INTEGRATED NITROGEN MANAGEMENT WITH GREEN MANURES IN RICE-CHICKPEA CROPPING SYSTEM

A field experiment was conducted during wet and dry seasons of 1987-88 and 1988-89 to evaluate the performance of green manures with and wit hout fertilizer nitrogen in lowland rice and their residual effect on succeeding crop of chickpea grown under rice-chickpea cropping system. Incorporation of Ipomea carnea (green leaves), Cassia tora and Parthe nium hysterophorus (green young plants) ca. 5 t/ha fresh weight signif icantly improved yield and yield components namely panicles per hill, panicle length, grains per panicle and test weight of transplanted ric e. The results showed that at least 20 kg/ha fertilizer nitrogen appli ed to rice could be replaced by incorporation of 5 t/ha fresh weight g reen manure. Supplementation of 60 kg N/ha through urea to the green m anures treated plots proved to be the best in respect of grain yield a nd was comparable to the yield obtained under 80 kg N/ha as urea alone . Plant N-uptake followed the similar pattern of rice grain yield. Res idual fertility in terms of available nitrogen increased under the gre en manure treatments, whereas urea nitrogen alone made no impact on fe rtility build-up. Green manures showed significantly higher residual r esponse than fertilizer N alone to seed yield and N uptake of chickpea .