Preplant cover crops affect weed and vine growth in first-year vineyards

Use of in-row cover crops for weed management in first-year vineyards was investigated in two studies. In the first study, rye (Secale cereal L. 'Wheeler') was fall-planted, overwintered, then managed by three methods before vine planting. Rye was either herbicide-desiccated with glyphosate and left on the surface as a mulch, mowed, or incorporated into the soil (cultivated). Weed density and growth of grapevines (Vitis spp.) were evaluated. Herbicide desiccation was superior to the other methods for weed suppression, with weed densities 3 to 8 times lower than for mow ed or cultivated plots. Vine growth was similar among treatments, but the trend was for more shoot growth with lower weed density. In a second study, four cover crops, rye, wheat (Triticum aestivum L. 'Cardinal'), oats (Avena sativa L. 'Ogle'), and hairy vetch (Vicia villosa Roth), mere compared. Wheat and rye were fall-and spring-planted, and oats and vetch were spring-planted, then desiccated with herbicides (glyphosate or sethoxydim) after vine planting and compared to weed-free and weedy control plots for weed suppression and grapevine growth. Cover crops provided 27 % to 95 % reduction in weed biomass compared to weedy control plots. Total vine dry mass was highest in weed-free control plots, was reduced 54 % to 77 % in the cover crop plots, and was reduced 81 % in the weedy control. Fall-planted wheat and rye and spring-planted rye plots produced the highest vine dry mass among cover crop treatments. Spring-planted rye provided the best combination of weed suppression and vine growth. Chemical names used: N-(phosphonomethyl) glycine (glyphosate isopropylamine salt); 2-[1-(ethoxyimino)butyl]5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim).