The increasing use of plastics in agriculture, for instance mulching film, contributes to plastic residues in soils. Soil microplastic (MP) concentrations are expected to keep rising due to growing use of agricultural plastics, the application of plastic-contaminated biosolids and aerial deposition of MPs. Experiments to date revealed initial effects of MPs on soil physicochemical properties, invertebrates, microorganisms and plants, but rarely studied complex interactions between organisms in the soil. Therefore, this study evaluated the effects of MPs on soil ecosystem functioning using a more holistic approach that reflects these complex ecological interactions using environmentally realistic mesocosm systems. A simulated agricultural ecosystem was made using Lufa 2.2. natural soil in which we introduced two species of earthworms (Aporrectodea caliginosa and Dendrobaena veneta), three species of springtails (Heteromurus nitidus, Ceratophysella denticulata and Protaphorura fimata) and lettuce (Lactuca sativa) as crop. MP types tested were conventional low-density polyethylene (LDPE) and biodegradable starch-polybutadiene adipate terephthalate (PBAT) blend, both sourced from agricultural mulching films. The aim was to investigate the interactions and impacts on physical, (bio)chemical and biomolecular responses within the system after 13 weeks of exposure. Soil physicochemical properties were affected by both MP types. Springtail community composition was not affected, nor was earthworm survival and reproduction, although molecular biomarkers show affected Electron Transfer System and Glutathione S-transferase activity in the earthworms, indicating oxidative stress. Plants exhibited adverse effects, showing strong activation of defense mechanisms and lowered chlorophyll content. Microbial community composition changed due to MP exposure and microbial activity was significantly enhanced. By combining all non-correlating and non-redundant response variables into a single multivariate analysis, we show that the overall profile of soil properties and biological functioning of the soil system significantly shifted in a treatment-specific manner, already at environmentally relevant concentrations of 0.05% LDPE (w/w dry soil). By linking MP-induced effects on soil properties, fauna and flora, this study demonstrates that mulching film-derived MPs, even at levels currently observed in the environment, may pose a risk to agricultural soil health and functioning.
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https://setac.confex.com/setac/europe2026/meetingapp.cgi/Paper/32626