Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 421 | Thousand metric tons of contained nitrogen | NA |
| 2004 | 380.399993896484 | Thousand metric tons of contained nitrogen | -9.64% |
| 2005 | 360 | Thousand metric tons of contained nitrogen | -5.36% |
| 2006 | 380 | Thousand metric tons of contained nitrogen | 5.56% |
| 2007 | 380 | Thousand metric tons of contained nitrogen | 0.00% |
| 2008 | 380 | Thousand metric tons of contained nitrogen | 0.00% |
| 2009 | 380 | Thousand metric tons of contained nitrogen | 0.00% |
| 2010 | 392 | Thousand metric tons of contained nitrogen | 3.16% |
| 2011 | 386 | Thousand metric tons of contained nitrogen | -1.53% |
| 2012 | 330 | Thousand metric tons of contained nitrogen | -14.51% |
