Assessing the potential for short-duration legumes in South Asian rice fallows. Final Technical Report.
Rice is the most extensively grown crop in South Asia (Bangladesh, India, Nepal, and Pakistan; Sri Lanka is not included in this study), occupying nearly 50 million ha. Much of it is grown in the kharif (rainy) season. A substantial part of this area remains fallow during the rabi (postrainy) season because of several limitations, the prime one being limited availability of soil moisture. Precise estimates of such rice-fallows and their spatial distribution are not available. Since rice is grown on some of the most productive lands of this region, there is substantial scope to increase cropping intensity by introducing a second crop during the rabi season. This project has quantified rice-fallows in South Asia by using satellite image analysis and has documented their spatial distribution. Using geographical information system (GIS) tools, we have overlaid the spatial distribution of the rice-fallows on to the available climatic and soil information data to identify possible strategies to utilize these lands for suitable short-season crops. Satellite image analysis estimated that rice-area during 1999 kharif season was about 50.4 million ha (Table 1). Rice-fallows during the 1999/2000 rabi season were estimated at 14.29 million ha. This amounts to nearly 30% of the rice-growing area. These rice-fallows offer a huge potential niche for legume production in this region. Nearly 82% of the rice-fallows are located in the Indian states of Bihar, Madhya Pradesh, West Bengal, Orissa, and Assam. The GIS analysis of these fallow lands has indicated that they represent diverse soil types and climatic conditions; thus a variety of both warm season legumes (such as soybean, mung bean, black gram, pigeonpea, groundnut) and cool season legumes (such as chickpea, lentil, khesari [lathyrus], faba bean, pea) can be grown in this region. Available soil water-holding capacity (1 m soil profile) for most of these lands ranges from 150 mm to 200 mm. If it is assumed that the soils in these lands are fully saturated during most of the rice growing season, the residual moisture left in the soil at the time of rice-harvest may be sufficient to raise a short-season legume crop. A number of abiotic (soil acidity, salinity, alkalinity, and terminal drought), biotic (diseases and insect pests), and socioeconomic (social unrest, lack of awareness among farmers of legume technologies, and lack of effective policy initiatives to promote legumes, etc.) constraints contribute to the lack of cropping during this period in this region. These will have to be addressed by appropriate research and policy initiatives in addition to developing suitable legume varieties that have targeted adaptation to these rice-fallows.