(a) Except as otherwise provided by this section, a substance is a commercial fertilizer subject to this chapter if it is:
(1) a fertilizer material;
(2) a mixed fertilizer;
(3) a customer-formula fertilizer; or
(4) another substance, material, or element, including a pesticide, that is intended for use or is used as an ingredient or component of a mixture of materials that is used, designed or represented for use, or claimed to have value, in promoting plant growth.
(b) Unprocessed, unpackaged, or unmanipulated lime, limestone, marl, or gypsum is not a commercial fertilizer subject to this chapter.

(c) Animal manure, plant remains, or mixtures of those substances are not commercial fertilizers subject to this chapter if no specific nutrient analysis claim indicates guaranteed nutrient levels.
(d) A plant food element or additive other than nitrogen, phosphorus, or potassium, determinable by an acceptable laboratory method, may be incorporated into a commercial fertilizer and guaranteed only if, and in the manner, authorized by rule of the director. Any additional plant food element or additive is subject to the inspection, analysis, and other provisions of this chapter.