Neb. Rev. Stat. § 10-804

The proposition, when submitted, shall state the amount necessary to be raised each year for the payment of the interest on the bonds and for the payment of the principal thereof at maturity. When such bonds shall have been issued or authorized to be issued, the proper officers of such county shall cause to be annually levied and collected a special tax upon all taxable property of such county to raise the annual amount designated in the proposition and to pay the interest and principal of such bonds.