(a) This chapter does not apply to, restrict, or void the sale of a commercial fertilizer by an importer, manufacturer, or manipulator to an importer, manufacturer, or manipulator who mixes fertilizers for distribution. This chapter does not prevent the free and unrestricted shipment of a commercial fertilizer to a manufacturer or manipulator who has registered the brand name as required by this chapter.
(b) This chapter does not apply to the mixing, milling, or processing of a material produced by a purchaser of commercial fertilizer or acquired by the purchaser from a source other than the person who mixed or processed the material.