New Technologies to Help Win the War against Cheatgrass

This article was originally published in The Midden – Great Basin National Park: Vol. 21, No. 2, Winter 2021.

Figure 1. Illustration of an annual grass infested area that was planted with native seed coated in activated carbon. The site is treated with pre-emergent herbicide, which controls weed species while activated carbon deactivates herbicide in the immediate vicinity of the sown seed and allows for

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By Matthew Madsen, Professor, Brigham Young University

The sagebrush ecosystem is considered one of the most imperiled habitats in the United States. At one time, it covered over 150 million acres, but since European settlement, it has shrunk to only 56% of its historic range due to impacts from altered fire regimes, invasive species, conversion to conifer woodlands, and various human disturbances.

Research conducted at Great Basin National Park by graduate student Tyson Terry and others with Brigham Young University and the National Park Service evaluated new seeding technologies to help restore lost sagebrush habitat. Their work was focused on restoring areas that had been invaded by the exotic annual weed, cheatgrass (Bromus tectorum).

Seeding efforts in cheatgrass invaded areas typically fail due to high competition for limited resources. The use of soil-active herbicides is commonly needed to control cheatgrass prior to seeding. However, when seeding is performed concurrently with herbicide application, practitioners struggle with applying herbicide at rates sufficient to achieve weed control without damaging the seeded species.

Tyson’s group tested two different approaches to lower the impact of pre-emergent herbicide on a native bunchgrass species, bluebunch wheatgrass (Pseudoroegneria spicata). Their first approach was to coat seeds with activated carbon. Activated carbon has a high adsorption capacity for many organic compounds, including many pre-emergent herbicides. When applied within a seed Figure 1. Illustration of an annual grass infested area that was planted with native seed coated in activated carbon. The site is treated with pre-emergent herbicide, which controls weed species while activated carbon deactivates herbicide in the immediate vicinity of the sown seed and allows for plant growth. Weed weeds carbon coated seed area impacted by herbicide coating, activated carbon may limit the impact of a pre-emergent herbicide on seeded species (Figure 1).

Figure 2.

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Figure 2. Illustration of a proposed technique to remove invasive annual grasses and seed desired species at the same time by A) spraying the site with a premergent herbicide, B) removing the herbicide within a deep furrow, which is planted with seed and C) provides a microsite for the seeds to grow while the herbicide controls invasive weeds in-between the furrows (Taken from Terry et al. In 2021a).

The second approach the researchers took was to remove the herbicide from around the seed physically. This was accomplished by spraying the site and then creating a furrow that side-casted the herbicide-treated soil to produce a zone where seeds could be planted that would not be in contact with the herbicide (Figure 2).

Figure 3. Students from Brigham Young University conducting research at Great Basin National Park.

Photo by Tyson Terry

This research demonstrated that activated carbon coatings and deep furrow treatments provide unique mechanisms for mitigating the effects of pre-emergent herbicide on seeded species and that the combination of the treatments was most successful. In this trial, when both activated carbon and deep furrow treatments were combined, there was a 7.7-fold increase in bluebunch wheatgrass biomass compared to untreated seed.

These innovative technologies have the potential to provide land managers with the tools they need to reclaim areas invaded by exotic annual grasses. Improved restoration success in exotic annual grass invaded sites will result in many benefits, including lower firefighting costs, improved forage production for livestock, increased recreational activities, and enlarged habitat for wildlife.

Citations:
Terry, J.T., M.D. Madsen, R.A. Gill, V.J. Anderson, and S.B. St. Clair. 2021a. Selective herbicide control: using furrows and carbon seed coatings to establish a native bunchgrass while reducing cheatgrass cover. Restoration Ecology: Published ahead of press. https://onlinelibrary.wiley.com/doi/ abs/10.1111/rec.13351

Terry, J.T., M.D. Madsen, R.A. Gill, V.J. Anderson, and S.B. St. Clair. 2021b. Herbicide effects on the establishment of a native bunchgrass in annual grass invaded areas: indaziflam versus imazapic. Ecological Solutions and Evidence: 2021;2:e12049. https://doi.org/10.1002/2688- 8319.12049