Sustainability Aspects of Perennial Grass Feedstock Production in the Southeastern Coastal Plain.

Two sites in the southeastern Coastal Plain are being used for trials of two bioenergy grasses - elephant grass (Pennisetum purpureum (L.) Schum.) and energy cane (Saccharum officinarum L.) to obtain data for Life Cycle Analysis (LCA) of the crop production enterprise.  The sites are located in Tift County, GA (Tifton loamy sand soil) and Peach County, GA (Orangeburg loamy fine sand soil) on marginal lands that were previously weed fallow.  The grasses were established in a randomized complete block design (four replicates) in August, 2011.  Treatments for the grasses include different winter covers (clover, lupine, or no winter cover) and different fertilizer N rates (0, 75 kg N /ha and 150 kg N /ha).  Changes in soil carbon and physical properties will be determined by comparing starting conditions to conditions at the end of the 5 year project.  Biomass production for each growing season will be determined.  First year harvest was done after the short growing season (from August-December).  To provide specific data for the LCA, weekly sampling of greenhouse gas fluxes (methane, nitrous oxide, and carbon dioxide) using vented chambers were started shortly after planting for the clover cover treatments receiving the three N rates.  Data for August, 2011 through February, 2012 showed that there were no treatment differences but there were significant differences between sites for carbon dioxide flux (positive) from the soil.  Methane (negative) and nitrous oxide (positive) fluxes were low from both sites and were not significantly different between the two sites. Future research will provide data for LCA of these two bioenergy crops and provide data on the potential production of these crops under non-irrigated conditions with varying levels of N input.