Dr. Garry Lacefield and others conducted a survey of forage specialists across the U.S. a few years ago on the reasons orchardgrass hay fields seem to be thinning out in recent years. Survey respondents identified lower fertility, severe weather conditions, insects, and diseases as factors contributing to stand loss, but they felt that the number one reason for shorter stand life was low cutting heights. And low cutting heights were mainly attributable to disc mowers. Disc mowers are great hay cutting tools, with their ease of operation, speed of harvest, and ability to easily harvest thick stands. These mowers allow producers to easily harvest at 1 to 2 inches. Low cutting heights like this are fine for alfalfa since it regrows from energy stored below ground in it's large taproot, but can be disastrous for grasses like orchardgrass. Orchardgrass has a more upright growth habit and low cutting removes all the leaves needed for photosynthesis and the base of tillers (stems) where carbohydrates are stored for regrowth.
An Asbury University student, Leah Saylor, conducted a research experiment on orchardgrass cutting height at UK 4 years ago. Leah found that just one season with low cutting heights significantly reduced stand longevity and increased weed infestation, regardless of the addition of fertilizer treatments.
The results show that the recommended cutting height of 3 to 4 inches for orchardgrass and similar grasses is essential to maintain thick, weed free stands. Most disc mower manufacturers sell skid shoes to insure higher cutting heights. These are well worth the price.