Satisfactory plant growth requires all nutrients being simultaneously available and in sufficient quantity.  The 6 “macronutrients” are those needed in the largest quantities. Of these, the 3 most important ones are the NPK fertilizers – nitrogen (N), phosphorus (P) and potassium (K). The “trace elements” are also needed but only in small amounts.

Generally speaking, nutrients can only be rapidly absorbed by plant roots if they are in the form of mineral “ions”.  An “ion” is an atom or group of atoms which has gained or lost one or more electrons, and therefore carries a positive or negative charge. This “charge” enables ions to either repel or attract other ions. Ions with a positive charge (+) are called “cations” and are attracted to a root hair containing negative (-)