S.C. Code Ann. § 46-25-540: Filler.

It shall be unlawful for any person to manufacture, offer for sale, or sell in this State any commercial fertilizer containing any substance used as a filler that is injurious to crop growth or deleterious to the soil, or to use in such commercial fertilizer as a filler any substance that contains inert plant nutrient material or any other substance for the purpose of or with the effect of deceiving or defrauding the purchaser. The commission shall determine what inert material or substance is injurious or objectionable.