Optimizing photosynthesis, resource use efficiency, and yield in maize–soybean intercropping through row configurations in Southwest China

Intercropping is widely practiced in Southwest China, but studies on optimizing aboveground light use and enhancing photosynthetic capacity through row configuration to improve productivity remain limited. In this study, a randomized block design was used to systematically compare photosynthetic performance, resource use efficiency, and yield advantages between intercropping and monoculture systems, as well as among different row configurations within the intercropping system. Photosynthesis (Pn), leaf area index (LAI), dry matter accumulation (DMA), and intercepted photosynthetically active radiation (IPAR) of intercropping maize increased by 11.47%, 17.72%, 24.07%, and 9.91%, respectively. Among all configurations, the M2S4 arrangement had the highest average LAI for both maize (3.10) and soybean (2.56). A higher LAI facilitated increased light interception, with IPAR values of 84.78% for maize and 73.67% for soybean, thereby enhancing radiation use efficiency (RUE). Under the M2S4 configuration, both Pn (increased 8.51% in maize and 11.95% in soybean) and DMA (increased 14.95% in maize and 32.67% in soybean) were significantly higher than in other configurations. Improved Pn promoted grain development, resulting in increased maize 1000-grain weight (TGW) by 6.68% and soybean 100-grain weight (HGW) by 6.26%, contributing to higher total yields and improved land equivalent ratios (LER). Furthermore, correlation analysis revealed significant positive relationships among LAI, IPAR, RUE, and LER with yield. Principal components analysis further indicated that the M2S4 configuration had highest overall performance. This study suggests that maize-soybean intercropping under the M2S4 configuration in Southwest China enhanced photosynthetic capacity and optimized resource utilization, leading to improved yield performance.