Answer to Question 1F
Answer to Question 2Soil organic matter is one of the Earth's largest reservoirs of carbon. When it decays, carbon
dioxide, the main greenhouse gas, is released into the atmosphere. When more soil organic matter is
created, carbon dioxide is removed from the atmosphere. And so, soil carbon affects global climate.
If the Earth warms, decay rates probably will increase, releasing more carbon dioxide and
increasing climate changes. Or, higher carbon dioxide levels might increase plant growth, and more
carbon would return to the soil. The former is more likely.
Growers, by affecting the carbon content of soils, have some influence on global climate.
Serious efforts to reduce carbon dioxide in the atmosphere could mean soil users may be asked to
grow carbon in their soils. Two simple objectives would go a long way toward sequestering more
carbon in farmland soil: soil carbon conservation in prime farmland and converting marginal farmland
to permanent vegetative cover.
While much carbon can be stored in agricultural soils, the amount is limited. Changes to
cropping practices that store carbon would cause soil organic matter content to rise. Further, if
cropping practices changed again, the previously stored carbon re-enters the atmosphere.
Histosols and gelisols are gigantic carbon reservoirs held in place by cold and/or wetness.
Climatic warming and drying could result in the release of substantial amounts of greenhouse gases,
further accelerating climate change. Drainage of wetlands for agriculture or peat harvest presents the
same possibility.
