Nitrogen fertilizer is a major input in terms of cost and energy into production of com, wheat, and other nationally important crops such as cotton and rice. Anhydrous ammonia is the most popular form of nitrogen application. In Iowa, 623,000 tons of anhydrous ammonia were applied in 1997 (Terry and Kirby, 1997). In the United States, 4.9 million tons of anhydrous ammonia were applied in both 1996 and 1997. Comparing fertilizer usage by source, anhydrous ammonia supplied 1.0 billion pounds of N (nitrogen) to Iowa cornfields in 1997 while the next most popular source, nitrogen solutions, supplied just 0.5 billion pounds of N. Nationwide, 8.0 billion pounds of N were applied to crops as anhydrous ammonia in both 1996 and 1997. At a cost of $200 to $275/ton of anhydrous ammonia, typical Iowa grower applications of 120 lbs of N per acre on com result in purchased crop input costs of about $15 to $20 per acre, respectively.