7 C.F.R. § 1221.130
(a) For the purpose of ascertaining whether the persons subject to this part favor the continuation, suspension, or termination of this part, the Secretary shall conduct a referendum among persons subject to assessments under § 1221.116 who, during a representative period determined by the Secretary, have engaged in the production or importation of sorghum.
(b) The Secretary shall conduct a subsequent referendum: