Vegetation-Free Strip Width Affects Growth, Berry Composition, and Yield of Cabernet franc in Vigorous Growing Environments

Summary Goals: In regions such as the eastern United States, excess vine vigor can be problematic. In this region, it is common to plant a perennial grass between rows, which can compete with vines for water and nutrients. The purpose of this research was to determine the effect of vegetation-free strip (VFS) width beneath the planted row on vine growth and fruit quality. The current recommendation for VFS width is 90 to 120 cm. However, modification of the VFS width can provide additional competition, limiting vine vigor. Determining the optimal width and effect of the VFS on vine size, berry composition, and yield would allow growers to optimize groundcover management in this region. Key Findings: Reducing VFS width decreased pruning weight/m cordon, shoot number/m cordon, lateral shoot number/cane, and summer fresh hedging weights. Narrowing the VFS width was most effective in the two of four years with the least rainfall. Yield/m cordon was reduced by narrowing VFS width, but not to below normal adjusted crop loads. Cluster weight, number of berries/cluster, and cluster number/m cordon were also reduced by narrowing VFS width. Berry soluble solids and total anthocyanins increased and TA decreased with decreasing VFS width, improving berry quality. Postveraison natural weed population growth in the VFS did not affect vine growth or fruit yield and composition. Impact and Significance: In the eastern United States, high rainfall and humidity promote excessive vine growth and immense pest pressure for Vitis vinifera production. Improved canopy characteristics could increase fruit quality by reducing pest pressure, by increasing soluble solids and total anthocyanin concentrations, and by improving the balance between pH and titratable acidity (TA). Increasing competition for water and nutrients during the growing season (by narrowing the VFS or allowing late-season weed competition) may be an effective way to accomplish these improvements. In this study, narrower VFS width in a tall fescue ( Festuca arundinacea var. ‘Kentucky 31’) groundcover reduced vine vegetative growth and positively influenced berry composition. Vineyard weed populations that established naturally postveraison did not affect vine size, yield, or fruit quality.