The bonds issued under the provisions of this chapter shall be signed by the chairman of the board of county commissioners of the county and countersigned by the county auditor, who shall keep a record of such bonds. Such board shall have the power to negotiate such bonds at not less than the par value thereof as it may deem for the best interests of all persons interested in the flood irrigation project for the cost of which the bonds are issued. Such bonds shall contain a recital that the same are issued in accordance with the provisions and pursuant to the authority of this chapter and that they are to be paid out of the sinking funds to be created as provided for in this chapter, if issued serially. Whenever such bonds shall be issued, the tax provided for in section 61-12-27 shall not be collected all in one year but shall be divided into parts corresponding with the amounts and maturities of the bonds. Such parts shall be extended year by year upon the tax lists by the county auditor against the parcels of land and property liable to taxation for that purpose and collected in such year, and such fund shall constitute the sinking fund provided by this section. Should the bonds be issued and made payable under the amortization plan of payment, the tax provided for in said section shall be divided into parts corresponding with the principal payment required to be made each year under the said amortization plan, and such parts shall be extended year by year upon the tax lists in the manner and form provided herein for the retirement of bonds issued with serial maturities.