As used in this chapter, the term "basic agricultural commodity" means wheat, rye, flax, barley, cotton, field corn, grain sorghums, hogs, cattle, rice, potatoes, tobacco, sugar beets and sugarcane, peanuts, and milk and its products, and any regional or market classification, type, or grade thereof; but the Secretary of Agriculture shall exclude from the operation of the provisions of this chapter, during any period, any such commodity or classification, type, or grade thereof if he finds, upon investigation at any time and after due notice and opportunity for hearing to interested parties, that the conditions of production, marketing, and consumption are such that during such period this chapter can not be effectively administered to the end of effectuating the declared policy with respect to such commodity or classification, type, or grade thereof. As used in this chapter, the term "potatoes" means all varieties of potatoes included in the species Solanum tuberosum.