Handbook for Irrigation of Wine Grapes in South Africa

Figure 7.6

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FIGURE 7.6. Example of a micro-sprinkler (A) without a cap and (B) fitted with the cap to restrict the water distribution pattern.

Figure 7.7 i u e . LOW FREQUENCY IRRIGATION Irrigations are usually applied to wine grapes at low frequencies, i.e. six or less irrigations per season, in regions where water resources are limited, e.g. the Coastal region of the Western Cape (Fig. 7.7). Under low frequency irrigation, grapevines are normally subjected to strong, or even severe water constraints. Yield generally increases with the number of low frequency irrigations, compared to dryland conditions. This trend is not only valid at the single vineyard level (Fig. 7.7A), but also at the regional level (Fig. 7.7B). It is important to note that yields do not increase linearly with the number of irrigations, i.e. the volume of water applied. A major reason for this trend is that the pruning and/or training systems restrict the bearing capacity of grapevines. Therefore, when the effect of irrigation reaches its maximum effect on berry and bunch mass, yield will show no further increase if additional irrigations are applied, i.e. if the crop load remains the same. 7.2.2

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Yield (t/ha) Yield (t/ha

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FIGURE 7.7. Yield increases with the number of irrigations for (A) Chenin blanc in the Coastal region and (B) various cultivars based on a survey carried out in the Upper-Berg River region (adapted from Van Zyl, 1981).

Figure 7.8 Figure 7.8

184 CHAPTER 7 – IRRIGATION STRATEGIES

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Sauvignon blanc

Sauvignon blanc

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