Herbicide Management for <em>Bromus tectorum</em> to Enhance Rangeland Productivity in Western Nebraska

Cheatgrass, Bromus tectorum (L.), has increased in the mixed-grass prairies of the Nebraska Panhandle. Limited research is available in these ecosystems on the ecological factors that influences its spread and options for management. This study focuses on the efficacy of herbicide treatments (indaziflam and imazapic) as a cheatgrass control method on the native rangelands of western Nebraska. In September of 2022, a mixture of indaziflam (73 g ai ha-1, Rejuvra) and imazapic (70 g ai ha-1, Plateau) was aerially applied at 6 unique upland ecological sites (1-3 ha) near Scottsbluff, NE. Functional group plant biomass data were collected in treated and closely associated untreated rangelands in late June through early July of 2023 and 2024. Cheatgrass biomass in treated areas was 98% less (p < 0.01) than in untreated control areas in both year one and two following herbicide treatment. Perennial grass biomass in herbicide treated areas was 3.2 times greater (p < 0.01) than untreated areas and trends showed increasing forage nutritive values as the percent of cheatgrass in the plot decreased. We also used greenhouse gas analyzers (LI-COR LI-7820 N2O/H2O trace gas analyzer for N2O emissions and a LI-COR LI-7810 CH4/CO2/H2O trace gas analyzer for CO2 and CH4 emissions) to explore differences in GHG emissions within different treated and untreated plant communities. While more years of data will give us a better understanding of the long-term influence of indaziflam and imazapic to remove cheatgrass on western Nebraska rangelands, the first two years of this study show promise for success of these treatments in western Nebraska ecosystems. Advisors: Mitchell B. Stephenson, Nicholas A. McMillan