Bad idea.

Least, an unadvised one.

Centrum is made for people. The amounts of the trace minerals in them FAR exceed what a plant would utilize. Too many minerals in the soil will cause the root hairs to lock out.

15 mg of zinc in a Centrum vs .0009 mg in a serving of a good nute.

Water solubility would be another issue. As would if the source of the individual minerals is chelated or not. (organisms prefer chelated).