Abstract: The multiple microsplit experiment of ¹⁵N-labeled urea were carried out at the CNRRI in 1987. When N applied as basal, N uptaked by rice plants was no significant difference under different N applied level, the N recovery in soil decreased, and N losses increased significantly with the increase of N applied. N applied as basal combined with P,K has no significant effect on the fate of N, basal dressing of urea with a moderate amount of straw increased the N efficiency and recovery in soil, and reduced the N losses. N efficieny of topdressing was higher than basal dressing. Fertilizer N uptaked by rice plants substantially increased with the technique for deep placement of urea topdressed in rice field with reftooding. It is shown that this technique is one of the most economical and practical techniques.

Key words: Rice, Urea, 15N-labeled, Fate of nitrogen, Deep placement of N fertilizer, Rice straw

摘要： 1987年在中国水稻研究所试验场应用15N示踪技术进行了多处理的田间微区试验。结果表明： 氮肥作基肥使用时，水稻对N素的吸收利用率差异不显著，而随着施用量的增加，在土壤中的N素残留率降低，而氮肥损失率显著提高；基肥配施PK肥对肥料N的去向无显著影响响，但配施适量稻草有助于提高水稻对肥料N的吸收量和土壤残留量，降低氮索损失；氮肥的使用期对肥料15N去向的影响十分显著，追肥的K素利用率比基肥高。稻田采用以水带氮施肥技术能明显地提高水稻的氮素吸收，增加土壤残留率和减少氮素损失，表明此技术是一项合理的稻田氮肥深施技术。

关键词: 水稻, 尿素, 示踪技术, 氮素去向, 氮肥深施, 稻草