Handbook for Irrigation of Wine Grapes in South Africa

Chapter 7

Irrigation strategies

7.1 INTRODUCTION Due to the Mediterranean climate, summer rainfall alone is too low for grape production in most districts, particularly where winter rainfall is also low, as discussed in Chapter 1. In addition to the natural limitation, water restrictions are imposed during the droughts that periodically occur in the grape growing regions. Furthermore, the South African Water Act enables catchment management authorities to terminate water use licences if growers misuse their allocated water resources. Based on the drive towards more environmentally friendly practices, a general reduction in the water “footprint” of wine production will certainly improve the public image of the South African wine industry. The foregoing is increasingly putting growers under pressure to adopt practices which will contribute towards more efficient use of irrigation water. This means that the primary objective of grape growers must be to apply the right amount of irrigation at the right time to avoid insufficient vegetative growth and to prevent crop losses (Fig. 7.1). On the other hand, not only does over-irrigation waste valuable water, but it could have devastating effects on the environment. The latter occurs particularly where salts are leached into natural water resources or lower lying land (Fig. 7.2). In severe cases, the damaged land might not be reclaimable.

Figure 7.1 Figure 7.1

A

B

FIGURE 7.1. Under-irrigation may cause extremely poor vegetative growth (A) and crop losses due to severe berry shrivelling (B).

178 CHAPTER 7 – IRRIGATION STRATEGIES

Figure 7.2