Effects of plastic fragment size and concentration on plant performance are mediated by soil properties and water availability

Abstract Purpose: Increasing attention has been devoted to the effects of plastic contamination on soil water content and plant performance. However, little is known about how plastic in soil may interact with climate change factors, such as drought. We hypothesized that 1) Plastic affects soil water content negatively, and such effect is mediated by plastic size and concentrations, water availability and soil texture; 2) plants attain higher growth in soil where the negative effects of drought and plastic are small. Methods: We tested the joint effects of water availability, soil texture, and plastic fragments (varying in concentration and size), on soil water content and growth of the model plant Arabidopsis thaliana . Results: While increasing concentrations and size of plastic negatively affected soil water content, likely by favoring the formation of fractures within soil aggregates, they positively affected plant growth, likely by increasing soil porosity and facilitating root growth. In low water availability such responses were generally stronger, while soil texture mediated linear vs. unimodal responses in soil water content. Conclusion: Plastic contamination in soil is bound to increase overtime, and it may interact with drought in affecting soil and plants in non-linear ways. This implies that plastic contamination may either amplify or mitigate the effects of climate change on plants, soil and their interactions.