Enhancing carbon sequestration and greenhouse gas mitigation in semiarid farmland: The promising role of biochar application with biodegradable film mulching

Long-term mulching has improved crop yields and farmland productivity in semiarid areas but also increased greenhouse gas (GHG) emissions and depleted soil fertility. Biochar application has emerged as a promising solution for addressing this issue. In this study, we investigated the effects of four biochar application rates (no biochar (N)=0 t ha–1, low (L)=3 t ha–1, medium (M)=6 t ha–1, and high (H)=9 t ha–1) under film mulching and no mulching over three growing seasons. We assessed the impact on greenhouse gas emissions, soil organic carbon sequestration (SOCS), and maize yield to evaluate the productivity and sustainability of farmland ecosystems. Our results demonstrated that mulching increased maize yield (18.68–41.80%), total fixed C in straw (23.64%), grain (28.87%), and root (46.31%) biomass, and GHG emissions (CO2, 10.78%; N2O, 3.41%), while decreasing SOCS (6.57%) and greenhouse gas intensity (GHGI; 13.61%). Under mulching, biochar application significantly increased maize yield (10.20%), total fixed C in straw (17.97%), grain (17.69%), root (16.75%) biomass, and SOCS (4.78%). Moreover, it decreased GHG emissions (CO2, 3.09%; N2O, 6.36%) and GHGI (12.28%). These effects correlated with the biochar addition rate, with the optimal rate being 9.0 t ha–1. In conclusion, biochar application reduced CO2 and N2O emissions, enhanced CH4 absorption, and improved maize yield under film mulching. It also improved the soil carbon fixation capacity while mitigating the warming potential, making it a promising sustainable management method for mulched farmland in semiarid areas.