1. As used in this section:

 a. “Local governmental entity” means any political subdivision, or any state authority which is not the general assembly or under the direction of a principal central department as enumerated in section 7E.5, including a city as defined in section 362.2, a county as provided in chapter 331, or any special purpose district.
 b. “Local legislation” means any ordinance, motion, resolution, amendment, regulation, or rule adopted by a local governmental entity.
 2. The provisions of this chapter and rules adopted by the department pursuant to this chapter shall preempt local legislation adopted by a local governmental entity relating to the use, sale, distribution, storage, transportation, disposal, formulation, labeling, registration, or manufacture of a fertilizer or soil conditioner. A local governmental entity shall not adopt or continue in effect local legislation relating to the use, sale, distribution, storage, transportation, disposal, formulation, labeling, registration, or manufacture of a fertilizer or soil conditioner, regardless of whether a statute or rule adopted by the department applies to preempt the local legislation. Local legislation in violation of this section is void and unenforceable.
 3. This section does not apply to local legislation of general applicability to commercial activity.