Assessing the impact of changes in climate and CO₂ on potential carbon sequestration in agricultural soils

Changes in soil management can potentially increase the accumulation of soil organic carbon (SOC), thereby sequestering CO₂ from the atmosphere. However, the amount of carbon sequestered in soils can be augmented or lessened due to changes in climate and atmospheric CO₂ concentration. The purpose of this paper is to study the influence of climate and CO₂ feedbacks on soil carbon sequestration using a terrestrial carbon cycle model. Model simulations consist of observed adoption rates of no-tillage practices on croplands in the U.S. and Canada between 1981 - 2000. Model results indicate potential sequestration rates between 0.4-0.6 MgC/ha/yr in the Midwestern U.S. with decreasing rates towards the western, dryer regions of the U.S. It is estimated here that changes in climate and CO₂ between 1981 - 2000 could be responsible for an additional soil carbon sequestration of 42 Tg. This is 5% of the soil carbon estimated to be potentially sequestered as the result of conversion to no-tillage in the U.S. and Canada.