|| Doxon, E., Keyser, P., Ellis, F., Bates, G., Harper, C.
||Switchgrass (Panicum virgatum L.) is often promoted as a high-yielding forage species. However, it is less understood how different varieties compare and how cutting height may influence yield. To examine the impact of varietal type and cutting height, we established 48 plots representing 3 varieties of switchgrass in 1990. These varieties included one upland variety (Cave-in-Rock) and two lowland varieties (Kanlow and Alamo). Beginning in 2008 and continuing to the present, we harvested the 18-year-old switchgrass plots at 4-, 8-, 12-, and 16-in cutting heights in June and August to determine if cutting height or variety influenced yield. We determined yields were similar among the 3 varieties examined. However, we determined yield interacted with year and cutting height. Yield was 55% higher in 2008 compared to 2009. In tons/acre, yield was 4.1 in June 2008 and 2.9 in September 2008. In 2009, yield was 2.3 and 2.2 in June and August, respectively. In June 2008, yields were similar among the four cutting treatments. However, in August 2008, the 8-in cutting height produced higher yields than the 16-in cutting height. In 2009, we documented the reverse trend. In June and August 2009, the 16-in cutting treatment had higher > 70% higher yields than the 4- and 8-in cutting treatments, the equivalent of > 1.2 tons/acre. These results suggest Kanlow, Cave-in-rock, and Alamo switchgrass will produce comparable yields given similar growing conditions. However, harvesting switchgrass at shorter cutting heights did not necessarily produce higher yields. Yield differences in cutting height became more apparent after two consecutive years of 2-cut harvesting which may suggest shorter cutting heights may have negative impacts on long-term yields.