Antagonistic Effect of Microplastic Polyvinyl Chloride and Nitrification Inhibitor on Soil Nitrous Oxide Emission: An Overlooked Risk of Microplastic to the Agrochemical Effectiveness

Microplastics are widely persistent in agricultural ecosystems and may affect soil nitrous oxide (N₂O) emissions. Nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is applied to decelerate nitrification and reduce soil N₂O emission. Nevertheless, the interactive effects of nitrification inhibitors and microplastics on soil N₂O emissions have not been investigated. Sole DMPP, polyvinyl chloride (PVC), and polystyrene (PS) substantially reduced agricultural soil N₂O emission rates by 25.93%, 69.04%, and 73.89%, respectively. Nevertheless, PVC and DMPP had antagonistic effects on the N₂O emission rates. The observed reductions in N₂O emissions could be attributed to variations in soil oxygen availability, electron transport system activities, and <i>Firmicutes</i>, nap, and GDH genes. Moreover, the DMPP, PVC, and PS alone or copresences significantly enhanced the soil ecosystem multifunctionality (EMF). The findings shed light on the role of microplastics in soil N₂O emission, EMF, and the microbial community, expanding the understanding of microplastics' effects on agrochemical effectiveness.