[Objective] The purpose of this paper was to estimate the fate of fertilizer N applied to winter wheat under optimum nitrogen (N), phosphorus (P) and potassium (K) rates in north China plain. [Method] A field micro-plot experiment was adopted and high abundance of 15N was applied to wheat in this study. After harvest of wheat, the fate of 15N was measured. [Result] The result showed that about 26.6%-33.6% of the N taken up by winter wheat was derived from the applied fertilizer N, and 66.4%-73.4% of that was derived from the soil. The plant recoveries of N were in the range of 22.11%-32.36%, and soil residual N from applied N fertilizer were ranged in 29.6%-56.3%, of which 60.3%-76.5% centralized in 0-40 cm soil layer, and the amount of fertilizer N residue in soil profile decreased rapidly with the increase of soil depth. [Conclusion] More than 66% of nitrogen absorbed by winter wheat was derived from soil, the nitrogen utilization rate was 28.2% in the first season on average, about 40% of applied fertilizer N were remained in the soil, which might be a necessary supplement for the soil N pool.%[目的]在氮磷钾合理供应前提下,研究华北平原冬小麦肥料氮的去向.[方法]采用微区试验的方法,供给小麦高丰度的15N,在小麦收获时,测定15N的去向.[结果]冬小麦吸收的氮素来自肥料的比例为26.6％33.6％,对土壤氮的依赖程度在66％以上.肥料氮施入土壤后,小麦当季利用率为22.1％-32.4％,当季肥料氮的土壤残留率约占施氮量的29.6％-56.3％,其中60.3％-76.5％集中在0-40 cm土层,在土壤剖面中的残留率随土层深度增加而迅速降低.[结论]小麦生育期吸收的氮素66％以上来自土壤,氮肥当季平均利用率为28.2％,约40％的肥料残留在土壤中,成为土壤氮库的补充.
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