旱地土壤硝态氮与氮素平衡、氮肥利用的关系

利用长期肥料试验资料研究了土壤氮素平衡、氮肥利用率和土壤硝态氮之间的相互关系。结果表明，小麦不同施肥处理的氮肥利用率（NUE）为30.9%~65.8%，平均53.6%；土壤硝态氮累积率2.3%~44.1%，平均13.2%；氮素表观损失率25.0%~42.7%，平均33.2%。一般情况下，氮素盈余值与氮肥用量呈正相关，与磷肥用量呈负相关；土壤中硝态氮的数量与氮素盈余值呈正比，与氮肥利用率呈反比。黄土旱塬地区，小麦在经济合理施氮条件下，氮素盈余值为13.79 kg/hm2，硝态氮累积量为23.00 kg/hm2，说明过量施用一定数量的氮肥对保持作物生产力和土壤氮素营养是必要的。

Relationship between soil nitrate, nitrogen balance and utilization in rainfed land

Based on the long-term field experiments, the relationships between soil nitrogen balance, nitrogen utilization efficiency (NUE) and soil nitrate were studied. The results show NUE of wheat is 30.9%–65.8% with an average of 53.6%, soil nitrate accumulation rate is 2.3%–44.1% with an average of 13.2%, and apparent nitrogen loss rate is 25.0%–42.7% with an average of 33.2%. In general, there is a positive correlation between nitrogen balance value and nitrogen fertilizer application rate, while the correlation for phosphorus fertilizer application is negative. Soil accumulated nitrate is positively related to the nitrogen balance value and negatively related to NUE. Nitrogen balance value is about 13.79 kg/hm², and nitrate accumulated amount is about 23.00 kg/hm² in the condition of economic rational fertilization for wheat production in rainfed lands of the Loess Plateau. It is showed that a rational rate of nitrogen overuse is necessary for keeping crop productivity and soil nitrogen supply.