A hearing on the amendment or termination of a stabilization and marketing plan may be held upon the motion of the director and shall be held upon receipt of a petition which is signed by producers, or by the board of directors of any nonprofit agricultural cooperative marketing association which is authorized by its members to so petition. Such petition shall represent not less than 55 percent of the total number of all producers and not less than 55 percent of the total production of all producers that are eligible to petition the director for the formulation of such a plan.