Potassium deficiency (K)
A lack of potassium will initially show on young leaves, with necrotic tips and spotting along the leaf’s outer edge. These spots will be more or less evenly distributed. Later onset of deficiency (during the ripening process of the grapes) will result in `browning´ between the leaf veins. Potassium deficiency is one of the causes of `grape withering´.
Treatment: The best option for preventing potassium deficiency is to maintain balanced soil nutrition, based on a soil analysis. It is particularly important to apply a sufficient amount of potassium prior to planting, and to regularly provide nutrients, throughout the year. This will also serve to replenish `washed out´ nutrients. Potassium sulphate (KALISOP®, Patentkali®) should be given preference to potassium chloride. Should deficiency symptoms appear during the vegetation period it is advisable to use foliar fertilisation in order to supply potassium. If the deficiency is recognised early on, repeated applications during peak demand will raise their efficacy.