Extra-short-duration Pigeonpea-Wheat Rotation for Increased Productivity and System Sustainability

Introduction

The introduction of high yielding cultivars of rice ( Oryza sativa. L) and wheat ( Tritcum aestivum L.), and their intensive production technologies since the 1960s have contributed greatly to increased food production in the Indo-Gangetic Plain (IGP). Inevitably, this has lead to large-scale sequential cropping of rice and wheat in millions of hectares, in both traditional and non-traditional areas. However, in recent years growth of rice-wheat cropping system (RWCS) and its profitability is beginning to decline, and there are increasing concerns about its long-term sustainability ( Hobbs and Morris 1996 ). Some recent publications suggest that continuous adoption of RWCS in the same lands seems to be lowering soil fertility, depleting water table in the tube well irrigated areas, and exacerbating weed, disease and pest problems ( See Dahiya et al. 2001 for details ). It has also been suggested that if this system could be appropriately diversified with legumes that are good in fixing atmospheric nitrogen, depend less on irrigation and enrich soil with organic matter, the sustainability of these systems could be better ensured. The ameliorative effects of legumes in the cropping systems are well known to the farmers in the IGP. However, the area under the traditional legume types has been steadily declining because of their low yields, longer life cycle duration and high risks from insect-pests and diseases compared to rice and wheat crops. In recent years, however, a number of high yielding extra-short duration cultivars of several legumes that have resistance to common diseases and pests have been bred. The development of these new plant types with shorter life cycle duration has created a fresh opportunity for the greater inclusion of these legumes in the RWCS. Pigeonpea [ Cajanus cajan (L.) Millsp.] is one such legume in which breeding of high yielding extra-short-duration plant types has been successful (Singh 1996). However, the performance of these cultivars, which mature two to three weeks earlier than short-duration pigeonpea (SDP) cultivars, had not been previously tested. The widespread use of new and improved genetic resources depends a great deal on whether these can improve both productivity and sustainability of the wheat-based system. The information presented herein summarizes the work done from 1995-2000 on testing the potential of new plant types of extra-short-duration pigeonpea (ESDP) in rotation with wheat.

Pigeonpea-Wheat rotation

Since the 1960s the pigeonpea-wheat rotation has been based on SDP cultivars, which replaced rice or other crops in the rainy season. The available SDP cultivars are less acceptable to farmers in the system because they seem to reduce wheat yield in addition to themselves being low yielding and unstable. The need for finding a substitute for SDP in the SDP-wheat rotation system arose because with SDP the system was not finding anticipated growth in adoption and the area was stagnant at about 150,000 ha. The ESDP-wheat rotation is a new production system in which ESDP could replace SDP or a rice crop during the rainy season to overcome some of the limitations with existing pigeonpea-wheat or rice wheat systems.

The Simulated Yield Potential of ESDP vs. SDP and Wheat in Rotation

The yield potential of ESDP and SDP and following wheat crop was determined using the pigeonpea ( Robertson et al. 2001 ) and wheat modules of the Agricultural Production Systems Simulator (APSIM) Model ( McCown et al. 1996 ). The weather data of the nearest meteorological station in Delhi provided the climatic input for the model. The predicated mean yields for the 1995-1998 seasons under non-limiting moisture supplies were about 3.2 t ha -1 for May sowing in 150 days and 2.3 t ha -1 for the June sowing in 125 days ( Fig. 1 ). The maximum predicted yield is close to the maximum realized yield in farmers' fields in the region. The comparable yield potential of SDP was 2.5 t ha -1 for the May sowing in 167 days and 2.2 t ha -1 in about 137 days. The APSIM predicted 4.6 t ha -1 yield of wheat, after both the May and June-sown ESDP crop. The predicted yields of wheat after SDP were 4.3 t ha -1 after the May-sown crop and 3.9 t ha -1 after the June sown crop. The ESDP genotypes took fewer days to mature yet had a greater yield potential than SDP in both sowings. It appears that ESDP genotypes partition more dry matter into pods due to their relatively less photoperiod sensitivity. The simulated yield potential of wheat was also more after ESDP genotype, especially after the May-sown crop, which could be because it permitted sowing at about the optimum time.

Figure 1. The yield potential (t ha -1 ) of extra-short-duration pigeonpea (ESDP) and short-duration pigeonpea (SDP) genotypes and following wheat as predicted by the Agricultural Production Systems Simulator (APSIM) for the Sonepat environment.

Observed Performance of ESDP vs. SDP in Farmers Fields

Farmer participatory on-farm trials were conducted to assess the performance of ESDP in villages located in the vicinity of Sonepat city from 1995 to 2000 in collaboration with the Krishi Vigyan Kendra of Chaudhari Charan Singh Krishi Vishwa Vidyalaya, Harayana at Sonepat (28o N). Sonepat is a typical wheat growing area in the Haryana State of India. Sonepat receives about 650 mm rainfall. Use of SDP Manak was in vogue among farmers prior to the study period. Two ESDP genotypes, ICPL 85010 (determinate), ICPL 88039 (indeterminate) that were to be compared with an SDP cultivar Manak were offered to the farmers for cultivation in their fields in about 0.1 to 0.15 ha each. A pre-sowing irrigation was usually given to each trial site for establishing the pigeonpea crop. The crop was given a basal dose of 18 kg N and 20 kg P ha -1 and a seed rate of 15 kg ha -1 was used. The test genotypes were planted to 40 cm row-to-row and 10-12 cm plant-to-plant spacing. The sowing dates of different trials varied from 25 to 27 June in 1995, 1 May to 18 June in 1996, 8 May to 20 June in 1997, 22 May to 28 June in 1998, 19 May to 22 June in 1999, and 25 May to 15 June in 2000. Fields were hand weeded at about one month from sowing. Intensive plant protection measures were needed in case of ICPL 85010. Additionally, to compare the productivity of ESDP-wheat system with rice-wheat, rice cv. Tarawari Basmati was also grown in four trials during the 1998 and 1999 rainy seasons at a recommended agronomy which included fertilization with 125 kg diammonium phosphate, 125 kg urea and 25 kg ZnSO4, and frequent irrigation to maintain 3-4 cm water at the soil surface throughout the growing season.

The ESDP genotypes out yielded the control cultivar Manak ( Table 1 ). The mean yield advantage in six years of testing was 16% for ICPL 88039 ( Fig. 2 ). The mean yield advantage of ICPL 85010 in three years of testing was 4.4 %. ICPL 85010 being determinate was more attractive to insect infestation and thus required considerable insecticide protection. For this reason, farmers stopped growing it after 1997. The realized yields of ESDP were lower than their predicted potential yield for the IGP environment. Dahiya et al. (2001) have listed a number of biotic, abiotic and socio-economic constraints that could possibly limit the productivity of ESD genotypes in this environment. Their mitigation can help bridge the gap in realized and realizable yields of ESDP and enable it to compete with rice and other crops.

A wheat crop (cv. HD 2329 and PBW 343) was grown in the post-rainy season in each trial. However, its grain yield was recorded in 1997-1999 only. Wheat was sown with a pre-sowing irrigation at 20-cm row-to-row spacing at a seed rate 120 kg ha -1 . A fertilizer dose of 120 kg N and 60 kg P ha -1 was given to the crop. The N dose was split and applied with the first and second irrigation of about 30 to 40 mm each was given at 20 and 40 days after sowing. Additional three irrigations were given at about 3 weeks intervals. The mean yield of wheat over the three seasons was 4.51 t ha -1 after ICPL 88039 compared to 3.79 t ha -1 after Manak and 3.64 t ha -1 after rice ( Table 2 ). The higher yield was mainly due to timely sowings of wheat after ICPL 88039 compared to after Manak, and perhaps due to a legume effect when compared to after rice.

Figure 2. Under normal conditions, the extra-short-duration grow profusely in the Indo-Gangetic Plain posing difficulty in insecticide protection. Genotype ICPL 88039 seems to be less susceptible to pod borers requiring few insecticide sprays.

Table 1. Grain Yield (t ha -1 ) of extra-short-duration genotypes and short-duration pigeonpea cultivars at Sonepat (Haryana).

	ESDP genotypes		SD cultivar
Year	ICPL 85010	ICPL 88039	Manak
1995	1.46±0.103 (4) a	-- b	1.32±0.065 (4)
1996	1.28±0.078 (10)	1.42±0.091 (8)	1.19±0.088 (9)
1997	1.48±0.050 (5)	1.65±0.079 (11)	1.56±0.087 (9)
1998	--	1.20±0.045 (24)	0.90±0.038 (11)
1999	--	1.46±0.039 (15)	1.32±0.073 (10)
2000	--	1.65±0.023 (25)	1.40±0.019 (25)
Mean	1.41	1.48	1.28
CV%	7.83	12.7	17.4
a number of locations; b indicates not tested in that year

 

Table 2. Effect of rice (cultivar Tarawari Basmati), short-duration pigeonpea (cultivar Manak,) and extra-short-duration pigeonpea (genotype ICPL 88039) on the yield of following wheat crop during 1997-1999 at Sonepat, Haryana, India.

	Wheat Yield (t ha -1 )
Cropping Systems	1997 a	1998 b	1999 b	Mean
Rice-Wheat	-	3.58±0.074	3.69±0.078	3.64
SD -Wheat	3.93±0.076	3.67±0.066	3.76±0.062	3.79
ESD -Wheat	4.68± 0.066	4.46±0.061	4.39±0.068	4.51
a wheat (HD 2329) during1997. b wheat ( PBW 343) during 1998-99.

Farmers Perception of ESDP vs. SDP

At the end of the rainy season 2000, 63 small landholder farmers (<3 ha), who had grown ESDP and SDP pigeonpea during the preceding five years were interviewed for their perceptions of the new plant types and the traditional SDP cultivars using a structured questionnaire.

Of the farmers interviewed, 78% indicated that an early maturity of ESDP was a major advantage, 87% suggested that pest damage in ICPL 88039 was lower, 77% indicated that they obtained higher yield of wheat after ESDP as compared to SD cultivar Manak ( Fig. 3 ). Only 53% of the farmers perceived ESDP to have yield advantage over Manak. A small proportion of the farmers who had consumed it found it to have better taste than that of Manak. In general, there was considerable preference of an ESDP type, especially ICPL 88039 than a SDP type.

Figure 3. Collecting fuel-wood and fetching water from far-off places constitute drudgery for rural women. A farming couple discusses how extra-short-duration pigeonpea can reduce wife's burden by providing a ready source of fuel-wood.

Acknowledgements

Thanks are due to Dr SS Dahiya, Scientist, and Dr RS Waldia, Chief Scientist of the Krishi Vigyan Kendra for collaborating in the study; organizing on-farm trials and survey. Thanks are also due to Dr PK Joshi and his team of NCAP who organized the impact assessment survey. This work was partly supported by grants received from the Asian Development Banks for Legume-based Technologies for Rice and Wheat Production Systems in South and Southeast Asia (RETA No. 5711).

Publications prepared from this study:

Dahiya, S.S., Chauhan, Y.S., Johansen, C., Waldia, R.S., Sekhon, H.S. and Nandal, J.K. 2001 Extra-short-duration pigeonpea for diversification of wheat based cropping systems in the sub-tropics. Experimental Agriculture (accepted).

Dahiya, S.S., Chauhan, Y.S., Srivastava, S.K., Sekhon, H.S., Waldia, R.S., Gowda, C.L.L., and Johansen, C. 2001. Growing Extra-Short-Duration Pigeonpea in Rotation with Wheat in the Indo-Gangetic Plain. Natural Resources Management Program Report no.1. Patancheru 502 324, Andhra Pradesh, India: International Crops Research Institute for the Semi-Arid Tropics. 44 pp. (Limited Distribution).

References

Hobbs, P., and Morris, M . 1996. Meeting South Asia's future food requirements from rice-wheat cropping systems: priority issues facing researchers in the post-green revolution era. Natural Resource Group Paper 96-01. Mexico: CIMMYT.

McCown, R.L., Hammer, G.L., Hargreaves, J.N.G., Holzworth, D.P., and Freebairn, D.M. 1996. A novel software system for model development, model testing, and simulation in agricultural systems research. Agricultural Systems 50: 255-271.

Robertson, M.J., Carberry, P.S. Chauhan, Y.S., Rangnathan, R., and O'Leary, G.J. 2001. Predicting growth and development of pigeonpea: a simulation model. Field Crops Research (submitted).

Singh, L. 1996. The development and adoption prospects of extra-short-duration pigeonpea. Pages 1-5 in Prospects for growing extra-short duration pigeonpea in rotation with winter wheat crops: proceedings of IARI/ICRISAT Workshop and Monitoring tour 16-18 October 1995. New Delhi, India. (Singh, L. Chauhan, Y.S. Johansen, C., and Singh, S.P., eds.). New Delhi 110012 India Patancheru 502324, Andhra Pradesh, India: Indian Agricultural Research Institute and International Crops Research Institute for the Semi-Arid Tropics.

For more information please contact:

Dr Chauhan Y S
Senior Scientist
(Crop Physiology),
ICRISAT-Patancheru 502 324.