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The soil carbon content of cropland soils has been reduced through long-term cultivation. Cultivation enhances soil aeration and accelerates the break down of soil organic matter, the main source of soil carbon. Growing switchgrass provides an opportunity to sequester carbon in soil because tillage is removed from the system. Also, perennial grasses such as switchgrass can deposit organic matter deep within the soil profile as roots expand into the subsoil for nutrients and water.
Sequestration of carbon in soils removes CO2 from the atmosphere, which is considered a greenhouse gas contributing to global climate change. Its reduction in the atmosphere is one benefit of utilizing switchgrass as a fuel source to offset CO2 emissions from the combustion of fossil fuels. Much of the offset results from the fact that ethanol use reduces gasoline combustion. However, some CO2 offset results from sequestration of carbon in soils, particularly in soils cultivated prior to switchgrass establishment. Establishment of switchgrass on Conservation Reserve Program (CRP) land or rangeland, results in little or no net increased soil carbon sequestration because these systems contain relatively high levels of soil carbon; therefore, carbon accumulation is limited compared to previously cultivated land.
