For the payment of the principal and interest on such bonds as they respectively mature and for the creation of such sinking fund as may be necessary therefor, the full faith, credit and taxing power of the county are irrevocably pledged and there shall be levied annually by the county auditor and collected by the county treasurer in the same manner as other county taxes are levied and collected, a tax, without limit, on all taxable property in the county sufficient to pay the principal and interest of such bonds as they respectively mature and to create such sinking fund as may be necessary therefor.