Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/25/2011
Publication Date: 7/2/2012
Citation: Franzluebbers, A.J., Owens, L.B., Sigua, G.C., Cambardella, C.A., Haney, R.L. 2012. Soil organic carbon under pasture management. In: Liebig, M.A., Franzluebbers, A.J., Follett, R.F., editors. Managing Agricultural Greenhouse Gases: Coordinated Agricultural Research through GRACEnet to Address our Changing Climate. Amsterdam, Netherlands: Elsevier. p. 93-110. Interpretive Summary: Pastures are common in the eastern USA, but research documenting how pasture management affects soil organic carbon sequestration is limited. Scientists with the USDA Agricultural Research Service in Watkinsville GA, Coshocton OH, Brooksville FL, Ames IA, and Temple TX reviewed relevant literature and synthesized information into a recommendation for program development to better estimate soil organic carbon sequestration. Pastures are capable of large soil carbon storage potential; greater than cropland and equal to forested land. Moderate grazing and amendment with animal manures are beneficial to soil carbon sequestration. Significant research gaps were identified in understanding the effects of how a diversity of forage management systems might impact soil organic carbon. This review will be particularly valuable to pasture managers, industry consultants, carbon trading representatives, and government policy advisors.
Technical Abstract: Pastures are a significant land use in many eastern states of the USA (total of 31 Mha). Soil organic carbon (SOC) is generally greater under pastures than under row-cropping systems, and often equally as great as under forested land. There is great potential to improve the management of pastures, and subsequent improvement in SOC, partly because many pastures are currently minimally managed as they provide adequate services to landowners without much input. Additional SOC can be sequestered with attention to soil fertility (i.e. applying inorganic and organic fertilizer sources when needed, but avoiding them when nutrients are sufficient), botanical composition (e.g. warm- vs cool-season grasses and legumes, endophyte-infection status of tall fescue, annual vs perennial growth), stocking rate, and stocking method (e.g. continuous vs rotational, high vs low density, short vs long duration). Some information is available to characterize the response of SOC to management in particular soils or locations, but a much greater research effort is envisioned to provide more robust evaluation and recommendations. Soil organic C varies spatially under pastures in the vertical (depth) and horizontal directions (e.g. edaphic and animal behavior induced), and understanding this variation is essential to research and monitoring of pastures for SOC sequestration. Sequestration of SOC under pastures may occur for decades to centuries, but more long-term research is needed to establish these limits under different soil types and climatic conditions. Finally, SOC accumulation under pastures helps control a suite of other environmental effects in the landscape. An expanded network of comprehensive pasture-management research is needed for more complete information on SOC sequestration, but also for understanding and capturing the resiliency and sustainability of American agriculture for the future.