Preliminary Assessment of Dual Use Bioenergy-Forage Potential of Exotic and Native Grasses in Arkansas.

Some grasses may have dual use potential as bioenergy or livestock feed.  Experiments with exotic and native grasses were conducted on an upland soil near Booneville, AR in 2007-2010.  Experiment 1 determined leaf and stem+sheath quality (in vitro digestibility, total nonstructural carbohydrates [TNC], detergent fiber and lignin, cellulose, hemicellulose, and combustible energy) for the exotic grasses cold tolerant sugarcane (Saccharum hybrid) clone US84-1028, giant miscanthus (Miscanthus x giganteus, clone Q4264), and giant reed (Arundo donax).  The invasive giant reed was included to represent biomass eradicated from riparian areas.  Sugarcane stems had the most TNC among entries, while leaves and stems of giant miscanthus were low in digestibility and TNC.  Giant reed leaves had the highest digestibility, but its bamboo-like stems had the lowest digestibility, detergent fiber, and cellulose.  Overall, entries differed little in concentration of combustible energy.  Leaves and stems of sugarcane, and leaves of giant reed, appeared to have dual use potential for energy or animal fodder.  Experiment 2 examined the effect of growth stage on stem+sheath sugars (glucose, fructose, and sucrose) and combustible energy for two native grasses [‘Bumpers’ eastern gamagrass (Tripsacum dactyloides) and ‘Alamo’ switchgrass (Panicum virgatum)], and the exotic Amur silvergrass (Miscanthus sacchariflorus) clone Msanag.  Msanag had more glucose and fructose at boot than anthesis, and sucrose peaked at anthesis through mature seed.  Bumpers usually had more glucose and fructose at any given growth stage than Alamo, but across growth stages Alamo had more sucrose than Bumpers.  Sucrose decreased from jointing to post-freeze.  Alamo at head and anthesis had greater energy concentration than comparable stages in Bumpers.  Maturity-associated decreases in sugars paralleled decreases in nutritive value published elsewhere.  Results will guide selection of site-appropriate species and harvest schedules for dual use bioenergy-livestock production.