Nitrogen Use Efficiency and ¹⁵N Balance following Incorporation of Greenmanure and Urea in Flooded, Transplanted and Broadcast Seeded Rice

The use efficiency of nitrogen from incorporated greenmanure and urea in flooded rice soil were studied during dry season. Using ¹⁵N labelled Sesbania rostrata, Aeschynomene afraspera and prilled urea, fate of applied N was studied in the field. Broadcast seeded rice yielded significantly lower than did transplanted rice. However, the difference in biological yield was non-significant. ¹⁵N balance study shpwed that N losses from the soil-plant system were significantly higher with urea application than that with greenmanure. More ¹⁵N was retained in the soil from greenmanure than from urea, which indicates incomplete mineralization of N as organic source and supports its higher residual effect than urea.