitude of the response to applied NPK decreased as Y0 increased. Native nutrient supplying capacity of the soil for N was positive at all the locations, but for P and K, it was either negative or very small. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Agronomic ef®ciency; Fertilizer-use ef®ciency; Indo-Gangetic plains region; On-farm experiments; Rice±wheat systems
1. Introduction The rice±wheat rotation has been practised for over 1000 years in Asia. It, however, expanded during the period of green revolution in South Asia, i.e. in the mid 1960s, and is now estimated at 23.5 million ha * Present address: National Agricultural Technology Project, Krishi Anusandhan Bhawan-II, New Delhi 110012, India.
including about 10 million ha in China and about 13.5 million ha in South Asia. In South Asia, the area under the rice±wheat rotation is 10.0 million ha in India, 2.2 million ha in Pakistan, 0.8 million ha in Bangladesh and 0.5 million ha in Nepal. The rice± wheat rotation represents 32% of the total rice area and 42% of the wheat area in these countries (Ladha et al., 2000). Intensively cultivated rice±wheat systems are fundamental for employment, income generation
0378-4290/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 4 2 9 0 ( 0 2 ) 0 0 1 9 8 - 3
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R.L. Yadav / Field Crops Research 81 (2003) 39±51
and livelihood security of hundreds of millions of rural and urban people of South Asia. This system has also been adapted to a limited extent in countries such as Egypt, Mali, Niger and Senegal (Gupta et al., 2002). Rice is usually grown in the wet summer season (from May and June to October and November) and wheat in the dry winter season (from November and December to March and April). Even though most of the rice±wheat cropped area is under irrigation, the soil and crop management undergoes drastic changes during the yearly cropping cycle from wet season rice to wheat in winter season. Besides the contrasting needs of each crop, continuous cropping of the rice± wheat rotation for long periods has resulted in loss of soil fertility due to emerging de®ciencies of micronutrients and decline in factor productivity and crop yields. Evidence also shows that the system is suffering due to production fatigue (Chaudhary and Harrington, 1993). To overcome these constraints, farmers' simply apply greater than recommended levels of fertilizer N alone thus increasing the cost of production resulting in lowering of pro®ts. However, if fertilizers P and K are also applied with N, the pro®t margin may increase and yields might be sustained at higher level. The objectives of this study, therefore, were to (i) measure grain yield per unit of fertilizer N, P and K use, (ii) compare yield advantages of balanced application of N P K over N alone, (iii) elucidate the economics of fertilizer application in the rice±wheat system on farmers' ®elds in different regions of India. 2. Materials and methods 2.1. Study area The data utilized in this study were taken from onfarm experiments conducted in the districts of Ludhiana (Punjab state), Karnal (Haryana state), Rampur (Uttar Pradesh state), Banda (Uttar Pradesh state), Faizabad (Uttar Pradesh state), Samastipur (Bihar state), Ranchi (Jharkhand state) and Raipur (Chattisgarh state) under the umbrella of the Experiments on
Cultivators' Fields Programme of the Project Directorate for Cropping Systems Research. For this paper, however, these districts will simply be referred to as Ludhiana, Karnal, Rampur, Banda, Faizabad, Samastipur, Ranchi and Raipur. Ludhiana, Karnal, Rampur, Faizabad and Samastipur are located in the IndoGangetic Plain Region (IGPR) where the rice±wheat rotation is a predominant production system, while Banda, Ranchi and Raipur are located outside the IGPR, but where the rice±wheat rotation is an emerging production system. Ludhiana, located at 30.568N, and 75.528E, and 247 m above mean sea level (a.m.s.l.), has a semi-arid sub-tropical climate with hot dry summers and cool winters. Soils are alluvial. The average annual rainfall is 628 mm. The rice±wheat rotation is cultivated on 0.241 m ha. On average, fertilizer application rates are 178.76 kg N ha 1, 59.88 kg P ha 1 and 5.03 kg K ha 1. Average yield of rice is 3273 kg ha 1 and of wheat is 4518 kg ha 1. Karnal, located at 29.428N, and 77.028E, has a semi-arid dry climate and alluvial soils. Average annual rainfall is 720 mm. The rice±wheat sequence is practised on 0.166 m ha. Average rates of fertilizer application are 211.29 kg N ha 1, 60.64 kg P ha 1 and 1.31 kg K ha 1. Average productivity of rice is 2203 kg ha 1 and of wheat is 4139 kg ha 1. Rampur, located at 28.488N, and 79.058E, has a dry sub-humid climate and receives 907 mm average annual rainfall. The rice±wheat rotation is cultivated on 0.123 m ha. Average rates of fertilizer application are 109.4 kg N ha 1, 27.6 kg P ha 1 and 8.8 kg K ha 1. The average yields of rice is 1843 kg ha 1 and of wheat is 3238 kg ha 1. Banda, located at 25.208N and 80.228E, receives about 900 mm rainfall annually. In the district, soil erosion is high and land productivity low. The rice± wheat rotation is practised on 0.061 m ha. Average rates of fertilizer applications are 13.5 kg N ha 1, 8.1 kg P ha 1 and 0.1 kg K ha 1. Average yields of rice is 1488 kg ha 1 and of wheat is 1588 kg ha 1. Faizabad, situated at 27.28N and 82.58E in North Eastern Plain zone of Uttar Pradesh, has a moist subhumid to dry sub-humid climate with sandy loam to loam calcareous clay and deep alluvial soils. Average annual rainfall is 1210 mm. The rice±wheat rotation is practised on 0.085 m ha. Average application rates of fertilizers are 59.4 kg N ha 1, 21.1 kg P ha 1 and
R.L. Yadav / Field Crops Research 81 (2003) 39±51
2.2 kg K ha 1. Average productivity of rice is 1049 kg ha 1 and of wheat is 2313 kg ha 1. Samastipur, located at 25.558N and 85.508E in north Bihar plains, has a dry to moist sub-humid climate, and young alluvium saline to calcareous (pH 8.5±8.8) loamy sand to sandy loam and sometimes silt loam soils. Average annual rainfall is 1204 mm. The rice± wheat rotation is cultivated on 0.054 m ha. Average application rates of fertilizers are 58.9 kg N ha 1, 27.0 kg P ha 1 and 5.3 kg K ha 1. Average productivity of rice is 1269 kg ha 1, and of wheat is 2086 kg ha 1. Ranchi, located at 22.238N, and 85.238E and 655 m a.m.s.l., has moist sub-humid to sub-humid climate and red sandy loam to loam soil. The annual average rainfall is 1482 mm. The rice±wheat rotation is practised on 0.008 m ha. Average application rates of fertilizers are 59.4 kg N ha 1, 34.6 kg P ha 1 and 4.5 kg K ha 1. The average annual productivity of rice is 1045 kg ha 1 and of wheat is 1697 kg ha 1. Raipur, located at 23.108N and 83.158E, has a moist to dry sub-humid climate, and red and yellow and red sandy soils. Annual average rainfall is about 1436 mm. The rice±wheat rotation is an emerging sequence in the areas where rice-fallow is used, i.e. about 0.335 million ha. 2.2. Treatments and crop culture Experiments were conducted during 1999 and 2000 in the ®elds of 81 farmers. The number of farmers' ®elds selected in different districts were: 15 in Ludhiana, eight in Karnal, 12 in Rampur, 10 in Banda, nine
41
Table 1 The recommended levels of fertilizer N, P and K (kg ha 1) in rice and wheat in different districts Districts
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
Rice
Wheat
N
P
K
N
P
K
120 150 120 120 80 100 80 100
13 33 26 26 17 22 17 26
24 48 48 32 16 40 16 32
120 150 120 120 120 120 100 100
26 33 26 26 26 26 22 26
24 48 48 32 32 48 20 32
in Faizabad, six in Samastipur, 15 in Ranchi and six in Raipur. Five 100 m2 plots were established in the each farmers' ®eld. Each plot was assigned one fertilizer treatment randomly. The fertilizer N±P±K treatments were: control (0±0±0), N (N±0±0), NP (N±P±0), NK (N±0±K) and NPK (N±P±K), all at recommended rates (the recommended rates of fertilizer N, P and K for each district are mentioned in Table 1). Each farmer was considered a replication and a randomized block design was used for statistical analysis of the data. Rice was transplanted into the plots. The rice harvest was followed by seeding of wheat. The fertilizer treatment assigned to a particular plot remained the same for both rice and wheat. Varieties of rice and wheat used in this study and dates of transplanting rice and seeding of wheat in different districts are presented in Table 2. Urea (46.4% N), single super phosphate (16% P2O5) and muriate of potash (60% K2O) were used to supply N, P and K, respectively.
Table 2 Varieties and dates of transplanting rice and seeding of wheat in different districts Districts
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
Varieties Rice
Wheat
PR111 IR 64 Pant Dhan-4 Sarju-52 Pusa 834 Ashwani IR 64 IR 36
PBW 343 PBW 343 PBW 343 HUW 67 PBW 343 Raj 3007 UP 262 WH 147
Date of transplanting rice
Date of seeding wheat
14±29 June 1999 10±25 June 2000 15±30 June 2000 5±20 July 1999 7±28 July 2000 25±30 July 1999 15±30 July 1999 15±30 July 1999
29 October±16 November 99 10±20 November 2000 5±15 November 2000 1±10 December 1999 9±12 December 2000 29 November±3 December 1999 25±30 November 1999 25±30 November 1999
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R.L. Yadav / Field Crops Research 81 (2003) 39±51
A half dose of fertilizer N, and full doses of P and K were applied as the basal application while the remaining N was top dressed at panicle initiation in rice, and at crown root initiation in wheat. With the except of fertilizer treatments, farmers utilized their own methods and resources for growing the crops. Researchers recorded yield data and collected soil samples. The mean seedling age of rice at transplanting at all the sites was about 1 month. Farmers ploughed and then puddled and leveled their ®elds before transplanting. Transplanting was done using 2 seedlings per hill. The number of plants per meter square ranged between 20 and 30. Although ®elds were irrigated, in Banda, Faizabad, Samastipur, Ranchi and Raipur, rice was grown as rainfed crop. Farmers managed weeds in rice with one or two manual weedings. Pest management was carried out by the farmers, but was not monitored. Rice was harvested manually close to ground level with sickles. Prior to seeding wheat in the same plots, the land was ploughed three to four times to a 15 cm depth with a tractor-drawn harrow and cultivator in Ludhiana, Karnal and Rampur. In Banda, Faizabad, Samastipur, Ranchi and Raipur, however, land was ploughed ®ve to six times with a bullock-drawn plough. Wheat was sown using 100 kg seed ha 1 by a tractor-drawn seed drill in row 23 cm apart in Ludhiana. At other locations, wheat was sown by broadcasting and after seeding, a plank was dragged over the ®eld to cover the seed. The range of irrigation given to wheat ranged from three to ®ve waterings. Wheat was also harvested manually using sickles and the harvested above ground biomass was removed from the plots. The grain yield, however, was recorded from an area of 20 m2 in each plot. 2.3. Soil analysis Before commencement of the on-farm experiments, soil samples were taken at depths between 0 and 15 cm at ®ve sites in each farmers' ®elds. The samples per ®eld were pooled, mixed thoroughly and a representative homogeneous sample-drawn for the analysis of organic C (Walkley and Black method), available N (alkaline KMnO4 method), 0.5 M NaHCO3 (pH 8.5) extractable P and 1 N NH4OAc extractable K, following Page et al. (1982). The soil test values are presented in Table 3.
Table 3 SOC, available N, P and K contents of farmers' ®elds at different locations in India before commencement of on-farm experiments Locations
SOC (%)
N (kg ha 1) P (kg ha 1) K (kg ha 1)
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
0.58 0.53 0.44 0.51 0.54 0.44 0.34 0.50
163 136 156 126 163 146 120 148
0.23 0.21 0.11 0.16 0.06 0.09 0.12 0.03
22 18 19 17 20 18 16 19
36 18 36 13 8 15 8 8
23 6 6 3 1 1 1 1
288 277 282 165 97 150 148 203
95 81 36 11 2 15 8 17
2.4. Nutrient-use ef®ciency Nutrient-use ef®ciencies were measured in terms of partial factor productivity (PFP) and agronomic ef®ciency (AE) of fertilizers N, P and K. The PFP, a ratio of the grain yield to the applied nutrient, is a useful measure of nutrient-use ef®ciency as it provides an integrative index that quanti®es total economic output relative to the utilization of all nutrient resources in the system, including native soil nutrients and nutrients from applied fertilizers. It is possible to increase PFP by increasing the amount, uptake and utilization of indigenous nutrients, and by increasing the ef®ciency with which applied nutrients are taken up by the crop and utilized to produce grain (Cassman et al., 1996b). For applied fertilizers N, P and K, PFP was calculated as Yn Fn Ynp Yn PFPp Fp
PFPn
PFPk
Ynk Yn Fk
(1) (2) (3)
where PFPn, PFPp and PFPk were PFP of single use of fertilizer N, P and K, respectively, Yn the grain yield of N-fertilized plots, Ynp the grain yield of NP-fertilized plots and Ynk is the grain yield of NK-fertilized plots. Fn, Fp and Fk are the amounts of applied fertilizers N, P, and K, respectively. All these are expressed as kg ha 1. The AE, an incremental ef®ciency from applied fertilizer N, P and K over control, was calculated as AEN
Yn
Y0 Fn
(4)
R.L. Yadav / Field Crops Research 81 (2003) 39±51
AEP
Ynpk Ynk Fp
(5)
AEK
Ynpk Ynp Fk
(6)
where AEN, AEP and AEK were the AE of applied fertilizer N, P and K, respectively, Yn the grain yield of N-fertilized plots, Y0 the grain yield of unfertilizedplots, (control) Ynpk the grain yield of NPK-treated and Ynp is the grain yield of NP-treated plots. Fn, Fp and Fk are the amounts of fertilizer N, P and K applied. All these are expressed as kg ha 1. 2.5. Native nutrient supplying capacity of the soil For measuring native nutrient supplying capacity of the soil nutrient supplying capacity of soil (NNSCS), AE was subtracted from PFP as NNSCS PFP
AE
(7)
By substituting the values of PFP as in Eq. (1) and of AE as in Eq. (4) NNSCS
YF TN
YF
Y0 TN
!
(8)
where TN is the total nutrients available in soil includes nutrients supplied through fertilizers NF and nutrients supplied by native soil NS substituting TN by NF NS YF NF NS YF NNSCS NF NS Y0 NNSCS NF NS
NNSCS
YF Y0 NF NS YF Y0 NF NS NF NS
(9) (10) (11)
As fertilizers were not applied to supply nutrients in control plots, therefore NF was taken as zero. Hence NNSCS
Y0 NS
(12)
where, YF is grain yield obtained by applying fertilizers, Y0 grain yield obtained without applying fertilizers, TN the total nutrients available in the soil, NF the nutrient supplied through fertilizers and NS is the amount of nutrients supplied by the soil. All values are expressed in kg ha 1.
43
2.6. Economic analysis Economic evaluation of fertilizer N, P and K was made through marginal analysis. For this, the cost of cultivation (CC) of rice and wheat was calculated on the basis of different operations performed and materials used for growing the crops. For rice, the operations and materials used were: seed; nursery sowing for raising rice seedlings; their maintenance; transplanting of rice seedlings in the ®eld; irrigation; harvesting and threshing. For wheat, the operations and materials used were: seed; seedbed preparation; sowing operations; irrigation; herbicide application; harvesting and threshing. The prices of different materials used and operations performed were: rice seed Rs. 4.15 kg 1; wheat seed Rs. 5.10 kg 1; N Rs. 7.96 kg 1; P Rs. 6.42 kg 1; K Rs. 4.95 kg 1; irrigation Rs. 90 unit 1; labor Rs. 72 unit 1; ploughing Rs. 120 per operation. Gross returns (GR) were calculated by multiplying grain yield by grain price, i.e. Rs. 4.15 kg 1 of rice and Rs. 5.10 kg 1 of wheat. Net returns (NR) were calculated as NR GR
CC
(13)
Marginal returns (MR) for the given fertilizer application treatment over the control were calculated as MR
NRf CCf
NRC 100 CCC
(14)
where NRf is the net returns from a given fertilizer application treatment, f, NRC the net returns the from control plots (no fertilizer application), CCf the CC for a given fertilizer application treatment and CCC is the CC in the control plots. 2.7. Statistical analysis Firstly, descriptive statistical analysis was performed for measured parameters in each farmers' ®eld within the district to measure the range of variability and standard deviation. Thereafter, data were analyzed using standard procedures for the randomized block design in nonorthagonal form to compare treatment means within and between locations (Cocharn and Cox, 1957). Location differences in the measured variables were tested within the ANOVA by F-test at 0.05 level of probability using location as the error
44
R.L. Yadav / Field Crops Research 81 (2003) 39±51
term. The presence of differences within treatments or a signi®cant location treatment interaction was tested within the ANOVA using the residual as the error term. The treatments averaged across districts or within each district (when district treatment interaction was signi®cant) were compared using least signi®cant difference (LSD) at the 5% level of probability. Relationships between control plot yields (Y0) and soil organic C (SOC), available NPK contents and between PFP, AE and Y0, SOC and available NPK contents were established by least squares linear regression. The contribution of SOC, available N, P and K to Y0 was determined by the following multiple regression equation: Y b0 b1 SOC b2 N b3 P b4 K
(15)
where Y is estimated Y0 b0, b1, b2, b3 and b4 are the constants and SOC, N, P and K are SOC, available N, available P and available K contents. Y0, N, P and K are expressed as kg ha 1 while SOC as a percentage. Sestet (version 6.0.1) was the statistical package used. 3. Results 3.1. Effect of NPK on grain yield At all the locations, grain yields of rice and wheat in plots receiving N, NP, NK and NPK treatments were
signi®cantly greater than that in control plots (Table 4). However, the plots receiving NPK produced the greatest yields. The yields obtained in plots having fertilizer treatment NP were also at par, for rice in Ludhiana, Rampur, Samastipur and Raipur and for wheat in Karnal, Rampur, Samastipur and Raipur. When averaged over locations, fertilizer Ntreated plots produced greater yields over the control by 53% in rice and 59% in wheat. However, response to N application over controls ranged between 18 and 105% in rice and between 30 and 162% in wheat. Fertilizer P increased the yields over the control by 32% in rice and by 41% in wheat. The range, however, varied from 7% in Ludhiana to 86% in Banda and Raipur for rice and between 16% in Rampur to 100% in Banda for wheat. Fertilizer K increased the yields over the control by 18% in rice and 27% in wheat. The yield advantage due to K application, however, varied between 4% in Ludhiana and 40% in Faizabad for rice and between 7% in Rampur and 142% in Ranchi for wheat. Application of NPK, on average, increased the yields over the control by 102% in rice and 122% in wheat. The greatest increase of 238% in rice, however, was noted in Banda, and of 264% in wheat in Samastipur. The NP application increased the yields over the control by 84% in rice and by 95% in wheat. However, at different locations, the increase in yield due to NP application varied between 44% in Rampur and 201% in Banda in rice and between 45% in Rampur and 232% in Samastipur for wheat.
Table 4 Grain yield (t ha 1) of rice and wheat in rice±wheat systems on farmers' ®elds at different locations in India as in¯uenced by applied N, P and K Locations
Rice
Wheat
Control N
NP
NK
NPK
Mean
LSD (5%)a
Control N
NP
NK
NPK
Mean
LSD (5%)a
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
4.41 3.33 3.52 1.69 1.56 1.18 1.9 1.56
5.88 5.22 4.35 3.46 3.08 2.62 2.25 2.51
6.46 5.99 5.09 4.02 3.48 3.52 2.83 3.86
6.33 5.48 4.96 3.88 3.27 2.97 2.95 2.8
6.45 6.41 5.38 4.81 3.8 4 3.51 4.14
5.94 5.29 4.66 3.57 3.04 2.87 2.69 2.97
0.38 0.27 0.71 0.72 0.37 0.14 0.49 0.55
3.1 2.24 3.19 1.94 0.98 1.05 0.93 1.53
4.41 4.21 4.14 3.08 2.57 1.65 1.44 2.28
4.98 4.76 4.61 3.64 3.25 2.52 1.83 3.61
4.69 4.49 4.33 3.38 2.93 2.01 2.79 3.41
5.28 5 4.85 4.37 3.57 3.06 3.14 3.89
4.49 4.14 4.35 3.28 2.66 2.06 2.03 2.75
0.17 0.27 0.61 0.56 0.36 0.1 0.38 0.45
Mean
2.39
3.67
4.41
4.08
4.81
3.87
1.02
1.87
2.97
3.65
3.5
4.15
3.22
0.98
a
For fertilizer application at respective location.
R.L. Yadav / Field Crops Research 81 (2003) 39±51 Table 5 The PFP (kg grain kg locations in India Locations
1
45
applied fertilizer) of applied N, P and K in rice and wheat in the rice±wheat system on farmers ®eld at different
Rice
Wheat
PFPn Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
49 34.8 36.2 28.8 38.5 26.2 27.9 25.1
Mean
33.3
PFPp
13.7 5.4 11.2 8.4 9.7 2.9 10.2 4.3
44.9 23.2 28.4 21.8 23.9 43.7 33.8 52 34.0
PFPk
29.8 12.5 15.3 18.2 21.1 11.7 38.2 5.7
18.8 5.3 12.6 13.2 11.8 8.9 43.8 9.2 15.5
The increase in yield due to NK applications were not as great as that obtained with NP applications. On average, NK application increased the yields over the control by 70% in rice and 81% in wheat. At different locations, these advantages varied from 44% in Ludhiana to 152% in Banda for rice, and 36% in Samastipur to 201% in Ranchi for wheat. 3.2. PFP The PFP of applied N (PFPn), in rice ranged between 21 kg grain kg 1 N in Ranchi and 58.7 kg grain kg 1 N in Ludhiana (Table 5). In rice, mean PFPn, however, was the largest (49 kg grain kg 1 N) in Ludhiana and the lowest (25.1 kg grain kg 1 N) in Raipur. In wheat, PFPn ranged between 5.8 kg grain kg 1 N in Ranchi and 43 kg grain kg 1 N in Rampur. In wheat, the mean of PFP, however, was the largest (36.2 kg grain kg 1 N) in Ludhiana and the lowest (13.8 kg grain kg 1 N) in Banda. When averaged over locations, PFPn was greater in rice (33.3 kg grain kg 1 N) than in wheat (24.6 kg grain kg 1 N). The PFP for applied P (PFPp), when averaged over locations, was 33.96 kg grain kg 1 P in rice and 30.3 kg grain kg 1 P in wheat. PFPp in rice, however, ranged between zero in Samastipur and 148 kg grain kg 1 P in Ludhaina (Table 5). In wheat, PFPp ranged between 4.6 kg grain kg 1 P in Karnal and 100.5 kg grain kg 1 P in Ranchi. At different locations, greatest PFPp (52.0 kg grain kg 1 P) was noted in Raipur and the lowest (21.8 kg grain kg 1 P) in Faizabad. In wheat, the greatest PFPp (62.8 kg grain kg 1 P) was
PFPn
31.3 2.8 3.9 12.8 14.6 11.0 27.3 6.1
36.2 28 34.6 25.6 21.4 13.8 14.4 22.8
PFPp
4.6 2.8 8.3 7.6 6.4 1.5 9.8 6.5
24.6
11.7 16.7 18.3 21.7 26.3 33.6 62.8 51.2 30.3
PFPk
8.7 14.4 8.4 13.6 11.9 6.9 27.3 12.5
11.5 6 4.1 9.3 11.2 7.5 19.2 7.5
5.9 7.3 2.8 11.0 7.4 8.6 13.2 2.8
9.5
noted in Ranchi, and the lowest (11.7 kg grain kg 1 P) in Ludhiana. PFP of applied K (PFPk) was found to be negative in a few farmers' ®elds for rice in Ludhiana, Samastipur and Ranchi and for wheat in Ranchi and Raipur (Table 5). When averaged over locations, PFPk was found to be 15.45 kg grain kg 1 K for rice and 9.5 kg grain kg 1 K for wheat. The greatest PFPk was 43.8 kg grain kg 1 K for rice, and 19.2 kg grain kg 1 K for wheat was measured in Ranchi and the lowest which is 5.3 kg grain kg 1 K for rice and 4.1 grain kg 1 K for wheat was noted in Rampur. 3.3. AE of fertilizer NPK The AE of applied N (AEN), in general, was greater in rice (10.9 kg grain kg 1 N) than in wheat (8.6 kg grain kg 1 N). A negative AEN was also noted for both crops in Ranchi (Table 6). Maximum AEN of 28.81 kg grain kg 1 N in rice and 17.33 kg grain kg 1 N in wheat was observed in Samastipur. AE of applied P (AEP), in general, was greater in wheat (35.1 kg grain kg 1 P) than in rice (33.2 kg grain kg 1 P). In both the crops, AEP was greater in Ranchi than in other locations. However, the lowest AEP was noticed in Samastipur for rice (1.47 kg grain kg 1 P), and in Rampur for wheat (8.79 kg grain kg 1 P). AE of applied K (AEK), in general, was greater in rice (16.5 kg grain kg 1 K) than in wheat (11.8 kg grain kg 1 K). A negative AEK was also noted in rice in Ludhiana. The mean AEK across districts revealed
46 Table 6 The AE (kg grain kg India Locations
R.L. Yadav / Field Crops Research 81 (2003) 39±51
1
nutrient) of applied N, P and K in rice and wheat in the rice±wheat system on farmers' ®eld at different locations in
Rice
Wheat
AEn Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
12.3 12.6 6.9 14.7 12.9 14.0 4.3 9.5
Mean
10.9
AEp
5.5 1.6 3.3 5.5 5.8 1.2 3.7 1.5
24.4 28.3 12.8 35.9 31.4 48.0 32.9 51.7
AEk
16.9 10.1 6.8 12.6 20.0 9.0 34.1 9.9
33.2
7.7 8.8 8.9 24.7 19.8 11.0 42.6 8.9
AEn
8.6 7.0 5.6 6.4 7.8 4.0 15.3 3.7
16.6
10.9 13.1 7.9 9.5 9.9 5.0 5.2 7.5
AEp
2.6 2.6 2.7 4.7 2.8 1.3 4.7 1.7
8.6
that the greatest AEK was found in Ranchi for rice and in Faizabad for wheat.
28.3 15.2 15.8 38.3 24.7 40.3 61.3 57.0
AEk
8.6 3.9 5.3 16.6 4.3 5.3 29.1 11.0
35.1
12.4 4.9 7.3 22.8 9.9 11.2 17.5 8.8
2.9 2.8 5.2 12.6 2.1 2.5 4.1 2.5
11.9
3.4.2. On PFP The PFPn was signi®cantly in¯uenced by SOC and available NPK contents in both crops (Table 8). The PFPp on the other hand, was negatively in¯uenced by soil fertility parameters in wheat. The PFPp in rice, however, was not in¯uenced by soil fertility parameters. The PFPk was also not in¯uenced by soil fertility status, except that available N had a negative in¯uence on PFPk in rice.
3.4. Effect of SOC and available NPK contents 3.4.1. On-yield in control plots Grain yield in control plots (Y0) was in¯uenced signi®cantly by SOC and available NPK contents as indicated by signi®cant positive correlation coef®cients (Table 7). The linear regression, however, was very strong for available P (R2 0:44, 0.323 for rice and wheat, respectively) and weak for SOC (R2 0:113, 0.178 for rice and wheat, respectively) (Table 7). Amongst the four soil fertility parameters studied in this investigation, yield was in¯uenced in the most as per the following preferential order:
3.4.3. On AE of applied NPK The AEN in rice was in¯uenced signi®cantly by SOC content (Table 9). Available NPK contents in soils, however, did not in¯uence AEN in rice signi®cantly. But in wheat, AEN, was in¯uenced signi®cantly by SOC, available P and K contents. The AEP showed negative correlations with SOC, and available
available P > available K > N > SOC:
Table 7 Correlation coef®cients (r) and regression constants (a, b) coef®cients showing between linear relationship Y a bX, where Y is yields in controls plots (Y0) and SOC, and X is either or available N, P and K contents as per the case Soil parameters
r
Rice SOC Available N Available P Available K
0.34 0.53 0.66 0.55
Wheat SOC Available N Available P Available K
0.42 0.49 0.56 0.5
b
t-stat
R2
P-value
1265 1922 1579 783
3076.75 32.56 53.38 8.41
3.05 5.39 7.57 5.56
0.113 0.285 0.440 0.298
0.0032 >0.0001 >0.0001 >0.0001
658 1328 1313 671
3057.61 23.98 36.2 6.16
3.97 4.88 5.89 4.99
0.178 0.246 0.323 0.255
0.0002 >0.0001 >0.0001 >0.0001
a
R.L. Yadav / Field Crops Research 81 (2003) 39±51
47
Table 8 Correlation coef®cients (r) and regression constant (a, b) indicating extent of relationship y a bX between PFP of applied fertilizer N, P and K in rice and wheat, and SOC and available NPK contents (based on 81 observations in farmers ®elds across districts in India) Soil parameters
PFP in rice
PFP in wheat
N
P **
SOC (%) Available N (kg ha 1) Available P (kg ha 1) Available K (kg ha 1)
K
0.34 0.50*** 0.67*** 0.47***
0.19 0.21 0.05 0.11
N 0.12 0.26 0.24 0.18
P ***
0.40 0.46*** 0.54*** 0.48***
K 0.4 0.35 0.35 0.39
0.11 0.21 0.21 0.17*
*
Signi®cant at 0.05 level of probability. Signi®cant at 0.005 level of probability. *** Signi®cant at 0.0001 level of probability. **
Table 9 Correlation (r) and regression (a, b) coef®cients for relationships of AE of applied N (AEN), P (AEP) and K (AEK) with SOC and available N, P and K contents Soil parameters
r
a
b
t-stat
R2
P-value
AEN Rice SOC Available N Available P Available K
0.28 0.11 0.17 0.15
5.48 6.54 9.12 8.22
10.514 0.026 0.056 0.009
2.539 0.918 1.496 1.26
0.081 0.011 0.029 0.021
0.0136 0.3612 0.1390 0.2116
Wheat SOC Available N Available P Available K
0.25 0.19 0.26 0.3
4.97 3.14 6.92 4.94
7.295 0.036 0.067 0.015
2.194 1.624 2.31 2.714
0.062 0.035 0.068 0.092
0.0314 0.1086 0.0237 0.0083
AEP Rice SOC Available N Available P Available K
0.15 0.16 0.37 0.35
41.56 53.64 41.47 51.21
22.541 0.158 0.499 0.089
1.281 1.352 3.441 3.164
0.022 0.025 0.140 0.121
0.2041 0.1803 0.0010 0.0023
Wheat SOC Available N Available P Available K
0.39 0.4 0.42 0.51
64.7 96.72 47.89 66.69
64.147 0.434 0.607 0.139
3.655 3.721 3.989 5.021
0.155 0.159 0.179 0.257
0.0005 0.0004 0.0002 >0.0001
AEK Rice SOC Available N Available P Available K
0.38 0.55 0.44 0.59
37.05 76.02 26.69 42.7
42.109 0.412 0.433 0.111
3.482 5.691 4.195 6.236
0.143 0.307 0.194 0.348
0.0008 0.0000 0.0001 >0.0001
Wheat SOC Available N Available P Available K
0.13 0.29 0.23 0.37
15.71 27.15 14.82 20.14
6.829 0.103 0.109 0.033
1.087 2.55 2.015 3.393
0.016 0.082 0.053 0.136
0.2806 0.0128 0.0475 0.0011
48
R.L. Yadav / Field Crops Research 81 (2003) 39±51
negative at four locations in rice (i.e. Karnal, Faizabad, Samastipur and Banda) and at ®ve locations in wheat (i.e. Ludhiana, Rampur, Faizabad, Banda and Raipur). Positive values, wherever they existed, were very low.
Table 10 Native nutrient supplying capacity of the soil (kg grain kg 1 available nutrients in the soil) for producing grain yields of rice and wheat in different locations in India Locations
Rice N
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur S.E.
Wheat P
K
N
P
3.6. Economic analysis
K
36.3 22.6 29.3 14.1 25.6 12.2 23.6 15.6
20.5 5.1 15.6 14.1 7.5 4.3 0.9 0.3
11.1 3.5 3.7 11.5 8 2.1 1.2 0.3
25.3 14.9 26.7 16.2 11.5 8.8 9.2 15.3
16.6 1.5 2.5 16.6 1.6 6.7 1.5 5.8
0.9 1.1 3.2 13.5 1.3 3.7 1.7 1.3
0.3
0.8
0.5
2.8
1.2
0.5
The mean data over farmers' ®elds for each location indicated that application of complete doses of fertilizer NPK resulted in signi®cantly greater net returns compared to the control and other fertilizer application treatments (Table 11). Compared to N alone, the net returns from NPK application were greater by 22% in Ludhiana, 28% in Karnal, 28% in Rampur, 68% in Faizabad, 55% in Samsatipur, 144% in Banda, 218% in Ranchi and 126% in Raipur. The NR from application of N alone, however, were greater than that in the control by 51% in Ludhiana, 118% in Karnal, 34% in Rampur, 195% in Faizabad, 119% in Samastipur, 625% in Banda, 74% in Ranchi and 119% in Raipur. The differences in net returns from fertilizers NP and NPK were 5.5% in Ludhiana, 7.2% in Karnal, 6.5% in Rampur, 30.6% in Faizabad, 14.3% in Samastipur, 25.1% in Banda, 91.2% in Ranchi, and 9.9% in Raipur. Marginal analysis of different fertilizer application treatments for each location (Table 12) indicated that the greatest marginal pro®ts either from N alone or from NPK application, were observed in Samastipur, and from the NP treatment in Karnal, Rampur and Ranchi.
N, P and K contents. The AEK in rice and wheat exhibited negative correlations with SOC and available NPK contents (Table 9). 3.5. Native nutrient supplying capacity of the soil The NNSCS for N was positive at all the locations, and was greater in rice than in wheat (Table 10). The NNSCS for P, however, was negative in four districts for both rice (i.e. Karnal, Faizabad, Samastipur and Banda) and wheat (i.e. Ludhiana, Faizabad, Banda, and Raipur). At places where, NNSCS for P was positive, the values were very low except for rice in Ludhiana and Rampur. The NNSCS for K was also
Table 11 Total CC (Rs. ha 1) and net returns (Rs. ha 1) from the rice±wheat rotation under different treatments of fertilizer N, P and K application in different districts of India Locations
CC
NR
Controls
N
NP
NK
NPK
LSD (5%)
Controls
N
NP
NK
NPK
LSD (5%)
Lundhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
12 665 12 215 12 215 11 135 10 373 9 083 9 083 9 083
14 575 14 603 14 125 13 045 11 965 10 834 10 516 10 675
14 826 15 027 14 459 13 370 12 241 11 142 10 766 11 013
14 813 15 079 14 601 13 361 12 202 11 270 10 694 10 991
15 063 15 503 14 935 13 675 12 478 11 578 10 944 11 325
218 402 309 211 318 212 195 187
21 454 13 056 18 645 5 758 1 095 1 163 3 538 5 197
32 301 28 566 25 036 17 005 13 901 8 442 6 167 11 361
37 390 34 109 30 191 21 900 18 803 16 483 10 266 23 417
35 351 30 555 28 054 19 960 16 274 11 384 15 779 18 026
39 445 36 569 32 147 28 592 21 489 20 625 19 634 25 727
1001 723 515 628 496 712 699 622
Mean
10 732
12 542
12 856
12 876
13 188
8 738
17 847
25 070
21 923
28 029
R.L. Yadav / Field Crops Research 81 (2003) 39±51 Table 12 Marginal analysis (%) of fertilizer N, P and K application versus control (no fertilizer) in the rice±wheat rotation at different locations in India Locations
Fertilizer application N
NP
NK
NPK
LSD (5%)
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
568 649 335 589 804 416 163 387
737 749 515 722 948 744 400 944
647 611 394 638 830 634 760 672
750 715 496 899 969 780 865 916
38 27 41 56 61 22 85 36
Mean
489
720
648
799
On average, farmers earned Rs. 4.98 Re 1 invested for N alone, Rs. 7.20 Re 1 invested for NP, Rs. 6.48 Re 1 invested for NK and Rs. 7.99 Re 1 invested for NPK. The pro®t per rupee invested for N alone, however, ranged from Rs. 8.04 in Samastipur to Rs. 1.63 in Ranchi, on NP application from Rs. 9.48 in Samastipur to Rs. 4.00 in Ranchi, or NK application from Rs. 7.60 in Ranchi to Rs. 3.94 in Rampur and on NPK application from Rs. 9.69 in Samastipur to Rs. 4.96 in Rampur. 4. Discussion The results have shown that, at all the locations, yields were signi®cantly greater in plots receiving N, NP, NK, NPK treatments compared to the un-fertilized control plots. Among fertilized plots, greatest yields, however, were obtained in those plots receiving complete doses of NPK. In the control plot where fertilizer were not applied, yields (i.e. Y0) were signi®cantly greater in Ludhiana, Karnal, and Rampur compared to that in Banda, Faizabad, Samastipur, Ranchi and Raipur (Table 4). These differences, in yield between the high productivity zone (i.e. Ludhiana, Karnal and Rampur) and the low productivity zone (i.e. Banda, Samastipur, Faizabad, Ranchi and Raipur), were primarily because of the differences in climatic conditions of the locations (Aggarwal and Kalra, 1994), date of transplanting/sowing of rice±wheat (Yadav et al., 1998a,b) and infra-structure development in
49
the area (Ladha et al., 2000). In Ludhiana, Karnal and Rampur, a high productivity zone, environmental conditions are suited to wheat cultivation, the irrigation infra-structure is good for cultivating rice, native soil fertility status is higher (Table 3) and use of fertilizer NPK inputs is greater (see Section 2.1). The low yields recorded in Faizabad, Samastipur, Banda, Ranchi and Raipur, a low productivity zone, were associated with un-irrigated lands and rainfed situations, shorter growing period due to delayed transplanting/sowing beyond optimum recommended dates in the middle of June for rice and between 10 and 15 November in wheat (Table 2, Yadav et al., 1998a,b), and low status of native soil fertility especially P and K (Table 3) because of sub-optimum input use and land degradation status. Many parts of this region are saline/sodic and suffer from waterlogging (Aggarwal et al., 2000). The skewed distribution of land and higher incidence of crop-sharing tenancy arrangements in Faizabad, Samastipur, Banda, Ranchi and Raipur, where farmers are generally reluctant to purchase fertilizer inputs for their crops, may also be responsible for low yields in these districts (Ladha et al., 2000). Under such complex situations of multiple constraints in the low productivity zone, the easiest way of increasing yields is through timely transplanting/sowing of crops, as each day's delay in sowing beyond the optimum dates results in a 50 kg ha 1 reduction in yields (Aggarwal et al., 2000). Timely rice transplanting maybe ensured by providing irrigation support to farmers through exploitation of un-tapped underground water potential by digging shallow tube-wells in the area, and wheat maybe zero-tilled soon after the rice harvest to avoid further delay in preparation of the seedbed for wheat sowing (Gupta et al., 2000). It appears that in the higher productivity zone, apart from favorable conditions for crop growth, continuous use of high fertilizer doses might have resulted in increased yields. These improved yields could also be associated with production of large stubbles and root biomass, which when decomposed add to the total organic matter content of the soil. Probably because of this, native soil fertility in the high productivity zone is showing a gradual build up (Yadav, 2001). The response of crops to applied fertilizer N, P and K was smaller in the high productivity zone compared to that in the low productivity zone. In the high
50
R.L. Yadav / Field Crops Research 81 (2003) 39±51
productivity zone, at recommended levels of application, rice yielded 21.8 kg grain kg 1 P and wheat 19.9 kg grain kg 1 P. This response increased in the low productivity zone to 40 kg grain kg 1 P in rice and 44.3 kg grain kg 1 P in wheat. Earlier, Yadav et al. (1998b) obtained 40 kg grain kg 1 P in rice and 74 kg grain kg 1 P in wheat at Faizabad. The response to K application in the high productivity zone was 8.5 kg grain kg 1 K in rice and 8.2 kg grain kg 1 K in wheat. The response increased to 21.4 kg grain kg 1 K in rice and 14.0 kg 1 K in wheat in the low productivity zone. Regarding the N response, both crops yielded 10.6 grain kg 1 N in the high productivity zone, but in the low productivity zone, rice yielded 11.1 kg grain kg 1 N and wheat yielded 7.4 kg grain kg 1 N. Adhikari et al. (1999) observed 10±12 kg grain kg 1 N in farmers' ®elds in Nepal and Bangladesh while Cassman et al. (1996b) obtained 15±18 kg grain kg 1 N in well managed on-station experiments in the Philippines. It may thus be inferred that the crops response to applied NPK decreased when Y0 increased. Y0 was highly dependent on native soil fertility status. The four soil fertility parameters, i.e. SOC, and available N, P and K contents evaluated in the present study contributed 48.9% variation in the Y0 of rice, and 38.6% variation in the Y0 of wheat as per following equations: in rice; Y0 70:41
706:09SOC 10:97N
40:36P 2:40K;
R2 0:489
on NPK, were greater in the low productivity zone. Farmers earned additional Rs. 6.54 Re 1 invested in complete doses of NPK in the high productivity zone compared to Rs. 8.86 Re 1 in the low productivity zone. The marginal pro®ts from NP treatments were Rs. 6.67 Re 1 in the high productivity zone compared to Rs. 7.52 Re 1 in the low productivity zone. Thus, it maybe inferred that in the low productivity zone, all the three nutrients, NPK are required to be applied at recommended rates to earn greater pro®ts, whereas in the high productivity zone, despite heavy K removal resulting in a decline in available K (Yadav et al., 1998a), additions of K through fertilizers has not been a pro®table proposition in the rice±wheat system probably because of replenishment of available K from the nonexchangeable pool and added K through irrigation water. Since the nonexchangeable fraction is a potential source of available K and contributes more than 50% of total K uptake in the rice±wheat system (Tiwari et al., 1992), signi®cant K releases from this pool can mask the dynamics of the initial pool of available K. This is particularly true in alluvial soils, such as those of the Indo-Gangetic plains, with high K-®xing capacity owing to the presence of ellite as the dominant clay mineral (Tandon and Sekhon, 1988). Potassium thus always remained readily available to meet requirements of crop plants, but the soil was eventually depleted of available K under the rice± wheat system (Yadav, 2001). The negative or very low NNSCS in the present study (Table 10) may also indicate the same.
(16) in wheat; Y0
197:52 866:26SOC 8:13N 23:75P 1:00K;
2
R 0:386 (17)
As far as the economics of fertilizer N, P and K is concerned, it was observed that at all the locations complete doses of NPK resulted in signi®cantly greater net returns compared to the control, and other combinations of fertilizer N P and K. It was interesting to note that wherever the CC was greater, such as that in the high productivity zone, net returns were also larger. Although net returns from complete NPK doses were greater in the high productivity zone, marginal pro®ts, i.e. additional pro®t earned per rupee invested
5. Conclusions and recommendations Crop yields in this study varied from location to location and within location from ®eld to ®eld. Even then, the entire rice±wheat area maybe categorized in two distinct productivity zones: a high productivity zone located west of 808E longitude, comprising trans- and upper-Gangetic plains of IGPR including Punjab, Haryana and Western Uttar Pradesh; a low productivity zone located east of 808E longitude comprising middle- and lower-Gangetic plain of IGPR which includes eastern Uttar Pradesh, Bihar and West Bengal, and then states outside IGPR, i.e. Jharkhand and Chattisgarh. Although response to fertilizer application was highly location speci®c, in general in the
R.L. Yadav / Field Crops Research 81 (2003) 39±51
high productivity zone, where fertilizer application rates are already very high, current recommended fertilizer rates were not as pro®table as that were in the low productivity zone. Research must therefore focus on improving fertilizer-use ef®ciency by developing improved agronomic methods such as raisedbed planting in the high productivity zone. In the low productivity zone, improved information on timing of transplanting/sowing crops and use optimum recommended rates of fertilizer NPK for high yields and marginal pro®t should be made widely available to farmers. Acknowledgements I am thankful to the Chief Agronomist and ECF Agronomists of Cropping Systems Research at PAU, Ludhiana, GBPUAT, Pantnagar, NDUA and T Faizabad, CSAUA and Kanpur, RAU, Samastipur, IGKV Raipur for HAU, Karnal for conducting on-farm experiments in their areas of jurisdiction and providing data. References Adhikari, C., Bronson, K.F., Pnuallah, G.M., Regmi, A.P., Saha, P.K., Dobermann, A., Olk, D.C., Hobbs, P.R., Pasuqnin, E., 1999. On-farm soil N supply and N nutrition in the rice± wheat system of Nepal and Bangladesh. Field Crop. Res. 64, 273±286. Aggarwal, P.K., Kalra, N., 1994. Analyzing the limitations set by climatic factors, genotype and water and nitrogen availability on productivity of wheat. II. Climatically potential yields and management strategies. Field Crop. Res. 38, 93±103. Aggarwal, P.K., Talukdar, K.K., Mall, R.K., 2000. Potential yields of rice±wheat systems in the Indo-Gangetic plains of India. In: Proceedings of the Rice±Wheat Consortium Paper Series 10,
51
Rice±Wheat Consortium for the Indo-Gangetic Plains, IARI Campus, Pusa, New Delhi, India. Cassman, K.G., Gines, G.C., Dizon, M.A., Samson, M.I., Alcantara, J.M., 1996b. Nitrogen use ef®ciency in tropical lowland rice systems: contribution from indigenous and applied nitrogen. Field Crop. Res. 47, 1±12. Chaudhary, M.K., Harrington, L.W., 1993. The Rice±Wheat Systems in Haryana: Input±Output Trends and Sources of Future Productivity Growth. CIMMYT, Mexico, DF, C.C.S. Haryana Agricultural University Regional Research Station, Karnal. Cocharn, W.G., Cox, G.M., 1957. Experimental Designs. Wiley, New York. Gupta, R.K., Hobbs, P.R., Ladha, J.K., Prabhakar, S.V.R.K., 2002. Resource Conserving Technologies: Transferring the Rice± Wheat Systems of the Indo-Gangetic Plains. Asia-Paci®c Association of Agricultural Research Associations, APAARI Publication, Bangkok, pp. 42. Ladha, J.K., Fischer, K.S., Hassain, M., Hobbs, P.R., Hardy, B. (Eds.), 2000. Improving the Productivity and Sustainability of Rice±Wheat Systems of the Indo-Gangetic Plains: A Synthesis of Nars±Irri Partnership Research. IRRI Discussion Paper Series No. 40. International Rice Research Institute, Makati City, Philippines, 31 pp. Page, A.L., Millar, R.H., Keeney, D.R., 1982. Methods of Soil Analysis. Part 2. American Society of Agronomy/Soil Science Society of America, Madison, WI. Tandon, H.L.S., Sekhon, G.S., 1988. Potassium Research and Agricultural Production in India. Fertilizer Development Consultancy Organisation, New Delhi. Tiwari, K.N., Dwivedi, B.S., Subba Rao, A., 1992. Potassium management in rice±wheat cropping systems. In: Pandey, R.K. (Ed.), Rice±Wheat Cropping Systems, PDCSR, Modipuram, India, pp. 94±114. Yadav, R.L., 2001. On-farm experiments on integrated nutrient management in rice±wheat cropping systems. Exp. Agric. 37, 99±113. Yadav, R.L., Prasad, K., Gangwar, K.S., 1998a. Analysis of ecoregional production constraints in rice±wheat cropping system. Bulletin No. 98-2. Project Directorate For Cropping Systems Research, Modipuram, Meerut, India, 73 pp. Yadav, R.L., Yadav, D.S., Singh, R.M., Kumar, A., 1998b. Longterm effects of inorganic fertilizer inputs on crop productivity in a rice±wheat cropping systems. Nutr. Cyc. Agroecosyst. 51, 193±200.
Assessing on-farm ef®ciency and economics of fertilizer N, P and K in rice wheat systems of India R.L. Yadav* Project Directorate for Cropping Systems Research, Modipuram, Meerut 250110, India Received 8 May 2002; received in revised form 12 September 2002; accepted 4 October 2002
Abstract On-farm experiments were conducted in the Indian districts of Ludhiana (Punjab province), Karnal (Haryana province), Rampur, Faizabad, and Banda (Uttar Pradesh province), Ranchi (Jharkhand province) and Raipur (Chattisgarh province) to (i) measure grain output per unit of fertilizer-use through agronomic ef®ciency (AE) and partial factor productivity (PFP), and (ii) elucidate the economics of N, P and K applications in rice±wheat systems through marginal analysis. Five treatments of fertilizer N±P±K, i.e. un-fertilized control (0±0±0), N (N±0±0), NP (N±P±0), NK (N±0±K) and NPK (N±P±K) were tested on 81 farmers' ®elds during 1999 and 2000. The levels of N±P±K used were as per locally recommended rates. The AE of applied nutrients, in rice varied from 4.3 kg grain kg 1 in Ranchi to 14.7 kg grain kg 1 in Faizabad for N, from 12.8 kg grain kg 1 in Rampur to 51.7 kg grain kg 1 in Raipur for P, and from 7.7 kg grain kg 1 in Ludhiana to 42.6 kg grain kg 1 in Ranchi for K. In wheat, AE for N varied from 5.0 kg grain kg 1 in Banda to 13.1 kg grain kg 1 in Karnal, for P from 15.2 kg grain kg 1 in Karnal to 61.3 kg grain kg 1 in Ranchi, and for K from 4.9 kg grain kg 1 in Karnal to 22.8 kg grain kg 1 in Faizabad. The marginal pro®ts earned per rupee invested on fertilizer application varied from Rs. 1.63 in Ranchi to Rs. 8.04 in Samastipur for N alone, from Rs. 4.00 in Ranchi to Rs. 9.48 in Samastipur for NP, from Rs. 3.94 in Raipur to Rs. 7.60 in Ranchi for NK and from Rs. 4.96 in Raipur to Rs. 9.69 in Samastipur for NPK. Grain yield in control plots (i.e. Y0) exhibited a positive correlation with soil organic C (SOC) (r 0:34, 0.42 in rice and wheat, respectively), available N (r 0:53, 0.49 in rice and wheat, respectively), P (r 0:66, 0.56 in rice and wheat, respectively), and K (r 0:55, 0.50 in rice and wheat, respectively) contents. Both rice and wheat responded to applied NPK. However, the magnitude of the response to applied NPK decreased as Y0 increased. Native nutrient supplying capacity of the soil for N was positive at all the locations, but for P and K, it was either negative or very small. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Agronomic ef®ciency; Fertilizer-use ef®ciency; Indo-Gangetic plains region; On-farm experiments; Rice±wheat systems
1. Introduction The rice±wheat rotation has been practised for over 1000 years in Asia. It, however, expanded during the period of green revolution in South Asia, i.e. in the mid 1960s, and is now estimated at 23.5 million ha * Present address: National Agricultural Technology Project, Krishi Anusandhan Bhawan-II, New Delhi 110012, India.
including about 10 million ha in China and about 13.5 million ha in South Asia. In South Asia, the area under the rice±wheat rotation is 10.0 million ha in India, 2.2 million ha in Pakistan, 0.8 million ha in Bangladesh and 0.5 million ha in Nepal. The rice± wheat rotation represents 32% of the total rice area and 42% of the wheat area in these countries (Ladha et al., 2000). Intensively cultivated rice±wheat systems are fundamental for employment, income generation
0378-4290/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 4 2 9 0 ( 0 2 ) 0 0 1 9 8 - 3
40
R.L. Yadav / Field Crops Research 81 (2003) 39±51
and livelihood security of hundreds of millions of rural and urban people of South Asia. This system has also been adapted to a limited extent in countries such as Egypt, Mali, Niger and Senegal (Gupta et al., 2002). Rice is usually grown in the wet summer season (from May and June to October and November) and wheat in the dry winter season (from November and December to March and April). Even though most of the rice±wheat cropped area is under irrigation, the soil and crop management undergoes drastic changes during the yearly cropping cycle from wet season rice to wheat in winter season. Besides the contrasting needs of each crop, continuous cropping of the rice± wheat rotation for long periods has resulted in loss of soil fertility due to emerging de®ciencies of micronutrients and decline in factor productivity and crop yields. Evidence also shows that the system is suffering due to production fatigue (Chaudhary and Harrington, 1993). To overcome these constraints, farmers' simply apply greater than recommended levels of fertilizer N alone thus increasing the cost of production resulting in lowering of pro®ts. However, if fertilizers P and K are also applied with N, the pro®t margin may increase and yields might be sustained at higher level. The objectives of this study, therefore, were to (i) measure grain yield per unit of fertilizer N, P and K use, (ii) compare yield advantages of balanced application of N P K over N alone, (iii) elucidate the economics of fertilizer application in the rice±wheat system on farmers' ®elds in different regions of India. 2. Materials and methods 2.1. Study area The data utilized in this study were taken from onfarm experiments conducted in the districts of Ludhiana (Punjab state), Karnal (Haryana state), Rampur (Uttar Pradesh state), Banda (Uttar Pradesh state), Faizabad (Uttar Pradesh state), Samastipur (Bihar state), Ranchi (Jharkhand state) and Raipur (Chattisgarh state) under the umbrella of the Experiments on
Cultivators' Fields Programme of the Project Directorate for Cropping Systems Research. For this paper, however, these districts will simply be referred to as Ludhiana, Karnal, Rampur, Banda, Faizabad, Samastipur, Ranchi and Raipur. Ludhiana, Karnal, Rampur, Faizabad and Samastipur are located in the IndoGangetic Plain Region (IGPR) where the rice±wheat rotation is a predominant production system, while Banda, Ranchi and Raipur are located outside the IGPR, but where the rice±wheat rotation is an emerging production system. Ludhiana, located at 30.568N, and 75.528E, and 247 m above mean sea level (a.m.s.l.), has a semi-arid sub-tropical climate with hot dry summers and cool winters. Soils are alluvial. The average annual rainfall is 628 mm. The rice±wheat rotation is cultivated on 0.241 m ha. On average, fertilizer application rates are 178.76 kg N ha 1, 59.88 kg P ha 1 and 5.03 kg K ha 1. Average yield of rice is 3273 kg ha 1 and of wheat is 4518 kg ha 1. Karnal, located at 29.428N, and 77.028E, has a semi-arid dry climate and alluvial soils. Average annual rainfall is 720 mm. The rice±wheat sequence is practised on 0.166 m ha. Average rates of fertilizer application are 211.29 kg N ha 1, 60.64 kg P ha 1 and 1.31 kg K ha 1. Average productivity of rice is 2203 kg ha 1 and of wheat is 4139 kg ha 1. Rampur, located at 28.488N, and 79.058E, has a dry sub-humid climate and receives 907 mm average annual rainfall. The rice±wheat rotation is cultivated on 0.123 m ha. Average rates of fertilizer application are 109.4 kg N ha 1, 27.6 kg P ha 1 and 8.8 kg K ha 1. The average yields of rice is 1843 kg ha 1 and of wheat is 3238 kg ha 1. Banda, located at 25.208N and 80.228E, receives about 900 mm rainfall annually. In the district, soil erosion is high and land productivity low. The rice± wheat rotation is practised on 0.061 m ha. Average rates of fertilizer applications are 13.5 kg N ha 1, 8.1 kg P ha 1 and 0.1 kg K ha 1. Average yields of rice is 1488 kg ha 1 and of wheat is 1588 kg ha 1. Faizabad, situated at 27.28N and 82.58E in North Eastern Plain zone of Uttar Pradesh, has a moist subhumid to dry sub-humid climate with sandy loam to loam calcareous clay and deep alluvial soils. Average annual rainfall is 1210 mm. The rice±wheat rotation is practised on 0.085 m ha. Average application rates of fertilizers are 59.4 kg N ha 1, 21.1 kg P ha 1 and
R.L. Yadav / Field Crops Research 81 (2003) 39±51
2.2 kg K ha 1. Average productivity of rice is 1049 kg ha 1 and of wheat is 2313 kg ha 1. Samastipur, located at 25.558N and 85.508E in north Bihar plains, has a dry to moist sub-humid climate, and young alluvium saline to calcareous (pH 8.5±8.8) loamy sand to sandy loam and sometimes silt loam soils. Average annual rainfall is 1204 mm. The rice± wheat rotation is cultivated on 0.054 m ha. Average application rates of fertilizers are 58.9 kg N ha 1, 27.0 kg P ha 1 and 5.3 kg K ha 1. Average productivity of rice is 1269 kg ha 1, and of wheat is 2086 kg ha 1. Ranchi, located at 22.238N, and 85.238E and 655 m a.m.s.l., has moist sub-humid to sub-humid climate and red sandy loam to loam soil. The annual average rainfall is 1482 mm. The rice±wheat rotation is practised on 0.008 m ha. Average application rates of fertilizers are 59.4 kg N ha 1, 34.6 kg P ha 1 and 4.5 kg K ha 1. The average annual productivity of rice is 1045 kg ha 1 and of wheat is 1697 kg ha 1. Raipur, located at 23.108N and 83.158E, has a moist to dry sub-humid climate, and red and yellow and red sandy soils. Annual average rainfall is about 1436 mm. The rice±wheat rotation is an emerging sequence in the areas where rice-fallow is used, i.e. about 0.335 million ha. 2.2. Treatments and crop culture Experiments were conducted during 1999 and 2000 in the ®elds of 81 farmers. The number of farmers' ®elds selected in different districts were: 15 in Ludhiana, eight in Karnal, 12 in Rampur, 10 in Banda, nine
41
Table 1 The recommended levels of fertilizer N, P and K (kg ha 1) in rice and wheat in different districts Districts
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
Rice
Wheat
N
P
K
N
P
K
120 150 120 120 80 100 80 100
13 33 26 26 17 22 17 26
24 48 48 32 16 40 16 32
120 150 120 120 120 120 100 100
26 33 26 26 26 26 22 26
24 48 48 32 32 48 20 32
in Faizabad, six in Samastipur, 15 in Ranchi and six in Raipur. Five 100 m2 plots were established in the each farmers' ®eld. Each plot was assigned one fertilizer treatment randomly. The fertilizer N±P±K treatments were: control (0±0±0), N (N±0±0), NP (N±P±0), NK (N±0±K) and NPK (N±P±K), all at recommended rates (the recommended rates of fertilizer N, P and K for each district are mentioned in Table 1). Each farmer was considered a replication and a randomized block design was used for statistical analysis of the data. Rice was transplanted into the plots. The rice harvest was followed by seeding of wheat. The fertilizer treatment assigned to a particular plot remained the same for both rice and wheat. Varieties of rice and wheat used in this study and dates of transplanting rice and seeding of wheat in different districts are presented in Table 2. Urea (46.4% N), single super phosphate (16% P2O5) and muriate of potash (60% K2O) were used to supply N, P and K, respectively.
Table 2 Varieties and dates of transplanting rice and seeding of wheat in different districts Districts
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
Varieties Rice
Wheat
PR111 IR 64 Pant Dhan-4 Sarju-52 Pusa 834 Ashwani IR 64 IR 36
PBW 343 PBW 343 PBW 343 HUW 67 PBW 343 Raj 3007 UP 262 WH 147
Date of transplanting rice
Date of seeding wheat
14±29 June 1999 10±25 June 2000 15±30 June 2000 5±20 July 1999 7±28 July 2000 25±30 July 1999 15±30 July 1999 15±30 July 1999
29 October±16 November 99 10±20 November 2000 5±15 November 2000 1±10 December 1999 9±12 December 2000 29 November±3 December 1999 25±30 November 1999 25±30 November 1999
42
R.L. Yadav / Field Crops Research 81 (2003) 39±51
A half dose of fertilizer N, and full doses of P and K were applied as the basal application while the remaining N was top dressed at panicle initiation in rice, and at crown root initiation in wheat. With the except of fertilizer treatments, farmers utilized their own methods and resources for growing the crops. Researchers recorded yield data and collected soil samples. The mean seedling age of rice at transplanting at all the sites was about 1 month. Farmers ploughed and then puddled and leveled their ®elds before transplanting. Transplanting was done using 2 seedlings per hill. The number of plants per meter square ranged between 20 and 30. Although ®elds were irrigated, in Banda, Faizabad, Samastipur, Ranchi and Raipur, rice was grown as rainfed crop. Farmers managed weeds in rice with one or two manual weedings. Pest management was carried out by the farmers, but was not monitored. Rice was harvested manually close to ground level with sickles. Prior to seeding wheat in the same plots, the land was ploughed three to four times to a 15 cm depth with a tractor-drawn harrow and cultivator in Ludhiana, Karnal and Rampur. In Banda, Faizabad, Samastipur, Ranchi and Raipur, however, land was ploughed ®ve to six times with a bullock-drawn plough. Wheat was sown using 100 kg seed ha 1 by a tractor-drawn seed drill in row 23 cm apart in Ludhiana. At other locations, wheat was sown by broadcasting and after seeding, a plank was dragged over the ®eld to cover the seed. The range of irrigation given to wheat ranged from three to ®ve waterings. Wheat was also harvested manually using sickles and the harvested above ground biomass was removed from the plots. The grain yield, however, was recorded from an area of 20 m2 in each plot. 2.3. Soil analysis Before commencement of the on-farm experiments, soil samples were taken at depths between 0 and 15 cm at ®ve sites in each farmers' ®elds. The samples per ®eld were pooled, mixed thoroughly and a representative homogeneous sample-drawn for the analysis of organic C (Walkley and Black method), available N (alkaline KMnO4 method), 0.5 M NaHCO3 (pH 8.5) extractable P and 1 N NH4OAc extractable K, following Page et al. (1982). The soil test values are presented in Table 3.
Table 3 SOC, available N, P and K contents of farmers' ®elds at different locations in India before commencement of on-farm experiments Locations
SOC (%)
N (kg ha 1) P (kg ha 1) K (kg ha 1)
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
0.58 0.53 0.44 0.51 0.54 0.44 0.34 0.50
163 136 156 126 163 146 120 148
0.23 0.21 0.11 0.16 0.06 0.09 0.12 0.03
22 18 19 17 20 18 16 19
36 18 36 13 8 15 8 8
23 6 6 3 1 1 1 1
288 277 282 165 97 150 148 203
95 81 36 11 2 15 8 17
2.4. Nutrient-use ef®ciency Nutrient-use ef®ciencies were measured in terms of partial factor productivity (PFP) and agronomic ef®ciency (AE) of fertilizers N, P and K. The PFP, a ratio of the grain yield to the applied nutrient, is a useful measure of nutrient-use ef®ciency as it provides an integrative index that quanti®es total economic output relative to the utilization of all nutrient resources in the system, including native soil nutrients and nutrients from applied fertilizers. It is possible to increase PFP by increasing the amount, uptake and utilization of indigenous nutrients, and by increasing the ef®ciency with which applied nutrients are taken up by the crop and utilized to produce grain (Cassman et al., 1996b). For applied fertilizers N, P and K, PFP was calculated as Yn Fn Ynp Yn PFPp Fp
PFPn
PFPk
Ynk Yn Fk
(1) (2) (3)
where PFPn, PFPp and PFPk were PFP of single use of fertilizer N, P and K, respectively, Yn the grain yield of N-fertilized plots, Ynp the grain yield of NP-fertilized plots and Ynk is the grain yield of NK-fertilized plots. Fn, Fp and Fk are the amounts of applied fertilizers N, P, and K, respectively. All these are expressed as kg ha 1. The AE, an incremental ef®ciency from applied fertilizer N, P and K over control, was calculated as AEN
Yn
Y0 Fn
(4)
R.L. Yadav / Field Crops Research 81 (2003) 39±51
AEP
Ynpk Ynk Fp
(5)
AEK
Ynpk Ynp Fk
(6)
where AEN, AEP and AEK were the AE of applied fertilizer N, P and K, respectively, Yn the grain yield of N-fertilized plots, Y0 the grain yield of unfertilizedplots, (control) Ynpk the grain yield of NPK-treated and Ynp is the grain yield of NP-treated plots. Fn, Fp and Fk are the amounts of fertilizer N, P and K applied. All these are expressed as kg ha 1. 2.5. Native nutrient supplying capacity of the soil For measuring native nutrient supplying capacity of the soil nutrient supplying capacity of soil (NNSCS), AE was subtracted from PFP as NNSCS PFP
AE
(7)
By substituting the values of PFP as in Eq. (1) and of AE as in Eq. (4) NNSCS
YF TN
YF
Y0 TN
!
(8)
where TN is the total nutrients available in soil includes nutrients supplied through fertilizers NF and nutrients supplied by native soil NS substituting TN by NF NS YF NF NS YF NNSCS NF NS Y0 NNSCS NF NS
NNSCS
YF Y0 NF NS YF Y0 NF NS NF NS
(9) (10) (11)
As fertilizers were not applied to supply nutrients in control plots, therefore NF was taken as zero. Hence NNSCS
Y0 NS
(12)
where, YF is grain yield obtained by applying fertilizers, Y0 grain yield obtained without applying fertilizers, TN the total nutrients available in the soil, NF the nutrient supplied through fertilizers and NS is the amount of nutrients supplied by the soil. All values are expressed in kg ha 1.
43
2.6. Economic analysis Economic evaluation of fertilizer N, P and K was made through marginal analysis. For this, the cost of cultivation (CC) of rice and wheat was calculated on the basis of different operations performed and materials used for growing the crops. For rice, the operations and materials used were: seed; nursery sowing for raising rice seedlings; their maintenance; transplanting of rice seedlings in the ®eld; irrigation; harvesting and threshing. For wheat, the operations and materials used were: seed; seedbed preparation; sowing operations; irrigation; herbicide application; harvesting and threshing. The prices of different materials used and operations performed were: rice seed Rs. 4.15 kg 1; wheat seed Rs. 5.10 kg 1; N Rs. 7.96 kg 1; P Rs. 6.42 kg 1; K Rs. 4.95 kg 1; irrigation Rs. 90 unit 1; labor Rs. 72 unit 1; ploughing Rs. 120 per operation. Gross returns (GR) were calculated by multiplying grain yield by grain price, i.e. Rs. 4.15 kg 1 of rice and Rs. 5.10 kg 1 of wheat. Net returns (NR) were calculated as NR GR
CC
(13)
Marginal returns (MR) for the given fertilizer application treatment over the control were calculated as MR
NRf CCf
NRC 100 CCC
(14)
where NRf is the net returns from a given fertilizer application treatment, f, NRC the net returns the from control plots (no fertilizer application), CCf the CC for a given fertilizer application treatment and CCC is the CC in the control plots. 2.7. Statistical analysis Firstly, descriptive statistical analysis was performed for measured parameters in each farmers' ®eld within the district to measure the range of variability and standard deviation. Thereafter, data were analyzed using standard procedures for the randomized block design in nonorthagonal form to compare treatment means within and between locations (Cocharn and Cox, 1957). Location differences in the measured variables were tested within the ANOVA by F-test at 0.05 level of probability using location as the error
44
R.L. Yadav / Field Crops Research 81 (2003) 39±51
term. The presence of differences within treatments or a signi®cant location treatment interaction was tested within the ANOVA using the residual as the error term. The treatments averaged across districts or within each district (when district treatment interaction was signi®cant) were compared using least signi®cant difference (LSD) at the 5% level of probability. Relationships between control plot yields (Y0) and soil organic C (SOC), available NPK contents and between PFP, AE and Y0, SOC and available NPK contents were established by least squares linear regression. The contribution of SOC, available N, P and K to Y0 was determined by the following multiple regression equation: Y b0 b1 SOC b2 N b3 P b4 K
(15)
where Y is estimated Y0 b0, b1, b2, b3 and b4 are the constants and SOC, N, P and K are SOC, available N, available P and available K contents. Y0, N, P and K are expressed as kg ha 1 while SOC as a percentage. Sestet (version 6.0.1) was the statistical package used. 3. Results 3.1. Effect of NPK on grain yield At all the locations, grain yields of rice and wheat in plots receiving N, NP, NK and NPK treatments were
signi®cantly greater than that in control plots (Table 4). However, the plots receiving NPK produced the greatest yields. The yields obtained in plots having fertilizer treatment NP were also at par, for rice in Ludhiana, Rampur, Samastipur and Raipur and for wheat in Karnal, Rampur, Samastipur and Raipur. When averaged over locations, fertilizer Ntreated plots produced greater yields over the control by 53% in rice and 59% in wheat. However, response to N application over controls ranged between 18 and 105% in rice and between 30 and 162% in wheat. Fertilizer P increased the yields over the control by 32% in rice and by 41% in wheat. The range, however, varied from 7% in Ludhiana to 86% in Banda and Raipur for rice and between 16% in Rampur to 100% in Banda for wheat. Fertilizer K increased the yields over the control by 18% in rice and 27% in wheat. The yield advantage due to K application, however, varied between 4% in Ludhiana and 40% in Faizabad for rice and between 7% in Rampur and 142% in Ranchi for wheat. Application of NPK, on average, increased the yields over the control by 102% in rice and 122% in wheat. The greatest increase of 238% in rice, however, was noted in Banda, and of 264% in wheat in Samastipur. The NP application increased the yields over the control by 84% in rice and by 95% in wheat. However, at different locations, the increase in yield due to NP application varied between 44% in Rampur and 201% in Banda in rice and between 45% in Rampur and 232% in Samastipur for wheat.
Table 4 Grain yield (t ha 1) of rice and wheat in rice±wheat systems on farmers' ®elds at different locations in India as in¯uenced by applied N, P and K Locations
Rice
Wheat
Control N
NP
NK
NPK
Mean
LSD (5%)a
Control N
NP
NK
NPK
Mean
LSD (5%)a
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
4.41 3.33 3.52 1.69 1.56 1.18 1.9 1.56
5.88 5.22 4.35 3.46 3.08 2.62 2.25 2.51
6.46 5.99 5.09 4.02 3.48 3.52 2.83 3.86
6.33 5.48 4.96 3.88 3.27 2.97 2.95 2.8
6.45 6.41 5.38 4.81 3.8 4 3.51 4.14
5.94 5.29 4.66 3.57 3.04 2.87 2.69 2.97
0.38 0.27 0.71 0.72 0.37 0.14 0.49 0.55
3.1 2.24 3.19 1.94 0.98 1.05 0.93 1.53
4.41 4.21 4.14 3.08 2.57 1.65 1.44 2.28
4.98 4.76 4.61 3.64 3.25 2.52 1.83 3.61
4.69 4.49 4.33 3.38 2.93 2.01 2.79 3.41
5.28 5 4.85 4.37 3.57 3.06 3.14 3.89
4.49 4.14 4.35 3.28 2.66 2.06 2.03 2.75
0.17 0.27 0.61 0.56 0.36 0.1 0.38 0.45
Mean
2.39
3.67
4.41
4.08
4.81
3.87
1.02
1.87
2.97
3.65
3.5
4.15
3.22
0.98
a
For fertilizer application at respective location.
R.L. Yadav / Field Crops Research 81 (2003) 39±51 Table 5 The PFP (kg grain kg locations in India Locations
1
45
applied fertilizer) of applied N, P and K in rice and wheat in the rice±wheat system on farmers ®eld at different
Rice
Wheat
PFPn Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
49 34.8 36.2 28.8 38.5 26.2 27.9 25.1
Mean
33.3
PFPp
13.7 5.4 11.2 8.4 9.7 2.9 10.2 4.3
44.9 23.2 28.4 21.8 23.9 43.7 33.8 52 34.0
PFPk
29.8 12.5 15.3 18.2 21.1 11.7 38.2 5.7
18.8 5.3 12.6 13.2 11.8 8.9 43.8 9.2 15.5
The increase in yield due to NK applications were not as great as that obtained with NP applications. On average, NK application increased the yields over the control by 70% in rice and 81% in wheat. At different locations, these advantages varied from 44% in Ludhiana to 152% in Banda for rice, and 36% in Samastipur to 201% in Ranchi for wheat. 3.2. PFP The PFP of applied N (PFPn), in rice ranged between 21 kg grain kg 1 N in Ranchi and 58.7 kg grain kg 1 N in Ludhiana (Table 5). In rice, mean PFPn, however, was the largest (49 kg grain kg 1 N) in Ludhiana and the lowest (25.1 kg grain kg 1 N) in Raipur. In wheat, PFPn ranged between 5.8 kg grain kg 1 N in Ranchi and 43 kg grain kg 1 N in Rampur. In wheat, the mean of PFP, however, was the largest (36.2 kg grain kg 1 N) in Ludhiana and the lowest (13.8 kg grain kg 1 N) in Banda. When averaged over locations, PFPn was greater in rice (33.3 kg grain kg 1 N) than in wheat (24.6 kg grain kg 1 N). The PFP for applied P (PFPp), when averaged over locations, was 33.96 kg grain kg 1 P in rice and 30.3 kg grain kg 1 P in wheat. PFPp in rice, however, ranged between zero in Samastipur and 148 kg grain kg 1 P in Ludhaina (Table 5). In wheat, PFPp ranged between 4.6 kg grain kg 1 P in Karnal and 100.5 kg grain kg 1 P in Ranchi. At different locations, greatest PFPp (52.0 kg grain kg 1 P) was noted in Raipur and the lowest (21.8 kg grain kg 1 P) in Faizabad. In wheat, the greatest PFPp (62.8 kg grain kg 1 P) was
PFPn
31.3 2.8 3.9 12.8 14.6 11.0 27.3 6.1
36.2 28 34.6 25.6 21.4 13.8 14.4 22.8
PFPp
4.6 2.8 8.3 7.6 6.4 1.5 9.8 6.5
24.6
11.7 16.7 18.3 21.7 26.3 33.6 62.8 51.2 30.3
PFPk
8.7 14.4 8.4 13.6 11.9 6.9 27.3 12.5
11.5 6 4.1 9.3 11.2 7.5 19.2 7.5
5.9 7.3 2.8 11.0 7.4 8.6 13.2 2.8
9.5
noted in Ranchi, and the lowest (11.7 kg grain kg 1 P) in Ludhiana. PFP of applied K (PFPk) was found to be negative in a few farmers' ®elds for rice in Ludhiana, Samastipur and Ranchi and for wheat in Ranchi and Raipur (Table 5). When averaged over locations, PFPk was found to be 15.45 kg grain kg 1 K for rice and 9.5 kg grain kg 1 K for wheat. The greatest PFPk was 43.8 kg grain kg 1 K for rice, and 19.2 kg grain kg 1 K for wheat was measured in Ranchi and the lowest which is 5.3 kg grain kg 1 K for rice and 4.1 grain kg 1 K for wheat was noted in Rampur. 3.3. AE of fertilizer NPK The AE of applied N (AEN), in general, was greater in rice (10.9 kg grain kg 1 N) than in wheat (8.6 kg grain kg 1 N). A negative AEN was also noted for both crops in Ranchi (Table 6). Maximum AEN of 28.81 kg grain kg 1 N in rice and 17.33 kg grain kg 1 N in wheat was observed in Samastipur. AE of applied P (AEP), in general, was greater in wheat (35.1 kg grain kg 1 P) than in rice (33.2 kg grain kg 1 P). In both the crops, AEP was greater in Ranchi than in other locations. However, the lowest AEP was noticed in Samastipur for rice (1.47 kg grain kg 1 P), and in Rampur for wheat (8.79 kg grain kg 1 P). AE of applied K (AEK), in general, was greater in rice (16.5 kg grain kg 1 K) than in wheat (11.8 kg grain kg 1 K). A negative AEK was also noted in rice in Ludhiana. The mean AEK across districts revealed
46 Table 6 The AE (kg grain kg India Locations
R.L. Yadav / Field Crops Research 81 (2003) 39±51
1
nutrient) of applied N, P and K in rice and wheat in the rice±wheat system on farmers' ®eld at different locations in
Rice
Wheat
AEn Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
12.3 12.6 6.9 14.7 12.9 14.0 4.3 9.5
Mean
10.9
AEp
5.5 1.6 3.3 5.5 5.8 1.2 3.7 1.5
24.4 28.3 12.8 35.9 31.4 48.0 32.9 51.7
AEk
16.9 10.1 6.8 12.6 20.0 9.0 34.1 9.9
33.2
7.7 8.8 8.9 24.7 19.8 11.0 42.6 8.9
AEn
8.6 7.0 5.6 6.4 7.8 4.0 15.3 3.7
16.6
10.9 13.1 7.9 9.5 9.9 5.0 5.2 7.5
AEp
2.6 2.6 2.7 4.7 2.8 1.3 4.7 1.7
8.6
that the greatest AEK was found in Ranchi for rice and in Faizabad for wheat.
28.3 15.2 15.8 38.3 24.7 40.3 61.3 57.0
AEk
8.6 3.9 5.3 16.6 4.3 5.3 29.1 11.0
35.1
12.4 4.9 7.3 22.8 9.9 11.2 17.5 8.8
2.9 2.8 5.2 12.6 2.1 2.5 4.1 2.5
11.9
3.4.2. On PFP The PFPn was signi®cantly in¯uenced by SOC and available NPK contents in both crops (Table 8). The PFPp on the other hand, was negatively in¯uenced by soil fertility parameters in wheat. The PFPp in rice, however, was not in¯uenced by soil fertility parameters. The PFPk was also not in¯uenced by soil fertility status, except that available N had a negative in¯uence on PFPk in rice.
3.4. Effect of SOC and available NPK contents 3.4.1. On-yield in control plots Grain yield in control plots (Y0) was in¯uenced signi®cantly by SOC and available NPK contents as indicated by signi®cant positive correlation coef®cients (Table 7). The linear regression, however, was very strong for available P (R2 0:44, 0.323 for rice and wheat, respectively) and weak for SOC (R2 0:113, 0.178 for rice and wheat, respectively) (Table 7). Amongst the four soil fertility parameters studied in this investigation, yield was in¯uenced in the most as per the following preferential order:
3.4.3. On AE of applied NPK The AEN in rice was in¯uenced signi®cantly by SOC content (Table 9). Available NPK contents in soils, however, did not in¯uence AEN in rice signi®cantly. But in wheat, AEN, was in¯uenced signi®cantly by SOC, available P and K contents. The AEP showed negative correlations with SOC, and available
available P > available K > N > SOC:
Table 7 Correlation coef®cients (r) and regression constants (a, b) coef®cients showing between linear relationship Y a bX, where Y is yields in controls plots (Y0) and SOC, and X is either or available N, P and K contents as per the case Soil parameters
r
Rice SOC Available N Available P Available K
0.34 0.53 0.66 0.55
Wheat SOC Available N Available P Available K
0.42 0.49 0.56 0.5
b
t-stat
R2
P-value
1265 1922 1579 783
3076.75 32.56 53.38 8.41
3.05 5.39 7.57 5.56
0.113 0.285 0.440 0.298
0.0032 >0.0001 >0.0001 >0.0001
658 1328 1313 671
3057.61 23.98 36.2 6.16
3.97 4.88 5.89 4.99
0.178 0.246 0.323 0.255
0.0002 >0.0001 >0.0001 >0.0001
a
R.L. Yadav / Field Crops Research 81 (2003) 39±51
47
Table 8 Correlation coef®cients (r) and regression constant (a, b) indicating extent of relationship y a bX between PFP of applied fertilizer N, P and K in rice and wheat, and SOC and available NPK contents (based on 81 observations in farmers ®elds across districts in India) Soil parameters
PFP in rice
PFP in wheat
N
P **
SOC (%) Available N (kg ha 1) Available P (kg ha 1) Available K (kg ha 1)
K
0.34 0.50*** 0.67*** 0.47***
0.19 0.21 0.05 0.11
N 0.12 0.26 0.24 0.18
P ***
0.40 0.46*** 0.54*** 0.48***
K 0.4 0.35 0.35 0.39
0.11 0.21 0.21 0.17*
*
Signi®cant at 0.05 level of probability. Signi®cant at 0.005 level of probability. *** Signi®cant at 0.0001 level of probability. **
Table 9 Correlation (r) and regression (a, b) coef®cients for relationships of AE of applied N (AEN), P (AEP) and K (AEK) with SOC and available N, P and K contents Soil parameters
r
a
b
t-stat
R2
P-value
AEN Rice SOC Available N Available P Available K
0.28 0.11 0.17 0.15
5.48 6.54 9.12 8.22
10.514 0.026 0.056 0.009
2.539 0.918 1.496 1.26
0.081 0.011 0.029 0.021
0.0136 0.3612 0.1390 0.2116
Wheat SOC Available N Available P Available K
0.25 0.19 0.26 0.3
4.97 3.14 6.92 4.94
7.295 0.036 0.067 0.015
2.194 1.624 2.31 2.714
0.062 0.035 0.068 0.092
0.0314 0.1086 0.0237 0.0083
AEP Rice SOC Available N Available P Available K
0.15 0.16 0.37 0.35
41.56 53.64 41.47 51.21
22.541 0.158 0.499 0.089
1.281 1.352 3.441 3.164
0.022 0.025 0.140 0.121
0.2041 0.1803 0.0010 0.0023
Wheat SOC Available N Available P Available K
0.39 0.4 0.42 0.51
64.7 96.72 47.89 66.69
64.147 0.434 0.607 0.139
3.655 3.721 3.989 5.021
0.155 0.159 0.179 0.257
0.0005 0.0004 0.0002 >0.0001
AEK Rice SOC Available N Available P Available K
0.38 0.55 0.44 0.59
37.05 76.02 26.69 42.7
42.109 0.412 0.433 0.111
3.482 5.691 4.195 6.236
0.143 0.307 0.194 0.348
0.0008 0.0000 0.0001 >0.0001
Wheat SOC Available N Available P Available K
0.13 0.29 0.23 0.37
15.71 27.15 14.82 20.14
6.829 0.103 0.109 0.033
1.087 2.55 2.015 3.393
0.016 0.082 0.053 0.136
0.2806 0.0128 0.0475 0.0011
48
R.L. Yadav / Field Crops Research 81 (2003) 39±51
negative at four locations in rice (i.e. Karnal, Faizabad, Samastipur and Banda) and at ®ve locations in wheat (i.e. Ludhiana, Rampur, Faizabad, Banda and Raipur). Positive values, wherever they existed, were very low.
Table 10 Native nutrient supplying capacity of the soil (kg grain kg 1 available nutrients in the soil) for producing grain yields of rice and wheat in different locations in India Locations
Rice N
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur S.E.
Wheat P
K
N
P
3.6. Economic analysis
K
36.3 22.6 29.3 14.1 25.6 12.2 23.6 15.6
20.5 5.1 15.6 14.1 7.5 4.3 0.9 0.3
11.1 3.5 3.7 11.5 8 2.1 1.2 0.3
25.3 14.9 26.7 16.2 11.5 8.8 9.2 15.3
16.6 1.5 2.5 16.6 1.6 6.7 1.5 5.8
0.9 1.1 3.2 13.5 1.3 3.7 1.7 1.3
0.3
0.8
0.5
2.8
1.2
0.5
The mean data over farmers' ®elds for each location indicated that application of complete doses of fertilizer NPK resulted in signi®cantly greater net returns compared to the control and other fertilizer application treatments (Table 11). Compared to N alone, the net returns from NPK application were greater by 22% in Ludhiana, 28% in Karnal, 28% in Rampur, 68% in Faizabad, 55% in Samsatipur, 144% in Banda, 218% in Ranchi and 126% in Raipur. The NR from application of N alone, however, were greater than that in the control by 51% in Ludhiana, 118% in Karnal, 34% in Rampur, 195% in Faizabad, 119% in Samastipur, 625% in Banda, 74% in Ranchi and 119% in Raipur. The differences in net returns from fertilizers NP and NPK were 5.5% in Ludhiana, 7.2% in Karnal, 6.5% in Rampur, 30.6% in Faizabad, 14.3% in Samastipur, 25.1% in Banda, 91.2% in Ranchi, and 9.9% in Raipur. Marginal analysis of different fertilizer application treatments for each location (Table 12) indicated that the greatest marginal pro®ts either from N alone or from NPK application, were observed in Samastipur, and from the NP treatment in Karnal, Rampur and Ranchi.
N, P and K contents. The AEK in rice and wheat exhibited negative correlations with SOC and available NPK contents (Table 9). 3.5. Native nutrient supplying capacity of the soil The NNSCS for N was positive at all the locations, and was greater in rice than in wheat (Table 10). The NNSCS for P, however, was negative in four districts for both rice (i.e. Karnal, Faizabad, Samastipur and Banda) and wheat (i.e. Ludhiana, Faizabad, Banda, and Raipur). At places where, NNSCS for P was positive, the values were very low except for rice in Ludhiana and Rampur. The NNSCS for K was also
Table 11 Total CC (Rs. ha 1) and net returns (Rs. ha 1) from the rice±wheat rotation under different treatments of fertilizer N, P and K application in different districts of India Locations
CC
NR
Controls
N
NP
NK
NPK
LSD (5%)
Controls
N
NP
NK
NPK
LSD (5%)
Lundhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
12 665 12 215 12 215 11 135 10 373 9 083 9 083 9 083
14 575 14 603 14 125 13 045 11 965 10 834 10 516 10 675
14 826 15 027 14 459 13 370 12 241 11 142 10 766 11 013
14 813 15 079 14 601 13 361 12 202 11 270 10 694 10 991
15 063 15 503 14 935 13 675 12 478 11 578 10 944 11 325
218 402 309 211 318 212 195 187
21 454 13 056 18 645 5 758 1 095 1 163 3 538 5 197
32 301 28 566 25 036 17 005 13 901 8 442 6 167 11 361
37 390 34 109 30 191 21 900 18 803 16 483 10 266 23 417
35 351 30 555 28 054 19 960 16 274 11 384 15 779 18 026
39 445 36 569 32 147 28 592 21 489 20 625 19 634 25 727
1001 723 515 628 496 712 699 622
Mean
10 732
12 542
12 856
12 876
13 188
8 738
17 847
25 070
21 923
28 029
R.L. Yadav / Field Crops Research 81 (2003) 39±51 Table 12 Marginal analysis (%) of fertilizer N, P and K application versus control (no fertilizer) in the rice±wheat rotation at different locations in India Locations
Fertilizer application N
NP
NK
NPK
LSD (5%)
Ludhiana Karnal Rampur Faizabad Samastipur Banda Ranchi Raipur
568 649 335 589 804 416 163 387
737 749 515 722 948 744 400 944
647 611 394 638 830 634 760 672
750 715 496 899 969 780 865 916
38 27 41 56 61 22 85 36
Mean
489
720
648
799
On average, farmers earned Rs. 4.98 Re 1 invested for N alone, Rs. 7.20 Re 1 invested for NP, Rs. 6.48 Re 1 invested for NK and Rs. 7.99 Re 1 invested for NPK. The pro®t per rupee invested for N alone, however, ranged from Rs. 8.04 in Samastipur to Rs. 1.63 in Ranchi, on NP application from Rs. 9.48 in Samastipur to Rs. 4.00 in Ranchi, or NK application from Rs. 7.60 in Ranchi to Rs. 3.94 in Rampur and on NPK application from Rs. 9.69 in Samastipur to Rs. 4.96 in Rampur. 4. Discussion The results have shown that, at all the locations, yields were signi®cantly greater in plots receiving N, NP, NK, NPK treatments compared to the un-fertilized control plots. Among fertilized plots, greatest yields, however, were obtained in those plots receiving complete doses of NPK. In the control plot where fertilizer were not applied, yields (i.e. Y0) were signi®cantly greater in Ludhiana, Karnal, and Rampur compared to that in Banda, Faizabad, Samastipur, Ranchi and Raipur (Table 4). These differences, in yield between the high productivity zone (i.e. Ludhiana, Karnal and Rampur) and the low productivity zone (i.e. Banda, Samastipur, Faizabad, Ranchi and Raipur), were primarily because of the differences in climatic conditions of the locations (Aggarwal and Kalra, 1994), date of transplanting/sowing of rice±wheat (Yadav et al., 1998a,b) and infra-structure development in
49
the area (Ladha et al., 2000). In Ludhiana, Karnal and Rampur, a high productivity zone, environmental conditions are suited to wheat cultivation, the irrigation infra-structure is good for cultivating rice, native soil fertility status is higher (Table 3) and use of fertilizer NPK inputs is greater (see Section 2.1). The low yields recorded in Faizabad, Samastipur, Banda, Ranchi and Raipur, a low productivity zone, were associated with un-irrigated lands and rainfed situations, shorter growing period due to delayed transplanting/sowing beyond optimum recommended dates in the middle of June for rice and between 10 and 15 November in wheat (Table 2, Yadav et al., 1998a,b), and low status of native soil fertility especially P and K (Table 3) because of sub-optimum input use and land degradation status. Many parts of this region are saline/sodic and suffer from waterlogging (Aggarwal et al., 2000). The skewed distribution of land and higher incidence of crop-sharing tenancy arrangements in Faizabad, Samastipur, Banda, Ranchi and Raipur, where farmers are generally reluctant to purchase fertilizer inputs for their crops, may also be responsible for low yields in these districts (Ladha et al., 2000). Under such complex situations of multiple constraints in the low productivity zone, the easiest way of increasing yields is through timely transplanting/sowing of crops, as each day's delay in sowing beyond the optimum dates results in a 50 kg ha 1 reduction in yields (Aggarwal et al., 2000). Timely rice transplanting maybe ensured by providing irrigation support to farmers through exploitation of un-tapped underground water potential by digging shallow tube-wells in the area, and wheat maybe zero-tilled soon after the rice harvest to avoid further delay in preparation of the seedbed for wheat sowing (Gupta et al., 2000). It appears that in the higher productivity zone, apart from favorable conditions for crop growth, continuous use of high fertilizer doses might have resulted in increased yields. These improved yields could also be associated with production of large stubbles and root biomass, which when decomposed add to the total organic matter content of the soil. Probably because of this, native soil fertility in the high productivity zone is showing a gradual build up (Yadav, 2001). The response of crops to applied fertilizer N, P and K was smaller in the high productivity zone compared to that in the low productivity zone. In the high
50
R.L. Yadav / Field Crops Research 81 (2003) 39±51
productivity zone, at recommended levels of application, rice yielded 21.8 kg grain kg 1 P and wheat 19.9 kg grain kg 1 P. This response increased in the low productivity zone to 40 kg grain kg 1 P in rice and 44.3 kg grain kg 1 P in wheat. Earlier, Yadav et al. (1998b) obtained 40 kg grain kg 1 P in rice and 74 kg grain kg 1 P in wheat at Faizabad. The response to K application in the high productivity zone was 8.5 kg grain kg 1 K in rice and 8.2 kg grain kg 1 K in wheat. The response increased to 21.4 kg grain kg 1 K in rice and 14.0 kg 1 K in wheat in the low productivity zone. Regarding the N response, both crops yielded 10.6 grain kg 1 N in the high productivity zone, but in the low productivity zone, rice yielded 11.1 kg grain kg 1 N and wheat yielded 7.4 kg grain kg 1 N. Adhikari et al. (1999) observed 10±12 kg grain kg 1 N in farmers' ®elds in Nepal and Bangladesh while Cassman et al. (1996b) obtained 15±18 kg grain kg 1 N in well managed on-station experiments in the Philippines. It may thus be inferred that the crops response to applied NPK decreased when Y0 increased. Y0 was highly dependent on native soil fertility status. The four soil fertility parameters, i.e. SOC, and available N, P and K contents evaluated in the present study contributed 48.9% variation in the Y0 of rice, and 38.6% variation in the Y0 of wheat as per following equations: in rice; Y0 70:41
706:09SOC 10:97N
40:36P 2:40K;
R2 0:489
on NPK, were greater in the low productivity zone. Farmers earned additional Rs. 6.54 Re 1 invested in complete doses of NPK in the high productivity zone compared to Rs. 8.86 Re 1 in the low productivity zone. The marginal pro®ts from NP treatments were Rs. 6.67 Re 1 in the high productivity zone compared to Rs. 7.52 Re 1 in the low productivity zone. Thus, it maybe inferred that in the low productivity zone, all the three nutrients, NPK are required to be applied at recommended rates to earn greater pro®ts, whereas in the high productivity zone, despite heavy K removal resulting in a decline in available K (Yadav et al., 1998a), additions of K through fertilizers has not been a pro®table proposition in the rice±wheat system probably because of replenishment of available K from the nonexchangeable pool and added K through irrigation water. Since the nonexchangeable fraction is a potential source of available K and contributes more than 50% of total K uptake in the rice±wheat system (Tiwari et al., 1992), signi®cant K releases from this pool can mask the dynamics of the initial pool of available K. This is particularly true in alluvial soils, such as those of the Indo-Gangetic plains, with high K-®xing capacity owing to the presence of ellite as the dominant clay mineral (Tandon and Sekhon, 1988). Potassium thus always remained readily available to meet requirements of crop plants, but the soil was eventually depleted of available K under the rice± wheat system (Yadav, 2001). The negative or very low NNSCS in the present study (Table 10) may also indicate the same.
(16) in wheat; Y0
197:52 866:26SOC 8:13N 23:75P 1:00K;
2
R 0:386 (17)
As far as the economics of fertilizer N, P and K is concerned, it was observed that at all the locations complete doses of NPK resulted in signi®cantly greater net returns compared to the control, and other combinations of fertilizer N P and K. It was interesting to note that wherever the CC was greater, such as that in the high productivity zone, net returns were also larger. Although net returns from complete NPK doses were greater in the high productivity zone, marginal pro®ts, i.e. additional pro®t earned per rupee invested
5. Conclusions and recommendations Crop yields in this study varied from location to location and within location from ®eld to ®eld. Even then, the entire rice±wheat area maybe categorized in two distinct productivity zones: a high productivity zone located west of 808E longitude, comprising trans- and upper-Gangetic plains of IGPR including Punjab, Haryana and Western Uttar Pradesh; a low productivity zone located east of 808E longitude comprising middle- and lower-Gangetic plain of IGPR which includes eastern Uttar Pradesh, Bihar and West Bengal, and then states outside IGPR, i.e. Jharkhand and Chattisgarh. Although response to fertilizer application was highly location speci®c, in general in the
R.L. Yadav / Field Crops Research 81 (2003) 39±51
high productivity zone, where fertilizer application rates are already very high, current recommended fertilizer rates were not as pro®table as that were in the low productivity zone. Research must therefore focus on improving fertilizer-use ef®ciency by developing improved agronomic methods such as raisedbed planting in the high productivity zone. In the low productivity zone, improved information on timing of transplanting/sowing crops and use optimum recommended rates of fertilizer NPK for high yields and marginal pro®t should be made widely available to farmers. Acknowledgements I am thankful to the Chief Agronomist and ECF Agronomists of Cropping Systems Research at PAU, Ludhiana, GBPUAT, Pantnagar, NDUA and T Faizabad, CSAUA and Kanpur, RAU, Samastipur, IGKV Raipur for HAU, Karnal for conducting on-farm experiments in their areas of jurisdiction and providing data. References Adhikari, C., Bronson, K.F., Pnuallah, G.M., Regmi, A.P., Saha, P.K., Dobermann, A., Olk, D.C., Hobbs, P.R., Pasuqnin, E., 1999. On-farm soil N supply and N nutrition in the rice± wheat system of Nepal and Bangladesh. Field Crop. Res. 64, 273±286. Aggarwal, P.K., Kalra, N., 1994. Analyzing the limitations set by climatic factors, genotype and water and nitrogen availability on productivity of wheat. II. Climatically potential yields and management strategies. Field Crop. Res. 38, 93±103. Aggarwal, P.K., Talukdar, K.K., Mall, R.K., 2000. Potential yields of rice±wheat systems in the Indo-Gangetic plains of India. In: Proceedings of the Rice±Wheat Consortium Paper Series 10,
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Rice±Wheat Consortium for the Indo-Gangetic Plains, IARI Campus, Pusa, New Delhi, India. Cassman, K.G., Gines, G.C., Dizon, M.A., Samson, M.I., Alcantara, J.M., 1996b. Nitrogen use ef®ciency in tropical lowland rice systems: contribution from indigenous and applied nitrogen. Field Crop. Res. 47, 1±12. Chaudhary, M.K., Harrington, L.W., 1993. The Rice±Wheat Systems in Haryana: Input±Output Trends and Sources of Future Productivity Growth. CIMMYT, Mexico, DF, C.C.S. Haryana Agricultural University Regional Research Station, Karnal. Cocharn, W.G., Cox, G.M., 1957. Experimental Designs. Wiley, New York. Gupta, R.K., Hobbs, P.R., Ladha, J.K., Prabhakar, S.V.R.K., 2002. Resource Conserving Technologies: Transferring the Rice± Wheat Systems of the Indo-Gangetic Plains. Asia-Paci®c Association of Agricultural Research Associations, APAARI Publication, Bangkok, pp. 42. Ladha, J.K., Fischer, K.S., Hassain, M., Hobbs, P.R., Hardy, B. (Eds.), 2000. Improving the Productivity and Sustainability of Rice±Wheat Systems of the Indo-Gangetic Plains: A Synthesis of Nars±Irri Partnership Research. IRRI Discussion Paper Series No. 40. International Rice Research Institute, Makati City, Philippines, 31 pp. Page, A.L., Millar, R.H., Keeney, D.R., 1982. Methods of Soil Analysis. Part 2. American Society of Agronomy/Soil Science Society of America, Madison, WI. Tandon, H.L.S., Sekhon, G.S., 1988. Potassium Research and Agricultural Production in India. Fertilizer Development Consultancy Organisation, New Delhi. Tiwari, K.N., Dwivedi, B.S., Subba Rao, A., 1992. Potassium management in rice±wheat cropping systems. In: Pandey, R.K. (Ed.), Rice±Wheat Cropping Systems, PDCSR, Modipuram, India, pp. 94±114. Yadav, R.L., 2001. On-farm experiments on integrated nutrient management in rice±wheat cropping systems. Exp. Agric. 37, 99±113. Yadav, R.L., Prasad, K., Gangwar, K.S., 1998a. Analysis of ecoregional production constraints in rice±wheat cropping system. Bulletin No. 98-2. Project Directorate For Cropping Systems Research, Modipuram, Meerut, India, 73 pp. Yadav, R.L., Yadav, D.S., Singh, R.M., Kumar, A., 1998b. Longterm effects of inorganic fertilizer inputs on crop productivity in a rice±wheat cropping systems. Nutr. Cyc. Agroecosyst. 51, 193±200.