Effects of Partial Substitution of Organic Fertilizer for Synthetic N Fertilizer on Yield and N Use Efficiencies in a Semiarid Winter Wheat–Summer Maize Rotation

Finding field management techniques that increase crop output while protecting soil sustainability is essential for maintaining a long-term food supply in a changing environment. However, comprehensive evaluation of the effects of nitrogen (N) reduction combined with organic fertilizer on grain yield, N use efficiency (NUE), water use efficiency (WUE), and soil organic carbon (SOC) and total N (TN) contents of winter wheat–summer maize double cropping systems in drought-prone areas remains limited. Therefore, a 3-year field experiment (2018–2021) was conducted in a winter wheat–summer maize double cropping system with five treatments: no N fertilizer (CK), conventional farmer fertilization (CF), recommended fertilization (R), organic N substitution of 20% of the recommended synthetic N (R20), and organic N substitution of 40% of the recommended synthetic N (R40). When results were averaged from 2018 to 2021, R20 had the highest annual grain yield, which increased by 42.15%, 7.69%, 7.58%, and 12.50% compared with CK, CF, R, and R40, respectively. Compared with CF, R20 increased winter wheat and summer maize NAE, NPFP, NUE, and WUE. In addition, the soil organic carbon content of R20 and R40 treatment increased with the increase in years. In conclusion, R20 was considered ideal for improving crop yield, promoting soil fertility, and increasing the fertilizer utilization rate in a semiarid winter wheat–summer maize rotation.