(1) The department may by rule establish standard grades to apply to all agricultural commodities for which a United States department of agriculture grade has not been established and that are bought by commodity dealers and stored or handled by warehouses in this state. The department shall adopt as state grade and dockage standards all grades for agricultural commodities established by the United States department of agriculture. For purposes of this chapter, any reference to a grade also includes a reference to a protein analysis or any other factor provided by department rule if the analysis affects the purchase price.
(2) Agricultural commodity standards adopted by the department do not apply to agricultural commodities contracted for before the effective date of the adoption of the standards.