Iowa Code § 257B.7
When lands are sold upon a partial credit, the contract therefor shall be at once reduced to writing, signed by the proper parties, recorded in the county where the land is situated, and immediately thereafter filed in the office of the county auditor. Any purchaser or the purchaser's assigns may at any time pay the full amount for lands with accrued interest, and receive from the county auditor a certificate of purchase, which shall be at once transmitted to the secretary of state and will entitle the holder to a patent for the lands, to be issued by the secretary of state and the governor. All school lands sold in pursuance of law shall be subject to taxation from and after the execution and delivery of a contract of purchase. All sales made, where the full price is not paid, shall be subject to the law relative to the prevention or punishment of waste, and in all such cases the township trustees in each township are charged with the duty of preventing the commission of waste upon any school lands lying in their township, and, if attempted, they shall apply by petition for an injunction to stay the same, and if granted the writ shall issue without bond, and the court issuing it may make such order in the premises as shall be equitable and best calculated to prevent threatened injury, and may adjudge damages for any injury done, the costs to abide the event of the action, and the damages adjudged shall be paid to the county treasurer and the county treasurer shall forthwith pay the same to the state treasurer which shall become a part of the permanent school fund.
Iowa Code § 257B.7