Soil Carbon Changes Following Five Years of Corn, Sweet Sorghum, and High Biomass Sorghum Production on Marginal Lands.

Emerging biofuel feedstock systems are poised to have a lasting effect on Midwestern USA marginal soils by altering soil organic carbon (SOC) stocks, and these alterations may be exacerbated by climate change. Producing biofuel feedstocks on marginal lands may result in a loss of SOC with the land conversion and accompanying tillage. Three crop rotations were evaluated for their theoretical ethanol yield and effects on soil carbon changes in the first five years (2010-2014) at two sites in Missouri, USA. Three crops: Corn (Zea mays), sweet sorghum (Sorghum bicolor (L.) Moench), and high biomass sorghum were grown, with each in 2-yr rotations with soybean (Glycine max L.). The two sites chosen were previously in perennial grasses and managed for hay production and each present respective challenges for row-crop production. Soil cores were collected following the first, second, and fifth years to a depth of 300 mm and divided into three layers (0-50 mm, 50-100 mm, 100-200 mm) for analysis of the soil carbon, which included SOC and an active SOC fraction. Initial soil carbon loss in the first two years were remedied by year 5, such that over the long-term there were few overall losses in soil carbon, but generally sweet sorghum and high biomass sorghum yielded greater and sequestered greater SOC to the marginal lands.