A long-term experiment was carried out to investigate the effects of nitrogen fertilizer on the NO3-- N content and distribution in the soil. Six nitrogen application rates of 0, 75, 150, 225, 300 and 375 kg/hm2 were used. The results showed that crop yields increased with N application rate but nitrogen utilization efficiency decreased at the same time. In addition, soil NO3--N content increased with N rates. There were significant downward movements of NO3-- N in the soil profile, especially when the N ra...