The other source is urea which is formulated by a reaction between anhydrous ammonia and carbon dioxide, also at high temperature and pressure. Ammonium nitrate is formulated by combining anhydrous ammonia and nitric acid in a very corrosive manufacturing climate. Solution liquid fertilizers (28 to 32 percent nitrogen) are composed of one-half urea and one-half ammonium nitrate. It’s pretty hard to apply a nitrogen fertilizer formulation that doesn’t have natural gas in its manufacturing process.

If you want to discontinue using nitrogen fertilizers or reduce rates until the prices come down you collect soil samples to see if they have high levels of residual nitrogen. If so, you can reduce or even eliminate the use of nitrogen fertilizers without reducing yield. The very wet winter we had this year makes it unlikely that large amounts of nitrogen carried over, but it doesn’t hurt to check.