SOIL PREPARATION

CHAPTER 5

tractor or an excavator. The operation starts at the bottom of the slope after the required lime and fertiliser have been applied on the soil surface. Terraces are then sequentially constructed higher up on the slope. Construction must be such that the terrace slightly slopes from the outside to the inside. Saayman & Van Huyssteen (1981a) recommended that the soil on the terrace now be loosened by using a delve plough and a ripper in combination. The delve plough should, however, be positioned to plough a furrow in the exposed subsoil on the inside of the terrace, i.e . where the inside vine row will be planted. Simultaneously the ripper breaks the soil on the outside edge, i.e . where the future outside vine row will be planted. Ameliorants such as lime and phosphate for amendment of the subsoil should be applied at this stage. The second terrace, i.e. the next one higher up on the slope, is subsequently made in a position that will allow sufficient topsoil to spill over its edge to cover the subsoil and fill up the delve furrow at the lower terrace. When an excavator is used, topsoil from the second terrace can actually be placed on the lower one to replace the topsoil that was removed during its construction. This construction method will ensure that the topsoil is preserved and concentrated in the position on a terrace where the new grapevines will be planted.

FIGURE 5.9: Table grapes on terraces in Paarl. Note that concrete walls were constructed to contain the terraced soil. This expensive method is nowadays replaced by slanted earthen walls between terraces (Photo: J.E. Hoffman, Stellenbosch University).

SOIL PREPARATION | 71