After receiving from the county auditors the certifications provided for in section 426.6, and during the following fiscal year, the director of revenue shall authorize the department of administrative services to draw warrants on the agricultural land credit fund created in section 426.1, payable to the county treasurers in the amount certified by the county auditors of the respective counties and mail the warrants to the county auditors on July 15 of each year taking into consideration the relative budget and cash position of the state resources. However, if the agricultural land credit fund is insufficient to pay in full the total of the amounts certified to the director of revenue, the director shall prorate the fund to the county treasurers and notify the county auditors of the pro rata percentage on or before June 15.