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Managing agricultural lands to increase soil organic carbon (SOC) could help counter the rising atmospheric CO2 concentration as well as reduce soil degradation and improve crop productivity. However, soils, climate, and management practices vary over space and time, creating an almost infinite combination of factors that interact and influence how much carbon is stored in soils. Thus, quantifying soil carbon sequestration under widely varying conditions is complicated. Furthermore, SOC changes slowly over time; experiments for quantifying carbon gain under different practices must be conducted over a number of years. Due to the human and financial resources and time needed to conduct such experiments, it may not be practical to rely on this approach alone to provide needed information. Further complicating the picture is climate change. As temperature and atmospheric CO2 increase and rainfall changes, new combinations of factors will occur that have not been studied. For these reasons, models are needed to complement information gained from experiments to help understand and predict SOC and food production responses to soil, climate, and management combinations.