Seed Coatings and Furrows: New Tools Against Cheatgrass

Written from an article by Matthew Madsen, professor, Brigham Young University, in The Midden (Great Basin National Park), Vol. 21, No. 2, Winter 2021.

Figure 1. Native seed coated in activated carbon, sown on land treated with a pre-emergent herbicide: the herbicide controls the weeds, while the carbon neutralizes it right around each seed so the seedling can grow. NPS.

A shrinking ecosystem

The sagebrush ecosystem is one of the most imperiled habitats in the U.S. It once covered more than 150 million acres; since European settlement it has shrunk to only 56% of its historic range, because of changed fire regimes, invasive species, spread of conifer woodland and other human disturbance.

Graduate student Tyson Terry and colleagues at Brigham Young University and the National Park Service tested new seeding methods at Great Basin National Park to restore sagebrush habitat overrun by the exotic annual grass cheatgrass (Bromus tectorum).

The problem

Seeding into cheatgrass usually fails: the natives can't compete. Soil-active herbicides are needed to control cheatgrass first — but when seeding and spraying happen together, it's hard to use enough herbicide to stop the weed without killing the seeded plants.

Two fixes

The team tried two ways to protect a native bunchgrass, bluebunch wheatgrass (Pseudoroegneria spicata), from a pre-emergent herbicide:

1. Activated-carbon seed coatings: activated carbon adsorbs many organic compounds, including many pre-emergent herbicides, so a coating can shield the seed (Figure 1).
2. Deep furrows: spray the site, then plow a furrow that throws the treated soil aside, leaving a strip where seed can be sown out of contact with the herbicide, while the herbicide keeps weeds down between furrows.

Results

Both methods reduced herbicide damage, and together they worked best: combining carbon coatings and deep furrows gave a 7.7-fold increase in bluebunch wheatgrass biomass over untreated seed.

These tools could help land managers reclaim land invaded by exotic annual grasses — with benefits including lower firefighting costs, better forage for livestock, more recreation, and more wildlife habitat.

Further reading

• Terry, J.T., Madsen, M.D., Gill, R.A., Anderson, V.J., and St. Clair, S.B., 2021, "Selective herbicide control: using furrows and carbon seed coatings to establish a native bunchgrass while reducing cheatgrass cover," Restoration Ecology.
• Terry, J.T., and others, 2021, "Herbicide effects on the establishment of a native bunchgrass in annual grass invaded areas: indaziflam versus imazapic," Ecological Solutions and Evidence.

Sources

Based on "New Technologies to Help Win the War against Cheatgrass," by Matthew Madsen, Brigham Young University, published by the National Park Service in The Midden and in the public domain; rewritten in hubnx's own words. A diagram taken from a journal article and a photograph credited to an individual are left out.