Microplastics in Soil–Plant Systems: Current Knowledge, Research Gaps, and Future Directions for Agricultural Sustainability

With the increasing accumulation of plastic residues in agricultural ecosystems, microplastics (MPs) have emerged as a novel and pervasive environmental risk factor threatening sustainable agriculture. Compared to aquatic systems, our understanding of MP dynamics in agricultural soils—particularly their transport mechanisms, bioavailability, plant uptake pathways, and ecological impacts—remains limited. These knowledge gaps impede accurate risk assessment and hinder the development of effective mitigation strategies. This review critically synthesises current knowledge in the study of MPs within soil–plant systems. It examines how MPs influence soil physicochemical properties, plant physiological processes, toxicological responses, and rhizosphere interactions. It further explores the transport dynamics of MPs in soil–plant systems and recent advances in analytical techniques for their detection and quantification. The role of plant functional traits in mediating species-specific responses to MP exposure is also discussed. In addition, the review evaluates the ecological relevance of laboratory-based findings under realistic agricultural conditions, highlighting the methodological limitations imposed by pollution heterogeneity, complex exposure scenarios, and detection technologies. It also examines existing policy responses at both regional and global levels aimed at addressing MP pollution in agriculture. To address these challenges, we propose future research directions that include the integration of multi-method detection protocols, long-term and multi-site field experiments, the development of advanced risk modelling frameworks, and the establishment of threshold values for MP residues in edible crops. Additionally, we highlight the need for future policies to regulate the full life cycle of agricultural plastics, monitor soil MP residues, and integrate MP risks into food safety assessments. This review provides both theoretical insights and practical strategies for understanding and mitigating MP pollution in agroecosystems, supporting the transition toward more sustainable, resilient, and environmentally sound agricultural practices.