Each landowner who has not signed the petition is a respondent. The designated officer shall issue a summons to be served on each respondent. A summons may be served by publication as to any respondent who cannot be served as provided by law. If a mortgage is held on land in the proposed drainage district, notice of the proceedings shall be given to the holder of the mortgage in the same manner as to a respondent. A mortgage holder may appear before the county commissioners or county council in person or by counsel.