Each qualified voter of a diking improvement or drainage improvement district who owns more than ten acres of land within the district shall be entitled to two additional votes for each ten acres or major fraction thereof located within the district, up to a maximum total of forty votes for any voter, or in the case of community property, a maximum total of twenty votes per member of the marital community: PROVIDED, That this additional voting provision shall only apply in districts that were not in operation and did not have improvements as of May 14, 1925.