The objective of this field study was to determine the N application rate which would both maximize yield and protect the environment in a wheat-maize rotation district of the Guanzhong Plain, Shaanxi Province. The study included six treatments replicated three times: N0 (no N application to either wheat or maize), N1 (113 kg N/hm² to wheat + 135 kg N/hm² to maize), N2 (150 kg N/hm² to wheat + 180 kg N/hm² to maize), N3 (188 kg N/hm² to wheat + 225 kg N/hm² to maize), N4 (225 kg N/hm² to wheat + 270 kg N/hm² to maize), and N5 (300 kg N/hm² to wheat + 360 kg N/hm² to maize). The study was conducted over 1.5 yr (maize-wheat-maize). The effects of N application rate on crop yield, N fertilizer use efficiency, apparent N loss, and N budget in the 0-100 cm depth were determined. The results showed that annual crop yield and cumulative crop yield both increased and then decreased as N application rate increased. In contrast, cumulative N agronomic efficiency, apparent N utilization, N uptake efficiency, and N partial productivity decreased significantly as N application rate increased. Calculation of the N budget in the 0-100 cm depth showed that residual mineral-N concentrations were significantly higher in the N2 treatment than in the N1 treatment, but apparent N loss and loss rates were nearly the same in the two treatments. In contrast, residual mineral-N concentrations were nearly the same in the N3, N4, and N5 treatments, but apparent N loss and loss rate increased significantly in the order N3 < N4 < N5. Regression and correlation analysis indicated that excessive N fertilizer application resulted in the build-up of mineral-N concentrations in the deep soil profile. This build-up contributed significantly to apparent N loss. In conclusion, the application of 150 kg N/hm² to wheat and 180 kg N/hm² to maize resulted in relatively high yield and N use efficiency. These application rates also maintained residual mineral-N concentrations and reduced apparent N losses.