“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.
Source:
Section 14512.5, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=FAC§ionNum=14512.5..