The bluish-silvery, soft alkali metal is the seventh most abundant element (K) in the earth's crust with a share of about 2.5%. The name is derived from the Arabic "al kalja" for "potash" (potassium), an old name for potassium carbonate obtained from wood ashes. The reactive element occurs in nature only in bound form. It is contained in many minerals such as mica, feldspar, kainite, potassium salt, polyhalite and clay. Experiments with increased potassium fertilisation have shown that vines react to this with an increased production of malic acid. Potassium thus has an influence on the acidity in wine. Wines rich in potassium have a "buffered or integrated acidity" that is perceived as balanced. Compared to other minerals, potassium is contained in high amounts in must (up to 1.5 g/l) or wine.
Potassium is one of the most important nutrients for the growth and metabolism of plants as well as the vine by activating numerous enzymes. Simplified, one can say that potassium strengthens wood formation and plant statics. In detail, it increases soil permeability, promotes photosynthesis, flower and fruit formation, wood ripening and sugar formation, as well as regulating protein metabolism and the water balance via the stomata (stomata ) of the leaves. A high potassium content gives a soil a permeable crumbliness with good water drainage.
In heavy soils, potassium can be bound to clay minerals and is thus no longer available to plants. Too low a potassium content leads to water loss through evaporation. It manifests itself through dark purple, dark brown or blackish leaf discolouration, wavy warping and oily shiny leaves, as well as conspicuously small grapes. Fertilisation is in the form of potassium salts (potassium chloride) and potassium sulphates. A balanced ratio to calcium and magnesium is very important and must therefore be taken into account. The potassium compound potassium pyrosulphite is used in viticulture as an antioxidant. See also a list of all ferments under vineyard care.
Potassium: by BXXXD - Own work, CC BY-SA 3.0, Link
Potassium carbonate: by User:Walkerma, Public domain, Link
Potassium dichromate: by Benjah-bmm27 - Own work, Public domain, Link
