EFFECT OF SUMMER LEGUMES ON GROWTH AND YIELD OF LOWLAND RICE (ORYZA-SATIVA) AND ITS RESIDUAL EFFECT ON SUCCEEDING WHEAT (TRITICUM-AESTIVUM) IN RICE-WHEAT SYSTEM

Summer cropping of prickly sesban or dhaincha [Sesbania cannabina (Red.) Pers.] for green-manure and of cowpea [Vigna unguiculata (L.) Walp.] for fodder had significant effect on growth. yield and nitrogen uptake of rice crop. Mean data of 2 years showed that green-manure crop (helping produce 5.7 tonnes/ha rice grain) and fodder cowpea (helping produce 4.3 tonnes/ha rice grain) could contribute equivalent to 90 and 60 kg N/ha applied through prilled urea respectively in lowland transplanted rice. The mean yields obtained with 120 kg Nma applied through prilled urea(6.50 tonnes/ha) and dhaincha green-manuring + 30 kg N/ha through prilled urea (6.45 tonnes/ha) were at par. The difference in yield and nitrogen uptake by rice could be attributed to significant difference in ammonium-N of the soil at tillering and panicle-initiation stages, and was significantly positive. Summer cropping of Sesbonia and cowpea significantly increased the yield and nitrogen uptake by the succeeding wheat compared with 120 kg N/ha applied to rice through prilled urea. This could be attributed to significant positive correlation with available soil N at rice harvesting and nitrate production at the time of planting.