"Ammonium nitrate" means solid ammonium nitrate that is chiefly the ammonium salt of nitric acid, contains not less than 33 percent of nitrogen, one-half of which is in the ammonium form and one-half of which is in the nitrate form, and is produced, imported, stored, offered for sale, sold, offered for distribution, received, or intended for use as a plant nutrient.
Ca. Food and Agric. Code § 14512.5