The National Corn Growers Association says one of the top fertilizer companies has erected an insurmountable barrier to keep top competitors out of the U.S. market. An NCGA letter says the barrier is hurting America’s farmers. NCGA and its state affiliates signed a letter sent to Mosaic, one of the nation’s top fertilizer producers. The letter takes Mosaic to task for the tariffs that were imposed in March by the International Trade Commission at the fertilizer company’s request. “Mosaic’s posture to date has been a masterpiece of irresponsible corporate social responsibility,” the letter adds. “Only 15 percent of phosphorous imports now come into the U.S. without tariffs.” The organization also points out that experts say using the Commerce Department and the Trade Commission to manipulate the supply curve does indeed dictate the price to farmers. The Corn Growers are asking Mosaic to reverse course and allow critical supply back into the U.S.