Short-term effects of microplastics and earthworms on greenhouse gases emissions from a sandy-loam soil

The widespread use of plastics in agriculture has led to the co-existence of microplastics (MPs) and earthworms in soil ecosystems. While both MPs and earthworms are known to influence soil greenhouse gas (GHG) emissions, their interactive effects on CO2, N2O, and CH4 emissions remain poorly understood. To address this gap, a 21-day incubation experiment was conducted to examine the impact of MPs (0 %, 0.1 %, 0.5 %, 1 %) on soil GHG emissions in the presence and absence of earthworms. The results showed that MPs significantly reduced cumulative N2O emission and enhanced CH4 oxidation, with effects intensifying at higher concentrations, but had no significant effect on CO2 emissions. In contrast, earthworms increased soil CO2 and N2O emissions while promoting CH4 oxidation. MPs also lowered the global warming potential (GWP) by reducing N2O emissions, whereas earthworms had an opposite effect. Interestingly, MPs reduced earthworm mortality in this study. Additionally, the interaction between MPs and earthworms significantly influenced soil pH and mineral N (NH4+- N and NO3--N) content. These findings the critical role of earthworms in amplifying soil CO2 and N2O emissions and CH4 oxidation. This study provides new insights into GHG emissions in sandy-loam soils under the combined influence of MPs and earthworms.