Switchgrass Composition and Quality Changes Across a Landscape Gradient.

Agricultural producers in Iowa and throughout the Midwestern United States are gearing up to meet the increased biomass demands associated with world and regional bioenergy production.  Among biomass crops, switchgrass shows particularly promising agronomic, conservation, and energy potential.  Efficient conversion of biomass crops to fuel or power requires an understanding of plant quality, including cell wall composition and mineral composition.  This switchgrass quality experiment was part of the Landscape Biomass Project (Boone County, IA), a larger, transdisciplinary study evaluating food, feed, and fuel crops. Specifically, we compared key quality parameters of two exemplary switchgrass varieties (lowland Kanlow and upland Cave-in-Rock) over two growing seasons and across five landscape positions (elevation: 325 to 300 m).  Few varietal differences were noted; however, plant mineral composition was influenced by landscape position.  Switchgrass at the bottom of the hill slope in the floodplain position was “dirtier” containing more minerals known to contaminate biochemical and thermochemical conversion processes.  Plant cell wall components (hemicellulose, cellulose, and lignin) varied more with growing season than with landscape, and that temporal variability was greater than that of plant mineral composition (total ash, [N], and N content).