Net Carbon Sequestration in Soils: Let's Be Realistic About the Potentials.

Each year heralds rising concentrations of carbon dioxide and other greenhouse gases in our atmosphere. Agriculture is at least partially responsible for emissions of carbon dioxide, by stimulating losses of soil organic matter and by using fossil fuels directly and indirectly to enhance crop yield. Reducing the contribution of greenhouse gases to the atmosphere is an admirable goal that should be pursued with all vigor, but it will take real reductions in the amount of carbon dioxide accumulating in the atmosphere to avoid the continued onslaught of global warming. Here, we need to be realistic about what agriculture can do to restore carbon to soil organic matter to provide a permanent “sink” for atmospheric carbon dioxide. I will argue that conservation tillage, enhanced use of fertilizer and irrigation, manuring, and applications of biochar and ground silicate rock can reduce carbon dioxide emissions from agriculture, but not carbon dioxide concentrations in the atmosphere. Subsidies for these efforts cannot be justified as offering realistic solutions to a critical global problem.