Timing and Intensity of Steer Use on Old World Bluestem (Bothriochloa Ischaemum) and Blue Grama (Bouteloua Gracilis) in Southern Mixed-Grass Prairie

Yellow bluestem (Bothriochloa ischaemum), an invasive species, was introduced as a forage species and as a roadside grass for erosion control. Yellow bluestem can negatively interact with native grasslands and reduce biodiversity. Livestock tend to avoid yellow bluestem after accumulation of standing lignified tissue, particularly at the end of the growing season. Mowing has been used in pasture situations to remove excess grass for hay and over coarse grass left from the previous season. It is essential to understand the role livestock play as either a catalyst for control or preventing further invasion of yellow bluestem. Quantification of the timing and intensity of yellow bluestem defoliation by livestock after mowing compared to native grass has not been previously documented. To evaluate this, I recorded steer utilization of yellow bluestem and blue grama (Bouteloua gracilis) in a southern mixed grass prairie following two mowing treatments during 2012-2013. I also recorded cover by litter. In 2012, mean utilization of blue grama (12%) was lower than mean utilization of yellow bluestem (22%), but in 2013, mean utilization of blue grama (20%) was higher than mean utilization of yellow bluestem (15%). Timing of utilization of yellow bluestem was different than was suggested previously, with utilization of yellow bluestem occurring late in the season. These data could be used to help assess the potential shifts in steer utilization of native rangelands where yellow bluestem is present and aid in making future grassland management decisions. However, the system that I worked with experienced a high degree of variation in temperature and precipitation between years, a longer-term experiment could distinguish between year to year utilization variation and an overall trend in yellow bluestem utilization