Microplastics (plastic particles smaller than 5 mm) are a global problem. In addition to marine ecosystems, agricultural soils are particularly contaminated with these particles, as they are not only passively introduced, but are also part of agricultural management. The ‘μPlastic’ research network is investigating the effects of microplastic particles, particularly in the rhizosphere, the interface between plants and soil.
To this end, the researchers, led by Freie Universität Berlin, are investigating the changes in soil processes and microbial biodiversity caused by different microplastic particles in the root zone of important crops. The research network is also analysing the consequences for yield and plant quality. The focus of the project is on greenhouse experiments, but laboratory and mesocosm experiments are also being carried out in the field. The soils, important agricultural soils in Germany, are cultivated with wheat and other crops as part of the project after they have been mixed with various microplastic particles. Among other things, the aim is to understand (a) in which soils (b) in which crops the microplastic effects are particularly pronounced and (c) why and how microplastics interact with other abiotic and biotic soil factors.
The team is analysing the soil and root-associated microbiome, including the arbuscular mycorrhizal fungi, and relating this data to plant growth and important rhizosphere processes. Already at the beginning of the project, a pioneering categorisation of microplastics among other environmental pollutants could be made: In some cases, microplastics have completely different mechanisms of action than other chemical pollutants. It could be shown that microplastic effects on the growth of wheat plants depend very strongly on the soil type, even the direction of the effects (from positive to negative) was strongly influenced by the soil type. Soil properties such as soil aggregation and hydraulic conductivity also depended strongly on the soil type. Further experiments will now investigate which mechanisms are mainly responsible for these effects and how crops differ in their reactions to microplastics.