[Effects of Microplastics on Growth Characteristics and Rhizosphere Soil Enzymatic Activity of Maize].

Abstract

Microplastics （MPs）， as emerging global pollutants， may disrupt agricultural ecosystems and affect crop growth and development. To clarify the impact of MPs on the soil-maize system， this study investigated the effects of traditional non-degradable MPs [polyethylene （PE） and polyvinyl chloride （PVC）] and biodegradable MPs [polylactic acid （PLA）] on rhizosphere soil nutrient content， organic acids， enzyme activity， as well as maize height and biomass. The results showed that the addition of conventional MPs reduced rhizosphere soil total nitrogen （TN）， total phosphorus （TP）， dissolved organic carbon （DOC）， and available phosphorus （AP） content； decreased extracellular enzyme activities related to carbon， nitrogen， and phosphorus cycling； and inhibited the shoot and root biomass of maize. Compared with that in the control （CK）， the aboveground biomass decreased by 33.29% and 22.86% after the addition of PE-MPs and PVC-MPs， respectively， while the belowground biomass decreased by 44.96% and 27.94%. In contrast， the addition of biodegradable PLA-MPs significantly increased rhizosphere soil organic carbon， TN， TP， DOC， and AP content； enhanced rhizosphere organic acid levels and extracellular enzyme activities related to soil carbon and phosphorus cycling； and reduced rhizosphere pH. Notably， PLA-MPs exhibited no significant inhibitory effects on maize height or biomass. Furthermore， Mantel tests revealed that the key factors influencing maize growth were rhizosphere soil TN， organic acid content， and cellulase activity （P<0.05， R<0.4）. These findings provide a data foundation and theoretical basis for evaluating the effects of conventional and biodegradable MPs on plant growth and soil ecological environmental responses.