Polyethylene and Polylactic Acid Microplastics Reshape Soil Phosphorus Cycling by Modulating Microbial Function and Aggregate Stability in Maize‐Growing Soil

ABSTRACT Microplastics (MPs) are increasingly recognized as pervasive soil contaminants with the potential to disrupt soil biogeochemical processes and ecosystem functioning. Phosphorus (P), an essential yet often limiting nutrient in agroecosystems, may be sensitive to MPs inputs, while the mechanisms governing MPs‐induced alterations in soil P‐cycling remain poorly understood. In this study, we conducted a pot experiment to evaluate the impacts of polyethylene (PE) and polylactic acid (PLA) MPs (at 0.1% and 1%, w/w) on maize ( Zea mays L.) growth, soil aggregate structure, microbial community assembly, and the expression of functional genes associated with P‐cycling. Both PE and PLA MPs consistently suppressed maize growth and reduced the contents of available P (by 7.0%~28.0%) and microbial biomass P (by 10.7%~46.7%). MPs addition promoted the transformation of middle macroaggregates into large macroaggregates and improved soil aggregate stability. MPs also induced a functional reassembly of the soil microbial community, characterized by the selective enrichment of specific bacterial ( Actinomycetota and Pseudomonadota ) and fungal ( Basidiomycota and Ascomycota ) taxa. In response to MPs‐induced P starvation, microbial communities exhibited enhanced organic P mineralization, with increases of 20.3%~44.9% in associated functional potential. Multivariate analyses identified microbial community diversity, plant growth performance, and soil aggregate stability as potential factors associated with soil P‐cycling under MPs exposure. Results of this study provide mechanistic insights into how MPs alter soil P‐cycling through coupled changes in microbial functioning and soil structure in agroecosystems.