Developing an integrated management decision framework for cheatgrass control in the northeastern region of the sagebrush steppe

Progress report for SW20-915

Project Type: Research and Education
Funds awarded in 2020: $349,315.00
Projected End Date: 12/31/2023
Grant Recipient: Montana State University
Region: Western
State: Montana
Principal Investigator:
Lisa Rew
Montana State University
Jim Berkey
The Nature Conservancy
Amber Burch
Beaverhead County Weed District
Kyle Cutting
US Fish, Wildlife Service
Eric and Stephanie Hansen
Hansen Livestock Company
Jeff Johnson
Johnson Ranch
Dr. Jane Mangold
Montana State University
Kara Maplethorpe
Beaverhead County Weed District
Allen and Yvonne Martinell
Lee Martinell Ranch
Dr. Bok Sowell
MSU- Animal & Range Sciences
Dr. Catherine Zabinski
Montana State University
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Project Information


Cheatgrass has invaded millions of acres of the sagebrush biome, impacting forage production for cattle and habitat quality for wildlife such as sage-grouse. Restoring highly infested rangeland to a more desired state is impossible. Therefore, areas with moderate and patchy cheatgrass infestations should be prioritized for control to thwart further expansion and rangeland degradation. Much of the northeastern region of the sagebrush steppe (e.g., Montana and Wyoming) falls into this moderate risk category, and producers in this region are concerned that cheatgrass is expanding and want help now, before the problem gets worse.

Our team will field test combinations of strategies to determine which control cheatgrass most effectively and restore desired vegetation. Firstly, the effectiveness of cheatgrass control using targeted grazing, herbicide, and seeding will be tested in different combinations in a producer-initiated, large scale study at three sites. However, restoration seeding is expensive and may be less effective where the desired vegetation is more abundant.  Therefore, in the second highly replicated study we will evaluate the threshold of desired vegetation below which seeding after herbicide application is beneficial to decrease cheatgrass and increase desired vegetation. Thirdly, the effectiveness of cheatgrass control will be tested using innovative, non-herbicide approaches (soil micronutrient and two biofumigation techniques —mustard mulch and mustard seed meal) and compared with herbicide. Additionally, we will seed half of each of those treatments.  We will evaluate the cost of all the different control strategies and combinations.

Finally, our research, extension and producer team will use the results of our studies to develop a decision framework for producers. The framework will guide users to the most appropriate combination of management strategies to control cheatgrass and ensure recovery of desired vegetation for their ranch sustainability and livelihood. The project will be performed in southwest Montana and is applicable to the northeastern region of the sagebrush steppe.

We will extend the results of our studies using a range of formats including field days, tailgates, meetings, and workshops, as well as digital social media forums and websites.  The management options in our decision framework will be based on the best management approaches from our studies. However, it will require producers to supply information on the invasion status of cheatgrass and site conditions, in order to guide them to the best management approaches for their ranch. We will use our different outreach events to obtain feedback on the framework from a broad range of producers and land managers to ensure clarity, usefulness, and high rates of adoption.

Project Objectives:

Concern about cheatgrass is increasing in southwest Montana, where it is a particular problem on south-facing slopes. Our study will be performed on cheatgrass patches established on south-facing, high elevation sagebrush rangeland sites. Different combinations of control strategies will be assessed in a series of studies with the goal of promoting good stewardship of rangelands in the northeastern region of the sagebrush steppe. 

1) Evaluate combinations of targeted & simulated grazing, herbicide, and seeding for cheatgrass management and desired species restoration, rancher-initiated study.

      Assess abundance of (a) cheatgrass, and (b) seeded and all other species, in treatment plots over three years.

2) Determine a threshold for restoration seeding after herbicide application for cheatgrass control.

      Assess abundance of (a) cheatgrass, and (b) seeded (native perennial grasses and annual forbs) and all other species, across a gradient of native grass cover (0-30%) present at the site prior to treatment, to determine when seeding is most beneficial (e.g. <20 % cover).

 3) Quantify the effectiveness of six control strategies, with and without seeding to control cheatgrass.

      Assess abundance of (a) cheatgrass, and (b) seeded and all other species to six treatments (herbicide, soil micronutrient application, mustard seed meal, and no action), with and without seeding, over two years.

 4) Develop a decision framework to help livestock producers effectively control cheatgrass on their property.

Through objectives 1-3 we will develop effective combinations of strategies to control cheatgrass and improve range quality and productivity. The decision framework will use information on cheatgrass, site conditions, and desired grass cover to help producers select the most appropriate management approaches for their property and resources. The management decision framework will be extended through our outreach and educational activities (see that section) throughout the project period and beyond.



Objective 1. Evaluate combinations of targeted and simulated grazing, herbicide, and seeding for cheatgrass management and desired species restoration, rancher-led study.

Hypothesis 1: Integration of more management approaches (herbicide, grazing and seeding) will reduce cheatgrass and increase abundance of desired species more than individual approaches.

Objective 2. Determine a threshold for restoration seeding after herbicide application for cheatgrass control.

Hypothesis 2: Establishment and survival of seeded native perennial grasses will be most effective in areas with low desired vegetation. The threshold for seeding will be quantified after two years of observation, and is expected to be ~20% cover of desired grasses.

3. Quantify the effectiveness of different control strategies, with and without seeding to control cheatgrass.

Hypothesis 3: Alternative strategies, soil amendment fertilizer and mustard seed meal, will control cheatgrass as effectively as herbicide over a two year period. Seeding of desired species will generate greater abundance and further reduce cheatgrass abundance.


Materials and methods:

Objective 1:  Sites were sprayed with herbicide (imazapic) to control cheatgrass in fall 2019, control was good.  Due to the drought and lack of cheatgrass emergence these sites were not sprayed a second time as planned in fall 2020. Grazing and seeding treatments were performed in fall 2021 on 13 sites (cheatgrass restoration sites).  The treatments: herbicide only, herbicide & seeding, herbicide & grazing, and herbicide & grazing & seeding. The continuing drought has meant that many of our collaborators are selling off cattle early, continually changing their grazing strategy to manage the forage they do have, and moving cattle out of the Centennial Valley earlier than usual (August instead of October) - we expect this to occur in 2022 too.  Our targeted grazing needed to occur after cheatgrass has emerged in the fall. For these reasons we had to alter our methodology.  We increased the number of sites (from 2-3 to 13), but reduced the area of our plots and use weed strimming to simulate cattle grazing on some sites.  Three sites have cattle grazing and weed strimming for comparison of the grazing versus weed strimming treatments, plus a no-grazing control, the other 10 sites have weed strimming and a no-grazing control. Broadcast seeding has continued as a split plot treatment.  Plots were evaluated for cheatgrass, native grass, forb cover and percent of bareground/litter/rock in fall 2021 prior to application of the grazing treatment.  The amount of biomass removed by the grazing treatment was evaluated in fall 2021. Organic matter and available nitrogen will be assessed in spring of 2022 in the control, grazed and weed strimmed sites (3). All plots will be assessed for abundance (cover) and volume (cover * height) for cheatgrass and functional groups, sub-samples of biomass will be collected to enable us to relate volume to biomass and overall productivity of the treatments.

Objective 2: Six sites are being evaluated to determine a threshold for restoration seeding.  At four sites within the Centennial Valley herbicide was sprayed in 2020 and then a seeding treatment was imposed (no seed, fall broadcast, spring broadcast, spring seed pellets). Due to the drought two other sites were prepared (herbicide sprayed) and seeded (no seed,  fall broadcast, fall seed pellets, and spring broadcast) in 2021. Cover of all species is recorded each summer, and this will continue for two more years.

Objective 3: Three sites were established in fall 2020 and again in 2021 to evaluate alternative cheatgrass management strategies.  Management strategies included two rates of mustard seed meal, three rates of soil amendment fertilizer plus two controls - herbicide and no-spray.  All plots were assessed for cover of individual plants species, and a subset of the plot was harvested to determine differences in biomass.  All sampling was performed during the summer at peak vegetation. 

Objective 4: The decision framework will commence after another season of data collection.

Research results and discussion:

Objective 1: Cheatgrass was effectively controlled by herbicide application in 2019, and was at very low abundance in 2020 and 2021 due both to the herbicide treatment and drought.  Targeted grazing (with cattle or simulated with a weed strimmer) reduced the fall cover by 70%.   A split plot broadcast seed treatment was then imposed on the 13 sites across the valley (Fig 1. cheatgrass restoration sites). Sites will be assessed for functional plant cover at peak season in 2022.

Objective 2: Cheatgrass was effectively controlled by herbicide application in 2019 and had low abundance in fall 2020. Data on all species were recorded in summer 2021 on the different seeding treatments (no seed, fall broadcast, spring broadcast and spring seed pellet).  Abundance of cheatgrass remained very low along the native grass gradient, and we did not observe a growth response of the perennial grasses. Unfortunately no or very low numbers of seedlings were recorded in seed treatments such that there was no difference.  In addition, not many seed pellets had not broken down (Fig 2). Seed pellets are made from clay:organic matter:seed at a recommended ratio of 5:3:1. We are conducting a small study to determine a better ratio for the cold and dry Montana climate.  Visual evidence suggests the lack of precipitation over the 2021 winter and low growing season precipitation reduced growth of all plants including establishment from the sown seed.  For this reason we have repeated the study at two new sites (fall 2021).

Fig 2. Seed pellets that had not broken down in Centennial Valley, MT.

Objective 3: Data were collected in summer 2021 to evaluate our alternative cheatgrass management strategies.  Cheatgrass was reduced in all of the management strategies including two rates of mustard seed meal, three rates of soil amendment fertilizer plus two controls - herbicide and no-spray (Fig 3). We will continue to evaluate these plots for the next two summers to determine if the control of cheatgrass continues.  This experiment was repeated at -three sites fall 2021, we will record species cover at two sites from 2020 (one site was sold and we are not permitted access) and three sites established in 2021.

Participation Summary
5 Producers participating in research

Research Outcomes

2 New working collaborations

Education and Outreach

15 Consultations
1 Tours
4 Webinars / talks / presentations

Participation Summary:

90 Farmers participated
40 Ag professionals participated
Education and outreach methods and analyses:

We have completed one year of the project. During the second summer (2021) Drs. Rew, Mangold and Cutting participated in Range Days in Dillon in June 22nd, 2021. All presented at 2 or 3 of the three stops made during the day and discussed our WSARE project and broader aspects of annual grass and rangeland management. ~45 people were present.

Dr. Rew gave an evening presentation on annual grasses with an update on the project on June 21st, 2021 at the Fairgrounds in Dillon.  There was some but not complete overlap in the audience. ~60 people were present.

Drs. Rew and Mangold, and graduate student Colter Mumford gave evening presentations on annual grasses management with an update on the project on February 15th, 2022 at the Fairgrounds in Livingston, Park County, MT. 70 people were in attendance.

70 Farmers intend/plan to change their practice(s)

Education and Outreach Outcomes

70 Producers reported gaining knowledge, attitude, skills and/or awareness as a result of the project
Key areas taught:
  • annual grass identification
  • annual grass management
  • biodiversity
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.