Iowa Code § 297.30: Public sale.

If the owner of the tract from which said site was taken fails to pay the amount of such appraisement to the department within thirty days after the filing of the same with the sheriff, the department may sell said site or building to any other person at the appraised value, or may sell the same at public sale to the highest bidder and the proceeds of such sale are to be added to the permanent school fund of the state.