Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 235 | Thousand metric tons of contained nitrogen | NA |
| 2004 | 233.399993896484 | Thousand metric tons of contained nitrogen | -0.68% |
| 2005 | 250 | Thousand metric tons of contained nitrogen | 7.11% |
| 2006 | 250 | Thousand metric tons of contained nitrogen | 0.00% |
| 2007 | 225 | Thousand metric tons of contained nitrogen | -10.00% |
| 2008 | 175 | Thousand metric tons of contained nitrogen | -22.22% |
| 2009 | 173 | Thousand metric tons of contained nitrogen | -1.14% |
| 2010 | 160 | Thousand metric tons of contained nitrogen | -7.51% |
| 2011 | 189 | Thousand metric tons of contained nitrogen | 18.13% |
| 2012 | 200 | Thousand metric tons of contained nitrogen | 5.82% |
