Food and Agricultural Code § 14522

“Commercial fertilizer” means any substance which contains 5 percent or more of nitrogen (N), available phosphoric acid (P₂O₅), or soluble potash (K₂O), singly or collectively, which is distributed in this state for promoting or stimulating plant growth. “Commercial fertilizer” includes both agricultural and specialty fertilizers. “Specialty fertilizers” may contain less than 5 percent nitrogen (N), available phosphoric acid (P₂O₅), or soluble potash (K₂O), singly or collectively.