Refrigeration of the root zone to delay budbreak in grapes (Vitis vinifera)

This experiment evaluated refrigeration of the root zone to delay budbreak for two genotypes of Vitis vinifera L., 'Cabernet Sauvignon' and 'Chardonnay'. For experiments one and two, one-year-old vines that had been grafted to '5BB Kober' rootstocks were used. For experiment three, three-to-five-year-old vines of each genotype on their own roots were used. All three experiments were conducted under greenhouse growing conditions. Water bath chillers were used to implement two root zone temperature treatments 7.2°C, and 1.7°C and an unchilled control temperature. The experimental design followed a randomized split plot, with main plots being temperatures and the sub plot being genotype. Evaluation of budbreak was performed on a daily basis. Other data collected included shoot dry weights for all three experiments, and root dry weights for experiments one and two. Type T thermocopules (copper-constantan) attached to a datalogger and multiplexer were used to measure soil, water, and air temperatures. In experiment three, short wave radiation and relative humidity were measured using a portable weather station. The experiments indicated that budbreak could, in fact, be delayed by the refrigeration of the root zone. Shoot growth was also reduced. However, there are likely other factors responsible for delaying budbreak in grapes.