Aiming at the low water use efficiency in rain-fed farmlands of the semi-arid region in Northwest China, this study explored the effects of ridge-furrow intercropping (RFIC) of maize and soybean on soil hydrothermal conditions, crop yield and water utilization, and clarified its advantages in optimizing crop growing environments and improving water use efficiency.

A two-year consecutive located field experiment was conducted from 2023 to 2024 in Yangling, Shaanxi, a typical rain-fed agricultural area in the semi-arid zone of Northwest China. Four planting patterns were set up, including sole maize (SM), sole soybean (SS), conventional intercropping with a maize-soybean row ratio of 2:4 (IC), and ridge-furrow intercropping (RFIC), where maize was planted in furrows and soybean on ridges with the same row ratio as IC. Soil temperature, soil water content, soil evaporation, crop photosynthetic physiology, leaf area index (LAI) and dry matter accumulation were measured during the growing period. Grain yield was determined at harvest. Land equivalent ratio (LER), water use efficiency (WUE) and water equivalent ratio (WER) were calculated to comprehensively evaluate the performance of different planting patterns in crop production and water utilization.

Compared with IC, RFIC significantly increased maize LAI (by 8.5%), net photosynthetic rate (by 7.2%), and dry matter accumulation (by 10.4%). Relative to SM and SS, RFIC significantly increased maize yield without causing a significant reduction in soybean yield. The LER ranged from 1.14 to 1.18, indicating improved land-use efficiency under RFIC. By reshaping surface microtopography, RFIC reduced non-productive evaporation; during the maize jointing stage, soil water content in the 0-20 cm layer under RFIC was significantly higher than that under IC by 11.2% and 6.8% in 2023 and 2024, respectively. Although RFIC did not reduce total water consumption, WUE increased by 7.9%-9.2% relative to IC. Over the two years, the WER ranged from 1.06 to 1.18, demonstrating more effective water use under RFIC.

Overall, compared with IC, RFIC created a more favorable early-season growth environment by reducing surface-layer evaporation and improving the thermal regime during early growth stages. Under RFIC, maize-having a competitive advantage-achieved higher yield, while interspecific competitive suppression of soybean was alleviated, thereby enhancing overall land-use efficiency. Given the increasing global constraints on land and water resources, RFIC showed promise for optimizing cropping systems and promoting sustainable agricultural development in Northwest China.