Response of Maize Yield and Water Productivity to Different Long-Term Fertilization Strategies in Semi-arid Regions in Northern China

The scarcity and uneven distribution of precipitation present significant challenges for agriculture in arid regions. Fertilization can improve crop yields and water productivity (WP) under these conditions. However, the effects of different long-term fertilization practices on maize yield and WP under varying precipitation patterns require further research. A 30-year fertilization experiment was conducted to investigate the effects of different fertilization treatments on maize yield, WP, soil organic carbon (SOC), and the correlations among these factors. The treatments included no fertilization, application of chemical fertilizers alone, combined application of chemical fertilizers and cattle manure, and application of a high amount of cattle manure alone. Chemical fertilizers, cattle manure, and the combined application of chemical fertilizers and cattle manure significantly increased maize yield by 61.81–86.14%, 121.0%, and 114.5–125.5%, and increased WP by 59.4–84.9%, 119.4%, and 111.9–126.5%, respectively, compared to the unfertilized control. The combined application of chemical fertilizers and cattle manure resulted in optimal maize yield and WP, while also substantially reducing the coefficient of variation in maize yield (by 19.9–25.9% compared to the control) under interannual precipitation fluctuations. Compared with the no fertilization treatment, the average increase in maize yield peaks in very wet years, while WP reaches its highest level in relatively dry years. Maize yield was significantly positively related to SOC, WP, and water consumption during growth (p < 0.01). SOC was also significantly positively correlated with WP (p < 0.01). For every unit increase in SOC, the WP increased by 0.3955 kg ha−1 mm−1. In summary, the integrated application of organic and inorganic fertilizers is a proven strategy to enhance crop productivity and resilience, while concurrently improving WP and SOC. This synergistic approach represents a cornerstone for climate-resilient and sustainable dryland agriculture.