Crop residue decomposition contributes to soil phosphorus availability by promoting microbial phosphorus transformation

• Crop residue decomposition elevated the soil P bioavailability with quick P release. • The organic P contents were increased at early stage of residue decomposition. • Residue decomposition conduced to higher positive cohesion between P cycling genes and AP. • Residue decomposition shifted microbial P turnover strategies from P acquisition to organic P mineralization. Crop residue decomposition is an effective strategy for reducing phosphorus (P) loss and improving soil P availability, yet the underlying microbial mechanisms remain unclear. This study investigated the microbial mechanisms driving P transformations during a 98-day (d) decomposition of Italian ryegrass residue. The residue decomposition significantly increased soil available P and microbial biomass P, accompanied by higher phosphatase activities. Both inorganic and organic P fractions, including calcium phosphate, pyrophosphate, orthophosphate, and orthophosphate diester were significantly accumulated at 14–28 d decomposition. During the early stage of decomposition, relative abundances of genes involved in organic P mineralization were significantly elevated and positively correlated with phosphatase activities and available P. Genes involved in P uptake and transportation ( ugpC and phnS ) exhibited higher relative abundance with residue addition, whereas genes involved in P starvation response regulation ( phoB and phoR ) and P uptake and transportation ( pstA and phnD ) exhibited higher relative abundance without residue addition. Furthermore, residue decomposition enhanced the positive cohesions among gene compositions, enzyme activities, available P, and organic P fractions. These findings indicate that residue decomposition is associated with shifts in microbial functional gene abundance related to organic P mineralization, which may contribute to increased P availability in acidic paddy soils.