Persons engaged in the conduct of any agricultural, horticultural, dairy, livestock, mercantile, mining, or manufacturing business in the manner provided in section 500.3 may act together in associations, corporate or otherwise, for the purpose of collectively producing, processing, preparing for market, handling, and marketing the products of their members. Such persons may organize and operate such associations, and such associations may make the necessary contracts and agreements to effect that purpose, any law to the contrary notwithstanding.