Implementing strip configurations in cotton-soybean intercropping systems improves crop productivity and optimizes land use efficiency

Intercropping improves cotton leaf photosynthesis and nitrogen uptake, ensuring high lint yield. Both intercropping systems are suitable for agricultural mechanization. The 3C5S row ratio configuration increases crop revenue and land use efficiency. Strip configurations play a crucial role in mediating crop productivity and resource utilization in intercropping systems. However, there remains a substantial knowledge gap concerning the mechanization-adaptive strip widths for cotton-soybean intercropping systems. Specifically, understanding how these strip widths can enhance synergies in crop productivity and land use efficiency is imperative. This study evaluated the impact of row ratio (strip) configurations on crop growth, physiology, productivity and land use efficiency in intercropped and monoculture systems. Treatments included two intercropping treatments (two rows of cotton plants alternating with three rows of soybean plants (2C3S), and three rows of cotton alternating with five rows of soybean (3C5S)), and two monoculture controls (monoculture cotton (MC), and monoculture soybean (MS)). Compared with monoculture cotton, the 3C5S system significantly increased both years averaged based chlorophyll content (SPAD value) by 6.64% at the peak boll-setting stage with increased leaf area index (LAI) and canopy photosynthetically active radiation interception ratio (In) during the early flowering stage. Furthermore, at the boll-opening stage, this system further enhanced boll and total plant nitrogen uptake. Intercropping significantly increased cotton boll density by enhancing dry matter translocation to reproductive organs with high lint yield. The 3C5S configuration outperformed 2C3S, increased the land equivalent ratio by 9.2% and net revenue by 15.87% over both years. The PCA results showed stronger relationships between cotton harvest index and other physiological parameters in 3C5S. The Mantel test indicates that yield of cotton-soybean intercropping was closely associated with cotton leaf area index and soybean aboveground biomass. Structural equation modeling identified nitrogen uptake as the key driver of yield in 3C5S. Overall, 3C5S improved crop productivity and land use efficiency compared to both 2C3S and monoculture systems, representing the optimal cotton-soybean intercropping strategy. The 2C3S and 3C5S intercropping systems were designed with a standard 2:1 row spacing (76 cm for cotton and 38 cm for soybean), compatible with mainstream agricultural machinery in China. A 55 cm operational clearance was maintained between crop strips to support fully mechanized sowing and harvesting, thereby reducing labor cost with high production revenue.