Effect of Irrigation, Crop Level and Potassium Fertilization on Carignane Vines. II. Grape and Wine Quality

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Abstract
The influence of two irrigation regimes (none and frequent), two levels of K fertilization (0 and 2.2 kg potassium sulfate per vine per year) and two crop levels (not thinned and thinned to one cluster per shoot) on grape and wine quality from field grown Carignane vines was studied at Davis, California, over a period of three years (1979 to 1981). Irrigation, K fertilization and crop level had a minor and inconsistent effect on petiole K concentration. Irrigation and crop level had no effect of lamina K concentration. Irrigation, K fertilization and crop level did not affect the rate of increase in berry weight after the data were transformed to remove the inherent variability of final berry size. Concentration of soluble solids in fruits was reduced by irrigation, but the pH and K concentrations were increased by irrigation. The rate of increase of berry juice K concentration with increasing soluble solids followed a sigmoidal pattern. K accumulated rapidly until fruit reached about 10°Brix, followed by relatively slow accumulation between 10° and 17°Brix, and then there was a second rapid period of accumulation during the final stages of ripening. The concentration of K in nonirrigated fruits at maturities greater than 10°Brix was less than in irrigated fruits. The increase in pH at soluble solids concentration greater than 17°Brix was associated with increase in K concentration. Crop level and K fertilization had no effect on grape juice pH, titratable acidity and K. Concentrations of arginine and proline in berry juice of nonirrigated vines were significantly less than in irrigated vines on a given date. Irrigation reduced the concentration of anthocyanins in berry skin and wine compared to nonirrigated fruit. Water stress was more important in regulating wine pH than crop level or soil K level, suggesting that irrigation management may be a useful method to help reduce high pH problems and improve wine quality.