Exhibit 31(a)**CERTIFICATION**I, William J. Doyle, certify that:     1. I have reviewed this Amendment No. 1 to the annualreport on Form 10-K of Potash Corporation of SaskatchewanInc.;     2. Based on my knowledge, this Amendment No. 1 doesnot contain any untrue statement of a material fact or omit tostate a material fact necessary to make the statements made, inlight of the circumstances under which such statements weremade, not misleading with respect to the period covered by thisannual report;     3. Based on my knowledge, the financial statements, andother financial information included in this AmendmentNo. 1, fairly present in all material respects thefinancial condition, results of operations and cash flows of theregistrant as of, and for, the periods presented in this annualreport;     4. The registrant’s other certifying officer and I areresponsible for establishing and maintaining disclosure controlsand procedures (as defined in Exchange Act Rules 13a-15(e)and 15d-15(e)) and internal control over financial reporting (asdefined in Exchange Act Rules 13a-15(f) and 15d-15(f)) forthe registrant and have:          (a) designed such disclosure controls and procedures, or    caused such disclosure controls and procedures to be designed    under our supervision, to ensure that material information    relating to the registrant, including its consolidated    subsidiaries, is made known to us by others within those    entities, particularly during the period in which this report is    being prepared;           (b) designed such internal control over financial    reporting, or caused such internal control over financial    reporting to be designed under our supervision, to provide    reasonable assurance regarding the reliability of financial    reporting and the preparation of financial statements for    external purposes in accordance with generally accepted    accounting principles;           (c) evaluated the effectiveness of the registrant’s    disclosure controls and procedures and presented in this report    our conclusions about the effectiveness of the disclosure    controls and procedures, as of the end of the period covered by    this report based on such evaluation; and           (d) disclosed in this report any change in the    registrant’s internal control over financial reporting that    occurred during the registrant’s most recent fiscal quarter    (the registrant’s fourth fiscal quarter in the case of an    annual report) that has materially affected, or is reasonably    likely to materially affect, the registrant’s internal    control over financial reporting; and     5. The registrant’s other certifying officer and Ihave disclosed, based on our most recent evaluation of internalcontrol over financial reporting, to the registrant’sauditors and the audit committee of the registrant’s boardof directors (or persons performing the equivalent functions):          (a) all significant deficiencies and material weaknesses in    the design or operation of internal control over financial    reporting which are reasonably likely to adversely affect the    registrant’s ability to record, process, summarize and    report financial information; and           (b) any fraud, whether or not material, that involves    management or other employees who have a significant role in the    registrant’s internal control over financial reporting.Date: April 22, 2005           By:     /s/ WILLIAM J. DOYLE             William J. Doyle    *President and Chief Executive Officer*