Soil–plant–microplastic interactions and their ecological impacts for agricultural sustainability

Since their formal definition in 2004, microplastics (MPs) have rapidly become a pressing environmental challenge due to their persistence, ubiquity, and potential ecological risks. While research on MPs in terrestrial environments has progressed in recent years, it still lags behind the extensive work done in aquatic systems. Important uncertainties remain, especially regarding their behaviour in soil matrices and their consequences for agroecosystems. Agricultural soils, covering approximately 38% of the global land area, serve as both major sinks and sources of MPs. Intensive farming practices, such as the widespread use of plastic mulch and the application of sewage sludge as fertilizer, contribute to MP accumulation and raise concerns about their uptake by crops. As integral components of agricultural ecosystems, plants not only sustain soil functionality but also serve as bioindicators in ecotoxicological evaluations. Understanding the transport mechanisms and ecological impacts of MPs in soil–plant systems is therefore essential for evaluating risks to agricultural sustainability, food safety, and human health. This study em-ploys soil-based experiments to closely simulate real-world terrestrial plant growth conditions. Through a multidisciplinary approach, it investigates the role of particle type, concentration, morphology, and plant species in shaping soil-MP-plant interactions, uncovering their complex interdependencies. Furthermore, an innovative staining technique was applied to enable the visualization of microfibers (MFs)—the predominant MP form in agricultural soils—under multimodal microscopy, addressing a critical knowledge gap. The findings reveal: (1) MPs exert diverse effects on soil properties and plant performance, influenced by particle type, plant species, and potential synergistic interactions; (2) MPs alter soil total organic carbon stocks under specific cropping conditions at environmentally relevant concentrations; (3) plant responses to MP exposure exhibit non-linear patterns, governed by species-specific mechanisms affecting growth and stress responses; (4) microfibers, owing to their unique shape, large surface area, and physicochemical properties, can penetrate certain plant root tissues via crack-entry pathways and apoplastic transport; and (5) the adsorption and accumulation patterns of microfibers are closely linked to plant root traits and antioxidant capacity. These insights significantly advance the understanding of MP risks in soil–plant systems and offer valuable information to a wide range of stakeholders, including environmental scientists, agricultural managers, policymakers, and public health professionals. Future research should prioritize the use of environmentally relevant MP concentrations and diverse MP types, while fully considering plant species variability to enhance ecological risk assessments and the development of effective mitigation strategies.