Exhibit 10(aa)
POTASH CORPORATION OF SASKATCHEWAN INC.
AMENDMENT NO. 2 TO THE
PCS SUPPLEMENTAL RETIREMENT PLAN FOR U.S. EXECUTIVES
     The PCS Supplemental Retirement Plan for U.S. Executives, effective as of
January 1, 1999 (the “Plan”), as heretofore amended, is hereby further amended
effective as specified herein as follows:

1.   Section 4.2(a) of the Plan is hereby amended in its entirety to read as
follows:

  “(a)    is the monthly benefit that the Participant would have accrued under
the Pension Plan had the monthly benefit been determined without regard to Code
sections 401(a)(17) and 415; provided, however, that the accrued benefit
attributable to service credited on and after July 1, 2009 shall be determined
without regard to any bonus amounts paid or payable to the Executive for any
calendar year under the Corporation’s annual short-term incentive plan to the
extent that such amounts in the aggregate exceed the Executive’s annual base pay
on which such bonus amounts were based.”

2.   In all other respects the Plan remains unchanged.       EXECUTED on this 23
day of February, 2009.

            POTASH CORPORATION OF
SASKATCHEWAN INC.
         /s/ Barbara Jane Irwin     By:   /s/ John W. Estey