Jaclyn Fiola,* Greg Evanylo, Tony Wolf, and Ryan Stewart
*Virginia Tech, 342 Smyth Hall, 185 Ag-Quad Ln, Blacksburg, VA 24061 (jcfiola@vt.edu)

The ability of mid-Atlantic states to support high-quality winegrape production can be hindered by excessive plant-available water and nutrients. Such excesses can neg- atively influence fruit composition and potential wine quality by producing vigorous vegetative growth. A major source of water and nutrients in the soil is the topsoil: the upper horizons of the soil profile that are dark-colored and rich in organic matter. Topsoil management is a potential approach for growers to influence hydrology and fertility of vineyard soils, but very little is known about topsoil’s contribution to vine growth and fruit composition, especially in the mid-Atlantic region. We investigated topsoil’s contributions at two vineyards in Maryland and Virginia with different topsoil thickness while other factors (climate, vine spacing, training, management, cultivar/ clone/rootstock) were constant. First, we surveyed topsoil thickness along transects in each vineyard. Then, at each panel corresponding to the topsoil measurement locations, we analyzed vine and fruit properties. Results from the 2019 and 2020 growing seasons suggest strong relationships between topsoil and fruit titratable acidity, cluster compactness (berries per length of rachis), and vine size (dormant pruning weights) at both sites. Compared to thick topsoil, vines growing in thinner topsoil had significantly lower vine size, cluster compactness, and titratable acidity. Topsoil effects on fruit pH and Brix varied by site and year but showed some relationship between thinner topsoil and higher pH and Brix. Specific mechanisms for these effects are still being investigated, but it appears that vines growing in thinner topsoil ripen faster than vines in thick topsoil. Results from this project will provide guidance for better site selection and soil preparation in the mid-Atlantic. Our results may also help inform decisions about soil management and harvest timing in established vineyards.

Funding Support: Maryland Wine and Grape Promotion Fund, Virginia Tech Institute of Critical Technology and Applied Science