This project seeks to develop an approach to vine water management appropriate to cooler growing regions that will provide growers the tools they need to know when to begin to irrigate, when to schedule subsequent irrigations and how much water to apply each time they irrigate. This research project utilized midday measurements of leaf water potential (LWP) as a threshold or trigger point to determine when to begin supplying irrigation water. After a threshold LWP has triggered the start of the irrigation season, water was supplied at a fraction of full vine water use. It was our goal to use water management, defined as the timing and quantity of applied water, to impose vine water deficits as a means of producing desirable must and wine characteristics. In order to fully evaluate such an approach, vine and must/wine measurements must be taken over numerous years. Irrigation management strategies for red winegrape varieties, which rely on methods that can insure repeatable results, have not been developed for mature vines in cool regions. Climatic water demand and soil moisture loss variables are commonly used to schedule irrigations in the warmer growing regions in the state; however, these can grossly over estimate the amount of water necessary to insure high fruit quality. Growers are aware of this and realize they must “deficit irrigate” their vines in order to maximize fruit quality.
This project will give them the tools they need to select an irrigation management strategy that integrates climate variables common to the cooler growing areas such as spring rains and summer fog.