Common sources of NPK fertilisers

1. Common sources of NPK fertilisers Common sources of NPK fertilisers include ammonia (NH3), diammonium phosphate ((NH4) 2HPO4), ammonium nitrate (NH4NO3), ammonium sulphate ((NH4) 2 SO4), calcium cyanamide (CaCN2), calcium nitrate (Ca(NO3) 2), Sodium Nitrate (NaNO3), Urea (N2H4CO). Phosphorus is commonly provided as a phosphate such as diammonium phosphate ((NH4)2HPO4) or calcium dihydrogen phosphate (Ca(H2PO4)2). Potassium is formed from potassium sulphate (K2SO4) or potassium chloride (KCl), also known as the potassium salt. The phosphorus content of fertilisers is expressed as the amount of P2O5, as it is the anhydrous form of phosphoric acid. In this sense, it is the most concentrated form of phosphate and the form of phosphorus that plants require. Potassium content is indicated in the form of K2O, also called potash. Potassium is a component of the residue left over when plant material is burned. Sprinkling ash on fields is an ancient method for replenishing potassium. Modern chemical fertilisers usually contain KCl instead, but the potassium content is still given as the equivalent of potash. Potassium chloride is 52% K by weight. Potash is made up of 83% potassium. Therefore, KCl provides only about 2/3 as much potassium as K2O for the same weight. So if the fertiliser contains 25% of the KCl by weight, the potassium rating based on potash will be only 16.