2017 ASHS Annual Conference

In most Midwestern vineyards a three to four-foot weed-free strip is maintained directly beneath the vines to reduce vine-weed competition. Conventionally, this strip has been conserved with repeated applications of herbicide, mainly glyphosate. The necessity for this weed-free strip to reduce vine-weed competition has been well documented in more arid climates. However, in areas with higher soil fertility and adequate rainfall, this strip may be unnecessary. Moreover, stand establishment and early vine growth have not been well documented when planting groundcovers (GC) immediately following the vine planting. The main objective of this project is to assess the severity of competition for water between ‘Edelweiss’ grapevines and neighboring permanent native grass and legume GC combinations. The project is currently in its fourth year. In year one (2014), the vineyard and GCs were established, where the GCs were planted immediately after the vines. Preliminary data were collected including rate of GC establishment and vine length. In the summer of year two, water stress measurements were begun by means of mid-day leaf water potential (LWP) and infrared thermography (IRT) to measure leaf temperature. In warm and arid regions leaf temperature has been shown to be highly correlated with plant water stress through the use of the crop water stress index (CWSI). Moderate to low correlations between the LWP and CWSI were observed in 2015 (R² = 0.23) using single leaf images. In 2016, images were taken of the grape canopy for a better representation of the water status of the entire plant. Higher correlations between the LWP and CWSI were observed using this method. Vine-GC competition was more apparent in three years of pruning weights, where the most extreme GC treatment had up to 99% in 2014, 193% in 2015 and 183% in 2016 lower weights than the control. Harvest in 2016 showed significant differences in total yields between GC treatments and the control. However, no differences were found in berry quality (pH, Titratable Acidity, °Brix). Preliminary results suggest that planting groundcovers in both the alleyways and in-row areas of the vineyard during the first year of establishment is detrimental to vine growth. Furthermore, if water stress can be assessed using non-destructive thermal imagery, grape growers will be able to rapidly evaluate the water status of vines over large areas and make educated decisions regarding irrigation regimes.