In this subtitle the following words have the meanings indicated. “Agricultural commodity” means livestock, poultry, field crops, including nursery stock, bulbs, and flowers; and other agricultural products having a domestic or foreign market. “Certified agency” means any association, board, council, or other entity authorized by the Secretary to conduct a referendum under this section among the persons qualifying as voters. “Voter”, with respect to a referendum on the question of an annual assessment on a particular agricultural commodity, means any person engaged in the production of the commodity, and includes the owner of the farm on which the commodity is produced, tenants, and sharecroppers.