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.