Fall is the time of year when managing annual forages is critical for livestock producers. Now is the time to not overgraze pastures, especially those with annual lespedeza.
“It's important when we talk about annual lespedeza not to confuse it with sericea lespedeza, which is a perennial,” says Craig Roberts, University of Missouri Extension forage specialist. He notes that sericea lespedeza is a high-tannin forage, which can cause bloat in livestock.
“Sericea lespedeza is thought of as nothing more than a noxious weed and an invasive plant,” he adds. But that is not annual lespedeza.
Benefits of lespedeza
Annual lespedeza is a high-quality forage that fixes nitrogen. “No one really knows how much nitrogen,” Roberts says, “but probably 50 pounds to the acre on a pure stand.”
It fills the summer grazing gap, growing in pastures in Missouri from June all the way through September.
While annual lespedeza has tannins, they are at moderate to low levels, Roberts explains. “Tannins are important for bypass proteins and the absorption of amino acids in the lower digestive track,” he says. “Tannins help with parasites.”
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SEE THE DIFFERENCE: Sericea lespedeza is considered a noxious weed by many. There is a difference in the leaf structure and plant. It grows taller than annual lespedeza, which stays close to the ground.
With low tannin levels, annual lespedeza is non-bloating. Actually, Roberts says that it provides “excellent animal performance,” when cattle are turned out to graze and plant seed heads are present. He notes that historically, cattle producers would graze annual lespedeza seed heads as they believed it caused white fat in the meat.
However, the greatest benefit to annual lespedeza, Roberts says, is it grows well in poor soils. “We call it the 'poor man’s alfalfa' because it can grow on a pH 5 soil,” he says. “Of course, it will grow on a pH 6 soil as well. It can really take over a field.”
But all of these benefits can be negated by overgrazing annual lespedeza in the fall.
Watch stubble height
Roberts says managing annual lespedeza for yield and productivity is related to stubble height. “It has to be grazed to a moderate height,” he says. “Five inches is ideal.”
These plants germinate well before June and start expressing in July. Some fields are clipped in August. Roberts says research studies show if annual lespedeza is clipped at 5 inches, it has a good forage yield all the way through October. “But if we clip down to 2 to 2½ inches,” he notes, “we have a significant drop in yield.”
That “clipping” can be done either mechanically with a mower or by grazing cattle or sheep. When it comes to grazing, the same data holds true.
“We need to keep the grazing pressure low,” Roberts adds. “If we graze or clip and leave a 5-inch stubble, we will have quite a bit of yield. But if we pressure that plant and leave only a 2½-inch stubble, we'll see a significant drop in yields.”
The later in the season you graze, the more damage you can do to next year’s yields.
While annual lespedeza grows well into October providing fall forage, Roberts says to pay attention when grazing this late.
September is the critical time for seed development as plants are flowering. “Be careful not to graze low, particularly from Sept. 1 through Oct. 10,” Roberts warns. “We say graze annual lespedeza 40 days and 40 nights, but be careful. Too much grazing, and there won’t be enough seed for next year.”