Organic acid‐mediated microbial influence on soil phosphorus transformation in a maize– <i>Bupleurum chinense</i> intercropping system

Abstract The maize‐ Bupleurum chinense intercropping system improves soil nutrient acquisition, yet the underlying rhizosphere mechanisms remain unclear. This study investigates the phosphorus transformation processes in the soil and compares the functional microbial communities and root exudates of corn and Bupleurum under both monoculture and intercropping conditions to reveal the mechanisms behind the increased yield. In the intercropping system, the available phosphorus content in the rhizosphere soil of maize increased by 18.38%, while the organic phosphorus content rose by 15.85%. Additionally, there was an increase in microbial diversity. Changes in relative abundance were also observed in key phosphorus cycling genes, including gcd , phoA , and phoX . To construct a SynComm, Bacillus velezensis , Bacillus subtilis , and Klebsiella oxytoca , which harbour these genes, were screened. Additionally, distinct differences in organic acid metabolism were evident between the roots of the two intercropped plants, with piperonylic acid, 3‐methyl‐2‐oxobutyric acid, and 4‐oxopentanoic acid identified as key metabolites. Pot experiments indicated that the combination of organic acids and microbial agents stimulated soil phosphatase activity and available phosphorus content (with maximum increases of 224% and 74% respectively for pots containing only soil, and 190% and 92% for pots containing soil and corn plants). The results showed that the intercropping system improved the rhizosphere soil environment for corn by enhancing nutrient availability and optimizing soil metabolic profiles.