Microbial mechanisms underlying enhanced salt tolerance in soybean through sorghum–soybean intercropping

Background and Aims: Intercropping is an effective cultivation practice for enhancing biodiversity in agroecosystems, which can improve soil environment and enhance crop adaptability by regulating rhizosphere microorganisms. However, the rhizosphere microbial regulatory mechanisms underlying the improved salt tolerance of soybean intercropped with salt-tolerant crops remain unclear. Methods In this study, high-throughput sequencing technology was employed to compare the rhizosphere soil physicochemical properties and microbial community structure characteristics under monoculture and intercropping systems of sorghum and soybean under salt stress. Results The results showed that, compared with monoculture, sorghum-soybean intercropping (IS/IG) significantly reduced soil pH and total salt content, while increasing soil organic matter content. The improvement in soil environment effectively promoted soybean growth, with aboveground biomass and net photosynthetic rate increasing by 23.5% and 18.9%, respectively. Meanwhile, intercropping alleviated oxidative damage induced by salt-alkali stress in soybean, with root ABA and H₂O₂ accumulation decreasing by 9.53% and 72.29%, respectively. Principal coordinate analysis (PCoA) of rhizosphere microbial communities revealed that intercropping significantly altered the overall structure of the rhizosphere bacterial community. Differential genus screening showed that beneficial bacterial genera such as Bacillus and Pseudomonas were significantly enriched in the rhizosphere of intercropped soybean. Conclusions Based on these findings, sorghum–soybean intercropping remodels rhizosphere bacterial communities and optimizes saline soil microenvironments, effectively alleviating salt-induced oxidative stress and improving soybean salt tolerance. This study reveals the core microbial mechanism by which intercropping enhances soybean salt tolerance, providing a practical strategy for soybean production in saline soils.