INFLUENCE OF NEEM OIL-COATED UREA AND MAXICAN LILAC (GLIRICIDIA-SEPIUM) AS GREEN-MANURE ON TRANSFORMATION OF SOIL-NITROGEN IN RICE (ORYZA SATIVA)-WHEAT (TRITICUM-AESTIVUM) SYSTEM IN TYPIC HAPLUESTERT

A study was carried out to evaluate the influence of neem oil-coated u rea and green-manure on N-use efficiency and transformation of organic fractions of soil nitrogen and their residual effect under rice (Oryz a sativa L.)-wheat (Triticum aestivum L. emend. Fiori & Paol.) system in Vertisol. Application of neem oil-coated urea and lac-coated urea i ncreased the grain yield of rice respectively by nearly 15 and 16%, wi th a residual effect of 41 and 48% compared with prilled urea. Incorpo ration of green-manure through mexican lilac (Gliricidia sepium L.) al so increased the grain yield of both the crops. The coating of neem oi l on urea increased the N-use efficiency by 13.8%. Application of N th rough neem oil-coated urea anti lac-coated urea and the incorporation of green-manure to rice increased the total hydrolyzable N, amino acid N, amino sugar N, hydrolyzable ammonia N, hydrolyzable unidentified N and non-hydrolyzable N. Their application after wheat reduced the ami no acid N, amino sugar N and hydrolyzable ammonia N, but their level w as more than under prilled urea and the initial level. Incorporation o f mexical lilac increased the hydrolyzable unidentified N after rice a s well as wheat. Correlation studies between different fractions of or ganic N and yield and the uptake of rice and wheat indicated that tota l hydrolyzable N, amino sugar N, hydrolyzable ammonia N and amino acid N are the active components of the available pool of nitrogen in the plant.