Implications of tall fescue for inter-row water dynamics in a vineyard

Vineyards in the southeastern United States face challenges including poor internal soil drainage, high precipitation, and warm temperatures. This environment causes elevated humidity, creating ideal conditions for fungal diseases. Maintaining tall fescue (Schedonorus arundinaceus Shreb) and resident vegetation ground cover in vineyard inter-rows is a common cultural practice in the region, believed to benefit grape (Vitis vinifera L.) production by increasing competition for soil water and thereby favorably reducing vine vegetative growth. We hypothesized that, although inter-row fescue may reduce soil water availability, it may also increase humidity within the vineyard. Our objectives were to assess surface vapor flux from two inter-row treatments (bare soil and tall fescue) and to determine any corresponding effects on soil water content and humidity within the inter-row. Surface vapor flux, soil water content, and vapor pressure (30 cm height aboveground) were measured in inter-rows subjected to each treatment. Observed surface vapor flux for fescue inter-row exceeded that of bare soil by a daily average of 1.1 mm during the grape growing season. Despite fescue inter-row evapotranspiration (ET), soil water depletion was insufficient to produce stress in the vines. Fescue inter-row vapor pressure increased compared to bare soil inter-rows by an average of 2% (P < 0.09) during the growing season. Data suggest that fescue ET may increase inter-row humidity in warm, humid environments, while providing only modest influence on soil water availability. Additional work including increased plot size to accommodate fetch for microclimate measurements, and biological assessment of humidity implications for disease is warranted.