TITLE: Weed Management in a Newly Established Organic Wine Grape Vineyard

SUMMARY Weed management in new wine grape vineyards was identified by local growers and wine makers in a 2007 meeting at WSU Mount Vernon NWREC as the primary constraint to organic production in the region. This project investigates weed management options in two wine grape cultivars „Pinot Noir Precoce‟ and „Madeleine Angevine‟ grafted on Couderc 3309 rootstock. The experiment was established at WSU Mount Vernon NWREC in a 3-acre newly established transition to organic vineyard and includes 5 weed control treatments: standard control of rototilling and mowing, the Wonder Weeder (a mechanized apparatus), and three grain/legume cover crop treatments. Cultivars and weed control treatments were selected by the local growers and wine makers. While comparable cover crop research studies have been conducted elsewhere in the U.S. and the world, climate and soil variations preclude directly transferring these results to western Washington. The experimental vineyard was established in June 2009. Preliminary results indicate vine length was reduced when grapevines were grown with cover crops as compared to hand-weeding (standard and Wonder Weeder plots), and winter wheat reduced vine length more than other cover crop treatments. Vine length reduction by cover crop treatments as compared to hand weeding was greater in August than in July. Total between-row plant biomass was greater in cover crop plots than in standard or Wonder Weeder plots at both evaluation dates. Total in-row plant biomass did not differ among treatments in August but in September winter pea and wheat/pea plots had greater total plant biomass than the standard treatment. Between-row weed biomass was greater in cover crop treatments than in standard or Wonder Weeder plots in August. In September, winter pea contained the greatest amount of weed biomass between rows,