Simulating Impacts of Bioenergy Sorghum Residue Return on Aboveground Biomass Carbon, Soil Organic Carbon, and Greenhouse Gas Emissions.

Different residue management practices can affect carbon (C) allocation and thus soil C and nitrogen (N) turnovers. A biogeochemical model, DAYCENT, was used to simulate the effects of residue return on soil temperature, aboveground biomass carbon, soil organic carbon (SOC), and greenhouse gases [carbon dioxide (CO₂) and nitrous oxide (N₂O)] emissions under bioenergy sorghum production. A correlation coefficient (r²) was used to test the model performance. The correlation coefficients between the observed and simulated soil temperature, aboveground biomass C, soil organic C, CO₂ and N₂O were 0.91, 0.68, 0.80, 0.81, and 0.27, respectively, indicating that the DayCent model caught the major effect of residue return on biomass sorghum production and C and N turnovers. Compared with the simulated control (0% residue return), the simulated 50% residue return treatment had greater aboveground biomass, SOC, CO₂ and N₂O emissions, respectively. Such changes in the simulated outputs were also observed in our field trials. The amount of accumulative greenhouse gases emissions was lower than that of field observation. Also, the biannual variations in the simulated outputs were also comparable with the field observations. Our study indicated that the biogeochemical model, DayCent, can reasonably simulate the main effect of residue return on biomass production, soil organic C, and greenhouse gas emissions in biomass sorghum production.