Nitrogen fertilization effects on nitrogen balance and use efficiency for film-mulched maize in a semiarid region

Efficient nitrogen (N) applications are crucial for sustainable agricultural development. A three-year field study was conducted to evaluate the effects of N fertilization on soil NO3-N contents, N balance, grain yield, and N use efficiency of film-mulched maize (Zea mays L.) in the semiarid northwest China. Six N levels were examined: 0 (N0), 100 (N100), 200 (N200), 250 (N250), 300 (N300), and 400 (N400) kg N ha−1. Results showed that residual soil NO3-N contents after harvest and apparent N losses markedly increased with increased N fertilizer rate. High accumulations of soil NO3-N were detected in the 80–200 cm layers in the N300 and N400 treatments in 2010 and 2011, indicating that excessive N applications resulted in NO3-N leaching in this semiarid region. The N use efficiency decreased with increased N fertilizer rate, but insignificant differences in agronomic efficiency, apparent recovery efficiency, and physiological efficiency were observed between N100, N200, and N250 treatments. Maize grain yields increased with N fertilization, but it did not further increase when N application was higher than plant N requirements. A linear plateau relationship was observed between grain yield and N supply (fertilizer N plus initial soil NO3-N in the 0–100 cm layers). The minimal N supply rate required to obtain the maximum yield (13.9 Mg ha−1) was 279 kg N ha−1, which was similar to plant N uptake and simultaneously reduced apparent N losses. We conclude that N fertilizer recommendations which consider soil NO3-N contents can simultaneously provide sufficient N for high yields and improve N fertilization of film-mulched maize in the semiarid areas.