(a) Except as otherwise provided by this section and Kan. Stat. Ann. §§ 12-770 and 12-771, and amendments thereto, regulations adopted under authority of this act shall not apply to the existing use of any building or land, but shall apply to any alteration of a building to provide for a change in use or a change in the use of any building or land after the effective date of any regulations adopted under this act. If a building is damaged by more than 50% of its fair market value such building shall not be restored if the use of such building is not in conformance with the regulations adopted under this act.

(b) Except for flood plain regulations in areas designated as a flood plain, regulations adopted by a city pursuant to Kan. Stat. Ann. § 12-715b, and amendments thereto, or a county pursuant to this act shall not apply to the use of land for agricultural purposes, nor for the erection or maintenance of buildings thereon for such purposes so long as such land and buildings are used for agricultural purposes and not otherwise.