South Africa Wine Technical Yearbook 2025

MAY

Profile pit stories with Johan By Johan de Jager

Francois Conradie (Idiom), Johan de Jager and Dirk Coetzee (L’Avenir).

How should high sodium (Na) levels in the soil be managed? In relation to the other basic cations, sodium (Photo 2) should comprise less than 3 - 5% of the cation ratio. This is monitored through routine soil analyses. As soon as the level rises above the critical norm, all manure applications should be discontinued due to the possible high sodium content. Secondly, optimal drainage of the soil should be ensured so excessive sodium can be leached out effectively. Furthermore, calcium levels should comprise at least 68 - 72% of the cation composition. Lastly, organic material should also be built up in the soil. If a sodium problem still occurs after these interventions, it should be washed out with sulphur via a gypsum application.

It often happens that producers jump into the profile pit with me when I am conducting a soil survey and start digging to open the walls. As we discuss the soil, the conversations often evolve and digress to other themes – from how the Boks played over the weekend to our children’s latest antics, and back to the right foliar nutrition or the correct timing for a specific fertilisation. With this article, I will summarise a few regular soil-related questions and answers. Is one element more important than another? Although producers sometimes wrongly focus on a specific element, the aim should instead be an optimal balance of all the cations (Ca, Mg, K and Na). When the correct balance of all the cations is reached in the soil, the pH naturally normalises. Other elements that are dependent on optimal pH also then become more accessible. How should problems with immobile elements like phosphate (P) be handled? Phosphate is largely immobile in the soil. Both short- and long-term strategies should therefore be followed to address phosphate accessibility and concentrations sufficiently. If I want to correct my soil entirely over the long term, the product should be applied through broadcast spreading to increase the concentration in the soil, and the crop will gradually take up the element via the roots. To address variation within blocks, the additions can be broadcasted with varying spreaders (Photo 1). Over the short term, phosphate should still be included in the fertilisation programme until the roots are able to utilise the long-term solution additions.

PHOTO 1. Example of varying spreader.

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TECHNICAL YEARBOOK 2025