A commercial fertilizer that either:
a) contains important quantities of no more than one of the primary plant nutrients: nitrogen, phosphate, or potash;
b) has eighty-five percent or more of its plant nutrient content present in the form of a single chemical compound; or
c) is derived from a plant or animal residue or byproduct or natural material deposit that has been processed in such a way that its content of plant nutrients has not been materially changed except by purification and concentration.