Microplastics in Agroecosystems: Effects on Soil Microbiome, Nutrient Dynamics, and Fungal Interactions

Microplastics (MPs) have emerged as pervasive contaminants in agricultural soils, posing significant threats to soil health, microbial functionality, and sustainable crop production. This review comprehensively evaluates the sources, characteristics, detection approaches, and functional impacts of MPs on soil ecosystems, with a particular focus on microbiome dynamics, nutrient cycling, and fungal interactions. Major input pathways, including plastic mulching, organic amendments, irrigation, and atmospheric deposition, contribute to MP accumulation, reaching thousands of particles per kilogram of soil. Experimental evidence demonstrates substantial reductions in key enzymatic activities and alterations in carbon use efficiency, indicating impaired microbial metabolism due to mechanistic disruption of soil processes. MPs significantly disrupt nitrogen cycling, causing 15–40% declines in nitrogen fixation, 10–25% inhibition of nitrification, and shifts in functional gene abundance (nifH, amoA). Furthermore, MPs modify soil physicochemical properties and reshape rhizosphere interactions, adversely affecting plant growth and microbial colonization. Fungal systems, particularly basidiomycetes, exhibit altered biomass, reduced mycorrhizal associations, and limited polymer degradation potential, highlighting both ecological risks and bioremediation prospects. Additionally, MP exposure compromises biofertilizer efficiency, reducing microbial viability and root colonization. At the ecosystem level, these impacts may impair soil fertility and crop productivity. The potential transfer of MPs into the food chain raises critical concerns for food safety and human health. Despite growing evidence, major gaps remain in long-term field validation, mechanistic understanding, and methodological standardization, emphasizing the urgent need for mitigation strategies to ensure sustainable agroecosystem functioning.