Handbook for Irrigation of Wine Grapes in South Africa

Chapter 7

TABLE 7.5. The Ψ PD at harvest, cane mass, berry mass, yield and wine quality of two cultivars subjected to two medium irrigation frequencies under the same conditions in the Breede River valley. Data are means for three seasons (Myburgh, 2011d, e, f & g). Cultivar Irrigation frequency Medium Medium Interval ca. 7 days ca. 14 days Sauvignon blanc Ψ PD (MPa) -0.2 a* -0.3 b Cane mass (t/ha) 3.1 a 2.3 b Berry mass (g) 2.0 a 1.8 b Yield (t/ha) 15.8 a 15.8 a Juice pH 3.2 a 3.2 a Juice TTA (g/  ) 10.0 a 9.3 a Vegetative character (%) 37.0 a 35.4 a Fruity character (%) 40.0 a 41.8 a Wine quality (%) 45.4 b 51.8 a Pinotage Ψ PD (MPa) -0.2 a -0.4 b Cane mass (t/ha) 2.0 a 1.7 a Berry mass (g) 1.6 a 1.4 b Yield (t/ha) 21.1 a 18.6 b Juice pH 3.27 b 3.34 a Juice TTA (g/  ) 8.0 a 7.3 a Anthocyanin (mg/  ) 377 b 458 a Cultivar character (%) 58.3 a 59.6 a Wine quality (%) 49.4 b 54.4 a * For each cultivar, values followed by the same letter within a row do not differ significantly (p ≤ 0.05). High yielding, micro-sprinkler irrigated Colombar grapevines on a T-trellis in fertile, alluvial soil near Grootdrink in the Lower Orange River region were less vigorous when irrigated at a range of medium frequencies, compared to weekly irrigation (Table 7.6). Likewise, berry mass and yield were reduced when the irrigation intervals were fourteen days or longer. However, these high yielding grapevines only tended to produce better wine as the irrigation intervals increased, and less water was applied. As expected, the ET decreased as irrigation frequency decreased, but was comparable for the two lowest frequencies (Table 7.6). The foregoing indicated that Colombar yield and wine quality were fairly insensitive over the range of medium irrigation frequencies under the prevailing conditions.

IRRIGATION OF WINE GRAPES 191