(1) On the day fixed for hearing on such petition, all parties owning lands or any interest or easement in land within said proposed district or who would be affected thereby may appear and contest:
(a) the sufficiency of the petition;
(b) the sufficiency of the signers of the petition;
(c) the sufficiency of the notice;
(d) the constitutionality of the law; and
(e) the jurisdiction of the court, specifying their objections to such jurisdiction.
(2) The petitioners and contestants may, on the trial, offer any competent evidence in regard thereto. All notices of contest shall be in writing and shall clearly specify the grounds of contest.