FERTILISER GUIDELINES FOR THE WINE INDUSTRY

INTRODUCTION Soil sampling for analysis is regularly done by viticul turists and wine grape producers. Interpretation of the chemical results is often complicated by the variety of extraction methods and ways in which results are expressed. In this chapter the acknowledged analytical methods and the expression of the results thereof are discussed, as well as how to interpret them. Other typical analysis methods and ways in which analytical methods are expressed are also discussed and com pared with the accepted South African norms. Soil analysis reports in South Africa typically contain the following information and analytical results: TEXTURE Soil texture determines the water holding capacity of a soil and the extent to which cations are bound to the soil (negatively charged clay particles). The rate at which nutrients are leached from the root zone is there fore largely dictated by the soil texture. Furthermore, potassium (K) and phosphor (P) norms in particular are influenced by soil texture, making it essential to distinguish between sandy, loamy and clayey soils. Not all laboratories report soil texture by default – in which case the texture is established by the “finger method” and the soil classified as sandy, loamy or clayey. Most laboratories will only report texture when specifically requested, upon which a full textural anal ysis is carried out and the exact percentages of sand, silt and clay then specified.

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