Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2013
Publication Date: 1/30/2014
Publication URL: http://handle.nal.usda.gov/10113/58781
Citation: Madsen, M.D., Davies, K.W., Mummey, D.L., Svejcar, A.J. 2014. Improving restoration of exotic annual grass-invaded rangelands through activated carbon seed enhancement technologies. Rangeland Ecology and Management. 67(1):61-67. Interpretive Summary: This paper describes a laboratory evaluation of a new seed enhancement technology designed to allow seeding concurrently with high rates of pre-emergent herbicide application. Designated as “herbicide protection pods” (HPP’s), a rectangular pod is formed from a dough mixture containing seed, activated carbon, and other additives. The HPP produces a microenvironment within the soil that minimizes herbicide uptake to the seeded species, while pre-emergent herbicide controls invasive weeds outside of this zone. Additional research is merited for the further development and evaluation of HPP technology, including field studies, before it can be recommended as a restoration treatment.
Technical Abstract: Cost-efficient strategies for revegetating annual grass-infested rangelands are limited. Restoration efforts typically comprise a combination of pre-emergent herbicide treatments and seeding to restore desired plant materials. However, practitioners struggle with applying herbicide at rates sufficient to achieve weed control without damaging non-target seeded species. The objective of this research was to determine if seed enhancement technologies using activated carbon would improve selectivity of the pre-emergent herbicide imazapic. Bluebunch wheatgrass seed was either left untreated, coated with activated carbon using a rotary coater, or incorporated into “herbicide protection pods” (HPP’s) made of activated carbon through a newly developed seed extrusion technique. In a grow-room facility, bluebunch wheatgrass seeds were sown in pots that contained cheatgrass seed. After planting, pots were sprayed with 70, 105, 140, or 210 g active ingredient (ai)/ha of imazapic, or left unsprayed. Where herbicide was not applied, cheatgrass biomass dominated the growing space. Imazapic effectively controlled cheatgrass and untreated bluebunch wheatgrass. Activated carbon-coated seed showed some resistance to imazapic at 70 g ai/ha. Seeds that were incorporated into HPP’s were protected from imazapic at all application rates. When untreated seeds and HPP’s are compared at the 4 levels of herbicide application (excluding the no herbicide level), the HPP treatment was on average 4.8, 3.8, and 19.0-fold higher than untreated seeds in density, height, and biomass, respectively. These results indicate that HPP’s and, to a lesser extent, activated carbon seed coatings may further enhance a single-entry revegetation program by providing land practitioners with the ability to apply imazapic at rates necessary for weed control while minimizing non-target plant injury.