V. Vinifera Water Dynamics in the Southeast: Observations and Modeling.

As North Carolina wine grape (V. vinifera) production intensifies, water management guidelines should be developed. Grape yield and composition, and consequently wine quality, are greatly influenced by the water regime under which the grapes were produced. Despite the importance of water management, related research in the Southeastern U.S., and especially North Carolina’s primary wine grape region, the Yadkin Valley Appellation, is extremely limited. This region has unique soils and climate, which differ considerably from other established wine regions where water management practices have been developed. To date, NC vineyards are often equipped with costly permanent irrigation systems for vine establishment and occasional watering; however, rainfall generally exceeds evapotranspirative demand. It is known that water stress can enhance grape quality. Thus, there is need to adapt local water management strategies to enhance the quality of wine grapes produced and to lower input costs. A field experiment was initiated in 2011 at Dobson, NC with a goal of inducing vine stress and assessing corresponding soil moisture conditions. Experimental treatments with and without rainfall exclusion were established for two hydraulically dis-similar cultivars, Grenache and Syrah. Monitoring included soil volumetric water content, grape leaf stomatal conductance, and stem potential; basic grape chemistry analysis was also performed. While some treatment differences were significant, desirable stress levels were not attained. Measured climatic and soil physical properties data were utilized as inputs for soil hydrology modeling with Hydrus-1D. Observed soil and plant parameters from the field experiments were used to assess the accuracy of the model. Modeling efforts will be expanded to include sites throughout the Southeast using existing climatic databases. Frequency and severity of historical drought conditions will be identified, assisting growers in decisions regarding grape planting sites and irrigation management.