Abstract
The contamination of terrestrial ecosystems, particularly agricultural soils by microplastics has emerged as a significant concern for soil health and sustainable agricultural production. Recent estimates indicate that microplastic concentrations in terrestrial habitats may be 4–23 times higher than those reported in aquatic environments, emphasising the importance of understanding their impacts on soil ecosystems. Microplastic smaller than 5mm affects the physical characteristics of the soil, which negatively impacts the capability of the soil to supply nutrients to plants, which in turn affects the productivity of crops. The presence of plastics alters microbial composition and productivity, affecting nutrient turnover and the breakdown of organic matter. It has been shown in laboratory tests that there was a decrease in nitrogen-fixing bacteria and the total microbial density in soil samples containing microplastics. Furthermore, these pollutants affect the lives of some fauna in the soil, like earthworms, by inhibiting their growth. The other factor contributing to the severity of soil pollution risks is the nature of microplastics to adsorb and transport hazardous compounds such as organic contaminants and toxic metals, which are present in the food web and have profound impacts on both human well-being and the biosphere. More effort and a prompt response are necessary to accurately estimate the extent of microplastics and their persistent effects on soil health, remediate the problems associated with plastic use in the agricultural sector and effectively control plastic use in agriculture. This review critically synthesises current knowledge on the sources of microplastics and their effects on soil physical, chemical and biological health indicators while highlighting key research gaps relevant to sustainable agricultural management.