SOIL PREPARATION

CHAPTER 5

5.2 Terraces The terracing of steep slopes has been done widely in the world since ancient times for the purpose of production, but also for aesthetic reasons (Gardner & Gerard, 2003). Terraces are indeed one of the most distinctive features of European mountainous agriculture (Figure 5.7). The old terraces have the building of walls and filling with soil behind the walls as well as construction of drainage channels as a common factor. Since around 1970, however, land terracing using heavy earth moving machinery has been used to create bench terraces on steep slopes that can each usually accommodate two vine rows. These operations involved cutting and filling, causing a huge displacement of soil and even a transformation of the landscape (Cots-Folch et al ., 2006; Stanchi et al ., 2012).

FIGURE 5.7: Terraces built with stone on steep slopes in the Ribeiro region in Spain (Photos: J.E. Hoffman, Stellenbosch University).

Terracing of vineyard soils is not as common in South Africa as in Europe, but vineyards planted against steep slopes have become a more regular sight in this country in recent times. This is on the one hand an indication that more new land is needed and secondly of the fact that these slopes are often at higher altitudes and therefore cooler, an advantage in the case of wine grapes. The cultivation of vine rows on sloping land normally leads to the shifting of soil and subsequently to a fairly level area between rows (Figure 5.8). However, when slopes become too steep, i.e. more than approximately 20 % (11º) (Saayman & Van Huyssteen, 1981a), the construction of terraces has to be considered since the use of tractors and other implements becomes too dangerous. Without terracing, displacement of soil due to normal tillage over time can cover the graft unions of grapevines in the lower vine row and also cause implements to work too close to the upper row. Zeeman (1981) consequently recommended that row width be increased by 15 cm for each 5º increase in slope.

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