A study was conducted in the field on Vitis vinifera L. (cv. Thompson Seedless) to compare various measurements of vine water status under high-frequency drip irrigation. Water use at 100% of vine evapotranspiration (ETc), was determined with a weighing lysimeter. Vines in the vineyard were irrigated at 0, 0.2, 0.6, 1.0, or 1.4 times the amount of water used by the lysimeter vines. Water applications occurred each time the lysimeter lost 16 L of water (2 mm depth; 8 L vine−1). Soil water content (𝛉v) was measured in the 0.2, 0.6, 1.0, and 1.4 irrigation treatments. Predawn (ΨPD), midday leaf (Ψl), and midday stem (Ψstem) water potentials were measured at the ends of the 1991 and 1992 growing seasons and almost monthly during 1993. Soil water content in 1993 remained constant throughout the growing season for the 1.0 irrigation treatment, increased in the 1.4 treatment, and decreased in the 0.2 and 0.6 treatments. Both Ψl and Ψstem measurements detected differences among irrigation treatments to a greater extent than did ΨPD until very late in the 1993 growing season. There was a linear relationship between Ψl and Ψstem. All three measurements of water potential were related to soil water content (using a quadratic function); however, the relationship between SWC and ΨPD had the lowest R2 value, 0.52 compared to 0.90 and 0.94 for Ψl and Ψstem, respectively. Results indicated that ΨPD would not be useful in accurately determining vine water status under high-frequency deficit irrigation.
- Copyright © 2005 by the American Society for Enology and Viticulture