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: 05/31/2023
Grant Recipient: Montana State University
Region: Western
State: Montana
Principal Investigator:
Lisa Rew
Montana State University
Co-Investigators:
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
Dr. Bok Sowell
MSU- Animal & Range Sciences
Dr. Cathy Zabinski
Montana State University
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Project Information

Abstract:

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 grazing, herbicide, and seeding for cheatgrass management and desired species restoration, in a large-scale, rancher-initiated study.

      Assess abundance of (a) cheatgrass, and (b) seeded and all other species, in large 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, grass mulch, mustard crop mulch, 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.

Research

Hypothesis:

Objective 1. Evaluate combinations of targeted grazing, herbicide, and seeding for cheatgrass management and desired species restoration, in a large-scale, 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 six 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 are going to be performed in fall 2021.  The treatments are: herbicide only, herbicide & seeding, herbicide & grazing, and herbicide & grazing & seeding. The continuing drought has meant that many of our collaborators have already sold off cattle and are continually changing their grazing strategy to manage the forage they do have, they are also planning to move cattle out of the Centennial Valley earlier than usual (August instead of October).  Our targeted grazing needs to occur after cheatgrass has emerged in the fall. For these reasons we need to alter our methodology.  We are going to increase the number of sites, but reduce the area of our plots and use weed strimming to simulate cattle grazing on some sites.  Four sites will have cattle grazing and weed strimming for comparison of the two treatments, the other 4-6 sites will have weed strimming not cattle due to cattle not being present.  Seeding will continue as planned.  Plots will be evaluated for cheatgrass, native grass, forb cover and percent of bareground in fall 2021 prior to application of the grazing treatment.  The amount of biomass removed by the grazing treatment will be evaluated in fall 2021.

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 seeded in the spring using broadcast seed and seed pellets.  Due to the drought two other sites have been evaluated and prepared for seeding in fall 2021 (broadcast and seed pellets) and spring (broadcast). A no seed control is included at each site.  Basal cover of all species is evaluated in summer prior to and after treatments have been imposed, and this will continue for two more years.

Objective 3: Three sites were established in fall 2020 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.  The experiment is being repeated at two sites (one site was sold) in fall 2021.  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.  The other treatments will be imposed in fall 2021.

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, but not yet analyzed.  Visual evidence suggests the lack of precipitation since winter has meant no new seedlings have established and survived.  For this reason we have established two new sites to repeat the study on in fall 2021.

Objective 3: Data were collected in summer 2021 but not yet collated. Visual evidence suggests that the higher rate of mustard seed meal, all rates of the soil amendment and herbicide were effective at controlling cheatgrass. Impact on the desired vegetation was not easily determined visually.

Participation Summary
5 Farmers participating in research

Education

Educational approach:

During our first summer and fall (2020) we established our sites and began data collection.  Two graduate students and five undergraduates have been trained in field sampling protocols over the summer of 2020 and 2021 by Drs. Rew, Mangold, Zabinski and Cutting. 

Drs. Rew, Mangold, Cutting and Sowell have interacted with our project collaborators and presented at Range Days and other meetings.  During the following seasons we plan to use a range of educational approaches to extend our results to our audiences. 

Educational & Outreach Activities

10 Consultations
1 Tours
1 Webinars / talks / presentations

Participation Summary:

30 Farmers
20 Ag professionals participated
Education/outreach description:

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.

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.

 

Learning Outcomes

25 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas taught:
  • annual grass management
  • biodiversity

Project Outcomes

15 Farmers intend/plan to change their practice(s)
2 New working collaborations
Project outcomes:

Agriculture is the most important industry in Montana (USDA-NASS 2018). Over $5.2 billion in commodity cash receipts are generated annually, and cattle and calf production account for ~42% of these receipts (USDA-NASS 2018). Most beef cattle producers in Montana are cow-calf operators that graze rangelands. Approximately 70% of the state is considered rangelands, and cattle grazing is the most dominant land use. This is also true for the entire western United States. Profitability of livestock production is directly dependent on the amount of forage produced on rangelands. Two factors that reduce forage production and therefore profitability are invasive species and grazing management. If livestock operators want to sustainably graze rangelands and remain profitable, they must also be environment stewards that maintain rangeland productivity which simultaneously conserves habitat for priority wildlife species such as the sage-grouse.

One of the most challenging invasive plant species in the western United States is cheatgrass (Bromus tectorum). Cheatgrass was first observed in North America in Pennsylvania in 1861 and first recorded in the West in 1893 (Young and Allen, 1997). By 1930 it had spread to all 50 states (Kitchen 2014 ). It is an annual plant that germinates in the fall, overwinters and starts growing again early in the spring, providing it with an advantage over native perennial grasses that start growing later in the spring (Mack 1981). Cheatgrass does best in areas with hot, dry summers and less native grass cover (Brummer et al. 2016 ). In southwest Montana, cheatgrass is expanding on south-facing slopes, environments known to be less resistant to cheatgrass invasion (Chambers et al. 2014) because they are warmer in the spring, and hotter and drier as the season continues. Climate models for Montana (Whitlock et al. 2017) project that the state will become warmer with increased drought severity and a possible change in precipitation patterns, which would favor cheatgrass expansion. Cheatgrass is an insurmountable problem in hotter and drier areas of sagebrush rangelands to the south (e.g. Great Basin; Bradley 2009; Brummer et al. 2016). Cheatgrass invasions in our northeastern region of the sagebrush steppe are currently considered to be at moderate levels and should be targeted for control now while success is possible (Rowland et al. 2010; Sheley and Smith 2012; Mealor et al. 2013).

Our study site in the Centennial Valley, southwest Montana, is within the northeastern region of the sagebrush steppe. The valley has over a million acres of land that is owned by private producers, Red Rock Lakes Wildlife Refuge (USFWS), Bureau of Land Management and the State of Montana. The valley has less pressure from invasive plants, due to the lack of paved roads and traffic. Cheatgrass invasions have been limited to road construction and cable installation areas, but over the last 5-10 years, local producers and land management agencies have noticed new infestations of cheatgrass on south-facing hillsides. They believe cheatgrass encroachment is negatively impacting forage production, quality of the range, and natural resources. Furthermore, they are interested in herbicide management but also innovative, non-herbicide methods, and how to integrate targeted grazing in fall with other control strategies would work to make management more sustainable and maintain rangeland productivity.

Herbicide, grazing, seeding and combinations of these are the most commonly used methods to control cheatgrass (Kelley et al. 2013). The most effective herbicide currently labelled for use on grazed lands is Plateau (a.i. imazapic), applied in fall after cheatgrass emergence, but this can impact non-target plant species (Mangold et al. 2013). Grazing cheatgrass can provide livestock forage in the fall or early spring and can reduce biomass. Heavier use or more targeted grazing during these times in combination with other approaches may be more effective at reducing cheatgrass abundance and seed production rather than just providing a forage opportunity, but results can be variable (Lehnhoff et al. 2019) so additional research is needed. The other commonly used approach is seeding following herbicide application, which can also have variable effectiveness (James et al. 2012; Monaco et al. 2017). Since cheatgrass reproduces from seed, control strategies have focused on killing plants or reducing seed production, but few methods exist to target seed bank reserves.  Our first objective assesses the effectiveness of an integrated weed management approach and after three years we will be able to evaluate the sustainability of the different approaches.   

We are evaluating some non-herbicide approaches that will decrease seedling establishment. One promising, innovative approach is the soil micronutrient application of boron (Edaphix, LLC). In the 1930’s, Crafts and Raynor (1936) examined the use of minerals to sterilize soil for use on gravel roads. The low toxicity of boron suggested it might be a good approach. The primary site of action of boron appears to be the young roots of seedlings. However, the use of boron and other minerals was not pursued due to the popularity of herbicides following World War II. Stuart Jennings, Edaphix LLC, an independent researcher and restoration specialist, has been working with boron as a soil micronutrient application to control cheatgrass and other invasive species over the last 5 years and has had success reducing cheatgrass emergence in trials in southwest Montana. Another innovative approach is the use of biofumigation crop products (e.g Indian/oriental mustard) to reduce pests such as nematodes, fungi and weeds. Mustards, applied as meal or mulch, negatively impact weed seeds (Lefebvre et al. 2018; De Cauwer et al. 2019). Neither the soil micronutrient nor the biofumigation products have been tested experimentally in rangelands. An advantage of these products, if successful, is that they would improve worker safety by reducing exposure to hazardous chemicals.  We have established an experiment evaluating these novel approaches and herbicide at three sites in 2020, and are going to establish another 2-3 in fall 2021.

In summary, our multi-partner interdisciplinary team are evaluating different control strategies to limit cheatgrass invasion and thereby improve or maintain the sustainability of ranching, enhance wildlife habitat for sage-grouse, and consequently improve quality of life for producers and local communities but we are in our first year. After three years of study our results will be incorporated into a management decision framework to control cheatgrass and improve desired species that will be relevant to producers and managers in the larger northeastern region of the sagebrush steppe biome of the American West.

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.