When the directors of the district have decided to issue revenue bonds as herein provided, they shall call a special election in the irrigation district at which election shall be submitted to the electors thereof possessing the qualifications prescribed by law the question whether revenue bonds of the district in the amount and payable according to the plan of payment adopted by the board and for the purposes therein stated shall be issued. The election shall be called, noticed, conducted, and canvassed in the same manner as provided by law for irrigation district elections to authorize an original issue of bonds payable from revenues derived from annual assessments upon the real property in the district: PROVIDED, That the board of directors shall have full authority to issue revenue bonds as herein provided payable within a maximum period of forty years without a special election.