Phosphorus (P) versus phosphate (P2O5)

The terms phosphorus (P) and phosphate (P2O5) are often used interchangeably in soil science and fertilizer science.

P stands for the chemical element phosphorus, from the periodic table. P is essential for the functioning of animals and plants; it is part of cells, as a building material and in DNA.

The term P2O5refers to the crystal form in which P occurs in the soil. The use of this term was introduced around 1850 by Justus von Liebig, the founder of fertilizer theory and inventor of artificial fertilizer. Today it is still a commonly used term in soil science and fertilizer theory.

P is taken up by crops in the form of phosphate compounds such as H2PO4- and HPO42-. The term phosphate is mostly used in the context of fertilization and manure policy.

Conversion can be done as follows:

  • From kg P to kg P2O5, multiply by a fixed factor of 2.29: 100 kg P corresponds to 229 kg P2O5
  • From kg P2O5to kg P, multiply by 0.436

The complete soil analysis Fertilization Manager from Eurofins Agro provides insight into the phosphate status of the soil.

Fertilization Manager