Bright red, rather soft and tough heavy metal or element (Cu). The Latin name cuprum is derived from "aes cyprium" (ore from the island of Cyprus), where copper was extracted in ancient times. In nature, it is mostly found in minerals such as copper ore, chalcopyrite and copper glance. In all higher organisms, copper is an essential trace element as a component of many enzymes. As a nutrient, it is necessary for vine growth in small quantities, as it promotes the formation of chlorophyll, which is important for photosynthesis, and phytoalexins (growth substances). Copper deficiency is manifested by narrow pale green leaves, reduced shoot growth, shortened internodes and weak root formation.
Downy mildew, which was introduced to Europe in the 1870s, was subsequently successfully controlled by Bordeaux broth; this is a copper sulphate solution. Since then, copper or copper compounds have been used massively in viticulture as a fungicide. Over the last 100 years, this has tended to create a copper surplus in vineyards. Copper accumulates in the soil and is difficult to degrade. This leads to toxic conditions, especially in acidic soil. Too high a copper content impairs fertilisation, disturbs root function and causes the leaves to turn yellow. Fertilising with humus or calcium (lime) neutralises the effect. Too high a content in the wine leads to cloudiness and a metallic-bitter taste or the wine defect black fracture. The taste perception threshold is 2 mg/l. According to EU regulations, the maximum copper content in wine is 1 mg/l.
Copper nugget: by Jurii - image, CC BY 3.0, link
Copper crystals: by Rob Lavinsky, iRocks.com - CC BY-SA 3.0, Link
Copper oxide: by Nicole Schüler on Pixabay
