Composition and Yield of Eight Switchgrass Cultivars in Alabama

Abstract

Switchgrass (Panicum virgatum) is a viable cellulosic energy crop. Energy conversion technologies prefer cellulosic feedstock to contain low concentrations of lignin and ash and high concentrations of fermentable sugars. Research into chemical composition across species of cellulosic feedstocks has been analyzed. There has been little research however, dedicated to interspecies analysis between switchgrass cultivars. The research objectives of this study were to analyze chemical composition and biomass yields of eight switchgrass cultivars in a twenty-year (1989–2008) randomized complete block (rep = 4) experiment in Alabama. Near-infrared spectroscopy was used to evaluate concentrations of acetyl, arabinan, ash, glucan, lignin, protein, xylan in leaf and stem biomass for 2007 and 2008. Theoretical ethanol yields were determined from the composition of sugars using the National Renewable Energy Laboratory website’s ‘Theoretical Ethanol Yield Calculator’. Biomass yield data of eight cultivars in a twenty-year (1989-2008) study was analyzed using multiple linear regression analysis in SAS v9.1, proc STEPWISE and proc MIXED. Biomass yield data was regressed against weather and harvest data. Total biomass yields were affected significantly by the weather factors precipitation, harvest and frostdate. The months of March, May and September appeared in highest frequency across cultivars as significant and positive to biomass yields.

Highest biomass yields across 1989–2008 were observed in cultivars Alamo, Kanlow and Cave-In-Rock with averages of 10.27, 8.22 and 6.57 tons/acre respectively. Average annual ethanol yield totals from 2007 and 2008 for Alamo, Kanlow and Cave-In-Rock were 336.28, 248.75 and 201.03 gallons/acre respectively. Leaf and stem biomass had different composition and were analyzed using SASv9.1 proc GLIMMIX and proc CANDISC. Leaf biomass was higher in ash and protein while stem biomass was higher in glucan and lignin. Leaf and stem biomass composition analysis with ANOVA tests showed significance among chemistry at the interactions cultivar x year, cultivar x harvest and year x harvest. Differences in total chemical composition were analyzed for all cultivars using canonical discriminant analysis. Alamo, Kanlow and Trailblazer were significantly different from all other cultivars with respect to their composition. The other six cultivars were all similar to one another in composition. Desired composition of switchgrass could be manipulated for improved cultivars using genetic and plant breeding techniques.