Weed & Pest
Grazing a tool for cheatgrass controlWritten by Christy Martinez
Wheatland – According to UW Extension Rangeland Specialist Rachel Mealor, using grazing strategies for weed control is like putting a puzzle together.
“You have to know all the different components so you can make the most sustainable choices,” said Mealor at the Sept. 28 workshop in Wheatland that focused on strategic cheatgrass management in range and pastures.
“Controlling the intensity and frequency of grazing is something that’s within our power – how many times we graze those plants and our utilization levels,” she said, adding that land managers need to look across the entire landscape for that kind of management, and not just in one pasture.
“Often we find good grasses intermixed with cheatgrass. As managers we can come in and increase the good grasses or decrease the undesirable grasses with management strategies,” she stated. “Our systems are all about balance, and putting the competitive advantage toward the desirable species and less toward cheatgrass or undesirable weeds.”
“If we keep maintaining our same strategies, we may decrease that desirable population,” continued Mealor. “We’d still have the same amount of nutrients available, and maybe a little more, which would give cheatgrass as an excellent opportunity to come in.”
Mealor described grazing as a type of disturbance.
“Like any other disturbance, like fire, grazing can have bad, good or neutral impacts on our system. As land managers, we can look at our systems and select our species of livestock according to what’s complimentary and what will better utilize the system – match the animals to the resource,” she said.
“Targeted grazing is not just about utilizing animals to decrease weeds – it’s really just the application of a specific livestock at a determined season, duration and intensity to accomplish our goals as land managers,” stated Mealor.
To begin a management strategy using grazing to minimize cheatgrass or other weeds, Mealor said it’s important to first set goals.
“Taking a step back and determining goals will help us in the long term to see if we’re reaching those or not with different strategies,” she said, noting that those goals should be kept simple, attainable and measurable. “How do you know if you’re getting there if you can’t measure it? The goals could be something as easy as decreasing bare ground, where gathering the data is simple.”
Once goals are set, Mealor said a land manager should next have a thorough understanding of how plants grow, and the difference between annual and perennial grasses, which will help determine the impacts of grazing.
“Know what type of plant you’re dealing with, and how it reproduces. Cheatgrass puts all its energy into seed growth, while a perennial grass puts more energy into a root system,” she explained. “Knowing that, we can decrease cheatgrass seed production by stopping the process. Knowing if your target weed is an annual or perennial plant will not only help you control it, but also help you promote the good perennial grasses and their root growth.”
Mealor said grass species are unique compared to forbs and shrubs, in that their growing point is located at the base of the plant.
“I can cut down or mow the grass, and it will grow back. They have a system where you can graze them and decrease the amount of biomass without the plant having to start all over,” she noted. “Knowledge of the growing point is important to us as grass growers.”
However, grass plants aren’t completely immune to clipping, as the growing point elevates when the plant transitions from the vegetative to reproductive state.
“It’s more vulnerable at the reproductive state, and a rancher or livestock owner needs to be mindful of where the growing point is,” said Mealor.
In addition to the growing point, Mealor said the root systems of perennial grasses are also important from a management standpoint.
“A healthy root system has lots of roots that are fibrous and intermingling. Each year a perennial species loses 30 percent of its root system, so we have to promote root growth by leaving a little bit of stubble height so photosynthesis can take place to regenerate that lost 30 percent,” she said.
“When the root systems become weak because we continually take off the growing point, we weaken that system, which provides a great opportunity for cheatgrass to come use that excess moisture and nutrients,” she said of the root system’s importance. “If we don’t promote root systems we see a lot more cheatgrass come into the area.”
Grazing should be applied to ranch management goals when the plants are less susceptive to damage by grazing, so that grazing is used to increase the target species. Because cheatgrass is palatable in the spring, grazing can be used then as a method of control.
However, Mealor cautioned that the affects of grazing differ depending on what stage the plants are in, and that land managers need to be aware of how their grass is growing from year to year.
“On May 1 are your plants always doing the same thing, year after year? This year was really different – it was really slow, and plants weren’t growing, so paying attention to your plants annually is a smart idea,” she said.
Mealor said the bottom line with grazing is to time it to optimize the negative impacts on undesirable weeds – like early grazing on cheatgrass. However, she said land managers have to remember that the target plant is almost always embedded with desirable plants, so it’s a balancing act.
“The key is to shift the competitive balance to favor the good grasses and not the bad ones,” she said, mentioning that cool season and warm season grasses add another layer of complexity. “We need to know what’s out there and manage accordingly.”
Of using early-season grazing to control cheatgrass, Mealor said it’s not necessarily a good strategy to implement year after year.
“What would happen to our perennial species? We have to take a real systems approach, and there’s no silver bullet. You have to look at your system, know what’s there and what good grasses you have and what their growing season is. It gets really complex,” she said.
“A successful grazing strategy for weed control should cause as much significant damage to the target plant as possible, and it should be integrated with other control methods as part of a larger management scheme,” she noted. “Sustainable grazing practices over the long-term can reduce the impacts of weed invasion, but mis-managed grazing that contributes to weed invasions won’t solve the problem.”