Effects of Microplastic Pollution on Soil Microbial Functions and Crop Growth in Agricultural Ecosystems

Abstract:

Microplastic pollution has become a pervasive environmental problem globally, and its accumulation in agricultural soils poses potential threats to soil ecosystems and crop productivity. However, the mechanisms by which microplastics affect soil microbial functions and their cascading impacts on crop growth remain unclear. This study investigated the effects of two common agricultural microplastics (polyethylene, PE; polyvinyl chloride, PVC) at different concentrations (0, 0.1, 1, 10 g kg⁻¹ soil) on soil microbial communities, functional genes, nutrient cycling processes, and wheat (Triticum aestivum) growth through a 120-day pot experiment. The results showed that microplastic addition significantly altered soil microbial community composition, with PVC exerting a more pronounced inhibitory effect than PE. High concentrations of PVC (10 g kg⁻¹) reduced bacterial and fungal alpha diversity by 23.6% and 18.9%, respectively, compared to the control. Functional gene analysis revealed that microplastics suppressed the relative abundance of genes involved in nitrogen fixation (nifH), nitrification (amoA), and phosphorus solubilization (phoD), leading to decreased soil available nitrogen (AN) and phosphorus (AP) contents. Moreover, microplastic pollution inhibited wheat root development and photosynthetic efficiency, resulting in a 15.2%–32.7% reduction in aboveground biomass at the highest pollution level. Structural equation modeling indicated that the decline in crop growth was indirectly driven by microplastic-induced changes in microbial functional genes and subsequent alterations in soil nutrient availability. Our findings highlight the negative impacts of microplastic pollution on agricultural soil ecosystems and provide critical insights for assessing and mitigating microplastic risks in agricultural environments.