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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED PLANT GENETIC RESOURCES FOR PASTURES AND RANGELANDS IN THE TEMPERATE SEMIARID REGIONS OF THE WESTERN U.S.

Location: Forage and Range Research

Title: Comparison of herbicides for reducing annual grass emergence in two great basin soils

Authors
item Hirsch, Merilynn -
item MONACO, THOMAS
item Call, Christopher -
item Ransom, Corey -

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 29, 2011
Publication Date: January 20, 2012
Citation: Hirsch, M.C., Monaco, T.A., Call, C.A., Ransom, C.V. 2012. Comparison of herbicides for reducing annual grass emergence in two great basin soils. Rangel Ecol Manage. 65:66-75.

Interpretive Summary: A greenhouse experiment was conducted to evaluate the effects two pre-emergence acetolactate synthase (ALS)-inhibiting herbicides (rimsulfuron and imazapic) on germination and emergence of downy brome and two revegetation grass species (crested wheatgrass and bottlebrush squirreltail, which were grown in representative soils from salt desert and sagebrush shrublands. Pre-emergence herbicides reduced seedling emergence and biomass production of downy brome and crested wheatgrass, and increased mortality more so in sagebrush compared to salt desert soil, suggesting that these common Great Basin soils fundamentally differ in herbicide bioavailability. Also, germination and emergence of the two highly responsive species (crested wheatgrass and downy brome) were clearly more impacted by rimsulfuron than imazapic. This paper discusses how specific soil physiochemical properties influence herbicide adsorption and leaching. Our results shed new light on the relative performance of these two promising herbicides and the importance or considering soil properties when applying pre-emergence herbicides to reduce germination and emergence of invasive annual grasses and create suitable seedbed conditions for revegetation.

Technical Abstract: Reducing seed germination and seedling emergence of downy brome (Bromus tectorum L.) improves the success of revegetating degraded shrubland ecosystems. While pre-emergence herbicides can potentially reduce these two processes, their impact on germination and emergence of downy brome and revegetation species in semi-arid ecosystems is poorly understood, and has not been comprehensively studied in soils with potentially contrasting herbicide bioavailability; i.e., residual plant activity. We designed a greenhouse experiment to evaluate the effects two pre-emergence acetolactate synthase (ALS)-inhibiting herbicides (rimsulfuron and imazapic) on germination and emergence of downy brome and two revegetation grass species (crested wheatgrass [Agropyron cristatum {L.} Gaertn.] and bottlebrush squirreltail [Elymus elymoides {Raf.} Swezey)], which were grown in representative soils from salt desert and sagebrush shrublands. Pre-emergence herbicides significantly (P<0.05) reduced seedling emergence and biomass production of downy brome and crested wheatgrass, and increased mortality more so in sagebrush compared to salt desert soil, suggesting that these common Great Basin soils fundamentally differ in herbicide bioavailability. Also, germination and emergence of the two highly responsive species (crested wheatgrass and downy brome) were clearly more impacted by rimsulfuron than imazapic. We discuss these results in terms of how the specific soil physiochemical properties influence herbicide adsorption and leaching. Our results shed new light on the relative performance of these two promising herbicides and the importance of considering soil properties when applying pre-emergence herbicides to reduce germination and emergency of invasive annual grasses and create suitable seedbed conditions for revegetation.

Last Modified: 9/10/2014
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