Black biodegradable mulching increases grain yield and net return while decreasing carbon footprint in rain-fed conditions of the Loess Plateau

Mulching with polyethylene film is a common technique in rain-fed regions used to address insufficient precipitation and heat, and thus promote crop growth, but it can lead to soil pollution from plastic residues. Biodegradable film mulch (BDM) is assumed to be a viable solution to address this concern. To evaluate the effects of polyethylene and biodegradable film mulching on socio-economic and environmental benefits, a two-year study was conducted on wheat. This experiment explored the influence of mulching practices differing in color and degradation: Black polyethylene mulching (Black PE), Black biodegradable mulching (Black BDM), Clear polyethylene mulching (Clear PE), Clear biodegradable mulching (Clear BDM) and No mulching (NM) on grain yield, economic benefits, greenhouse gas (GHG) emissions, and carbon footprint (CF). In comparison with NM, all four film mulching treatments improved soil hydrothermal conditions. The Clear PE, Clear BDM, Black PE, and Black BDM increased average annual wheat yield by 40 %, 47 %, 47 %, and 60 %, respectively, compared to NM. Clear PE, Black BDM, and Black PE enhanced net returns (17-124 %) compared to NM. However, Clear PE and Clear BDM increased CO2 emissions (43 % and 52 %) and net global warming potential (GWP) (49 % and 17 %) despite reducing yield-scaled GWP(direct) and CF compared to NM, likely due to higher wheat grain yields. In contrast, under Black BDM, GWP(direct) and yield-scaled GWP(direct) decreased significantly compared to NM (by 31 % and 58 %, respectively). When accounting for GHG emissions using soil organic carbon (SOC) sequestration rates and life cycle assessment, the annual CF of Clear BDM, Black PE, and Black BDM was significantly lower by 21.9 %, 30.4 %, and 67.9 %, respectively, compared to NM. Black BDM exhibited the lowest net GWP (1682.3-1727.3 kg CO2-eq ha(-1)) and CF (261.4-336.0 kg CO2-eq t(-1)), primarily attributed to increased SOC. In conclusion, the black biodegradable mulching might be a promising solution to enhance wheat grain yield and net returns while mitigate net GWP and CF, providing valuable technical guidance to promote a clean and sustainable agricultural production in rain-fed conditions, and possible support for future research.