Effects of microplastics derived from polymer-coated fertilizer on maize growth, rhizosphere, and soil properties

Agricultural microplastics (MPs) pollution resulting from the widespread and extensive use of polymer-coated fertilizer (PCF) is of great concern. However, little information is currently available concerning the influence of MPs derived from PCF (PCF-MPs) on the crop-soil system. Therefore, we investigated the impacts of PCF-MPs (0, 0.01, 0.1, 1% w/w) on the growth of maize cultivars (ZNT 488 & ZTN 182), rhizosphere metabolites, microbial community, and soil properties. The effects of PCF-MPs on plant growth varied with plant cultivars and exposure doses. MPs had no influence on the growth of ZNT 488, but significantly improved the plant performance of ZTN 182 at higher doses. PCF-MPs insignificantly altered the rhizosphere metabolite profile of two maize cultivars. Although soil PAEs contents and the microbial communities were unchanged, the phyla Fibrobacteres and Verrucomicrobia (associated with plant growth-promotion) were increased significantly in ZTN 182. Moreover, PCF-MPs stimulated the soil urease, acid phosphatase and nitrate reductase activities, especially the phytase activity in ZTN 182. Besides, significant alterations in soil properties were also discovered in a cultivar-dependent manner. Overall, our study highlighted that the potential environmental risk assessment of PCF-MPs is still needed, even though PCF-MPs did not show negative effect on maize growth and rhizosphere metabolic profiles.