Phosphorus is always found in nature in its highest oxidation state, i.e. as anion of trihydrogenphosphoric acid PO₄^3-. The most important natural source of phosphorus in the soil is the primary mineral apatite, and to a much lesser extent iron and aluminum phosphates. Through the weathering of primary phosphate minerals, phosphorus is transformed into various secondary forms of both inorganic and organic nature, some of which may be usable by plants.

It should be noted that natural apatite minerals are mainly used as raw materials in the production of phosphate mineral fertilizers (e.g. Kola apatite mined on the Russian peninsula of the same name, where there are huge deposits of these and other ores, Kola apatite contains a minimum of unwanted heavy metals) , especially cadmium, unlike those mined, for example, in Africa). In order to obtain phosphorus in a form that is accessible to plants, the apatite structure must be "broken" with strong mineral acids during production. Improper application of fertilizers can easily lead to the opposite reactions to those during their production, and thus to their deterioration, which of course entails significant financial losses, because of the basic nutrient elements, it is phosphorus that is the most expensive when converted per unit.

For a correct understanding, it is necessary to know how phosphorus fertilizers are actually produced and in what form phosphorus is contained in them. The vast majority of fertilizers containing phosphorus today are produced by the decomposition of natural phosphates with mineral acids. Here is a brief summary for the most important types of phosphorus-containing mineral fertilizers:

• The basic operation in the production of NPK fertilizers is the decomposition of phosphates in an excess of nitric acid HNO₃ (with a concentration above 53%), forming calcium nitrate Ca(NO₃)₂, trihydrogentetraoxophosphoric acid H₃PO₄ and hydrogen fluoride HF. The subsequent adjustment of the ratio of calcium and phosphorus is important, which takes place by neutralization with ammonia NH₃, whereby calcium hydrogen phosphate CaHPO₄, calcium fluoride CaF₂ and ammonium nitrate (NH₄)₂NO₃ are formed. The following steps differ depending on whether and in what form calcium remains bound in the final product (it is either filtered out after freezing, or bound, for example, in gypsum or calcium carbonate).

• Monoammonium phosphate (also abbreviated as MAP, trade name amophos, chemically ammonium dihydrogen phosphate (NH₄)H₂PO₄) is produced by neutralizing phosphoric acid with ammonia (this must not be in excess to prevent the formation of other unwanted products, which occurs anyway, so the reaction takes place gradually mixing and elevated temperatures). Diammonium phosphate (abbreviated DAP, chemically diammonium hydrogen phosphate (NH₄)₂(HPO₄)) is produced by the same reaction, but in a different ratio (usually 1 mole of phosphoric acid obtained by decomposition of phosphate with 2 moles of ammonia).

• The most classic single-component fertilizer is simple superphosphate. It is produced by decomposing ground natural phosphate with sulfuric acid H₂SO₄ (62 – 75%). The reaction takes place in two phases, in the first, part of the raw material is decomposed to form phosphoric acid, which then reacts with the rest of the phosphate over the course of the next few days. The product is calcium dihydrogen phosphate, which is well soluble in water, and calcium in the form of gypsum in an approximately 1:1 ratio, i.e. Ca(H₂PO₄)₂ and CaSO₄. Its powder form is partially neutralized with ammonia water (which also partially reduces the content of the water-soluble component) and then granulated. The production of so-called enriched superphosphate (sometimes also double superphosphate) proceeds analogously, but a mixture of phosphoric and sulfuric acid is used to break down the phosphates. In the production of triple superphosphate, only phosphoric acid is used to break down the phosphates. The reaction is faster than in the case of simple superphosphate, because there is no deposition of calcium phosphate on the surface of the rock, which slows down diffusion.

Soil pH plays a very important role in soil reactions of phosphorus supplied by fertilizers:

• In soils with a low pH (acidic soil), phosphorus is mainly bound to dixoxal-dihydrogn phosphates of aluminum and iron. These are stable crystalline minerals. Thus, there is a precipitation of dissolved phosphate ions with the help of iron and aluminum ions. In order to prevent such undesirable transformations of phosphorus into less soluble forms, it is necessary to limit the conditions that lead to this with suitable agronomic interventions. The inclusion of leguminous plants proves to be advantageous, because the excreta of their roots, as well as their higher sorption capacity, enable the use of some of the less soluble phosphorus. Adding organic matter to the soil is proving to be very suitable, which increases its biological activity and thus leads to reversible processes. Also, thanks to organic substances, phosphorus is bound into much less permanent organic bonds. And last but not least, free calcium is pumped into humus substances.

• In alkaline, neutral (or very weakly acidic) soils, retrogradation (degradation) of phosphorus occurs to a certain extent, by which we mean the formation of very poorly soluble tricalcium phosphate Ca₃(PO4)₂, but more often its combination with calcium hydrogen phosphate, called as octocalcium phosphate Ca₄H(PO₄)₃.2H₂O. Here, too, the recommendation to include leguminous plants in the crop sequence applies, as was described in the case of acidic soils.