Handbook for Irrigation of Wine Grapes in South Africa

Chapter 7

subjected to similar pre-véraison water deficits, the reduced vegetative growth caused more exposed berries which increased juice pH and decreased TTA (Table 7.10). Pinotage wine characteristics and overall quality appeared to be better where post-véraison water constraints occurred, compared to pre-véraison water constraints (Table 7.10). TABLE 7.10. Effect of pre- or post-véraison low frequency micro-sprinkler irrigation, compared to medium frequency irrigation throughout the season on cane mass, berry mass, yield and sensorial wine quality of two cultivars under the same conditions in the Breede River valley (Myburgh, 2011f & g). Data are means for three seasons.

Cultivar

RAW depletion pre-véraison→post-véraison 50%→50% 75%→50% 50%→75%

Sauv. bl.

Cane mass (t/ha)

3.2 a*

2.9 a

2.9 a

Berry mass (g)

2.0 a

1.8 b

1.8 b

Yield (t/ha)

15.8 a

16.5 a

14.0 b

Juice pH

3.22 a

3.16 a

3.19 a

10.0 a

9.9 a

9.3 a

Juice TTA (g/  )

Vegetative character (%)

37.0 a

38.1 a

35.7 a

Fruity character (%)

40.0 a

37.7 a

38.9 a

Wine quality (%)

45.4 a

48.1 a

48.4 a

Pinotage Cane mass (t/ha)

2.1 a

1.5 b

1.8 ab

Berry mass (g)

1.6 a

1.5 b

1.5 b

Yield (t/ha)

21.1 a

19.7 a

18.9 a

Juice pH

3.27 b

3.33 a

3.28 ab

8.0 a

7.1 b

7.8 ab

Juice TTA (g/  )

377 b

380 b

429 a

Anthocyanin (mg/  )

Cultivar character (%)

58.2 a

52.3 b

59.9 a

Wine quality (%) 51.7 a * For each cultivar, values followed by the same letter within a row do not differ significantly (p ≤ 0.05). Medium frequency irrigation before véraison reduced cane mass, but only tended to reduce yield of Sauvignon blanc in a sandy soil near Lutzville in the Lower Olifants River region, compared to high frequency irrigation throughout the season (Table 7.11). However, the pre-véraison water deficits resulted in more exposed berries causing higher juice pH and lower TTA (Table 7.11). Although pre-véraison water deficits enhanced the vegetative character and suppressed the fruity character, it did not reflect in the overall wine quality. On the other hand, where 49.4 ab 45.5 b

IRRIGATION OF WINE GRAPES 199