Handbook for Irrigation of Wine Grapes in South Africa

PHOTO: P. SNYMAN

FIGURE 9.8. Example where frost damage occurred on young grapevines trained onto a high wire in the Breede River valley.

9.4.2 SOILS AND TILLAGE Compared to light coloured soils, dark soil absorbs more heat during the day that can be irradiated during the night to warm the air above vineyards (Haasbroek & Myburgh, 1998). Therefore, the cold damage risk will be less where vineyards are planted in dark coloured soils. Since sand is a poorer heat conductor than clay or loam, and stores less energy during the day, vineyards in sandy soils are more prone to cold damage. The foregoing implies that monitoring conditions for possible cold damage is essential for vineyards in light coloured and/or sandy soils in areas where sub-zero temperatures often prevail during early spring. Keeping

294 CHAPTER 9 – PREVENTING COLD DAMAGE IN VINEYARDS