In this paper, the relations of nitrogen application at four stages with different amounts to accumulation of protein in brown rice were studied by soil cultivation and 15N tracing technique. The results showed that applying N at booting stage was most favourable to the accumulation of protein in brown rice and the ratio of 15N protein朜 in brown rice to applied 15N reached 36.15%. This effect of applying N before transplanting took second place, and those at tillering stage and milk stage were relatively disappointed. The results also demonstrated that, under the condition of fixation of N application at the rest 3 stages, 15N applied at one stage was significantly linearly correlative with 15N protein朜 in brown rice, but the relation between N application amount at all 4 stages and total protein-N in brown rice presented a parabolic curve, because of the decrease of brown rice yield and the descent of protein-N content under the condition of excessively applying N.%采用土培试验和15N示踪技术研究了高产施肥条件下4个时期不同施氮量与水稻糙米蛋白质含量的关系。结果表明，孕穗期施氮最有利于糙米蛋白质的积累，糙米15N蛋白氮占施用15N的比例达36.15%，插植前施氮次之，分蘖期和乳熟期施氮效果较差。当其它3个时期施氮量一定时，某个时期的15N施量与糙米15N蛋白氮含量呈极显著的直线相关，但4个时期的施氮总量与糙米蛋白氮总量却呈一元二次抛物线关系，其原因是过量施氮使糙米产量和糙米中蛋白质含量下降。
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