Deep ploughing in the summer fallow season and optimizing nitrogen rate can increase yield, water, and nitrogen efficiencies of rain-fed winter wheat in the Loess Plateau region of China

BACKGROUND: About 60% of the annual precipitation in the Loess Plateau occurs during the summer fallow season, and does not align with the wheat growing season. In addition, the nitrogen use efficiency is low in this area because nutrient availability is affected by drought. As a result, rainwater storage during the summer fallow season is very important to increasing nitrogen use efficiency, and to the stable production of dryland wheat in the Loess Plateau. METHODS: A 3-year field experiment in the eastern part of the Loess Plateau was conducted with two tillage methods (no tillage (NT) and deep ploughing (DP)) and five N rates (0, 120, 150, 180, and 210 kg N ha(−1)) to study the effect of tillage on soil water utilization, plant nitrogen utilization, and wheat yield. RESULT: Compared to NT, DP showed a larger increase in soil water storage (SWS(f)) and precipitation storage efficiency (PSE(f)) during the two dry summer fallow seasons than in the normal summer fallow season. DP substantially increased the pre-anthesis soil water consumption (SWC(pre)) and N translocation. The average yield under DP was 12.46% and 14.92–18.29% higher than under NT in the normal and dry seasons, respectively. A 1 mm increase in SWC(pre) could increase grain yield by 25.28 kg ha(−1), water use efficiency (WUE) by 0.069 kg ha(−1) mm(−1), and nitrogen utilization efficiency (NU(t)E) by 0.029 kg kg(−1). DP could reduce the N rate by 11.49–53.34% in the normal seasons and 40.97–65.07% in the dry seasons compared to the same highest point of yield, WUE, and NU(t)E under NT. CONCLUSION: Deep ploughing in the summer fallow season, paired with optimized N application, could help increase wheat yield and nitrogen efficiency in dryland.