Every five years from the date of the imposition of the tax assessment on soybeans, another referendum shall be held to determine whether the assessment for research, education, publicity, and promotion of the sale and use of soybeans shall be continued. The Board, upon petition by a group of soybean producers representing at least 33 percent of the Commonwealth’s production, as determined by the Commissioner, may provide for an advisory referendum on the continuation of the assessment. Upon finding that sufficient interest exists among the producers of soybeans in the Commonwealth to justify a referendum, the Board shall authorize the holding of a referendum. The cost of conducting any such referendum as above prescribed shall come from funds paid into the Virginia Soybean Fund. The Board shall adopt regulations governing the conduct of referenda pursuant to § 3.2-112.