SOIL PREPARATION

Rippers used for vineyard soil have one long shank with a small shear at the bottom end (Figure 7.2) (ARC Infruitec-Nietvoorbij, 2002). These implements are mostly used on shallow soils with weathered rock (Glenrosa) and hardpans such as dorbank, hard plinthite (laterite, ferricrete) and hard carbonate horizons that limit soil depth. The hard layers are broken up and the soil loosened without mixing the soil. A ripper is obviously not the ideal implement for incorporating ameliorants into the soil.

FIGURE 7.2: Ripper mounted behind a large crawler tractor (left) (Photo: ARC Infruitec- Nietvoorbij) and sketch of ripper with dotted lines indicating the direction of soil movement (right) (Sketch: J.E. Hoffman, Stellenbosch University). A ripper is normally also used in conjunction with delve ploughs. The ripper will be mounted on the one side behind a tractor and the delve plough next to it (Figure 7.3). The ripper will pre-loosen the soil and allow the delve plough to reach its maximum depth while it does the mixing or shifting action during the same traverse. Such a setup also stabilises the tractor and allows it to move in a straight line. The wing plough is a variation of the ripper and is constructed by attaching two wings or sweeps (size can vary) to the bottom part of the ripper shank (Figure 7.4) (ARC Infruitec-Nietvoorbij, 2002). This plough has the advantage over the standard ripper that a larger volume of soil is loosened. Although the wing plough lifts the soil, similar to a ripper, it lacks the ability to mix ameliorants with the soil.

112 | CHOICE OF IMPLEMENT FOR SOIL PREPARATION