Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore - 641003, India.
Although fertilizer use is probably the easiest means of counteracting the pace of nutrient depletion, the spiraling cost, wide occurrence of multi-nutrient deficiencies and environmental degradation from inefficient use of fertilizers warrant the use of alternate sources atleast as supplement though not as substitute. Green manures seem to be an attractive alternate source to meet a substantial portion of the rice N requirement and provide organic matter to wetland rice soils. N substitution of 60–100 kg N ha−1 has been obtained by green manuring to rice. Yield responses of high yielding rice cultivars to green manures in India ranged from 0.65 to 3.1 t ha−1. An increase in soil nitrate ranging from 73 to 223 kg N ha−1 within a period of 90 days of greengram cropping. The use of green manures for improving the soil productivity and as a source of N has been recognized from early times in rice growing areas. The research findings on the effect of green manuring on rice yield, N economy and soil fertility have been reviewed.
