Soil C-N and microbial community were altered by polybutylene adipate terephthalate microplastics

The risks posed by biodegradable plastics to the plant-soil system have been increasingly studied due to potentially hazardous effects on soil properties and nutrient cycling. In this study, we investigated the effects of Poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) on soil carbon, nitrogen and microbial communities under different levels of contamination (0 % (control), 0.1 %, 0.2 %, 0.5 % and 1 %), in soils planted with soybean ( Glycine max ( Linn. ) Merr. ) and maize ( Zea mays L. ). The results showed that PBAT-MPs significantly altered soil dissolved organic carbon, dissolved organic nitrogen and nitrate nitrogen contents, and that these effects varied by plant type and growth stage ( p < 0.05). PBAT-MPs significantly increased soil microbial biomass carbon and nitrogen for both plants ( p < 0.05), except for microbial biomass nitrogen at the soybean flowering stage. PBAT-MPs altered the β-diversity and composition of bacterial and fungal communities, increasing the relative abundances of Proteobacteria but decreasing the relative abundances of Acidobacteriota for both plants. FAPROTAX analysis showed that PBAT-MPs had significant effects on functional bacterial groups related to the nitrogen and carbon cycle, that varied by plant type and growth stage. These results suggest that biodegradable microplastics may have plant-specific effects on soil microbial communities and microbial metabolism, and thereby influence soil carbon and nitrogen cycling. • PBAT-MPs significantly increased soil microbial biomass carbon. • Biodegradable microplastics might provide a source of carbon for soil microbes. • PBAT-MPs significantly increased the abundance of functional bacterial groups related to nitrogen fixation. • The affected functional bacterial groups are related to nitrogen and carbon cycle.