New York Senator Charles Schumer is calling for restrictions on the sale of ammonium nitrate fertilizer, which is commonly used in truck bombs. Schumer says truck bombs using ammonium nitrate are the weapon of choice of al-Qaida, and can be used by others as well. Schumer says he's introduced legislation to require that detection chemicals called taggants be added to ammonium nitrate, most of which is sold to farmers who use it as fertilizer. In addition, he says identification should be required for sales of ammonium nitrate, and anyone buying a large amount should be subject to a background check. After the 1993 bombing of the World Trade Center and the 1995 bombing of the federal building in Oklahoma City, Congress rejected several proposals to add taggants to ammonium nitrate. The National Rifle Association and the fertilizer industry were opposed.