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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #424009
Research Project: Sagebrush Rangeland Conservation and Restoration

Location: Range and Meadow Forage Management Research

Title: Deeper seeding allows bunchgrass establishment while the pre-emergent herbicide indaziflam controls invasive annual grasses

Author
item Davies, Kirk
item CLENET, DANIELLE - Oregon State University
item Olsoy, Peter
item Boyd, Chad
item Copeland, Stella
item Hamerlynck, Erik
item O'Connor, Rory
item Bates, Jonathan

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Restoration of annual grass-invaded rangelands is often a management priority. It would be advantageous if seeded species could establish while indaziflam, a pre-emergent herbicide, controls annual grasses. Seeding deeper in the soil may allow seeded species to largely avoid herbicide activity, but seeded species may struggle to emerge from greater seeding depths. We investigated seeding two bunchgrasses at 1, 3, 5, and 7 cm seeding depths before fall indaziflam application. Seeding deeper than the recommended depth of 1 cm increased seeding density and growth. This suggest that seeding at depths of 3-7 cm is likely a viable strategy for allowing some seeded species to establish while indaziflam controls invasive annual grasses in some sites. This research is of interest to restoration practitioners, invasive plant managers, land managers, and weed, rangeland, and natural resource scientists.

Technical Abstract: Restoration of annual grass-invaded rangelands is often a management priority. Pre-emergent herbicides are an effective restoration tool to reduce annual grass abundance, but they can negatively impact seeded vegetation. Hence, seeding is often delayed until herbicide activity has abated. With indaziflam, a pre-emergent with longer soil activity, seeding may need to be delayed for several years. It would be advantageous if seeded species could establish while indaziflam controls annual grasses, as competition with annual grasses would be limited and it would decrease the time that forage production and vegetation cover of the soil surface are reduced. Seeding deeper in the soil may allow seeded species to largely avoid herbicide activity, but seeded species may struggle to emerge from greater seeding depths. We investigated seeding bottlebrush squirreltail (Elymus elymoides (Raf.) Swezey) and crested wheatgrass (Agropyron cristatum (L.) Gaertn.) at 1, 3, 5, and 7 cm seeding depths just prior to a fall indaziflam application at two sites in two years. Seeding at ~1 cm is the recommended practice for both bunchgrasses. We found that seedling density in late June (end of the growing season) was greater at the 3 and 5 cm seeding depths and likely greater at the 7 cm seeding depths than at the 1 cm seeding depth. Seedling height was greater at the 3, 5, and 7 cm seeding depths compared to the 1 cm seeding depth. However, seedling density and height did not vary among the 3, 5, and 7 cm seeding depths. This suggests that indaziflam largely did not penetrate below the first centimeter or two of the soil profile the growing season after fall application. Seeding at depths of 3-7 cm is likely a viable strategy for allowing some seeded species to establish while indaziflam controls invasive annual grasses. Additional evaluations across a gradient of soil and site characteristics, with different plant species and functional groups, and other pre-emergent herbicides are needed to refine this restoration strategy and fully identify its benefits and limitations.