Iowa Code § 446.34
When any school, agricultural college, or university land sold on credit is sold for taxes, the purchaser shall acquire only the interest of the original purchaser therein, and no sale of any such lands for taxes shall prejudice the rights of the state, agricultural college, or university. In all cases where the real estate is mortgaged or otherwise encumbered to the school, agricultural college, or university fund, the interest of the person who holds the fee shall alone be sold for taxes, and in no case shall the lien or interest of the state be affected by any sale thereof. The foregoing provision shall include all lands exempt from taxation by law, and any legal or equitable estate therein held, possessed, or claimed for any public purpose, and no assessment or taxation of such lands, nor the payment of any such tax by any person, or the sale and conveyance for taxes of any such lands, shall in any manner affect the right or title of the public therein, or confer upon the purchaser or person who pays such taxes any right or interest in such land.
Iowa Code § 446.34