Year-round film mulching system with monitored fertilization management improve grain yield and water and nitrogen use efficiencies of winter wheat in the dryland of the Loess Plateau, China

Year-round film mulching in winter wheat field facilitates rainwater storage in summer fallow period and reduces water evaporation in growing reason, and then increases water use efficiency in the dryland of the Loess Plateau, China. Optimized fertilization further promotes fertilizer utilization efficiencies. In this study, plastic film mulching was extended from plant growth season to summer fallow, and fertilizers were applied by monitoring soil nutrient availability. Field trials were conducted in the dryland of the Loess Plateau over 4 years by using four types of cultivation to investigate the effects of year-round plastic film mulching with monitored fertilization on utilization efficiencies of rainwater and nitrogen (N), and winter wheat yield. The four types of cultivation were farmer practice (FP), ridge-furrow with plastic film mulching system plus conventional fertilization(RPCF), ridge-furrow with plastic film mulching system plus monitored fertilization (RPFM), and flat soil surface with plastic film mulching system plus monitored fertilization (FPFM). Our results indicate that the average yield of winter wheat in RPFM and FPFM treatments was 4491 kg ha⁻¹. Compared with FP treatment, the combined effects of monitored fertilization and film mulching(RPFM and FPFM treatments) could increase grain yield in the range of 24.7 to 42.1%. The film mulching extended to the fallow season increased the water storage in 2 m depth of soil profile, and the amount of soil water storage in the summer fallow period increased by 27 to 30% in FPFM treatment than FP treatment. After 4-year consecutive planting of wheat, the accumulation of nitrate-N in 2 m soil reached 277 kg·ha⁻¹ in the FP treatment, which is 87.7% higher than of the level at the beginning of the experiment. Seventy-five percent of nitrate-N was distributed in the soil layer of 0–120 cm. In addition, the residual nitrate-N showed downward leaching with rainfall during the experiment. The RPFM and FPFM treatments reduced the apparent loss and residual levels of soil N, whereas increased its apparent mineralization compared with FP treatment. The FPFM treatment exhibited a greater utilization of residual nitrate-N from previous years and showed a higher amount of the mineralized N from soil organic matter, therefore leading to a relatively high apparent utilization rate of N (56.7%). Considering both grain yield production and utilization efficiencies of water and N, FPFM with year-round mulching was the most effective cultivation measure for winter wheat in the Loess Plateau.