Links and/or abstracts:

2011.  SRM meeting.  Impact of sheep grazing on demographic parameters of cheatgrass (Bromus tectorum) and wild oat (Avena fatua) in three common Montana agricultural systems.  Melissa Graves, Jane Mangold, Hayes Goosey, Patrick Hatfield, and Fabian Menalled

Cheatgrass (Bromus tectorum) and wild oat (Avena fatua) are problematic weeds in Montana agricultural systems spanning from rangeland to cropland.  The primary focus of this project is to investigate how the incorporation of sheep grazing into agricultural systems impacts grassy weeds.  Specifically, we evaluated the impact of incorporating sheep grazing into cropping systems on cheatgrass and wild oat populations at a large-scale replicated field experiment located at the Fort Ellis Research Farm near Bozeman, Montana.  Demographic parameters including seedbank decay, seedling recruitment, seedling survival, and plant fecundity were obtained in three agricultural systems commonly used in Montana: continuous spring wheat, continuous alfalfa, and a 3-year (wheat, pea-hay barley, summer fallow) rotation.  Two sets of paired quadrats were located within each plot and 5,150 seeds/m2 cheatgrass and 2,120 seeds/m2 wild oat were planted in each quadrat in fall 2009.  Rotation  plots were subjected to grazing or chemical treatment.  Stocking rates on grazed plots ranged from 134 sheep days/ha to 537 sheep days/ha and were based on weed densities.  Dicamba and/or glyphosate was applied at label rates in chemical treatment plots prior to planting.  Subsequent herbicide treatments were done as needed.   Weed seedling emergence, survivorship and seed production was monitored throughout the 2010 season.  Preliminary data indicated grazed fallow plots resulted in a reduction in weed biomass by up to 95% compared to chemical fallow plots.   Information gained from this study will be used to build a population growth model allowing producers to incorporate grazing into their agricultural management practices.

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