Effects of Native Warm-Season Perennial Plant Diversity in Grasslands Managed for Forage and Biofuel Biomass.

Native warm-season plants (NWSP) are infrequently used in forage-livestock grassland systems even though they possess characteristics that could boost forage system productivity.  Additional research suggests that more diverse mixtures may have higher productivity, lower weed invasion, and improved forage value.  Therefore, we hypothesized that managing NWSP mixtures for high diversity may enhance these benefits.  In 2008, we established an experiment using three native plant mixtures containing 1, 4, or 10 species to evaluate how sown forage diversity and management for grazing and biofuel production affected forage yield and plant species composition as stands matured.  The plots were grazed by beef cows starting in 2009, and cattle were excluded from portions of each plot to mimic a biofuel production situation.  Forage was sampled in June and July for nutritive value.  In both 2008 and 2009, forage yields were lowest in the monocultures and greatest in the 4- and 10-species mixtures; however, weed biomass was not affected by sown mixture in either year.  In grazing exclosures there was a similar effect, with multi-species exclosures producing 3.6 times more forage species biomass than monocultures.  Forage nutritive values were generally acceptable for maintaining grazing animals in all three treatments, and quality tended to decrease as native grass cover increased.  Results from the third season of this experiment will also be presented.  Our results from the first two years suggest that NWSPs can be a viable forage option and that managing for diverse NWSP mixtures may improve forage productivity.