Film mulching synergistically enhances water productivity and crop yield in maize-soybean intercropping

Water scarcity and limited arable land availability constrain dryland agriculture, requiring optimized resource allocation to achieve sustainable production. Film mulching and intercropping are widely applied as solutions to water and land constraints in dryland farming, but their synergistic effects and underlying mechanisms remain poorly understood. Therefore, five treatments with different planting patterns were tested in this study: monoculture maize without mulching, monoculture maize with mulching, monoculture soybean without mulching, maize–soybean intercropping without mulching, and maize–soybean intercropping with mulching in the maize strip. The soil water dynamics, crop growth dynamics, root system characteristics and root–shoot coordination, water productivity (WPc), land equivalent ratio (LER), and economic benefits were analyzed. Intercropping with mulching enhanced the resource use efficiency and reduced the risk due to yield variability. Intercropping significantly increased the soil water storage (at 120–200 cm) at harvest, lowering the drought risk compared with monoculture. The system adapted to late-growth water stress through increases in the deep-root density in maize and optimizing the maize–soybean root–shoot ratio, while mulching conserved moisture in the topsoil (0–40 cm) early. Their synergy enhanced WPc by 4.66 % and LER was 1.46. Mulched intercropping also compensated for the yield losses under no mulching, increasing the total production by 10.65–27.75 % and economic returns by 8.10–29.07 %. Intercropping with plastic film mulching can optimize the use of soil and water resources and achieves synergies to establish a sustainable cropping system that facilitates water conservation, yield increases, and efficiency improvements in dryland farming areas.