Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2011
Publication Date: 7/2/2012
Citation: Curran, W.S., Ryan, M.R., Myers, M.W., Adler, P.R. 2012. Effects of seeding date and weed control on switchgrass establishment. Weed Technology. 26:248-255. DOI: http://dx.doi.org/10.1614/WT-D-11-00078.1. Interpretive Summary: The optimal planting date for successful establishment of switchgrass has evolved over time, and the results have been shown to vary with weed management strategy. Switchgrass was established at 3 different times in the spring from early-May to mid-June, with 3 different weed control strategies, use of mowing and broadleaf and broad spectrum herbicides. We found that although later planting reduced weed competition, switchgrass yield increased with earlier planting when weeds were effectively controlled; effective weed control during the establishment year reduced costs in subsequent years. This research provides farmers with alternative weed management strategies, allowing them to increase switchgrass yield and reduce establishment costs.
Technical Abstract: An experiment evaluated the effects of seeding date and weed control during switchgrass (Panicum virgatum L.) establishment. Switchgrass was no-till seeded in early-May, late-May, and mid-June and three postemergence weed management treatments were evaluated including mow only, broadleaf herbicide only (2,4-D + dicamba), and broad spectrum herbicide (2,4-D + dicamba + atrazine + quinclorac). Switchgrass density increased with later planting, except in 2008 when the middle planting date was the lowest. Switchgrass biomass in the establishment year was lowest in the mow only treatment; however, there was a planting date × control method interaction resulting from differences at the early, but not later planting dates. Weed biomass tended to be greater at the early dates, which partially explains the interaction with switchgrass biomass. Weed biomass tended to be lowest in the broad spectrum control treatment. Total yield during the establishment year was lowest at the later planting dates and in the mow only control treatment. Control treatments during establishment influenced yield the next year with the lowest yield in treatments that received the mow only treatment. The year after establishment, plots were split to test the effects of supplemental weed control, comprised of metsulfuron + 2,4-D applied in May on total yield. Supplemental control affected yield in one of two years, where yield was lowest in the mow only treatment that did not receive supplemental control. Although later planting was better for switchgrass density and weed suppression, yields were greater at early planting dates, especially when weeds were effectively managed.