Handbook for Irrigation of Wine Grapes in South Africa

Figure 7.49 In another example, low frequency irrigated mechanically pruned Shiraz/110 R grapevines produced almost the same yield as high frequency irrigated vertical shoot positioning (VSP) trained grapevines near Robertson in the Breede River valley (Fig. 7.49A). The irrigation amounts were 483±45 and 139±64 mm, respectively, for the high and low frequency irrigation. The low frequency irrigation not only produced better overall sensorial wine quality than the high frequency irrigation (Fig. 7.49B), but increased the WUE substantially (Fig. 7.49C). Low frequency irrigated, mechanically pruned grapevines also increased the gross margin water use efficiency, compared to VSP trained grapevines irrigated at a high frequency (Fig. 7.49D). The foregoing shows that it is possible to obtain the same yield, better wine quality, higher WUE and use the irrigation water in a more profitable way by adapting the irrigation frequency, as well as the canopy management system.

25

0 10 20 30 40 50 60 70 10 15 20 25 30 35

A

B

20

15

10

Yield (t/ha)

Quality (%)

5

0

VSP

Mech. pruning

VSP

Mech. pruning

10 12 14

C

D

WUE GM (R/m 3 )

WUE (kg/m 3 )

0 2 4 6 8

0 5

VSP

Mech. pruning

VSP

Mech. pruning

FIGURE 7.49. Comparison between (A) yield, (B) overall sensorial wine quality, (C) WUE and (D) WUE GM of VSP trained and mechanically pruned Shiraz/110 R in the Breede River Valley region. The VSP trained and mechanically pruned grapevines were irrigated at high and low frequencies, respectively. The data are means for three seasons and the vertical bars indicate ±standard deviation (after Lategan & Howell, 2016).

232 CHAPTER 7 – IRRIGATION STRATEGIES