在中国东北稻区，肥料氮去向与施氮量间的关系以及残留氮的去向目前仍不清晰。为此本研究田间小区和¹⁵N微区试验，分别设置0、75、105、135和165 kg N/hm²五个施氮水平，对应处理为N0、N75、N105、N135和N165。微区试验在2017年施用¹⁵N标记尿素，2018年施用等量的普通尿素。分析了氨挥发、淋洗、地表径流、水稻产量以及植物和土壤中氮含量和¹⁵N丰度变化情况。结果表明，水稻产量与氮肥施用量呈线性平台关系，最佳施氮量为135 kg N/hm²；水稻氮吸收量随着氮量的增加而增加，差减法氮肥吸收利用率（RE_N）在2017年和2018年平均分别为45.23%和56.98%。2017年施氮量为135 kg N hm²时RE_N最高，2018年RE_N受施氮量影响不大，而氮量超过135 kg N hm²时氮肥农学利用率（AE_N）和氮肥生理利用率（PE_N）显著降低。在中国东北稻区肥料氮氨挥发、淋洗和径流的损失较少。2017年和2018年氨挥发量分别占总施氮量的0.81%和2.99%，氮通过淋洗和径流的损失比例分别为4.45%和不到1.05%，东北稻区表观反硝化损率失约为42.63%。2017年0-40cm土层中残留氮量为18.37-31.81 kg/hm²，残留率为19.28-24.50%。土壤中¹⁵N肥料的残留量随施氮量增加而增加，残留氮主要集中在0-10cm土层中，占总残留氮的58.45-83.54%，并随深度增加而减少，但0-10cm土层残留氮占0-40cm土层残留氮的比例却随施氮量增加而减少。平均约有5.4%的残留氮在下一季被水稻吸收利用，50.2%流失，44.4%继续残留在土壤中，因此在计算施氮量时应考虑残留氮的数量。考虑到水稻产量与氮效率的平衡，本试验中东北稻区适宜施氮量为105-135 kg N/hm²。

A plot experiment including four treatments, CK (N 105 kg ha-1 as urea, including a basal N application of 35 kg ha-1 and a topdressing N 70 kg ha-1 at turned green stage) and optimized N management (OPT1, OPT2 and OPT3, applied two-thirds, one-third and two-fifths N at jointing stage, respectively, total N 60 kg ha-1), was conducted to evaluate the effects of nitrogen management on growth and N uptake of winter wheat (Triticum aestivum), Dongnong 1, which is the first highly cold tolerant winter wheat in China. Index of population quality, N uptake and yield were determined. The ear-bearing tiller rate was increased by above 12%, and the leaf area index, biomass and N uptake were significantly decreased (P<0.05) at jointing stage. OPT treatments increased the grain to leaf area ratio at heading stage, the dry matter weight and N uptake after heading by 14.3-27.9%, 11.6-28.7% and 118.1-161.8 %, respectively. The yield of the OPT treatments was increased by 14.2-37.5% compared with CK, and there was a significant difference (P<0.05) between CK and OPT1 treatments. Harvest index and N partial factor productivity (PFP, kg grain yield per kg N applied) was clearly enhanced from 0.4 and 35.6 kg, respectively for CK to an average of 0.48 (P<0.05) and 77.6 kg (P<0.05) in the OPT treatments. These results indicated that the optimized N management increased the harvest index, yield and N use efficiency by decreasing the N application rate and postponing N application time, improved wheat population quality, controlled excessive growth in the vegetative stages and increased dry matter and N accumulation rates after heading.