SOIL PREPARATION

CHAPTER 2

2.4 Dense clay in the subsoil Many soils in the vineyard areas of South Africa contain dense clay in the subsoil. These clays can be dry structured B horizons, wet poorly structured G horizons or even unspecified material. In the South African soil classification system (Soil Classification Working Group, 1991), the type of clay layer, together with the overlying horizon, will determine the soil form. Fourteen soil forms, including duplex soils ( e.g. Kroonstad and Estcourt), typically contain such root impeding clay layers (Figure 2.5). Soil preparation methods will differ among them depending on depth and thickness of the clay layer, wetness and other factors. The presence of a clay layer in itself does therefore not dictate a standard soil preparation technique.

FIGURE 2.5: Duplex soil (Estcourt form) with dense clay layer at 60 cm that impedes root growth and water infiltration (Photo: ARC Infruitec-Nietvoorbij).

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