Microplastic contamination in agricultural soil ecosystems and the effect on soil and plant health

Introduction

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).

Research Gap

The lack of appropriate techniques and methodologies for sampling, extraction, and detection hampers the research concerning MP distribution in soil ecosystems. This research gap has led to fragmentary knowledge and even contradictory results in MP studies on soil ecosystems, as different concentrations, sizes, shapes, and MP polymer types were considered. Therefore, fundamental insights into the role of MPs on soil and plant health are missing.

Research Approach

We will advance the field by working in a three-step approach to mechanistically define how MP pollution outbalances the soil (and plant) ecosystem.

Step 1: Risk Assessment

1. The risk of MP pollution in soil will be assessed by correlating MP concentrations of 240 soils with soil health indicators.
2. 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.

Step 2: Validation and Testing

1. These correlations between MPs and the soil health indicators will be validated and tested in greenhouse experiments.
2. The biological underpinnings that drive these correlations will be understood.
3. MP-induced changes in the following will be studied:
   • Plant growth
   • Plant disease susceptibility
   • Soil texture
   • Soil chemical composition
   • The microbial community

Step 3: Biodegrading Organisms

To reduce the risk (introduction and accumulation) of MPs in soil ecosystems, we will actively search for biodegrading organisms using a novel sequencing approach.

Conclusion

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.