Soil phosphorus availability and potential mechanisms of microplastics-polluted soil by corn planting

As a typical pollutant in farmland soils, microplastics and their impact on the biogeochemical cycles of key soil elements have become a focus of current research. However, further investigation is needed to understand how microplastics interfere with soil phosphorus cycling and the regulatory role played by plants. This study was conducted through a 45-day indoor microcosm experiment. The effects of different concentrations (0.1% and 1%, w/w) of polyethylene (PE) microplastics on the growth of maize (Zea mays L.) were investigated; while the differential impacts of PE microplastics under planted and unplanted corn on soil phosphorus availability, activities of key phosphorus-transforming enzymes, and the structure and function of microbial communities were specifically examined. The results show that the addition of microplastics reduces the availability of phosphorus in the soil, particularly decreasing the content of available phosphorus in the planted soil by 17.3% - 27.1%. Furthermore, the presence of corn plants amplifies the inhibitory effects of microplastics on the activities of acid phosphatase, alkaline phosphatase, and phytase in the soil. Microbial community analysis reveals that microplastics significantly alter the structure of soil bacterial communities, resulting in the enrichment of functional taxa such as Pseudomonadota and Actinomycetota, which are positively correlated with phosphorus cycling functional genes. The interaction between corn planting and microplastics also increases the total abundance of functional genes involved in phosphorus cycling, specifically enhancing the relative abundances of phoD, phnP, and pstA. From the perspective of interactions between microbial communities and key environmental factors, this study provides mechanistic insights into how corn plants modulate the influence of polyethylene microplastics on soil phosphorus transformation. The results of this study offer a theoretical basis for assessing the ecological risks of microplastic pollution in agricultural soils.