Pasture, Hay and Biofuel Harvest Management of Dacotah Switchgrass, Pete Eastern Gamagrass and Osage Indiangrass Grown Under Irrigation.

This study investigated harvest management options for producers if biorefiners did not purchase cellulosic feedstocks for a year or more. A field study compared five harvest managements: 1. Pasture only, 2. Pasture-Hay, 3. Hay-Pasture, 4. Hay-Biofuel, and 5. Biofuel only for three perennial warm-season grasses over multiple years. Stubble heights were maintained at 15 cm for all harvest treatments and grasses. Fertility amendments were applied based on soil tests and irrigation water applied by solid set. Harvests ranged from four or five for pasture only to two for biofuel only. The study was repeated with initial planting dates in 2003 and final planting in 2005.

All main effects and many interactions were significant. Greatest interaction responses were grasses × harvest treatment and harvesting years × harvest treatment. Grasses and harvest management treatment were the most important main affect. Osage Indiangrass produced higher yields from biofuel harvests (16 Mg DM ha^-1 yr^-1) than Dacotah switchgrass (6 DM ha^-1 yr^-1) or Pete eastern gamagrass (6 Mg DM ha^-1 yr^-1). Pasture or pasture – hay harvest management for all grasses was lower yielding (range: 2-3 Mg DM ha^-1 yr^-1) than other harvest treatments (range: 5-9 Mg DM ha^-1 yr^-1). Hay – pasture and hay – biofuel harvest treatments generally produced more biomass than pasture only or pasture – hay but less than biofuel only. The 2003 planting produced more biomass by grass and harvest treatment than 2005 because it had one additional growing season to develop a fully productive stand. These results suggest producers have options for grass utilization if the biofuel industry will not purchase cellulosic feedstocks.