Intercropping enhances rhizosphere phosphorus mobilization by increasing plant carbon deposition

Enhancing rhizosphere phosphorus (P) mobilization is a vital strategy for plants to increase P uptake, and intercropping is an important agronomic practice to increase soil P utilization. However, it is not clear how intercropping affects rhizosphere processes involved in P mobilization. Through a 14-year maize/faba bean intercropping field experiment, this study elucidated the effects of intercropping on rhizosphere P availability and its associations with rhizosphere metabolite profiles, microbial community composition, and microbial P mobilization. Intercropping increased rhizosphere available P in maize and faba bean by approximately 16% and 19%, respectively, compared with sole cropping, and increased rhizosphere water-extractable organic carbon by 31% and 63%, respectively. Intercropping changed rhizosphere metabolite profiles and the microbial community assemblage significantly, increasing the contents of metabolites involved in P dissolution and enriching bacterial taxa involved in P mobilization. Rhizosphere P availability, carbon fractions, metabolite profiles, and microbial P-mobilizing taxa were significantly correlated with each other. Specific metabolites that increased under intercropping, such as citric acid, malic acid, and myristic acid, could enhance the growth and P-solubilizing capacity of soil bacteria significantly. These findings demonstrated that maize/faba bean intercropping facilitates crop P utilization through enhancing carbon-mediated microbial P mobilization in the rhizosphere, providing an important theoretical basis for designing P-saving yet efficient green cropping systems and for sustainable P management.