SOIL PREPARATION

The use of dynamite to break up hardpans before planting of new vineyards and even between rows of existing vineyards was propagated in South Africa early in the 20th century (Quinah, 1912). The extent to which ‘dynamite-ploughing’ was actually applied in practice for the modification of vineyard soils has been lost in the mist of time. Theron (1930), however, reported the use of dynamite to break up shale soils in Europe, specifically in Portugal and on the Moselle slopes in Germany. He also reported that soil was prepared at that stage using big steam tractors and single furrow ploughs. The ploughs reached a depth of 30-90 cm and ploughing was done in summer when the soil was hard and dry. They then passed a disc harrow over the land in winter, when the soil was wet, in order to render the soil in a good condition for planting. The first contractor to provide a soil preparation service for grape farmers in South Africa started operating around 1930 (Figure 1.1).

FIGURE 1.1: Equipment of yester year: Soil preparation with a McCormick crawler tractor on the farm Hoogstede of Mr S.J. du Toit in 1930 (left) (Photo: J. Nolte) and plough used for deep soil preparation on the Delheim wine estate in the Western Cape pre-1961 (right) (Photo: J.E. Hoffman, Stellenbosch University). Deep soil preparation has, however, only been scientifically grounded with the visit of Schulte-Karring (1976) and publication of the results of soil preparation trials at Robertson and Stellenbosch (Claassen, Van Zyl & Kleynhans, 1973; Saayman & Van Huyssteen, 1980; Saayman, 1982). Since then, deep soil preparation on wine farms has become an essential practice. The aim is to remove all impediments to root systems in the soil down to a depth of 800-1 000 mm. Soil preparation also provides an ideal (and often the only) opportunity to rectify unfavourable soil chemical conditions such as high acidity and low phosphorous (P) content in the subsoil. Deep tillage, i.e. tillage to a depth of 80 cm and more, is not the only component of soil preparation by far. Wet soils have to be drained, an action that can only be done before planting a permanent crop. The necessity for using big machines, vehicle traffic, depth at which subsoil drains have to be installed,

16 | INTRODUCTION