Handbook for Irrigation of Wine Grapes in South Africa

Chapter 1

region, the opposite is also possible. Wine quality potential of Cabernet Sauvignon in the Lower Olifants River region tended to be better where the HI, as well as CI ′ , are lower near the coastline (Bruwer, 2010). This trend was probably due to the extremely high HI and cool CI ′ near Klawer (Figs. 1.5 & 1.6). Traditionally, the terroir concept was developed for non-irrigated vineyards. Therefore, hydraulic properties of the soil, such as water holding capacity, within a terroir also play an important role in the wine style or quality. This is probably the reason for the trend towards better overall wine quality of Merlot in a heavier soil near Wellington compared to a sandy soil on Dorbank near Lutzville (Fig. 1.8).

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Wine quality (%)

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Wine quality (%) Wellington Ashton Lutzville

Wellington Ashton Lutzville

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Wellington Ashton Lutzville

Wellington Ashton Lutzville

FIGURE 1.7. The sensorial overall quality of Merlot wine (A) tends to increase where the heliothermal index is higher and (B) tends to decline where the cool night index is lower.

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Wellington Ashton Lutzville FIGURE 1.8. The sensorial overall quality of Merlot wine tends to increase where the clay content of the soil is higher.

Basically, the wine characteristics within a terroir are induced by the prevailing climate and soil properties under non-irrigated conditions. Therefore, it is important to note that the climate and soil seem to have a general terroir effect on wine quality although the vineyards need to be irrigated in the above-mentioned regions. However, it is important to note that the level of irrigation will affect wine quality

IRRIGATION OF WINE GRAPES 25