All oil produced or under the ground on producing properties within the State of Mississippi and all producing oil equipment, including wells, connections, pumps, derricks and other appurtenances actually owned by and belonging to the producer, and all leases in production, including mineral rights in producing properties, shall be exempt from all ad valorem taxes now levied or hereafter levied by the State of Mississippi, or any county, municipality, levee district, road, school or any other taxing district within this state. This exemption shall not apply to drilling equipment, including derricks, machinery, and other materials necessary to drilling, nor to oil gathering systems, nor to the surface of lands leased for oil production or upon which oil producing properties are situated, but all such drilling equipment, gathering systems, and lands shall be assessed as are other properties and shall be subject to ad valorem tax. However, no additional assessment shall be added to the surface value of such lands by reason of the presence of oil thereunder or its production therefrom. The exemption herein granted shall apply to all ad valorem taxes levied in the year 1944 and each year thereafter.