(a) Each county in a district shall elect two nonpartisan supervisors: Provided, That any county with a population of one hundred thousand based on the most recent decennial census shall elect one additional supervisor and any county with a population over one hundred thousand based on the most recent decennial census shall elect one additional supervisor for each fifty thousand residents over one hundred thousand.

(b) A candidate for supervisor must be a landowner and an active farmer with a minimum of five years' experience or a retired farmer who has had a minimum of five years' experience and must have the education, training and experience necessary to carry out the duties required by this article. The State Conservation Committee shall propose for promulgation in accordance with the requirements of article three-a, chapter twenty-nine of this code legislative rules to establish criteria for the necessary education, training and experience.

(c) All registered voters in the district are eligible to vote in the election for candidates from the county within the boundaries of the district in which the voter resides. The candidates in each county who receive the largest number of votes cast in the election shall be elected supervisors for that county.

(d) Supervisors shall be elected in the primary election and serve a term of four years. The provisions of chapter three of this code apply to election of supervisors.

(e) Persons holding the position of supervisor, regardless of the expiration of the designated term of office, continue to serve until the election and qualification of his or her successor.

(f) Any vacancy occurring in the office of supervisor shall be filled by the committee by appointment of a person from the county in which the vacancy occurs. Within fifteen days after the vacancy occurs, the district shall submit a list of names of persons qualified to be a supervisor. If the unexpired term is for less than two years and six months, the appointed person holds office until the expiration of the term. If the unexpired term is for more than two years and six months, the appointed person holds the office until a successor is elected in the next primary or general election and qualified.