Redemption from said tax sale shall be made on such terms as may be agreed upon between such board of supervisors or such trustees and the owner of the land involved; but in any case in which the owner of said land will pay as much as fifty percent of the value of the land at the time of redemption the owner shall be permitted to redeem. If the parties cannot agree upon such value, either of them may bring an action against the other in the district court of the county where the land is situated, and the court shall determine the matter. The proceeding shall be triable in equity.