Iowa Code
Chapter 200 - FERTILIZERS AND SOIL CONDITIONERS
Section 200.11 - Filler material.

200.11 Filler material.
It shall be unlawful for any person to manufacture, offer for sale or sell in this state, any commercial fertilizer, or soil conditioner 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, or soil conditioner as a filler any substance that contains inert or useless plant food material for the purpose or with the effect of deceiving or defrauding the purchaser.
[C46, 50, 54, §200.10; C58, 62, §200.12; C66, 71, 73, 75, 77, 79, 81, §200.11]