An action to enforce an agricultural production input lien may be brought in the district court in a county where some part of the crop or livestock was located after the lien is perfected. A lien-notification statement may be amended, except for the amount demanded, by leave of the court in the furtherance of justice. An agricultural production input lien is extinguished if an action to enforce the lien is not brought within eighteen months after the date the lien-notification statement is filed.