Plastic film mulch reshapes rhizosphere microbial drivers of phosphorus cycling and affects P resource sustainability in dryland maize

Plastic film mulch (PM) increases crop yield and nutrient use efficiency in arid regions by improving soil water and rhizosphere conditions. However, its impacts on microbially mediated phosphorus (P) bioavailability and soil P pools in dryland spring maize remain unclear. A field experiment (2019–2022) on the Loess Plateau with two P input (with/without) and two mulching (with/without) regimes was conducted to investigate the effects of PM on maize yield and rhizosphere bacterial and fungal communities. Results showed that PM increased maize yield by 14% and 11% and aboveground P uptake by 18% and 13% under P-unfertilized and P-fertilized conditions, respectively. PM increased bacterial alpha diversity, shifted community composition toward Proteobacteria, and reduced the relative abundance of Actinobacteriota, while bacterial assembly remained predominantly stochastic. In contrast, PM decreased fungal alpha diversity, with Ascomycota remaining the dominant phylum at both the V3 and V10 stages. Under P-unfertilized condition, PM weakened bacterial network connectivity and robustness but increased network size and centralization. Conversely, under P-fertilized conditions, PM induced contrasting patterns in fungal networks. PM also restructured microbial assemblages associated with soil available P, favoring functionally beneficial taxa (e.g., Proteobacteria) and genes (e.g., pqqC , gcd, based on functional prediction). Lastly, path analysis indicated that PM indirectly promoted the mobilization and depletion of soil available P through the suppression of enzyme activities and reorganization of microbial functional groups. These findings underscore the potential of optimized plastic mulch management in dryland agriculture, while emphasizing the importance of dynamic soil P monitoring to maintain long-term P sustainability.