The New Facts
Forget what you know about orchardgrass
by Curt Harler
For years, livestock producers have made a practice of cutting orchardgrass at a typical 1.5 or 2-inch height to maximize tonnage. Here's a shocker: Agronomists now recommend that producers cut orchardgrass at a 4-inch minimum height. It might help, too, if you don't use a disc mower.
Granted, a field mown to 4 inches hardly looks cut, but the research is fairly plain. If you want to maximize nutrient production as well as stand life, raise that cutter bar.
In fact, double the normal 2-inch mowing height and everything will still be just fine.
Paul Craig, extension program leader at Penn State University, is one of several agronomists who say producers need to change their mindsets when dealing with tall grasses and legumes. Craig, who has a background as a regional forage agronomist, points out that legumes store carbohydrates in their taproots or their crowns. "In grasses, energy is stored in the lower portion of the tiller," he says.
The tiller is the low, white, softish part of the plant. When a producer cuts orchardgrass, tall fescue, reed canary or similar tall-growing grasses too near the ground, the plant loses much of the energy stored for regrowth in the tiller. The grass plant relies on that energy to regenerate enough growth to get leafy again and begin photosynthesizing. A damaged tiller means stunted growth, slower recovery and, eventually, a plant that is going to fade.
Craig notes that many old-timers talk about having orchardgrass stands that would last 10 to 14 years. "With the new harvesting equipment, producers can cut down to 1.5 or 2 inches," he says.
Craig says Ray Smith and Leah Saylor, researchers at the University of Kentucky, spelled out the facts. Smith and Saylor did a study that was fairly broad in scope. The results of the study suggest that the low cutting heights prevalent with disc mowers may be a primary reason for observed declines in orchardgrass stands. They also found that 4 inches is the best height for cutting.
"Biologically, it makes sense," states Dan Hudson, University of Vermont Extension agronomist and nutrient management specialist. Hudson is working with a sheep producer who is gathering data that will be analyzed. So far the higher cutting height seems to be proving the point. Hudson is also looking for other producers--dairy or sheep--who would be interested in doing some on-farm research on the topic of mowing height.
Volunteers should be plenty, since many grass producers have become concerned about short stand life.
Since the late 1990s, producers across the eastern U.S. have reported reduced survival of orchardgrass hay stands.
The research from Kentucky finds that cutting orchardgrass at 4 inches (as opposed to 2 inches or lower) actually increases yield over the season and improves longevity of the plants in the field.
"Just because the Discbines [and other disc mowers] are tough enough to allow us to shave the ground doesn't mean we ought to," Hudson says.
Added benefits from the higher mowing can include:
Better quality--the material higher up on the plant tends to be more digestible and contains a higher percentage of protein.
Faster regrowth if we leave some leaf in the field to help the crop regrow--this assumes you are somewhat aggressive and harvesting early. If there are mature seed heads, there will probably not be many green leaves at 4 inches to make much of a difference.
Faster curing. If the mowed forage is up off the ground, we can get better air circulation under the plant.
For their study, Smith and Saylor cut a well-managed orchardgrass hayfield at three cutting heights: 0.5, 2 and 4 inches. Fertility treatments consisted of nitrogen (60 pounds per acre) and potassium (100 pounds per acre) applied after the first, second and fourth cuttings. Preliminary results showed a cutting height effect and a fertility effect even as soon as the first two harvests.
Orchardgrass stand persistence declined to less than 25 percent ground cover in all 0.5-inch cutting height treatments for both the control and fertility treatments.
At 2 inches, the fertility treatment provided higher yield and stand persistence over the control, and similar stand persistence to the 4-inch cutting height.
Not surprisingly, given what agronomists are learning, the 4-inch cutting height with fertilizer produced the highest yields, but the 4-inch cutting height without fertilizer also maintained an acceptable stand density. Hudson credits that to more leaf area and faster photosynthesis after mowing. He compares leaf area on the grass plant to a series of little solar panels. "If you cut off all those solar panels, the plant has no way to capture sunlight," he says.
Not only will extra leaf matter help the plant's physiology, but Hudson says more leaf matter can also be helpful with TDM (total digestible matter). While he concedes there is a good amount of stored energy in the stems, leaving some for future growth will usually pay off.
A producer trying to feed a group of dry cows might not care much about tip-top quality. However, anyone who is feeding milkers or running a sheep operation and wants to keep the bulk tank full or avoid thin ewes will be concerned about leafy matter.
"The results from Kentucky make it worth further research on any farm," Hudson says.
He recommends producers set aside one section of a field and cut it higher. Flag it or mark it with a geo-reference, and then use any of the several methods available for estimating biomass production in the second, third or fourth cutting to see how a higher cutting height works on your operation.
Handling various stands
"We recommend cutting orchardgrass at 4 inches everywhere in Pennsylvania," Craig says. Most forage agronomists in the Northeast echo that recommendation.
This is especially important if the grass has been subjected to a long, hot, dry summer. Grass cut too low simply will not have the reserves to bounce back.
Note that low-growing grass varieties, like the Kentucky bluegrasses common in home lawns, are bred specifically to be mowed close to the ground. Their whole growth attitude allows them to endure mowing heights of 1.5 inches and still pop back.
The 4-inch recommendation holds for any of the taller grasses, including orchardgrass and tall fescue.
Short field grasses like rye or timothy are a slightly different story. Timothy has an energy storage organ called a corm. A corm looks a bit like a bulb at the base of the tiller. Since the corm will provide the energy for the timothy to bounce back, it is safe to cut timothy down to about 2.5 inches without much concern.
In many cases, producers will mix stands of grass and nitrogen-producing legumes like clover or alfalfa. These require a bit more management, however.
Craig generally would advise mowing higher, favoring the grass, rather than lowering to favor the legume. "If the grass is getting aggressive and gets ahead of the legume, then mow once a year to favor the legume," he says.
Typically, this might be the first cutting, when the grasses rush out in the spring green-up and the legumes take a bit more time to get going. The result is better stand longevity and better nutrients for the livestock.
The longevity finding might not surprise anyone, but the increased yield surprises Hudson. "It hurts to see 4 inches of material still standing in the field after you go over it with the mower," he acknowledges, "but leaving that leaf area will allow the plants to bounce back faster for an earlier and higher-tonnage second cut."
Craig agrees that it might be a bit shocking to look over a field that is mown to a 4-inch height, but he promises, "It sure will look better when you see it thriving next fall!"
Curt Harler, who has a B.S. in agriculture from Penn State University and an M.S. in ag from Ohio State University, is a full-time freelance writer specializing in green topics.
Photo credits, from top:
Photo by doctor_bob/morguefile.com.
Photo by Matt Lavin, via Wikimedia Commons.
Photo by Marion Voss, via Wikimedia Commons.
Photo courtesy of North Carolina State University.
Photo by Matt Lavin, via Wikimedia Commons.