The legislature may hereafter, by general law, provide for the promotion of the production, distribution, improvement, marketing, use and sale of soybeans. The legislature may provide for the promotion of soybeans and soybean products by research, education, advertising and other methods, and the legislature is further authorized to provide means and methods for the financing of any such promotional activity by prescribing a procedure whereby producers of soybeans may by referendum among such producers levy upon themselves and collect assessments, fees, or charges upon the sale of soybeans for the financing of any such promotional program or activity in cooperation with buyers, processors, dealers, and handlers of soybeans. Provided, no assessment levied hereunder shall exceed one-half cent ( 1/2 ¢) per bushel on any soybeans sold by producers thereof. The legislature may make provisions for the nonpayment of assessments by soybean producers, and shall make provisions for the refund of assessments to any soybean producer who does not desire to participate in an assessment program. The legislature shall provide for the collection, disbursement, distribution or expenditure of assessments or charges authorized hereunder and to provide penalties for failure to make collection and distribution of assessments. The legislature shall provide for the designation of a nonprofit association or organization for the promotion and betterment of soybeans and soybean products to administer and carry out such promotional program which shall include the conducting of elections or referendums among producers of soybeans. The legislature may provide the manner by which such referendum is held, including the procedure for application for approval to conduct the referendum, the appropriate action to be taken by the state board of agriculture and industries on such application, the requirements and eligibility of the association or organization which will conduct such referendum, the procedures for voting and eligibility to vote in such referendum, the details of the conduct of such referendum. The legislature shall further provide for the deposit, withdrawal, disbursement and expenditure by the designated association of any funds received subject to the supervision and control of the activities as authorized herein by the department of agriculture and industries and the state board of agriculture and industries. The legislature shall further provide a procedure whereby said association or organization is bonded, for the examination and auditing of said association or organization, and for reasonably necessary rules and regulations to be adopted by the state board of agriculture and industries to effectively carry out the intent and purposes herein enumerated. Assessments, fees or other charges collected as authorized by any legislative act adopted under authority hereof shall not be considered as a tax within the meaning of this constitution or any provision thereof. Any uniformity requirements of this constitution shall be satisfied by the application of the program upon soybeans.