Response of root properties and soil enzyme activities to biodegradable microplastic in contaminated soil

To reduce plastic pollution in soil, biodegradable plastic film is used in agricultural production as an alternative product of conventional plastic. However, there is little known about its residues on plant growth and soil properties. In this study, we investigated the effects of Poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) on root properties and soil enzyme activities in soil with soybean (Glycine max (Linn.) Merr.) and maize (Zea mays L.), with the levels of 0% (CK), 0.1%, 0.2%, 0.5% and 1% (w/w). The results showed significant inhibitions of PBAT-MPs on the root properties, including total root length, root surface area, root volume and root biomass of soybean and maize. And the negative effects of PBAT-MPs on the root growth of maize was stronger than that on the root growth of soybean. Furthermore, C-enzyme activities (β-xylosidase, cellobiohydrolase, β-glucosidase) significantly decreased in non-rhizosphere soil with soybean at the harvesting stage and those in rhizosphere and non-rhizosphere soil with maize significantly decreased at the tasseling and harvesting stage. N-enzyme activities (leucine-aminopeptidase, N-acetyl--glucosaminidase, alanine aminotransferase) significantly increased in rhizosphere soil with soybean and non-rhizosphere soil with maize at the harvesting stage. In conclusion, PBAT-MPs accumulation could affect root growth negatively and alter soil enzyme activities in soil with soybean and maize differently, which related to soil carbon and nitrogen cycling. To identify the mechanism of effects of biodegradable microplastics on different plant-soil systems, further study should focus on the effects of biodegradable microplastics on soil microbial community.