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Title: Calibration of the soil conditioning index (SCI) to soil organic carbon in the southeastern USA

item Franzluebbers, Alan
item CAUSARANO, H - Universidad Nacional De Asuncion
item NORFLEET, M - Natural Resources Conservation Service (NRCS, USDA)

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2010
Publication Date: 2/24/2010
Citation: Franzluebbers, A.J., Causarano, H.J., Norfleet, M.L. 2010. Calibration of the soil conditioning index (SCI) to soil organic carbon in the southeastern USA. Plant and Soil Journal. DOI:10.1007/s11104-010-0310-9.

Interpretive Summary: Rapid and reliable assessments of the potential of various agricultural management systems to sequester soil organic carbon are needed to promote conservation and help mitigate greenhouse gas emissions. A collaborative effort to investigate the validity of the soil conditioning index for prediction of soil organic carbon sequestration was developed among scientists with ARS in Watkinsville GA, a former ARS research associate in Beltsville MD (now at the National University in Asuncion, Paraguay), and with NRCS in Temple TX. Published soil organic C from various studies throughout the southeastern USA were compared with simulations run by the soil conditioning index under the umbrella of the Revised Universal Soil Loss Equation (RUSLE2). Within a field study, soil conditioning index was usually highly related to soil organic carbon content. Across studies, soil organic carbon content would increase by 0.25 tons of CO2 per acre per year per unit change in SCI. These results will have important implications for farmers, crop advisors, scientists, and policy makers interested in carbon trading schemes throughout the 300 million acres of land in the southeastern USA.

Technical Abstract: Prediction of soil organic C sequestration with adoption of various conservation agricultural management approaches is needed to meet the emerging market for environmental services provided by agricultural land stewardship. The soil conditioning index (SCI) is a relatively simple model used by the USDA–Natural Resources Conservation Service to predict qualitative changes in soil organic matter. Our objective was to develop a quantitative relationship between soil organic C derived from published field studies in the southeastern USA and SCI scores predicted from matching management conditions. We found that soil organic C sequestration could be reliably related to SCI across a diversity of studies in the region using the regression slope: 0.81 kg C/m3 per unit of SCI (which translates into 0.17 Mg C/ha/yr for every unit increase in SCI score). The calibration of soil organic C on SCI scores will allow SCI to become a quantitative tool for natural resource professionals to predict soil organic C sequestration for farmers wanting to adopt conservation practices.