Plastics are found in nearly every environment and disrupt key ecosystem services. While the effect of plastic in marine and freshwater ecosystems has been studied extensively, effects of plastic on soil ecosystem functions such as plant growth, microbial biomass and water permeability have been mostly overlooked, particularly for the smallest particles, the microplastics (MPs; ≤ 5 mm). The lack of appropriate techniques and methodologies for sampling, extraction and detection hamper the research concerning MP distribution
in soil ecosystems. This research gap has led to fragmentary knowledge and even contradictory results in MP studies on soilecosystems, as different concentrations, sizes, shapes and   polymer types were considered. Therefore fundamental insights in the role of MPs on soil and plant health are missing. We will advance the field by working in a three step approach to mechanistically define how MP pollution outbalances the soil (and plant) ecosystem. First, the risk of MP pollution in soil will be assessed by correlating MP concentrations of 240 soils with soil health indicators. To measure the MP concentration, a fast, cost-effective and standardized method to detect, identify and quantify MPs (≥ 1 μm) in soils will be developed. Second, these correlations between MPs and the soil health indicators will be validated and tested in greenhouse experiments, to understand the biological underpinnings
that drive these correlations. MP induced changes in plant growth, plant disease susceptibility, soil texture, soil chemical composition and the microbial community will be studied. Third, to reduce the risk (introduction and accumulation) of MPs in soil ecosystems, we will actively search for biodegrading organisms making use of a novel sequencing approach. With this multidisciplinary approach, we will be able to mechanistically define the effects of MPs on soil and plant health and advance the field by identifying plastic biodegrading microorganisms.