EFFECTS OF GENETICALLY MODIFIED SWITCHGRASS CULTIVATION ON SOIL CARBON DYNAMICS

Though switchgrass is widely accepted as a bioenergy feedstock, there exists a major challenge in efficient conversion of switchgrass biomass to biofuel due to the high lignin content in its cell wall tissue. To solve this problem, transgenic switchgrass plants containing altered levels of lignin have been developed by genetic manipulation. However, lignin is an important component of soil organic matter (SOM). Plant residues with altered cell wall lignin might alter overall soil quality by affecting soil carbon and nutrient cycling. We hypothesized that soils planted with transgenic switchgrass impact SOM cycling differently than soils planted with non-transgenic switchgrass. We collected soil samples from two transgenic switchgrass experimental trials at the East Tennessee AgResearch and Education Center in Knoxville. Both trials included replicates of transgenic and non-transgenic switchgrass plants. Preliminary results indicate no difference in total SOM between transgenic and non-transgenic plots. Detailed examination is currently being undertaken on potentially mineralizable carbon content and microbially respired carbon to carbon dioxide. This research is expected to provide comprehensive understanding of the effect of genetically modified biofuel feedstock plants on soil processes leading to sustainability of production systems.