Integrated nitrogen management with in-situ green-manuring and urea application in wetland rice (Oryza sativa)

Abstract

A field experiment was carried out during 1988 and 1989 to study the effect of integrated nitrogen management using in-situ green-manuring with prickly sesban or dhaincha [Sesbania cannabina (Retz.) Pers., syn S. aculeata Pers. vat cannabina Baker] and urea N for a cropping sequence rice (Oryza sativa L.)-fallow-rice. Urca was applied to supply 60 and 120 kg N/ha in 3 splits, alone or with green-manuring, to supply 20 tonnes/ha green matter (equivalent to 60 kg N/ha). There was response only up to 60 kg N/ha applied as urea. Green-manure + 60 kg N/ha as urea was comparable to 120 kg N/ha in terms of grain and straw yields. The effect of green-manure compared with chemical fertilizer (urea) varied from 44 to 51 %
and increased the rice yield by 40% compared with 120 kg N/ha. Green-manuring + urea increased the N uptake, apparent recovery and N -use efficiency by 36, 67 and 101% compared with urca alone at 120 kg N/ha. There was no residual effect of fertilizer N, whereas the effect of green-manuring was Significant, giving 33-44% more grain yield and 20-29% straw yield compared with urea.