If the owner of the land is a nonresident of the county the sheriff may make service by leaving a copy of the notice of application with the occupant, or agent of the owner. If there is no occupant, or agent of the owner, the sheriff may place a copy in the post office addressed to the owner thirty days prior to the day set for the hearing. If the owner is a minor, insane, mentally incapacitated, or a decedent, notice shall be served on his guardian, administrator, or other legal representative.