Location: Livestock and Range Research Laboratory
Project Number: 3030-21500-001-001-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jun 30, 2020
End Date: Jun 29, 2025
Objective:
This study relies on herbicides indaziflam and glyphosate to increase success of reseeding areas that became invaded by downy brome after the original seeding and seeks to increase seeded species establishment by controlling downy brome on areas recently seeded for the first time.
Approach:
Study 1-Reseeding downy brome-infested fields
This study relies on herbicides indaziflam and glyphosate to increase success of reseeding areas that became invaded by downy brome after the original seeding. Indaziflam kills germinating seeds for <=3 years after application while not affecting emerged plants, whereas glyphosate kills only actively growing plants contacted by the herbicide. To determine if results are consistent, two identical experiments will be conducted, one beginning in 2019 and one beginning in 2020. Treatments will be:
Treatment 1) Fall seeding
Treatment 2) Indaziflam and glyphosate application followed by fall seeding
In the 2019 and 2020 experiments, treatments will be replicated three times in 0.5-acre plots. In September of the first year of the study, Treatment 2 plots will receive indaziflam at 102 g ai ha-1 (7 oz/ac for formulation with 1.67 lb ai/gal). If downy brome seedlings are present at application time, the indaziflam will be tank-mixed with glyphosate at 570 g ae ha-1 (13 oz/ac for formulation with 5 lb ae/gal) and methylated seed oil at 1% of spray volume. The following April or May, indaziflam plus glyphosate will be reapplied if downy brome seedlings are observed. After this, soil samples will be collected each August from Treatment 1 and 2 plots. Downy brome seed densities will be determined in the soil samples, and species of a Decker seed mix will be grown in the soil samples in a greenhouse to test for damage caused by residual indaziflam. Treatment 1 and 2 plots will be seeded the first fall after greenhouse testing reveals no indaziflam damage to seeded species and a >90% reduction in downy brome seed density. Based on past studies, we predict these conditions will be met three years after the initial herbicide treatment. Each fall until seeding occurs, glyphosate will be applied at 570 g ae ha-1 if downy brome seedlings are observed. Vegetation will be measured each summer after seeding.
Study 2-Controlling downy brome on new reclamation
This study will seek to increase seeded species establishment by controlling downy brome on areas recently seeded for the first time. Two identical experiments will be conducted, one beginning in 2019 and one beginning in 2020. Following topsoil laydown in summer of year 1, treatments will be:
Treatment 1) Fall seeding
Treatment 2) Fall seeding followed by indaziflam application after seeded species emerge
The soil source will be stockpiles containing high downy brome seed densities. Treatments will be replicated three times in 0.5-acre plots. Seeding of Treatment 1 and 2 plots will occur the first fall of each experiment. Then, plots will be scouted for downy brome each summer, and Treatment 2 plots will receive indaziflam at 102 g ai ha-1 in September of the year downy brome is observed. Based on experience at Decker, we predict appreciable downy brome will be observed the second year after seeding. The herbicide will be reapplied the year following the initial application if downy brome continues to be observed. Vegetation will be measured each summer after the first herbicide application.
