Transformation of Applied Urea and its Efficient Utilization in Rainfed Lowland Rice (Oryza sativa L.)

摘要

In rainfed lowland direct sown rice basal band placement of urea in seed furrows in solid /solution/suspension form or basal broadcasting and incorporation of urea or deep placement of urea supergranules/mudlumps, improved N availability in soil and significantly increased grain yield and N uptake by the crop over surface broadcasing of urea onto flood water at tillering stage. The apparent recovery oif applied N in rice crop ranged from 41 to 61% with placement and incorporation methods as against 16% with surface broadcasting method. Depletion of total mineral N at placement zone fitted well to a model similar to first order reaction kinetics. The recovery of applied N in flood water and the ratio of nitrate-N to total mineral-N in soil were minimum with deep placement of N. Initial plant vigour was promoted by basal band placement of N.