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 ef fect of summer green-manuring with 2 species of Sesbania, viz S. canna bina (Retz.) Pers. and S. rostrata Berm., and nitrogen in rice (Oryza saliva L.)-wheat (Triticum aestivum L. emend. Fiori & Paol.) cropping system. S. cannabina added 7.4 tonnes/ha dry biomass containing 186 kg Nka and S. rostrata added 8.5 tonnes/ha biomass containing 252 kg N/h a. N available to rice crop from S. rostraia was equivalent to 80 kg u rea N. Highest rice (7 180 kg/ha) and wheat (3 549 kg/ha) yields were obtained from green-manuring with S. rostrate and 120 kg urea N/ha app lied to rice crop, in this treatment the total N removal by rice and w heat crops was 179 kg/ha. This treatment left positive balance of N (2 70 kg N/ha) in the soil. The mineralization of N added through Sesbani a species was most rapid during the first 20 days after transplanting.