Cheatgrass has invaded millions of acres of North American rangeland, replacing more reliable perennial forage species, increasing fire frequency, and reducing native species diversity.
Herbicides can be used to manage cheatgrass (Bromus tectorum), but they are costly.
To address a problem at this scale, land managers need additional control methods that are both economical and effective.
Background photo: Targeted grazing study team surveying a cheatgrass-invaded section of a pasture near Scottsbluff, Nebraska. Photo by Julie Kray.
One approach that shows promise but has not been widely tested on cheatgrass in the Central Plains is targeted grazing: grazing designed to achieve specific vegetation management goals via specified timing, duration, and intensity of use. In our case, this would mean grazing at a very high stocking density for a brief period, timed carefully to maximize removal of cheatgrass and minimize negative effects on cool-season perennial grasses.
When done well, targeted grazing could increase cattle weight gains while suppressing cheatgrass—potentially a “win-win” outcome. But in order for this strategy to succeed, we need to know exactly when to begin and end the targeted grazing.
Background photo: Cattle graze cheatgrass at the Nebraska study site. Photo by Julie Kray.
What is the best time to apply targeted grazing to control cheatgrass?
Scientists at the USDA-ARS Rangeland Resources and Systems Research Unit and the University of Nebraska are working to identify the optimal timing for targeted cheatgrass grazing in two mixed-grass sites near Cheyenne, Wyoming, and Scottsbluff, Nebraska. Observations from both sites over several years will define the optimal times for targeted grazing as periods when cattle consume large amounts of cheatgrass, and select for cheatgrass over other plants.
Find out more about our study and what we are learning below.
Background photo: Scientists observe cattle behavior at the Wyoming study pasture in mid-April. Photo by Julie Kray.
HOW THE STUDY WORKS:
Our 10 acre study pastures are grazed by 3-4 yearling cattle from mid-April through late June or early July, to match the period when cheatgrass is actively growing. Half of each study pasture is covered by cheatgrass, and the other half by native vegetation.
Yearlings are outfitted with GPS collars to track time spent in cheatgrass versus native mixed-grass patches of vegetation.
Background photo: Cattle graze in cheatgrass patches in early May. Photo by Julie Kray.
Twice weekly fecal sampling helps us determine what the yearlings are grazing, and specifically, when they select cheatgrass versus cool-season perennial grasses.
Every two weeks, we measure how much forage is available to cattle, and the proportion of available forage made up by cheatgrass, perennial grasses (western wheatgrass and needle-and-thread), and forbs.
Background photo: Researchers clip plants in small plots throughout the study pasture to measure changes in forage available to cattle. Photo by Rachel Wolf.
To learn what might influence when cattle select or avoid eating cheatgrass, we measure nutrition in plant leaves (forage quality) and plant growth stage (height and flower development) every week.
The study is planned for five years (2017-2021) to determine how results are affected by year-to-year changes in weather.
Background photo: A re-grazed patch of cheatgrass remains in a vegetative stage, while surrounding cheatgrass plants are flowering in Wyoming in 2018. Photo by Julie Kray.