Greenhouse Gas Fluxes From Perennial Grass Bioenergy Feedstock Production.

Multiple 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 greenhouse gas Life Cycle Analysis (LCA) of the crop production enterprise.  Two sites are located in Tift County, GA (Tifton loamy sand soil), one site in Peach County, GA (Orangeburg loamy fine sand soil), and one site in Randolph County, GA (Greenville sandy clay loam soil) on lands that were previously weed fallow.  The grasses were established in a randomized complete block design in 2011.  Depending on the site, treatments for the grasses include different winter covers (Clover, lupine, or no winter cover), different fertilizer N rates (0, 75 kg N /ha and 150 kg N /ha), and different irrigation rates.  To provide specific data for the LCA, weekly or bi-weekly sampling of greenhouse gas fluxes (CH₄, N₂O, and CO₂) using vented chambers were started shortly after planting for the clover cover treatments receiving the three N rates.  Data for August, 2011 through February, 2013 showed that there were no treatment differences but  there were significant differences between sites for CO₂ flux from the soil.  CH₄ (negative) and N₂O (positive) fluxes were low from both sites but there were significant differences among the sites and among the N treatments.  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.