SOIL PREPARATION

CHAPTER 7

7.1.3 Direction of tillage In the case of single tilling, its direction should be downhill to facilitate drainage, especially on soils where wetness is a problem. When a soil is double-tilled, the second tilling, which is normally the deepest, should be perpendicular to the contour. From a drainage perspective it would also be ideal if the deepest tilling could be parallel to the direction of the grapevine rows, but this is not always possible. Generally, grapevine row direction is mainly dictated by the climatic conditions of the region and topography of the landscape and even by several other factors, e.g. grape and wine style objectives (Hunter & Volschenk, 2018). 7.1.4 cutting width Cutting width is important when soil is to be prepared effectively. Too large a distance between traverses will leave large undisturbed soil sections in the subsoil and large clods are likely to form (Figure 7.18). Cutting widths that are too closely spaced not only waste money, but also cause wheel slip and sideways sliding since the tractor then needs to drive on loose soil. As a general rule, the distance between ripper trenches should be approximately 66 % of its working depth. In practice, the working depth of a ripper used for vineyard soil preparation will be more than 80 cm which means that adjacent ripper trenches should be 60-70 cm apart. A cutting width of 60 cm is usually used for delve ploughs which are employed in conjunction with rippers, i.e. on the same drawbar behind the crawler tractor.

FIGURE 7.18: Ripper furrows showing poor soil loosening due to a cutting width which was too wide during soil preparation. Eight years after planting grapevine roots could still not exploit the compact soil volume between ripper furrows (Photo: ARC Infruitec-Nietvoorbij).

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