Pasture, Hay and Biofuel Harvest Management of Perennial Warm-Season Grasses Under Irrigation in the PNW.

This study investigated the influence of change in harvest management on DM yield and forage quality for three warm-season grasses (WSG) in Pacific Northwest under irrigation. Harvest treatments included biofuel only, hay-biofuel, hay-pasture, pasture-hay, and pasture only for eastern gamagrass [EG: Tripsacum dactylodies (L.) L.], indiangrass [IG: Sorghastrum nutans (L.) Nash], and switchgrass (SG: Panicum virgatum L.) during the study year of 2005 to 2008. Annual DM yield was decreased when harvest management was changed from hay to biofuel harvest in EG and SG as compared to biofuel treatment, indicating that hay producer needs to sacrifice the yield potential of EG and SG if changing the harvest management from hay to biofuel. In contrast, harvest management can be flexible between hay and biofuel for IG as no statistical difference was observed between biofuel and hay-biofuel treatments. When harvest management was changed from hay to biofuel treatment, fiber composition (NDF, ADF, and lignin) of WSG declined as compared to continuous biofuel production, indicating that biomass quality for biofuel production may change by the changing the harvest strategy. Regardless of the change in DM and forage quality of EG, IG, and SG following various harvest treatments, DM productivity and forage quality in terms of CP, NDFD, and RFV are comparable to CSG utilized in pasture or hay. These results suggest producers have wide options to utilize EG, IG, and SG as hay or pasture if the biofuel industry will not purchase cellulosic feedstocks.