The regular assessment in any one year shall not exceed two cents ($0.02) on each one hundred dollars ($100) of assessed valuation of the land, exclusive of improvements, trees, and mineral rights, within the district. The valuation shall be determined according to the last assessment roll, reduced proportionately when mineral rights, standing trees, or timber are involved.

The cost to the assessor, if any, of recomputing assessed valuations in accordance with this section shall be paid by the district requesting an assessment levy pursuant to this article.