SOIL PREPARATION

CHAPTER 5

will be removed effectively, but without causing soil erosion in the vineyard. It is self-evident that water courses must be constructed to take away the water which is discharged from the ditches between ridges.

FIGURE 5.3: Ridges must not be constructed in such a way that surface water ponds in the ditches and cannot flow out of the vineyard or orchard (Photo: J.E. Hoffman, Stellenbosch University).

5.1.3 Grapevine performance on ridges Ridging creates favourable soil conditions in the early parts of the growing season in Mediterranean climates by removing excessive water from the landscape in the form of run-off and improved internal drainage. The exposed soil surface area of a ridged soil does increase evaporation losses, especially on the shoulders of the ridges, which may lead to water stress during the late part of the growing season (Myburgh & Moolman, 1991a), i.e . between véraison and harvesting. In a field experiment on a waterlogged soil comparing ridges of different heights and widths to an un-ridged control, ridging improved internal drainage in the root zone (Myburgh & Moolman, 1991a; 1991b). This improvement can be attributed to the increased soil depth above the water table through an additional layer of soil, i.e. “the roots are lifted above the water table by the additional topsoil layer”.

SOIL PREPARATION | 63