Decreased carbon footprint and increased grain yield under ridge–furrow plastic film mulch with ditch-buried straw returning: A sustainable option for spring maize production in China

Ditch-buried straw returning with ridge-furrow plastic film mulch (RP+S) is a novel tillage measure in semiarid regions, but it is unclear whether RP+S can increase maize yield while reducing the carbon footprint (CF). Therefore, a six-year continuous experiment was conducted from 2016 to 2021 to quantify the effect of four straw returning and film mulching measures [conventional flat cultivation (CK), conventional flat cultivation with ditch-buried straw returning (CK+S), ridge-furrow plastic film mulch (RP), and RP+S] on soil organic carbon sequestration (SOCS), greenhouse gas (GHG) emissions, CF, and economic benefits. Straw returning and film mulching measures significantly increased total GHG emissions across the six seasons. For all treatments, nitrogen fertilizer was the most important source of GHG emissions (≥73%), followed by diesel (8-11%) and plastic film (8%, RP and RP+S only). RP+S significantly increased yield and partial factor productivity of nitrogen fertilizer by 8.7-59.1%, and net economic benefit by 7.37-57.76%, but decreased CF by 34-61% and CF per net return by 33-61% relative to the other treatments. RP+S had the highest GHG emissions, increasing by 6.11-16.47% relative to the other treatments. However, compared with the initial 0-40 cm SOCS in 2016, RP+S had the highest carbon sequestration rate (678.17 kg·ha-1·yr-1), increasing by 2.29% after six years, followed by CK+S (1.78%), CK (0.89%), and RP (-0.49%). Thus, RP+S had the lowest CF and CF per net return in four treatments. This comprehensive analysis of agronomic and environmental benefits revealed that RP+S is a high-yielding, economically and environmentally friendly measure in semiarid areas.