FERTILISER GUIDELINES FOR THE WINE INDUSTRY

The basic cation saturation ratio (BCSR) concept compared to the sufficiency level of available nutrients (SLAN). As guideline upon which soil analyses are interpreted and fertilisation is applied, the basic cation saturation ratio (BCSR) concept (better known as the Albrecht system) is based on an assumption that plants will only grow optimally if there is a balanced ratio of cations (Ca 2+ , Mg 2+ and K + ) for each soil according to its cation exchange capacity (CEC). Fertilisation is therefore done according to the soil’s needs, not the plant’s. In a review article, Kopittke & Menzies (2007) trace the BCSR concept back to the late 1800’s and found that since its origin, no research data has been able to prove the existence of any “ideal” basic cation saturation ratio. Instead, they found that promotion of the BCSR concept resulted (and will result) in inefficient use of re sources and fertilisers. Research by various scientists has shown that the SLAN (sufficiency level of available nutrients) concept, where a minimum concentration of available nutrients in the soil is required for optimal plant nutrition, also applies to vines. Although the “ideal” soil for grapevines can vary dramatically from region to region and between different soil types, its composition is based on a minimum level of nutrients that is re quired in the soil to supply the vine with its nutritional requirements. Nutrient element balancing is used in some cases to evaluate soil. This technique uses, for example, a Ca:Mg ratio of approximately 6 as indication as to whether calcitic or dolomitic lime should be used. For vineyard soils the ideal saturation percentage of exchang able cations is Ca 80%, Mg 15% and K 4%, which brings about a Ca:Mg:K ratio of about 20:3.75:1. In practice, however, it is not necessary to aspire to this “ideal” ratio for grapevines.

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