Grazing sheep in the late season, between August and October, could be a cost-effective way to help control the spread of sericea lespedeza, a noxious weed in parts of Kansas and neighboring states.
Research at Kansas State University has found that sheep will voluntarily graze, and therefore could help sustainably control, sericea lespedeza, a noxious weed in parts of Kansas and neighboring states.
By: Katie Allen, K-State Research & Extension News
A costly situation in the Kansas Flint Hills could become a scenario for profit, but it would require beef and sheep producers to work together to sustainably manage a noxious weed problem plaguing the area.
KC Olson, a beef cattle scientist for K-State Research and Extension, said sericea lespedeza is on the short list of noxious weed species people have thrown up their hands over, particularly those who own land in the Flint Hills. In the past, it has taken costly herbicide application to get rid of the weed.
"We have yet to learn to live with it, and we have yet to demonstrate that we can extinguish it on a large scale," he said.
Sericea is a tannin-rich perennial legume, and cattle grazing in the Flint Hills aren’t lining up to eat it, Olson said. His latest research that examines ways to control sericea in Kansas grasslands involves two cost-effective grazing approaches: supplementing grazing cows with a corn steep liquor byproduct to prompt them to eat sericea and using sheep as "clean up" grazers on sericea once stocker cattle are removed from pastures mid-summer.
Olson said both of these methods have worked to combat the spread of sericea, although he is in the initial stages of the research. The aim is to develop additional tools for the landowner’s toolbox to help deal with this problem in cheaper ways.
A costly nuisance
Sericea lespedeza is a durable weed that costs a lot of money to get rid of with herbicide, Olson said. Sericea has been labeled a noxious weed in Kansas the last 15 to 20 years, but landowners today are no closer to making it disappear.
If a person applies chemical to it immediately, it’s possible to make it go away for a short time, he said. But, sericea is a durable plant and is allelopathic, meaning as it grows it produces chemicals in the soil that prevent the germination and growth of native plants. It’s also canopy-dominant, meaning it can shade out its plant competitors and take over a field. Landowners usually don’t notice sericea until it is out of control.
"Any airily applied herbicide will probably kill adult plants at the top of the canopy," Olson said. "Because the tallgrass prairie has such a robust canopy structure, that herbicide does not filter down to ground level to get those juvenile plants, and it certainly doesn’t kill seed."
The amount of seed sericea produces is another major problem, he said. One adult plant can produce massive amounts of seed, and that seed has respectable durability in the soil. Even seed that has been in the soil for several years has potential to germinate.
Supplementation for cows
Olson has been studying ways to prevent sericea lespedeza from taking over fields in the Flint Hills since 2008. To cut down on costs, he has aimed to provide more grazing pressure on the plant.
"When a plant has been grazed, the rules of nature dictate that the plant directs its nutritional resources away from seed production and toward restoration of leaf area," Olson said. "That would be a small way we could cut into the reproductive capacity of that plant and get some control over it."