Technical Abstract: Addressing the emerging issues associated with managing soil C is needed to provide environmental services, including mitigation of climate change due to atmospheric enrichment of CO2, and necessitates the identification of important research and development priorities. Important among these are the following: • Techniques for measurement of C pool and flux at regional or national scale • Assessing the processes, forms, and permanence of C sequestered in soil • Evaluating competing uses of soil C pool for soil fertility enhancement versus climate change mitigation and providing other ecosystem service • Evaluating gross versus net C sequestration, with due consideration to hidden C costs of all input and of the ancillary benefits accrued by ecosystem services • Determining the importance of secondary carbonates and of the inorganic C pool in soils of dry climates • Establishing relationships between soil C pool and agronomic production, with a focus on achievement of global food security • Determining fate of C transported by erosional processes to resolve whether soil erosion is a source or sink for atmospheric CO2 • Assessing the importance of biochar as a by-product of the biofuel industry Creation of an effective program for soil C sequestration requires development of a multidisciplinary team, because several of the issues involved cut across thematic disciplines. Therefore, research teams may comprise many disciplines including, among others, soil scientists, foresters, climatologists, geologists, ecologists, biologists, sedimentologists, hydrologist, economists, and those dealing with policy implications. Furthermore, these studies must be conducted on an ecoregional basis, representing principal biomes and predominant soils, and for a long-term covering several generations. Commodification of soil C is an important issue because it may promote adoption of recommended technology by resource-poor farmers of developing countries. [GRACENet publication].