The board of supervisors shall have the right to issue certificates of indebtedness of the county for the purchase price of the necessary machinery for soil erosion work hereunder, or any part of such price, to be paid from the soil erosion fund of the county or part of the county for which such machinery is purchased, which certificates shall be payable in no more than three annual instalments, the first of which in the case of two instalments to be not less than one-half of the aggregate certificates issued for that purchase, and the first two of which in the case of three instalments to be for not less than one-third each of such aggregate, the first instalment in any case to be payable on the first Monday in April of the year following that in which the certificates are issued, and subsequent instalment on the first Monday in April each succeeding year. By its order purchasing such machinery the board may provide for the payment of interest at a rate of not more than six per cent (6%) per annum upon the deferred payments evidenced by said certificates, in which event said certificates shall show upon their face that fact, and shall be payable with interest accordingly; and said certificates shall also show upon their face the date when and the purpose for which issued, the principal amount of the certificate, the aggregate amount of the certificates issued for that particular purchase, the date when payable, and whether payable from the soil erosion fund of the whole county or of some named or numbered soil erosion district thereof; and all such certificates shall be signed by the president of the board, shall be countersigned by the clerk thereof, shall have the seal of the county impressed thereon, and shall be registered by the clerk when issued as is required in the case of bonds, and may be validated as such. The board shall also make appropriate provision, by budget and tax levy as in other cases, to so govern and supplement the soil erosion fund arising from performance of contracts for landowners, as to make prompt payments of all bills for labor, fuel, oil, supplies, repairs and other necessary cost and expenses incident to the operation of said machinery, the performance of said contracts, and the carrying out of the provisions hereof, and prompt payment of the certificates of indebtedness issued for the purchase of machinery, with interest, if any, as and when due. The board may also borrow money for the county in anticipation of taxes and the special assessments herein provided for, for the payment of current operating expenses of soil erosion work, as in case of other current operating expenses, the same to be paid out of the soil erosion fund, supplemented if necessary by a special tax as in other cases. Money so borrowed, as well as the certificates of indebtedness issued for the purchase of machinery, shall be a liability of the county until paid. The certificates herein provided for shall not be taken into consideration under any debt limitation statute.