An element (P) that is luminous by oxidation, whose name is derived from phosphoros (Greek for light carrier). In nature it occurs exclusively bound, mostly in the form of phosphates. Typical minerals are apatite, phosphorite, turquoise and wavellite. It is also contained in guano (bird excrements) and is used in this form as fertilizer. Pure, white phosphorus causes caustic wounds and is very toxic, even 50 mg is deadly for humans. Phosphorus compounds are essential for all living organisms and are involved in central areas such as DNA as a component of nucleic acids and cellular energy supply. In the metabolism of the vine, phosphorus fulfils a variety of functions. It plays a central role in the energy balance, in photosynthesis and as a component of proteins and enzymes. The proportion is particularly high in the grape seeds. To put it very simply, phosphorus is mainly used for flower and fruit formation.
In strongly acidic and also alkaline soils, phosphorus can be fixed (bound) and is therefore no longer available to plants. A phosphorus deficiency is manifested in the vine by blue-green to violet discoloration of the leaves and weak flower and fruit formation. Most soils used for viticulture have been supplied with large quantities of phosphorus fertilizers since the end of the 19th century. A deficient supply to the vine is therefore not fundamentally due to a deficiency in the soil, but often to low availability. Phosphates tend to form compounds that are difficult to dissolve and therefore difficult to obtain. Only a small proportion of the phosphorus in the soil is present in a water-soluble, absorbable form. Fertilisation with phosphates must therefore be precisely adapted to the soil depending on the pH value. Phosphates are also used as insecticides for pest control.