The National Corn Growers Association is concerned with the railroad industry’s request to discontinue shipment of anhydrous ammonia. Without anhydrous ammonia - a source of nitrogen fertilizer - NCGA says U.S. farmers would not be able to produce the amount or quality of food the world relies on. Ron Litterer - Iowa corn grower and NCGA President - says anhydrous ammonia is critical to the nation’s food supply - and rail is the safest, most efficient method of transport. These concerns are expressed in a letter to the Surface Transportation Board.