Five irrigation treatments (nonirrigated control; irrigation cut-offs imposed postbloom, lag phase, and veraison; and full season irrigation) were evaluated in an Ontario Chardonnay vineyard over a 4-yr period. The modified FAO Penman-Monteith evapotranspiration formula was used to calculate water budgets and schedule irrigations. Transpiration rate, midday leaf water potential, and soil moisture data suggested that the control and early cut-off treatments were frequently under low water status, despite ample precipitation in two of four seasons. Full season irrigation increased yield by 18% (2001) and 19% (2002) over the control due primarily to increased berry weight. Soluble solids were increased by irrigation, and full season irrigation showed similar or higher Brix than all other treatments in two of four years. Berry titratable acidity and pH also fell within acceptable levels for all five treatments, although titratable acidity was slightly higher in irrigated treatments in two of four years. Wines made from irrigated grapes had greater intensities of apple, citrus, and floral aromas and flavors, and less earthy aroma and flavor. These results strongly suggest that irrigation is a viable option for winegrape vineyards in Ontario and the northeast United States, with potential for simultaneous increases in yield, soluble solids, and desirable wine sensory attributes.
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