Carbon Sequestration in Soil Fractions of Switchgrass Cultivars for Informed Selection in Biofuel Cultivation

Bioenergy crops such as switchgrass have the potential to offset CO2 emissions in the bioenergy lifecycle by increasing soil carbon storage through their extensive root systems. Previous research has shown that switchgrass cultivars vary in root morphology and soil chemistry, suggesting different soil carbon stabilization mechanisms. After 10 years of growth, these differences in carbon storage begin to emerge in the topsoil. Our study aims to quantify how the switchgrass cultivars affect carbon sequestration after 14 years. Our fieldsite was established in 2008 at Fermilab in Batavia, IL. Previously, C3 plants grew for 36 years before removal and were replaced with C4 plants (switchgrass). This is important because carbon from C4 plants is easily identifiable from carbon fixed by C3 plants, allowing us to accurately measure the amount of carbon amassed by the C4 plants in soil. In 2022, we collected 3 soil cores from 9 plots of the following switchgrass cultivars (Cave-in-Rock, Kanlow, Southlow, n=3). Cores were taken from the crowns of the switchgrass at depths of 0-10 cm, 10-20 cm, and 20-30 cm; cores with C-3 root contamination were removed from the data pool. The soil samples were then fractionated into Coarse particulate matter, Fine particulate matter, silt, and clay. Since C associated with silt and clay is more persistent in soil than C associated with particulate organic matter which is vulnerable to decomposition, this method allows us to predict future soil C storage potential of the different cultivars. From there, the fractions are ball milled to homogenize the particulates. A small sample from each fraction is then sent to be analyzed by mass spectrometry to measure total C and C4 carbon levels. The data in this study could be used to improve bioenergy management and lower CO2 emissions through informed cultivar selection