Potato–Soybean Intercropping Increased Equivalent Tuber Yield by Improving Rhizosphere Soil Quality, Root Growth, and Plant Physiology of Potato

Potato–legume intercropping has been confirmed to increase productivity in modern agricultural systems. However, the physiological and ecological mechanisms of potato–soybean intercropping for promoting tuber yield formation in potato remain unclear. Field experiments were conducted in 2022 and 2023 to explore the responses of tuber yield formation, rhizosphere soil quality, root growth, and plant physiology of potato in potato–soybean intercropping. The soil at the experimental site is Cambisols. The treatments included sole cropping potato, sole cropping soybean, and potato–soybean intercropping. Our results indicated that potato –soybean intercropping decreased the water content, increased the total K content and activities of urease and catalase in rhizosphere soil, and enhanced the root mean diameter, root projected area, and root length density in the 0–5 cm and 15–20 cm soil layers of potato. Moreover, potato–soybean intercropping improved the plant photosynthetically active radiation and light transmittance rate of the middle and lower layers as well as the leaf area index, enhanced the leaf chlorophyll b content and ribulose-1,5-diphosphate carboxylase/oxygenase activity, and increased the leaf net photosynthetic rate and organ dry matter accumulation amounts of potato. The changes in the above parameters resulted in an increased tuber weight per plant (19.4%) and commercial tuber number (42.5%) and then enhanced the equivalent tuber yield of potato (38.2%) and land equivalent ratio (1.31 in 2022 and 1.33 in 2023). Overall, potato–soybean intercropping greatly increased the equivalent tuber yield by improving the rhizosphere soil quality, root growth, and plant physiology of potato and then achieved a higher land equivalent ratio.