Grape Response to Cooling with Sprinklers

Abstract

9Chardonnay,9 9Semillon,9 and 9Chenin blanc9 vines, grown in a large vineyard east of Reedley, California, were sprinkled sequentially during the daytime for a specific period when the berries reached the véraison stage and when air temperature exceeded 32 C. Sequential cooling continued until harvest. Air, leaf, fruit, and soil temperatures were measured and were usually 5-10 C lower on cooled vines during the peak temperature periods than the uncooled treatments. All cooled treatments increased the fresh weights of the berries in all varieties. Cooling also increased the shoot growth of all three varieties. Although in most cases the cooled treatments produced more acid berries with lower pH, these values were low and not statistically significant. Cooling definitely delayed fruit maturity by 2-3 weeks and reduced the levels of total soluble solids. Cooled treatments of these varieties showed limited benefits under field conditions of the San Joaquin Valley, which must be considered in relation to the investments made in permanent sprinklers for cooling objectives.