Carbon Sequestration in Agricultural Soils: Separating the Muck from the Magic

Intense interest in soil organic matter (SOM) over its role in the storage of terrestrial carbon (C) and in the release of greenhouse gases to the atmosphere manifests itself in a renewal of research efforts to assess the impacts of different soil management systems on C dynamics. This paper assesses the future role of selected systems for managing agricultural and pastoral land; addressing the global land area, potential to sequester carbon, side effects on other sources of greenhouse gases, and other limitations. Some systems such as organic farming and the use of biochar may have positive impacts over limited areas, but agroforestry, grazing lands and conservation agriculture appear to have the greatest potential to sequester carbon by covering vast areas on which C loss is reduced or positive C sequestration occurs. An over-riding problem is the difficulty of measuring changes in soil C. Isotopic techniques applied in comparative studies of different soil management systems offer new insights that will guide land managers and policy makers. (author)