October 23, 2023
A multi-year study involving University of Idaho researchers has found allowing late-fall and winter grazing on rangeland heavily infested with invasive Medusahead grass could provide extra forage for cattlemen while reducing wildfire fuel.
“Managing Medusahead Using Dormant Season Grazing in the Northern Great Basin,” recently published in the 2023 edition of Rangeland Ecology and Management, also concluded grazing in the fall and winter did not negatively affect native perennial grasses.
University of Idaho Extension Educator Scott Jensen, based in Owyhee County, and Eva Strand, an associate professor of rangeland ecology and management with U of I’s College of Natural Resources, were among the authors.
Other authors included William Price and Sergio Arispe, with Oregon State University (OSU) Extension; April Hulet, with Brigham Young University; Chad Boyd and Kirk Davies, with the U.S. Department of Agriculture Agricultural Research Service Eastern Oregon Agricultural Research Center; Dustin Johnson and Yanming Di, with OSU; and Barry Perryman, with University of Nevada-Reno.
Medusahead, an annual grass native to the western Mediterranean region of Eurasia, has invaded nearly 5 million acres of rangeland throughout the West, posing a host of problems for rangeland health including loss of species diversity, diminished forage quality and increased fine fuels for wildfires. It thrives in lower elevations, in areas in which soil is disturbed, and it germinates in the fall and dries much earlier during the following spring than other vegetation. It is fine stemmed, causing it to fall over and form mats that can choke out native perennials, and cattle tend to avoid eating it due to its long awns and high silica content.
“The heavily infested Medusahead areas are just a tinderbox waiting for some kind of ignition source,” Jensen said.
In June, the research team finished collecting its sixth year of data from the study, based in the 138,800-acre Three Fingers allotment, located within the federal Bureau of Land Management’s Vale, Oregon, district.
“It’s an area that sees a lot of lightning. Five or six ranchers who have had enough of frequent fires in that allotment approached my colleague in Malheur County, Oregon, Sergio Arispe, and said, ‘We’ve got a recurrent fire problem. Can you help us figure something out?’” Jensen said.
Following a year of gathering baseline data, the partners secured a $300,000 grant in 2018 covering five years of treatments from USDA’s National Institute of Food and Agriculture.
The allotment is divided into four pastures. There are two replications of the treatment plots in each of three of the four pastures. One treatment involved a traditional grazing season from May 1 through Nov. 1. The second treatment involved grazing during the season in which grasses are dormant, from Nov. 1 through March 1. The third treatment allowed grazing during both the regular season and dormant season combined. A control treatment in each set of plots is not grazed at any time or season. Grazing reduced Medusahead litter and provided forage for cattle without harming native perennials, though annual grass and native perennial grass cover did not differ significantly among treatments.
“Our control area has more pounds per acre of litter and biomass than areas that get grazed,” Jensen said.
Precipitation affected outcomes. In years with wet falls, Medusahead sprouted within the fallen weed litter, enabling cattle to feed on the emerging seedlings in the thatch. The moisture also softened the litter layer, making it easier for cattle to consume it. The researchers used protein supplements to lure cattle into weedy areas to feed, which also better balanced the nutritional value of the forage.
“When there has been no fall precipitation then we don’t get the fall germination, and we also have an issue with livestock water,” Jensen said.
Late fall and winter grazing also spared ranchers some expense of buying hay for winter feed.
William Price led the project in its first couple of years as a University of Idaho master’s student, prior to joining OSU Extension. Price and his wife have continued to assist each June with data collection. The grant also funded temporary help to aid gathering data. The researchers take detailed imagery from transects within three locations of the allotment. They also clip and weigh biomass within the transects.
Two other papers were previously published based on the project. “Strategic Partnerships to Leverage Small Wins for Fine Fuels Management,” was also published in Rangeland Ecology and Management, focusing on the collaborative nature of the research team. For the other paper, “Estimates of Fine Fuel Litter Biomass in the Northern Great Basin Reveal Increases During Short Fire-free Intervals with Invasive Annual Grasses,” the team collaborated with Spanish researcher Jose Manuel Fernandez-Guisuraga, who used their data and imagery to guide development of a tool using satellite imagery to predict forage amounts and types on range.
Jensen and his colleagues obtained a 10-year research exemption from the regular grazing plan for the Three Fingers allotment. They plan to continue the research project throughout the remaining four years of the exemption.
"I'm always hopeful that because of some of the things we learn from this that we could provide land managers an avenue to allow more flexibility in management,” Jensen said.
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