Published online July 6, 2006 Soil Organic Carbon Sequestration in Cotton Production Systems of the Southeastern United States: A Review H. J. Causarano, A. J. Franzluebbers,* D. W. Reeves, and J. N. Shaw Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ABSTRACT Past agricultural management practices have contributed to the loss of soil organic carbon (SOC) and emission of greenhouse gases (e.g., carbon dioxide and nitrous oxide). Fortunately, however, conservation- oriented agricultural management systems can be, and have been, developed to sequester SOC, improve soil quality, and increase crop productivity. Our objectives were to (i) review literature related to SOC sequestration in cotton (Gossypium hirsutum L.) production systems, (ii) recommend best management practices to sequester SOC, and (iii) outline the current political scenario and future probabilities for cotton producers to benefit from SOC sequestration. From a review of 20 studies in the region, SOC increased with no tillage compared with conventional tillage by 0.48 6 0.56 Mg C ha 21 yr 21 (H 0 : no change, p , 0.001). More diverse rotations of cotton with high-residue- producing crops such as corn (Zea mays L.) and small grains would sequester greater quantities of SOC than continuous cotton. No-tillage 21 cropping with a cover crop sequestered 0.67 6 0.63 Mg C ha 21 yr , while that of no-tillage cropping without a cover crop sequestered 0.34 6 47 Mg C ha 21 yr 21 (mean comparison, p 5 0.04). Current government incentive programs recommend agricultural practices that would contribute to SOC sequestration. Participation in the Conser- vation Security Program could lead to government payments of up to $20 ha 21 . Current open-market trading of C credits would appear to yield less than $3 ha 21 , although prices would greatly increase should a government policy to limit greenhouse gas emissions be mandated. C ONCENTRATION of CO 2 in the atmosphere has in- creased from 280 ppmv (parts per million by vol- ume) during preindustrial times to about 375 ppmv in 2002 at Mauna Loa Observatory, Hawaii, with most of the increase during the past 50 yr a result of fossil-fuel burning (Intergovernmental Panel on Climate Change, 2001). All indications suggest that atmospheric CO 2 con- centration will continue to increase, raising concern by the scientific community about the potential detrimental effects of rising CO 2 and other greenhouse gases (meth- ane, nitrous oxide, ozone, and chlorofluorocarbons) on global warming and climate change (U.S. Global Change Research Program, 2004). Greatest mitigation of rising CO 2 concentration would be attained with a reduction in the burning of fossil fuels, but the political and economical costs of such a major change are considered too drastic at this time. An alter- native strategy to reduce greenhouse gas emission and allow sufficient time for industries to develop and im- H.J. Causarano and J.N. Shaw, Department of Agronomy and Soils, Auburn University, Auburn, AL 36849. A.J. Franzluebbers and D.W. Reeves, USDA-ARS, 1420 Experiment Station Road, Watkinsville, GA 30677. Received 26 Apr. 2005. *Corresponding author (afranz@ uga.edu). Published in J. Environ. Qual. 35:1374–1383 (2006). Special Submissions doi:10.2134/jeq2005.0150 ª ASA, CSSA, SSSA 677 S. Segoe Rd., Madison, WI 53711 USA plement non-fossil-fuel-derived energy utilization strat- egies relies on understanding and manipulating to the greatest extent possible the natural processes of the global C cycle. Photosynthesis and respiration are the two largest fluxes on a global scale that have kept atmo- spheric CO 2 in balance in the past (Wofsy and Harriss, 2002). Either increasing photosynthesis or decreasing respiration would result in less CO 2 being returned to the atmosphere. This mitigation strategy relies on (a) maxi- mizing CO 2 uptake from the atmosphere primarily through reforestation and afforestation, which would sequester C in woody plants, and/or (b) minimizing CO 2 release to the atmosphere primarily by sequestering C in soil organic matter through conservation management systems that minimize soil disturbance (USDA Office of the Chief Economist, 2004). Landowners and agricultural producers who contribute to this mitigation would pro- vide an environmental service to society, and therefore could be monetarily compensated through government programs or through an open-market trading system in- volving emitters and sequesters of CO 2 and other green- house gases. Detailed descriptions of the global C cycle and how land use and management would affect pools and fluxes of C are available in several textbooks (Stevenson, 1986; Schlesinger, 1991; Lal et al., 1998; Follett et al., 2001). Most analyses highlight the biophysical potential of SOC sequestration under a variety of management sce- narios (Lal, 1997; Follett, 2001; West and Post, 2002; Sperow et al., 2003). All agree that more widespread adoption of conservation management practices could greatly increase the quantity of SOC currently being se- questered. Sperow et al. (2003) estimated the present rate of SOC sequestration in cropland of the United States at 17 Tg C yr 21 . With complete adoption of no- tillage management on all currently cropped land (129 Mha), SOC sequestration could increase to 47 Tg C yr 21 . Agriculture and forestry in the United States directly emit 8% of the total greenhouse gas (GHG) emission of the nation (USDA Office of the Chief Economist, 2004). This estimate does not account for a potentially large sink in wood and soil organic matter. Although agri- cultural emission is a relatively small portion of the total, the unaccounted potential sinks suggest that agriculture and forestry could act as key components to reduce the nation’s burden of GHG emission (USDA Office of the Chief Economist, 2004). Agricultural activities could mitigate GHG emission by (i) direct emission reduction, for example, lower fossil-fuel consumption with fewer field passes using conservation tillage, (ii) sequestering C in plant biomass and soil organic matter, (iii) pro- ducing biofuels that would substitute for fossil fuels, and Abbreviations: GHG, greenhouse gas; SOC, soil organic carbon. 1374