Iowa Code § 6B.24: Reduction of damages — interest on increased award.

If the amount of damages awarded by the commissioners is decreased on appeal, the reduced amount shall be paid to the landowner. If the amount of damages awarded by the commissioners is increased on appeal, interest shall be paid from the date of the condemnation. Interest shall not be paid on any amount which was previously paid. Interest shall be calculated at an annual rate equal to the treasury constant maturity index published by the federal reserve in the H15 Report settled immediately before the date of the award.