Agriculture is historically a source of atmospheric carbon. With the best management practices, this could be partly reversed, with a potential increase in size of the soil carbon pool that would have significant impact as a measure to mitigate climate change. This might benefit farmers twice over, as the carbon has a cash value, while the soil organic matter that contains it will assist productivity. There is therefore a business opportunity in carbon payments for farmers in the developed world. However, this article considers whether such payments might alleviate rural poverty and fund agricultural development in low-income countries. They might do so, but badly designed projects could lead to emission rather than sequestration, accompanied by productivity losses. Prevention of such perverse outcomes requires a multidisciplinary approach and an awareness of the political ecology context of sinks projects. An appropriate methodology is needed for the evaluation of soil carbon projects in developing countries.