Spatial Analysis of the Soil Carbon Sequestration Potential of Crop-residue Return in China Based on Model Simulation

Crop-residue return is a recommended practice for soil and nutrient management and is important in soil organic carbon (SOC) sequestration and CO₂ mitigation. We applied a process-based Environmental Policy Integrated Climate (EPIC) model to simulate the spatial pattern of topsoil organic carbon changes from 2001 to 2010 under 4 crop-residue return scenarios in China. The carbon loss (28.89 Tg yr^-1) with all crop-residue removal (CR0%) was partly reduced by 22.38 Tg C yr^-1 under the status quo CR30% (30% of crop-residue return). The topsoil in cropland of China would become a net carbon sink if the crop-residue return rate was increased from 30% to 50%, or even 75%. The national SOC sequestration potential of cropland was estimated to be 25.53 Tg C yr^-1 in CR50% and 52.85 Tg C yr^-1 in CR75%, but with high spatial variability across regions. The highest rate of SOC sequestration potential in density occurred in Northwest and North China while the lowest was in East China. Croplands in North China tended to have stronger regional SOC sequestration potential in storage. During the decade, the reduced CO₂ emissions from enhanced topsoil carbon in CR50% and CR75% were equivalent to 1.4% and 2.9% of the total CO₂ emissions from fossil fuels and cement production in China, respectively. In conclusion, we recommend encouraging farmers to return crop-residue instead of burning in order to improve soil properties and alleviate atmospheric CO₂ rises, especially in North China.