South Africa Wine Technical Yearbook 2025

FIGURE 1. The Kroonstad soil form which exhibited duplex character at a winery near Stellenbosch.

at much lower ESP values, even as low as 5, with the critical value varying between soils. 9, 12, 13 Therefore, the objective of the study was to investigate the effect of WWW irrigation on soil chemical properties and potential environmental impacts at a new paddock at a winery near Stellenbosch where no WWW had Details of the experimental site at a winery near Stellenbosch where no WWW had yet been applied were previously reported. 1, 2 The trial layout, description of the application of the WWW to the experimental site, as well as water quality have also been given previously. Characteristics and properties of the soil at the Stellenbosch site The soil was classified as a Kroonstad (orthic A-E-G horizon) 14 soil form previously been applied. Materials and methods

which is commonly found in the Stellenbosch winelands region. This specific Kroonstad soil had a bleached light grey structureless apedal sandy horizon (E horizon) beneath the topsoil to a depth of 50 cm. The grey E horizon of the Kroonstad soil turned yellow when moist (Figure 1). Below this horizon was a sticky gleyed clay layer, which indicated a zone of prolonged wetness. Thus, the soil was very poorly drained. In the 0-30 cm soil layer, the soil contained 7% clay, 6% silt and 87% sand. Soil sampling and analysis Soils were collected at the demarcated plot before the start of the study in March 2011. Thereafter, samples were collected twice a year. Samples were collected in May, before the winter rainfall began and in November, after the winter rainfall season. Soil samples were collected at 0-10 cm, 10-20 cm, 20-30 cm,

30-60 cm and 60-90 cm depth layers. All analyses were carried out by a commercial laboratory according to methods described previously. 2 Extractable K + percentage (EPP ' ) and extractable Na + percentage (ESP ' ) of the soil were calculated. Results Initial soil chemical status At the beginning of the study, the soil was acidic with average pH (KCl) of 4.6 for the profile (Table 1). The P level was acceptable throughout the soil profile, but seemed slightly high for a sandy soil. The Na extr was relatively low throughout the profile compared to K extr and Ca extr which seemed to dominate the exchange capacity. The EPP’ was relatively high compared to the ESP’ which was less than 10% throughout the profile. Soil potassium, sodium and pH High amounts of WWW irrigation

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TECHNICAL YEARBOOK 2025