The board shall be responsible for the administration of all subsequent appointments and may adopt rules and regulations to carry out such responsibility. The composition of the board as defined by section 2-4004 shall continue until such time as the board determines that the districts and at-large membership as defined by such section are incompatible with an equitable representation of producers of grain sorghum due to changing geographic distribution of grain sorghum production in the state, changing marketing patterns, or availability of qualified individuals to serve as board members. The board may, from time to time as appropriate, by rule and regulation, redesignate districts and the number of at-large members to provide for an equitable representation of producers of grain sorghum, except that the number of appointed members of the board shall be either seven or five and the number of districts shall be no greater than six nor fewer than three.