Optimized nitrogen application for maximizing yield and minimizing nitrogen loss in film mulching spring maize production on the Loess Plateau, China

Excessive use of N fertilizers (driven by high-yield goals) and its consequent environmental problems are becoming increasingly acute in agricultural systems. A 2-yr field experiment was conducted to investigate the effects of three N application methods (application of solid granular urea once (OF) or twice (TF), application of solid granular urea mixed with controlled-release urea once (MF)), and six N rates (0, 60, 120, 180, 240, and 300 kg N ha-1) on maize yield, economic benefits, N-use efficiency, and soil N balance in the maize (Zea mays L.) film mulching system on the Loess Plateau. The grain yield and economic return of maize were significantly affected by the N rate and application method. Compared with the OF treatment, the MF treatment not only increased the maize yield (increased by 9.0%-16.7%) but also improved the economic return (increased by 10.9-25.8%). The agronomic N use efficiency (NAE), N partial factor productivity (NPFP) and recovery N efficiency (NRE) were significantly improved by 19.3-66.7%, 9.0-16.7% and 40.2-71.5%, respectively, compared with the OF treatment. The economic optimal N rate (EONR) of the OF, TF, and MF was 145.6, 147.2, and 144.9 kg ha-1 in 2019 and 206.4, 186.4, and 146.0 kg ha-1 in 2020, respectively. The apparent soil N loss at EONR of the OF, TF, and MF were 97.1-100.5, 78.5-79.3, and 50.5-68.1 kg ha-1, respectively. These results support MF as a one-time N application method for delivering high yields and economic benefits, with low N input requirements within film mulching spring maize system on the Loess Plateau.