Petitions to include additional area within an existing district may be filed with the committee at any time, and the proceedings provided in connection with a petition to organize a district must be observed in the case of a petition for such inclusion. A portion of a district may upon petition of a majority of the qualified electors in that portion, and without an election, be annexed to an adjoining district, and become a part of that adjoining district upon filing the petition with the state soil conservation committee.