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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #228571
Title: Crested Wheatgrass Defoliation Intensity and Season of Use on Medusahead Invasion

Author
item Sheley, Roger
item Bingham, Brett
item Svejcar, Anthony
item Vasquez, Edward

Submitted to: Extension Reports
Publication Type: Experiment Station
Publication Acceptance Date: 5/1/2008
Publication Date: 6/1/2008
Citation: Sheley, R.L., Bingham, B.S., Svejcar, A.J., Vasquez, E.A. 2008. Crested Wheatgrass Defoliation Intensity and Season of Use on Medusahead Invasion . Extension Reports. Range Field Day 2008 Progress Report. Oregon State University Agricultural Experiment Station, Special Report 1085. Burns, OR. pp. 48-52.

Interpretive Summary: The objective of this study was to determine the effects of crested wheatgrass defoliation intensity and timing on medusahead density and biomass. Eighteen treatments (six defoliation levels, three seasons of defoliation) were applied to 21.5-ft2 plots on two sites with varying clay content. Plants were clipped in 2004 and 2005. Crested wheatgrass was hand clipped to defoliation levels of 0%, 20%, 40%, 60%, 80%, and 100% in the spring, summer, and fall. Density of crested wheatgrass and medusahead was sampled in June 2005 and 2006, but their biomass was harvested only in 2006. Over the two seasons, site had much more of an impact on medusahead invasion that either defoliation intensity or timing of defoliation. The results support previous suggestions that clayey soils favor medusahead and that perennial grasses with high biomass can resist this invasive species. On the clayey site where medusahead did persist, fall defoliation of crested wheatgrass reduced the density of this invasive species by 50% or more compared to spring defoliation. Given the developmental pattern of medusahead, the goal of any management program should be to maximize resources use by the desirable plant species from April to late July.

Technical Abstract: The objective of this study was to determine the effects of crested wheatgrass defoliation intensity and timing on medusahead density and biomass. Eighteen treatments (six defoliation levels, three seasons of defoliation) were applied to 21.5-ft2 plots on two sites with varying clay content. Plants were clipped in 2004 and 2005. Crested wheatgrass was hand clipped to defoliation levels of 0%, 20%, 40%, 60%, 80%, and 100% in the spring, summer, and fall. Density of crested wheatgrass and medusahead was sampled in June 2005 and 2006, but their biomass was harvested only in 2006. Over the two seasons, site had much more of an impact on medusahead invasion that either defoliation intensity or timing of defoliation. The results support previous suggestions that clayey soils favor medusahead and that perennial grasses with high biomass can resist this invasive species. On the clayey site where medusahead did persist, fall defoliation of crested wheatgrass reduced the density of this invasive species by 50% or more compared to spring defoliation. Given the developmental pattern of medusahead, the goal of any management program should be to maximize resources use by the desirable plant species from April to late July.