Effect of wheat, legume and legume-enriched wheat residues on the productivity and nitrogen uptake of rice-wheat cropping system and soil fertility

Field experiments were conducted for two crop years at the Indian Agricultural Research Institute, New Delhi to study the effect of enriching wheat residue with legume residue on the productivity and nitrogen uptake of a rice-wheat cropping system and soil fertility. The incorporation of wheat residue had an adverse effect on the productivity of the rice-wheat cropping system. When it was incorporated along with <i>Sesbania</i> green manure, not only did its adverse effect disappear but the response to fertilizer N was also increased. There was no response to fertilizer N when <i>Sesbania</i> green manure was incorporated. When wheat residue was incorporated along with <i>Sesbania</i> green manuring, rice responded significantly to fertilizer N up to 120 kg N ha^-1 in the first year and to 60 kgN ha^-1 in the second year and at these levels of N, <i>Sesbania</i> + wheat residue gave 0.8 to 1.2 t ha^-1 more grain, 0.6-1.0 t ha^-1 more straw and 8-15 kg ha^-1 more N uptake of rice resulting in 0.04-0.17% more organic C, 3-8 kg ha^-1 more available P and 17-25 kg ha^-1 more available K content in the soil than wheat residue alone at the same rates of N application. The respective increaseas caused by <i>Sesbania</i> green manure + wheat residue over <i>Sesbania</i> green manure alone were 0.3-0.5 t ha^-1 in the grain and straw yield, 1-9 kg ha^-1 in the N uptake of rice, 0.02-0.10% in organic C, 1-8 kg ha^-1 in available P and 35- 70 kg ha^-1 in available K content in the soil. These treatments also gave higher residual effects in succeeding wheat than wheat residue alone. The incorporation of residues of both wheat and <i>Sesbania</i> is thus recommended to eliminate the adverse effect of wheat residue and to increase the beneficial effects of <i>Sesbania</i> green manuring.