中文摘要：

【目的】研究华北平原耕层水氮调控对小麦利用土壤深层累积硝态氮的影响。【方法】设置0、150kgN·hm-22个氮水平和传统灌溉、优化灌溉2种灌水方式,共4个处理：不施氮传统灌溉（N0W1）、不施氮优化灌溉（N0W2）、施氮传统灌溉（N150W1）、施氮优化灌溉（N150W2）。采用15N微区注射技术,布置田间微区试验,将15N标记于110cm土层处。【结果】在本试验条件下,小麦能够吸收注射在110cm处的标记硝态氮;不施氮的传统及优化灌溉、施氮的传统及优化灌溉对深层标记氮的吸收量分别为336.7、900.3、497.4和657.1mg·m-2,利用率分别是8.4%、22.4%、12.4%和16.3%,适当的水氮胁迫有利于小麦对土壤剖面深层标记硝态氮的吸收利用。4个处理80—150cm土层根长密度占总根长密度（0—150cm）的24.4%、32.3%、26.4%和28.2%,氮素不足优化灌溉有利于小麦中下层根系发育。【结论】耕层氮素养分不足及水分适度胁迫促进小麦中下层根系发育,提高小麦对土壤深层硝态氮的利用。

英文摘要：

【Objective】 The purpose of this experiment was to study the effects of topsoil water and nitrogen control on utilization ratio of nitrate accumulated in deep soil by wheat in North China.【Method】 Two N levels including 0,150 kgN·hm-2 and two irrigation methods were designed.There were four treatments：N0W1,N0W2,N150W1,and N150W2.Field micro-plot experiments and the injection technique of labeled NO3--N were adopted.【Result】 Results showed that 15N which was injected into 110 cm soil layers could be absorbed by wheat with the nitrogen uptake of 336.7,900.3,497.4 and 657.1 mg·m-2 and nitrate utilization ratio of 8.4%,22.4%,12.4%,16.3% in four treatments of N0W1,N0W2,N150W1,N150W2.The root length density of 80-150 cm layer was 12.8,10.9,10.6,and 9.7 cm·cm-3 and accounted for 24.4%,32.3%,26.4%,and 28.2% of that of 0-150 cm layer in four treatments of N0W1,N0W2,N150W1,N150W2.Less nitrogen and intensifying irrigation made the roots in subsoil grow better,by which more deep soil nitrate could be assimilated by wheat and then the utilization ratio of nitrate by wheat be improved.【Conclusion】 Less nitrogen and reasonable water stress promoted the distribution of roots to subsoil layers and thus accelerated the absorption of nitrate accumulated in deep soil by wheat.