Handbook for Irrigation of Wine Grapes in South Africa

Chapter 7

Figure 7.39

A

B

FIGURE 7.39. Poor weed control (A) will cause unnecessary water losses via transpiration in a vineyard, compared to clean tillage (B).

Figure 7.40 It is advisable to terminate irrigation of windbreaks when water resources are limited. In this regard, it will be useful if windbreaks have separate irrigation valves. If there are indications that a windbreak competes with the adjacent grapevines for nutrients and water, the trees should be removed. Water plants, reeds and trees growing in, or on the banks of irrigation dams are further causes of substantial, unnecessary water losses via transpiration (Fig. 7.40). For example, it is estimated that Common reed uses approximately 500 mm water during the summer (Kabenge & Irmak, 2012). This implies that a 3 m wide and 300 m long stretch of Common reed on the banks of a dam, as indicated in Figure 7.41, will waste 450 000  of irrigation water via transpiration during summer. Therefore, it is essential to remove any unwanted vegetation in and around irrigation dams. This can be carried out when dams are empty at the end of the irrigation season, or during dry winters.

A

B

FIGURE 7.40. Water plants (A), as well as reeds and trees (B) will cause unnecessary water losses from dams via transpiration.

Figure 7.41

IRRIGATION OF WINE GRAPES 225