The effect of tillage on nitrogen use efficiency in maize (Zea mays L.) in a ridge–furrow plastic film mulch system

The widely adopted maize planting pattern of ridge–furrow plastic film mulch (RFPM) in rainfed agricultural areas of the Loess Plateau has resulted in water-saving and increased yields. However, tillage practices used before RFPM may have had varying effects on the spatiotemporal dynamics of surface fertilizers and soil nutrients. To date, no studies have investigated the combined effects of tillage type and RFPM on crop performance. A two-year trial incorporated three treatments—conventional flat planting (CK), rotary tillage before RFPM (MR), and plow tillage before RFPM (MP). Within each treatment plot, a micro-plot was established to trace the fate of urea-N (only 15N labeled in 2017 and 2018). This study aimed to explore the effects of two tillage practices before RFPM on urea-N recovery by crops, crop growth, and water use efficiency. The RFPM significantly improved soil hydrothermal conditions during maize growth—the ridges had lower surface soil moisture contents than the furrows, with more moisture accumulation in the furrows—but water use efficiency did not differ between MR and MP. The spatial distribution of nutrients under RFPM differed between the two tillage practices. The ridges under RFPM had significantly higher soil organic matter (SOM) and total nitrogen (TN) than the furrows, more so in the MP furrows than the MR furrows. Soil NO₃ ⁻-N did not significantly differ between ridges and furrows, but MP improved nitrogen use efficiency and significantly reduced N₂O emissions, relative to MR. At harvest, MP had significantly higher yields than MR and CK, and the highest net income of the three treatments. In conclusion, plow tillage before RFPM had better economic and ecological benefits than rotary tillage and has the potential to help establish sustainable agricultural systems in dryland China.