Timing and intensity of steer use on old world Bluestem (Bothriochloa ischaemum) and Blue Grama (Bouteloua gracilis) in southern mixed grass prairi
Casey, J. L. 2014. M.Sc. Fort Hays State University
Abstract
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.
