FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 4

4 CHEMICAL CORRECTION OF SOILS DURING SOIL PREPARATION

DAWI D SAAYMAN & P I ETER RAATH

NEGATIVE SO I L PROPERTI ES Soils upon which table grapes are generally cultivated in South Africa, are divergent as far as physical and chemical properties are concerned. In the coastal region (Paarl vicinity) the parent material consists of very old and highly weathered shale and granite, resulting in soils with a poor nutritional status, and a low exchangeable capacity, while acidity increases with soil depth. Even though these soils are generally well-drained, they are nevertheless compact. Together with the soil acidity this is restrictive to root development in the deeper layers. Vineyards next to the Berg River and in the Saron areas are generally situated on younger alluvial material, while acidity may also be relevant. In the inland areas, stony, alluvial soils, as well as soils characterised by hardpans occur within the profiles. Furthermore, heavy duplex soils occur in some areas, e.g. where salinity is present in the subsoil, implying that the soil can only be utilised by means of ridges. Along the Olifants and Orange River the alluvial soils are characterised by layering and at higher altitudes by varying degrees of lime accumulation and hardening. Along the lower course of the Orange River large areas of the so called “ghom” material are already utilised. The latter was initially physically weathered, brittle “gneiss”, but due to the actions of soil preparation it has been turned into “soil”. The soils on which table grapes are grown in Limpopo vary according to the parent material

FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY | 29