How Microplastics Are Affecting Soil Health in Agriculture
Microplastics (MPs), defined as plastic particles smaller than 5 mm, are increasingly recognized as a widespread contaminant in terrestrial ecosystems, particularly in agricultural soils. Their presence is linked to a variety of sources, including plastic mulching films, wastewater irrigation, compost, and biosolid applications (1). Due to their resistance to degradation, MPs can persist in soils for decades or even centuries, making them a long-term environmental concern. While research on microplastics initially focused on marine systems, growing evidence shows that terrestrial environments, especially agroecosystems, may act as major reservoirs. Understanding how MPs interact with soil systems is therefore critical for evaluating their implications for soil health, fertility, and long-term agricultural sustainability.
Alteration of Soil Physical Properties
One of the most immediate effects of microplastics in soil is the modification of physical structure (2). MPs interact with soil particles and organic matter, influencing aggregation processes. For instance, fibrous microplastics can bind soil particles together and enhance the formation of stable aggregates, whereas film-like plastics may disrupt aggregate stability and reduce the proportion of larger soil aggregates.
Changes in soil bulk density are also commonly observed. Because plastic particles are generally less dense than mineral soil components, their presence can decrease overall soil density and increase porosity. This may improve aeration and facilitate root penetration. However, such changes can also disturb natural soil structure and affect water retention and nutrient transport (3).
Microplastics can further alter soil pH, depending on polymer composition. These shifts in pH can have cascading effects on soil chemistry and biological activity. Additionally, MPs influence soil water dynamics: fine fibers may increase water-holding capacity, while larger particles can enhance evaporation or create localized oxygen-deficient conditions. These alterations in hydrological behavior are particularly significant in the context of climate change, where soil moisture regulation is increasingly important (4).
Effects on Soil Microbial Communities
Soil microorganisms are fundamental to ecosystem functioning, driving processes such as organic matter decomposition and nutrient cycling. Microplastics influence these microbial communities both directly and indirectly. A key concept emerging from recent studies is the “microplastisphere” defined as a unique habitat formed on the surface of plastic particles. This microenvironment can host distinct microbial communities, including plastic-degrading organisms and, in some cases, pathogenic species (4). By creating these new ecological niches, MPs can reshape microbial diversity and community composition. The effects of MPs on microbial activity are highly variable. Some studies report increased microbial biomass and enzyme activity, while others show suppression of key processes such as carbon and nitrogen cycling (4, 5). These differences are largely explained by the diversity of microplastic types, including variations in polymer composition, particle size, and surface properties. Smaller particles, particularly nanoplastics, pose additional risks. Due to their high surface area and ability to penetrate biological membranes, they can exert cytotoxic effects on microorganisms, potentially disrupting microbial networks that are essential for soil health (6).
Impacts on Soil Fauna
Microplastics also affect soil fauna, including earthworms, which play a crucial role in soil structure and nutrient cycling (7). At low concentrations, MPs may have minimal impact, but at higher levels they can reduce growth and increase mortality. The ingestion of microplastics is a key pathway for toxicity. Once ingested, MPs can cause physical damage and introduce harmful chemicals into the organism. Moreover, microplastics can act as carriers for pollutants such as heavy metals, increasing their bioavailability and ecological risk. Soil fauna can also contribute to the redistribution of MPs within the soil. Through their burrowing and feeding activities, organisms like earthworms can transport microplastics vertically and horizontally, facilitating their spread and increasing exposure to other organisms.
Disruption of Carbon and Nutrient Cycling
Microplastics play a complex role in soil carbon dynamics. As carbon-rich materials, they contribute to soil carbon pools, although their bioavailability varies. Conventional plastics are relatively inert, whereas biodegradable MPs can release labile carbon during decomposition. This additional carbon can stimulate microbial activity and accelerate the breakdown of native soil organic matter, a process known as the priming effect. As a result, MPs can influence whether soils function as carbon sinks or sources, with implications for greenhouse gas emissions. Nutrient cycling is also affected (5). Microplastics can alter nitrogen transformations by influencing microbial processes such as nitrification and denitrification. In some cases, MPs promote nutrient immobilization, reducing the availability of essential elements like nitrogen and phosphorus for plant uptake. Furthermore, MPs can interfere with enzymes responsible for nutrient mineralization, thereby disrupting soil fertility and productivity.
Role of InPlasTwin in Complex and Emerging Challenge
The effects of microplastics on soil health are highly dependent on environmental conditions and plastic characteristics. While some changes, such as improved soil aeration, may appear beneficial, they are often accompanied by negative impacts on microbial communities or nutrient cycling.
Importantly, biodegradable plastics, often promoted as sustainable alternatives, may pose even greater risks due to their higher bioavailability and stronger influence on microbial processes.
Given the increasing accumulation of micro- and nanoplastics in agricultural systems, further research is essential to better understand their long-term environmental and agronomic impacts. Addressing these challenges is at the core of the InPlasTwin project, which aims to strengthen research capacity and advance analytical expertise in micro- and nanoplastics. By fostering collaboration, knowledge exchange, and innovation in the analysis of plastics and their effects on crop systems and soil health, InPlasTwin contributes to improving environmental sustainability and food safety in the agri-food sector.
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References
- Xu, D., Jin, T., Xi, B., Gao, H., Li, X., Huang, L., & Song, J. (2025). Distribution characteristics, influencing factors, and future prospects of MPS derived from agricultural mulching film in farmland soil: a review. Current Opinion in Environmental Science & Health, 100652.
- Mondol, M., Angon, P. B., & Roy, A. (2025). Effects of microplastics on soil physical, chemical and biological properties. Natural Hazards Research, 5(1), 14-20.
- Umair, M., Hassan, M. I., Zia, H., Maqsood, F., Khalil, M. H., Ghafoor, I., & Mumtaz, T. (2025). Soil physical properties and their influence on plant growth. In Soils and Sustainable Agriculture: Interplay of Soil, Plant, Water and Environmental Systems for Sustainable Agriculture(pp. 79-131). Cham: Springer Nature Switzerland.
- Zhou, J., Wen, Y., Marshall, M. R., Zhao, J., Gui, H., Yang, Y., … & Zang, H. (2021). Microplastics as an emerging threat to plant and soil health in agroecosystems. Science of the Total Environment, 787, 147444.
- Wang, X., Guo, S., Zhang, X., Zhang, W., Xu, J., Zhao, J., & Wang, Q. (2025). Microplastics as drivers of carbon and nitrogen cycling alterations in aquatic ecosystems: A meta-analysis. Journal of Hazardous Materials, 491, 138033.
- Chintala, S., Asra, F., Kakarla, R., Thathapudi, D., Venkata, R. P., Jarapala, S. R., & Dumala, N. (2025). Toxicological impact of micro-and nano-plastics on organisms of soil and water, plants, and humans: a comprehensive review. Environmental Science and Pollution Research, 1-37.
- Quigley, E., Sousa, J. P., & Briones, M. J. (2026). Leaching of Microplastics Enhanced Through Complex Soil Meso-and Macrofaunal Community Transport. Environmental Pollution, 127638.
