SOIL PREPARATION

5.1.4 Vineyard practices adapted to ridging A unexpected benefit of ridges, pointed out by growers, is that their shape prevents tractor wheels from coming too close to young trees and vines in new plantings. Many viticulture practices such as pruning and harvesting, however, are more difficult to perform on ridges (Figure 5. 5). It is therefore important to only consider ridging of soil that requires it.

FIGURE 5.5: Well-constructed ridges (50 cm high) that were necessitated by dense clay in the subsoil of a table grape vineyard in the Hex River valley. The difficulty that such ridges cause during pruning, harvesting and other practices is obvious (Photo: J.E. Hoffman, Stellenbosch University). Grapevines can be planted on narrow ridges i.e. only one row per ridge or on ridges wide enough to accommodate two rows. An important requirement, however, is that the ditch between ridges must be wide enough to allow vehicle traffic without compacting and eroding the ridge sides. This requirement can be achieved by alternating double rows on top of the ridge with a wide inter-ridge space (Figure 5.6). A high planting density of 3 546 vines/ha is possible with 3.5 x 1.2 x 1.2 m spacing. This planting system allows for a 1.5 m tractor path between ridges. Grapevines should not be planted closer than 30 cm from the shoulder of a ridge to prevent excessive drying of the soil in the root environment.

66 | SPECIAL SOIL PREPARATION STRUCTURES