How is phosphorus supplied in commercial fertilizers?

Phosphorus is supplied in commercial fertilizers primarily as inorganic phosphate. The main source for this is phosphate rock, which consists largely of insoluble tricalcium phosphate.12

Because plants require phosphorus in a water-soluble form, the rock must be chemically processed. This is typically achieved through acidulation—treating the crushed rock with sulfuric acid or phosphoric acid—to convert the insoluble material into soluble monocalcium phosphate or other calcium hydrogen phosphates.23

Common variations include:
* Superphosphate: Produced by treating phosphate rock with sulfuric acid.2
* Triple superphosphate: Produced by using phosphoric acid, which increases the concentration of useful phosphoric oxide.2
* Mixed fertilizers: These may be created by using nitric acid or ammonia during the treatment process, resulting in products like ammonium phosphate, where both constituents provide essential nutrients.2