Regulation mechanism of N2O and CH4 emissions during the pig manure composting amended with Polygonum Multiflorum Thunb.

To mitigate N2O and CH4 emissions during pig manure composting, this study innovatively employed Polygonum multiflorum Thunb (PM, a traditional Chinese herb) powder to regulate microbial community structure to reduce greenhouse gas emissions. PM was added to pig manure at concentrations of 0% (CK, control), 0.05% (HL, low dosage), 0.1% (HM, medium dosage), and 0.5% (HH, high dosage) based on dry weight. A 30-day aerobic composting experiment was conducted. The results showed that PM addition had a stronger effect on bacterial alpha diversity than on fungal alpha diversity, and both composting process and PM addition jointly influenced microbial community succession. PM also altered the relative abundance of key potential functional microorganisms involved in N2O and CH4 transformations. Cumulative N2O emissions decreased significantly by 56.7%, 63.1%, and 71.8% in HL, HM, and HH, respectively, while cumulative CH4 emissions increased significantly by 51.8%, 381.1%, and 593.1%, respectively. Correspondingly, global warming potential decreased significantly by 56.6%-71.3% with PM addition. Mantel test and structural equation modeling analyses revealed that the standardized total effect of PM addition on N2O and CH4 emissions was -0.066 and 0.132, respectively, with temperature and NH4+-N as key drivers for N2O, and pH and moisture content for CH4. This study demonstrates that PM is a promising additive for reducing N2O while modulating microbial communities and enhancing the resource utilization of pig manure.