Submitted to: Proceedings of Carbon Sequestration in Soils Conference
Publication Type: Abstract Only
Publication Acceptance Date: April 24, 2000
Publication Date: N/A
Technical Abstract: Conversion of farmlands to grasslands has been proposed to sequester carbon in soil. We determined the effect of restoring grass and grazing on soil carbon storage in degraded farmland. The amount of soil organic carbon (SOC) in clay soils and the rate of carbon sequestration in soils after restoration of grass for periods of 6, 26 and 60 years was determined in central Texas. Agricultural practices resulted in a loss of 25 percent to 43 percent of SOC in the surface 120 cm of farmland compared to never-tilled prairie soils. After grass restoration, carbon sequestration occurred in the surface 60 cm at a rate of 447 kg C ha**-1 yr**-1. Nearly a century is required at this rate for the 60-year grass site to reach a carbon pool equivalent to that of native prairie soils. Grazing effects were determined following a stocking density trial conducted for 10 years in southern Oklahoma with four levels of stocking density: light, moderate, heavy and non-grazed on two soils, a Durant loam and Teller silt loam located within common paddocks. The soils responded differently to grazing intensity. The heavier textured Durant soil had less organic carbon in the soil profile as grazing intensity increased. The non-grazed exclosure had the greatest amount of soil carbon. The lighter textured Teller soil had greater amounts of organic carbon in the soil profile with grazing than without grazing. Conversion to grass can sequester carbon in Texas and Oklahoma, but the interaction of management and soil properties should be considered.