Optimizing plastic film mulching and organic-inorganic fertilization improves grain yield and water productivity of rainfed spring maize by ameliorating soil conditions

Plastic film mulching and organic-inorganic fertilization are important practices for enhancing crop productivity in rainfed regions, but the comprehensive effects of these measures on the soil environment and crop productivity are unclear. Therefore, we conducted a two-year field experiment by testing two experimental factors: planting methods (flat planting without mulching (FP), flat planting with plastic film mulching (FPFM), and ridge–furrow planting with plastic film mulching (RFPM)) and organic–inorganic fertilizer combinations (100% chemical fertilizer nitrogen (F1), 50% chemical fertilizer nitrogen + 50% sheep manure organic fertilizer nitrogen (F2), 50% chemical fertilizer nitrogen + 50% cattle manure organic fertilizer nitrogen (F3), and 50% chemical fertilizer nitrogen + 50% mushroom residue organic fertilizer nitrogen (F4)). We assessed the effects of planting methods and organic–inorganic fertilization on the soil properties, maize growth, yield, and water productivity. Combining plastic mulching with organic–inorganic fertilization synergistically improved the soil physicochemical properties, increasing the porosity, aggregate stability, organic carbon, and total nitrogen, while reducing the bulk density. These treatments enhanced soil water storage in the 0–100 cm layer (especially 0–40 cm) and sustained the nitrogen supply during late growth stages, promoting root and aboveground development. Consequently, the spring maize yield and water productivity increased significantly, where RFPM combined with F2 generally achieved the highest values. Correlation analysis confirmed that yield improvements were driven by enhanced soil conditions and plant growth. Our findings confirm the importance and complementary beneficial effects of plastic mulching and combined organic–inorganic fertilizer application, providing a theoretical basis for sustainable farmland utilization and high-efficiency, yield-increasing models in rainfed agricultural regions.