Exhibit 12

Potash Corporation of Saskatchewan Inc.

Ratio of Earnings to Fixed
Charges

(in millions of US dollars, except ratio amounts)

(unaudited)



|                                                        |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|------------------------------------------------------- |  | ---------------------- | ----- | - | ---- | - | ----- | ------- |  | - | ------- | - |  | ------- | ----- | - |  | - | ----- | -
|                                                        |  | Year ended December 31 |      
|                                                        |  | 2011                   |       |   | 2010 |   |       | 2009(1) |  |   | 2008(1) |   |  | 2007(1) |      
|IFRS                                                    |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|                                                        |  |                        |       |   |     
|Net income                                              |  | $                      | 3,081 |   |      | $ | 1,775 |         |  | $ | 981     |   |  | $       | 3,466 |   |  | $ | 1,104 |  
|Income taxes                                            |  |                        | 1,066 |   |      |   | 701   |         |  |   | 79      |   |  |         | 1,060 |   |  |   | 417   |  
|Share of earnings of equity investees                   |  |                        | (261  | ) |      |   | (174  | )       |  |   | (134    | ) |  |         | (256  | ) |  |   | (76   | )
|Fixed charges                                           |  |                        | 300   |   |      |   | 285   |         |  |   | 256     |   |  |         | 187   |   |  |   | 187   |  
|Amortization of capitalized interest                    |  |                        | 14    |   |      |   | 8     |         |  |   |        |   |  |         |      |   |  |   |      |  
|Distributed income of equity investees                  |  |                        | 128   |   |      |   | 79    |         |  |   | 131     |   |  |         | 89    |   |  |   | 41    |  
|Interest capitalized                                    |  |                        | (84   | ) |      |   | (107  | )       |  |   | (68     | ) |  |         | (43   | ) |  |   | (22   | )
|                                                        |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|Total Earnings Available for Fixed Charges              |  | $                      | 4,244 |   |      | $ | 2,567 |         |  | $ | 1,245   |   |  | $       | 4,503 |   |  | $ | 1,651 |  
|                                                        |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|Fixed Charges                                           |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|                                                        |  |                        |       |   |     
|Interest expensed and capitalized                       |  | $                      | 273   |   |      | $ | 259   |         |  | $ | 227     |   |  | $       | 161   |   |  | $ | 165   |  
|Amortization of debt issue costs                        |  |                        | 5     |   |      |   | 5     |         |  |   | 3       |   |  |         | 2     |   |  |   | 2     |  
|Estimated portion of rent expense representing interest |  |                        | 22    |   |      |   | 21    |         |  |   | 26      |   |  |         | 24    |   |  |   | 20    |  
|                                                        |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|Total Fixed Charges                                     |  | $                      | 300   |   |      | $ | 285   |         |  | $ | 256     |   |  | $       | 187   |   |  | $ | 187   |  
|                                                        |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  
|Ratio of Earnings to Fixed Charges                      |  |                        | 14.15 |   |      |   | 9.01  |         |  |   | 4.86    |   |  |         | 24.08 |   |  |   | 8.83  |  
|                                                        |  |                        |       |   |      |   |       |         |  |   |         |   |  |         |       |   |  |   |       |  



|(1) | As the company
adopted IFRS with effect from January 1, 2010, our 2007 to 2009 information is presented on a previous Canadian GAAP basis. Accordingly, information for prior years may not be comparable to 2010 and 2011.
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