Abstract:Based on an eight-year long stationary field experiment on Weibei Arid Tableland in Shaanxi Province, China, effects of Nitrogen (N) application rate on grain yield and nitrogen utilization, N residual, nitrate leaching and organic N mineralization in dryland soil were investigated with winter wheat as test crop. The experiment was designed to have 5 N application rates, i.e. 0, 80, 160, 240 and 320 kg hm-2. Results show that with increasing N application rate, the response of wheat in yield to N application weakened, whereas nitrate N residue in the soil rapidly increased. The nitrate N residue from the current wheat growing season was mainly distributed in the 0 ~ 60 cm soil layers, and when N application rate was raised beyond 160 kg hm-2, it reached up to 56.8 ~ 211.7 kg hm-2 in content of which 64% ~ 90% was found derived from the N fertilizer applied before seeding. Depth of the soil layer where leaching of nitrate occurred and amount of the nitrate N leached from the corresponding layer during the summer fallow season were all positively and parabolically related to N fertilizer rate, (r = 0.988 9 and 0.994 0). When N application rate went beyond 160 kg hm-2, every increment of 100 kg hm-2 of N would increase the depth of nitrate leaching by 27 cm and the amount of nitrate N leached off by 80.4 kg hm-2. On average, every 10 mm of rainfall during the summer fallow season would have nitrate N leached 2 ~ 4 mm deeper. However, N application rate did not have much effect on depth of nitrate leaching. During the summer fallow season, soil N mineralization reached 51.8 ~ 160.9 kg hm-2 of which 31.6 ~ 109.2 kg hm-2 was found to be N from the fertilizer applied for the current crop, fixed by soil microbes and then remineralized. Based on such findings, it is advisable to suggest that the N application rate for winter wheat in the region should be controlled within the range of 146~163kg hm-2, so as to guarantee high winter wheat yields, and prevent excessive residue of fertilizer N in the soil and reduce the risk of nitrate N leaching.