With the expansion of agriculture, the world´s soils have released a significant portion of the indigenous soil organic carbon (SOC) as CO2 into the atmosphere. This is mainly due to soil disturbance – ploughing, for example – and the removal of plant residues, causing the net oxidation of relevant fractions of the SOC, especially of those fractions related to fresh residues and less stabilized compounds. Today, it is well known that the process can not only be stopped but also reversed, if conservationist practices of soil management (for example, recycling of organic residues, non-disruptive tillage, measures against erosion, integrated production systems) are systematically applied as a permanent strategy. Thus soils can be used to remove atmospheric carbon and capture it permanently in the form of SOC, provided that the non-conservative practices which caused the loss of SOC are not resumed. A set of such soil management techniques can be proposed  as a Nationally Appropriate Mitigation Action (NAMA) if a national public entity takes charge of its administration (a Ministry, for example), providing incentives for farmers who adopt the proposed practices and who submit to monitoring and verification. The use of a web-based computer tool based on the soil carbon/nutrient-cycling model Century/DayCent is essential to planning and implementation of the proposed NAMA, because it permits the projection of effects in specific fields under particular practices. Its use can be largely automated through connection with geospatial databases of historic land use, climate and soil type.