Intercropping legume promotes sustainability of production through remodeling rhizosphere microbial community structure and soil properties in walnut.

Introduction: Intercropping is a critical agricultural practice that enhances farmland biodiversity and productivity. While extensive research has been conducted on legume-nonlegume intercropping systems, studies focusing on rhizosphere microbial communities in walnut-soybean intercropping systems remain limited.Methods: This study used a five-year-old walnut orchard in the Loess Plateau of Northwest China as the research site and systematically compared the effects of two planting patterns-intercropping with legumes (walnut-soybean) and bare inter-row (walnut monoculture)-on the rhizosphere soil health status and microbial community structure.Results: In the field experiment, intercropping significantly increased soil organic matter (SOM), microbial biomass carbon and nitrogen content, as well as the activities of key enzymes such as beta-glucosidase. However, concentrations of some nutrients, including total nitrogen (TN) and total phosphorus (TP), were reduced. Significant differences were observed in the composition and abundance of fungal and actinomycete communities between the two planting modes. Notably, the relative abundances of Mortierellomycota (fungi) and Proteobacteria (actinomycetes) were significantly higher under the intercropping pattern than under monoculture. Mantel analysis indicated that the actinomycete community was only extremely significantly correlated with SOM, while the fungal community was significantly correlated with both TN and SOM. Network analysis further revealed that actinomycete groups exhibited more frequent interactions and a significantly higher level of network complexity compared to fungi. Moreover, intercropping significantly enhanced soil multifunctionality, with actinomycetes identified as the key functional drivers.Conclusion: Walnut-soybean intercropping improves soil health and ecological functions by modifying soil properties and regulating microbial community dynamics. This study provides a theoretical basis and practical guidance for the sustainable management of walnut orchards in the Loess Plateau region of Northwest China.