Handbook for Irrigation of Wine Grapes in South Africa

distribution if the management is changed to conventional drip irrigation where larger soil volumes are wetted. Bearing in mind that irrigation with nutrient enriched water was initially developed to maximise fresh fruit production, this strategy is likely to induce excessive vegetative growth which may cause poor quality in the case of wine grapes. Furthermore, irrigation with nutrient enriched water requires sophisticated, expensive equipment, as well as skilled management inputs on a daily basis. Therefore, the OHS strategy cannot be recommended for wine grape production. However, it might be useful on a limited scale for drip irrigation in vineyards in extremely poor soils, e.g. gravelly soil with very low PAW and almost no cation exchange capacity. Figure 7.14 g .

FIGURE 7.14. Concentration of roots in the small wetted volume where grapevines had been drip irrigated with nutrient enriched water for three years. Irrigation was applied via a number of short pulses during daytime. Figure 7.15

0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 ECe (dS/m) 0 0 e /m

7 0

a

A

B

0-15 cm 15-30 cm 30-60 cm

0-15 cm 15-30 cm 30-60 cm

a

ab

6 5

abc bc abc b

6 0

bc

ab

bc

pH (KCl) pH l)

cd

5 5 5

cd

d

d d

d

5 0

d

d

d d d

d

4 5

e

e

4 0

BeneatK dripper i

30 cm away

30 cm away

BeneatK dripper

5 cm away

5 cm away

FIGURE 7.15. The pH (KCl)

(A) and electrical conductivity of the saturated extract (EC e ) (B)

at three depths beneath and around drippers where grapevines were irrigated with nutrient enriched water for three years (Howell & Conradie, 2013). For each graph, bars designated by the same letter do not differ significantly (p ≤ 0.05).

196 CHAPTER 7 – IRRIGATION STRATEGIES