FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 3

3 INTERPRETATION OF SOIL ANALYSIS REPORTS FOR VINEYARDS

P I ETER RAATH & KOBUS CONRAD I E

I NTRODUCTI ON Soil sampling for analysis is regularly done by viticulturists and producers. Interpretation of the chemical results is often complicated on account of the variety of extraction methods and ways in which results are expressed (Van Schoor et al ., 2000). In this chapter the well-recognized analytical methods and the ways in which analytical results are expressed, as well as the interpretation thereof, are discussed. Other typical analytical methods are also discussed and compared with the accepted South African norms. The analytical methods that will be discussed, are by no means fully comprehensive, but are the ones that are the most studied and best understood in South African for cultivation of grapevines. In South Africa, soil analysis reports typically contain the following information and analytical results: TEXTURE Soil texture dictates the water holding capacity of a soil and the extent to which cations are bound to the soil’s negatively charged clay particles. The rate at which nutrients are leached from the root zone is therefore largely dictated by soil texture. Furthermore, potassium (K) and phosphorus (P) norms are affected by soil texture, making it essential to differentiate between sandy, loamy and clayey soils.

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