Abstract: Urea ¹⁵N fertilizers were applied at different stages of rice growth to the soil mulched with half decomposed rice straw in which rice plants were grown on upland condition to study the distribution of ¹⁵N in different parts of rice plant. Results indicated that plant Ndff% (percentage of nitrogen content from nitrogen in fertilizer), ¹⁵N uptake, ¹⁵N use efficiency and ¹⁵N remained in soil were significantly affected by timing of ¹⁵N application treatments and 15 N rates. Maximum Ndff% was obtained with the ¹⁵N topdressing at tillering stage, and the minimum was found in the treatment of ¹⁵N applied as basal fertilizer. The minimum and maximum of total ¹⁵N use efficiency by the plant were 5.58% and 51.53%, and those remained in soil were 13.81% and 29.87%.

Key words: rice, upland cultivation, fertilizer use efficiency, nitrogen

摘要： 在模拟田间条件下的水泥池（微区）内，用半腐解秸秆覆盖旱作水稻，两个水平的15N标记尿素分别作基肥、分蘖肥和穗肥施用，研究了不同时期施用的15N在水稻各部位的分配、15N的利用率和土壤植株系统的氮素平衡。结果表明植株氮素含量中来自肥料氮的百分比（Ndff%）、水稻对15N的吸收和利用率以及15N的土壤残留率因标记肥料的施用时期和用量的不同而有很大差异。分蘖肥的15N在水稻各部位中的Ndff%最高，而作为基肥施入的15N在水稻体内的Ndff%最低。植株对氮肥利用率的最低和最高值分别为5.58%和51.53%，氮肥的土壤残留率最低和最高值分别为13.81%和29.87%。

关键词: 水稻, 旱作, 肥料利用率, 氮素