Effect of Sesbania green-manure and nitrogen fertilizer in rice (Oryza sativa)-wheat (Triticum aestivum) cropping system

An experiment was conducted during 1989-90 and 1990-91 to study the effect of summer green-manuring with 2 species of Sesbania, viz S. cannabina (Retz.) Pers. and S. rostrata Berm., and nitrogen in rice (Oryza sativa L.)-wheat (Triticum aestivum L. emend. Fiori & Paol.) cropping system. S. cannabina added 7.4 tonnes/ha dry biomass containing 186 kg N/ha and S. rostrata added 8.5 tonnes/ha biomass containing 252 kg N/ha. N available to rice crop from S. rostrata was equivalent to 80 kg urea N. Highest rice (7 180 kg/ha) and wheat (3 549 kg/ha) yields were obtained from green-manuring with S. rostrata and 120 kg urea N/ha applied to rice crop. In this treatment the total N removal by rice and wheat crops was 179 kg/ha. This treatment left positive balance of N (270 kg N/ha) in the soil. The mineralization of N added through Sesbania species was most rapid during the first 20 days after transplanting.