A meta-analysis of film mulching cultivation effects on soil organic carbon and soil greenhouse gas fluxes

The use of plastic film in agriculture strongly affects the decomposition of soil organic carbon (SOC) and the release of methane (CH4) and nitrous oxide (N2O) by influencing soil biogeochemical processes. However, no systematic conclusions have been reached regarding the effect of plastic film mulching on SOC stocks and greenhouse gas (GHG) budgets. In this study, a meta-analysis compiling data from 150 studies was used to assess the effects of film mulching on SOC and soil GHG fluxes across different agricultural systems. In addition, the net global warming potentials (GWPs) of SOC, CH4 and N2O were calculated with the GWP approach. Plastic film mulching significantly promoted crop yield by 48.6%; did not affect SOC; reduced CH4 emissions from paddy fields by 64.2% and CH4 uptake in uplands by 16.1%; and increased soil N2O emissions by 23.9%. The effect of mulching on SOC and GHG fluxes varied among agricultural systems. Compared with the non-mulched field, the use of plastic film significantly increased SOC and decreased CH4 uptake in rainfed uplands but reduced SOC in irrigated uplands. In paddy fields, this practice significantly reduced the SOC stock and CH4 emissions but increased N2O emissions. Our results suggest that a low coverage ratio (<50%), black film mulching and flat mulching effectively increase SOC levels compared to those in non-mulched fields, and a low coverage ratio, biodegradable film and ridge mulching could mitigate the positive effect of this practice on N2O emissions. Overall, our results suggest that plastic film mulching promotes crop productivity and slightly affects the net GWP in uplands. In paddy fields, this technology appears to be a "win-win" strategy for crop production and GHG mitigation, but additional practices (e.g., biochar application) should be adopted to maintain SOC levels for sustainable development in these fields because it greatly reduces SOC stocks.