In hydroponics, all essential elements are supplied to plants by dissolving fertilizer salts in water to make up the nutrient solution. The choice of salts to be used depends on a number of factors. The relative proportion of ions that a compound will supply must be compared with that required in the nutrient formulation. For example, one molecule of potassium nitrate (KNO3) will yield one ion of potassium (K+) and one of nitrate (NO3−), whereas one molecule of calcium nitrate (Ca(NO3)2) will yield one ion of calcium (Ca2+) and two ions of nitrate 2(NO3−). Therefore, if a minimum number of cations is required while supplying sufcient nitrate (anions) then calcium nitrate should be used; that is, half as much calcium nitrate as potassium nitrate would be required to satisfy the needs of the nitrate anion.