Carbon sequestration is the process whereby carbon is removed from the atmosphere and stored in natural reservoirs for an extended period. Plants naturally perform this function by converting atmospheric C, in the form of the greenhouse gas CO2, into organic C. This organic C can then be sequestered into the soil as soil organic carbon (SOC). By eliminating tillage on arable land, SOC mineralization can be reduced and SOC can be rebuilt over time. Various incentives have been proposed to encourage farmers to switch to no-till production, including payments per unit of soil C sequestered and market-based trading systems. Certain scenarios could arise, however, where a single tillage event might occur for crop production. The purpose of this study is to evaluate the impact on SOC when a no-till system is disturbed by a single tillage event. Dryland sites were chosen that have been in continuous no-till (wheat – sorghum - fallow) for at least five years. Silt loam and sandy loam soil types are being compared. Each location has four tillage intensities: control (no-till), sweeps (V-blade), disking, and field cultivator. Within a location, each tillage intensity is replicated four times in a randomized block design. Depths of sampling are from 0-5 cm, 5-15 cm, and 15-30 cm. Samples will be analyzed for the following properties: total C and N, mineralizable C and N, aggregate size and distribution, bulk density, and microbial biomass C and N. Samples will be taken on three different occasions: pre-tillage, after the first growing season, and again after the second growing season.