No public lands which were unentered at the time any tax or assessment was levied against same by such irrigation district shall be sold for such taxes or assessments, but such tax or assessment shall be and continue a lien upon such lands, and not more than one hundred and sixty acres of such land shall be entered by any one person; and when such lands shall be applied for, after said approval by the Secretary of the Interior, under the homestead or desert-land laws of the United States the application shall be suspended for a period of thirty days to enable the applicant to present a certificate from the proper district or county officer showing that no unpaid district charges are due and delinquent against said land.