The Hidden Threat Beneath: Fate, Behaviour and Effects of Microplastics in Agricultural Soils

Abstract

Microplastic contamination of agricultural soils represents one of the most pervasive and poorly understood facets of the broader plastic pollution crisis. Agricultural soils globally receive microplastics through multiple, often concurrent pathways — including the degradation of plastic mulch films, the land application of sewage sludge and compost, irrigation with contaminated water, and atmospheric deposition — and may harbour plastic particle concentrations considerably exceeding those found in marine surface waters. This narrative review synthesises current knowledge on the sources, fate, and ecological and agronomic effects of microplastics in agricultural soil systems, drawing on peer-reviewed literature published between 2004 and 2026. The literature search was conducted across nine electronic databases. Web of Science, Scopus, PubMed, and Google Scholar served as broad multidisciplinary repositories, providing comprehensive coverage of the mainstream soil science, ecotoxicology, and environmental chemistry literature. The available evidence indicates that microplastics alter fundamental soil physical properties such as aggregation, porosity, and water-holding capacity, whilst simultaneously disrupting microbial community structure, enzymatic activity, and nutrient cycling. Soil fauna — including collembolans, nematodes, and earthworms — suffer reduced reproductive success, altered gut microbiota, and heightened mortality at environmentally relevant concentrations. Crop plants exposed to microplastics exhibit impaired germination, reduced root elongation, and diminished biomass, with evidence of nanoplastic and submicrometre particle uptake into plant tissue raising serious food safety concerns. Human health implications range from chemical co-contaminant transfer to the detection of microplastic particles in human systemic tissues, including the placenta. Mitigation strategies remain at a nascent stage, encompassing biodegradable mulch film substitution, enhanced wastewater treatment, improved biosolid management, and emerging regulatory frameworks governing plastic use in agriculture. The review identifies critical knowledge gaps — particularly regarding long-term soil accumulation kinetics, nanoplastic behaviour, and the cumulative toxicity of plastic-associated contaminants — and calls for internationally coordinated monitoring and standardised analytical approaches to better characterise the threat that microplastics pose to agricultural productivity and global food security.