Mn Cu Zn Mo Na Cl ALL are essential, macro and micro refer to relative amounts required . CHO are obtained from H2O and CO2, all others are obtained from soil or media. We can judge what nutrients are present and estimate their availability from soil tests The tests report how much of an element is present and the pH. By knowing the pH we can estimate how much of the element is most likely available.
Most elements are cations and are 'stuck' to soil or media particles by - electrostatic forces.
For most elements, they 'unstick' satisfactorily at a pH of 6-6.5 for soil and a little lower for peat moss based medias. However, iron is held very tightly to soil at pH's above 6.5. Plants that need a lot of iron generally grow very poorly on alkaline soils. Many of Ohio's soils are 7.0 or greater because of a limestone base and that is why azaleas do not do well in parts of Ohio. NO3- is an anion and does not stick well to soil.