Handbook for Irrigation of Wine Grapes in South Africa

Chapter 2

35

Coarse sand Fine sandy loam

30

25

10 Cumulative E s (mm) 15 20

5

0

0

2

4

6

8

10

12

14

Days following irrigation

FIGURE 2.8. Evaporation E s

following an irrigation is substantially higher from sandy soils,

compared to heavier soils under the same conditions (after Myburgh, 1998).

Irrigation system: Drip irrigation or furrows wet a smaller percentage of the surface, compared to systems that wet the total surface, e.g. overhead sprinklers or full surface flood irrigation (Fig. 2.9). Therefore, smaller volumes of water will be lost via evaporation in the case of fractional wetting of the soil surface. This aspect will be discussed in more detail in Section 2.4.3.

A

B

C

D

FIGURE 2.9. Examples where different soil volumes are being wetted by (A) drippers, (B) furrows, (C) moveable sprinklers and (D) flood irrigation.

IRRIGATION OF WINE GRAPES 37