Quantitative Attribution of Major Driving Forces on Soil Organic Carbon Dynamics

Abstract:

Soil organic carbon (SOC) storage plays a major role in the global carbon cycle and is affected by many factors including land use/management changes. However, the contributions of various factors to SOC changes are not well understood and quantified. This study was to investigate the impacts of changing farming practices, initial SOC levels, and biological enhancement of grain production on SOC dynamics and to attribute the relative contributions of major driving forces (CO₂ enrichment and farming practices) using a fractional factorial modeling design. The case study using a crop site in Iowa in the United States demonstrated that the traditional corn-soybean (CS) rotation had the potential of accumulating SOC over this century under the current condition; whereas the continuous-corn (CC) system might have a higher SOC sequestration potential than CS. In either case, however, straw removal could reverse the sink potential to carbon neutral or a weak sink/source. Our results also suggested that the equilibrium SOC level may vary greatly depending on cropping systems and management practices. Importantly, the factorial design analysis indicated that residue management had the most significant impact on SOC changes, followed by CO₂ enrichment. In brief, this study is valuable for understanding the major forces driving SOC dynamics of agro-ecosystems and informative for decision-makers when seeking the enhancement of SOC sequestration potential and sustainability of biofuel production, especially in the Corn Belt region.