Whenever the county board deems it necessary to assess taxes the aggregate of which exceeds the rate of fifty cents on every one hundred dollars of the taxable value of all the taxable property in such county, the county board may, by an order entered of record, set forth substantially the amount of such excess required and the purpose for which the same will be required, and if for the payment of interest, principal, or both upon bonds, such order shall in a general way designate the bonds and specify the number of years such excess must be levied and provide for the submission of the question of assessing the additional rate required to a vote of the people of the county at the next election for county officers after the adoption of the resolution or at a special election ordered by the county board for that purpose. If the proposition for such additional tax is carried, the same shall be paid in money and in no other manner. The additional tax shall not have a duration greater than five years, except that such five-year limitation shall not apply to any additional tax approved by the voters of the county for payment of principal and interest on bonded indebtedness. The additional tax is excluded from the limitation in section 77-3442 as provided by section 77-3444.