Jennifer Burks PhD Defense Ecological Sciences and Engineering Agronomy Eco-Physiology of Three Perennial Bioenergy Cropping Systems Thursday, March 28, 2013 9:00 AM LILLY, Room 2-425 Everyone is welcome Abstract: Comparative data on biomass accumulation/partitioning and macronutrient cycling within perennial bioenergy cropping systems grown in the US Midwest are sparse. My objective was to compare energy densities, nutrient cycling, and potential ecosystem impacts of systems considered for commercial production to inform which, if any, are capable of meeting required targets outlined in government mandates. Results from this study assessing Miscanthus × giganteus, switchgrass (Panicum virgatum, 'Shawnee'), and an unmamaged big bluestem- (Andropogon girardii) dominated prairie indicate that Miscanthus annually accumulated more aboveground biomass, and thus attained higher ethanol production estimates (16 to 38 Mg ha-1; 5006 L ha-1) than switchgrass (9 to 13 Mg ha-1; 2430 L ha-1) and prairie (3 to 6 Mg ha-1; 1031 L ha-1). This high biomass production resulted in more nitrogen (N), phosphorus (P), and potassium (K) accumulation in Miscanthus than in the other crops. Miscanthus increased rhizome mass three-fold during this three-year study, resulting in the highest rhizome N, P, and K accumulation of the candidate systems. This high amount of biomass allocated belowground by Miscanthus was associated with a consistent ability to translocate nutrients (38% N, 76% P, 52% K) from shoots to rhizomes/roots/stem bases at the end of the growing season. The consistency of annual nutrient remobilization in switchgrass and prairie was less pronounced. Carbon (C) concentrations were similar among systems and tissues (mean: 443 mg C g-1 dry matter), identifying total belowground biomass accumulation as the main factor contributing to system soil C sequestration potential. Analyses of tissue composition to assess crop persistence and regrowth potential suggest Miscanthus relies primarily on organic reserve accumulation in rhizomes and exhibits more dramatic fluctuations in belowground organic reserve accumulation than the other systems. Results from this study identify Miscanthus as having high potential of meeting both energy density and environmental guidelines outlined in government mandates. Data from this research further our understanding of these novel cropping systems, and when used to parameterize large-scale models, can inform government policy on renewable energy strategies. Christal Musser Program Coordinator Ecological Sciences and Engineering Interdisciplinary Graduate Program Purdue University Young Hall, Room B-40 155 S. Grant Street West Lafayette, IN 47907 765-494-2102 musser@purdue.edu<mailto:musser@purdue.edu> http://www.purdue.edu/ese<http://www.purdue.edu/dp/ese> Like us on Facebook<https://www.facebook.com/?sk=welcome#!/ESEatPurdue>