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Exhibit
10(dd)
  Medium-Term
Incentive Plan




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Contents
  
 Section 1Establishment of the Plan
    
    
    11.01
    
    Purpose
    
    
    11.02
    
    Term
    
    
    1Section 2Definitions
    
    
    22.01
    
    Award Units
    
    
    22.02
    
    Board
    
    
    22.03
    
    Committee
    
    
    22.04
    
    Corporate TSR
    
    
    22.05
    
    Corporate TSR Award Units
    
    
    22.06
    
    Corporation
    
    
    32.07
    
    Effective Date
    
    
    32.08
    
    Entitled Executive
    
    
    32.09
    
    Index
    
    
    32.10
    
    Index Closing Price
    
    
    32.11
    
    Index Dividends
    
    
    32.12
    
    Index Opening Price
    
    
    32.13
    
    Index TSR
    
    
    42.14
    
    Index TSR Award Units
    
    
    42.15
    
    Just Cause
    
    
    42.16
    
    PCS Inc. Opening Share Price
    
    
    42.17
    
    PCS Inc. Closing Share Price
    
    
    42.18
    
    PCS Inc. Dividends
    
    
    52.19
    
    Performance Cycle
    
    
    52.20
    
    Permanent Disability or Permanently Disabled
    
    
    52.21
    
    Plan
    
    
    52.22
    
    Salary
    
    
    52.23
    
    Target Percentage
    
    
    52.24
    
    Tier Group
    
    
    52.25
    
    Vested Percentage
    
    
    5Section 3Participation
    
    
    63.01
    
    Initial Participation
    
    
    63.02
    
    Continued Participation
    
    
    6Section 4Allocation of Award Units
    
    
    74.01
    
    Allocation
    
    
    74.02
    
    Promotion to New Tier Group or Other Promotion
    
    
    74.03
    
    Corporate TSR Award Units and Index TSR Award Units
    
    
    74.04
    
    Target Percentage
    
    
    8Section 5Vesting of Award Units
    
    
    95.01
    
    Vested Percentages
    
    
    9Section 6Redemption of Award Units
    
    
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6.01
    
    Redemption Date
    
    
    106.02
    
    Value of Award Units
    
    
    106.03
    
    Early Redemption Date
    
    
    11Section 7Administration of the Plan
    
    
    127.01
    
    Powers of the Committee
    
    
    127.02
    
    Notification to Entitled Executives
    
    
    127.03
    
    Calculation of Award Payments
    
    
    127.04
    
    Delegation of Duties
    
    
    12Section 8General Provisions
    
    
    138.01
    
    Assignment or Alienation
    
    
    138.02
    
    Amendment or Termination
    
    
    138.03
    
    No Enlargement of Contractual Rights
    
    
    138.04
    
    Withholding of Taxes
    
    
    138.05
    
    Binding on Successors
    
    
    138.06
    
    Currency
    
    
    138.07
    
    Certain Adjustments
    
    
    148.08
    
    Governing Law
    
    
    14
   
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Section 1Establishment of the Plan
 
 
 1.01
    
    Purpose
 This Medium-Term Incentive Plan is established for the purpose of:
 (a)
    
    providing competitive compensation for Entitled Executives;
 (b)
    
    rewarding Entitled Executives for improving Total Shareholder Return;
 (c)
    
    rewarding Entitled Executives for attaining a Total Shareholder Return that is
equal to or in excess of the increase in the Dow Jones U.S. Basic Materials Companies
Index;
 (d)
    
    rewarding Entitled Executives for their efforts and contributions to the
achievement of the long-term success of the business interests of the Corporation;
 (e)
    
    aligning the interests of Entitled Executives more closely with the
shareholders of the Corporation; and,
 (f)
    
    enhancing the ability of the Corporation to recruit and retain high potential,
high value executives.
 
 1.02
    
    Term
 Subject to Section 8.02 (Amendment or Termination), this Plan shall be effective for
the Performance Cycle January 1, 2006 to December 31, 2008.
 
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Section 2Definitions
  
 
 2.01
    
    Award Units
 Award Units means, in respect of an Entitled Executive, the units allocated
pursuant to Section 4 (Allocation of Award Units).
 
 2.02
    
    Board
 Board means the Board of Directors of PCS Inc.
 
 2.03
    
    Committee
 Committee means the Compensation Committee of the Board.
 
 2.04
    
    Corporate TSR
 Corporate TSR means the total shareholder return of PCS Inc. in the Performance
Cycle, expressed as a percentage, and determined as follows:
 (i)
    
    PCS Inc. Closing Share Price
 MINUS
 PCS Inc. Opening Share Price
 PLUS
 PCS Inc. Dividends
 DIVIDED BY
 (ii)
    
    PCS Inc. Opening Share Price
 MULTIPLIED BY
 (iii)
    
    100
 
 2.05
    
    Corporate TSR Award Units
 Corporate TSR Award Units means, in respect of an Entitled Executive, one half of
the Award Units allocated to the Entitled Executive pursuant to Section 4 (Allocation of
Award Units).
 
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2.06
    
    Corporation
 Corporation means Potash Corporation of Saskatchewan Inc. and its direct and
indirect subsidiaries.
 
 2.07
    
    Effective Date
 Effective Date means January 1, 2006.
 
 2.08
    
    Entitled Executive
 Entitled Executive means an executive employee of the Corporation who is
recommended by the CEO and approved by the Committee to participate in this Plan.
 
 2.09
    
    Index
 Index means the Dow Jones U.S. Basic Materials Companies Index (DJUSBM).
 
 2.10
    
    Index Closing Price
 Index Closing Price means the average closing value of the Index, as reported by
the Dow Jones Company, for the last 30 trading days of the Performance Cycle or, in the case
of an Entitled Executive for whom an early redemption date applies pursuant to paragraph (a)
of Section 6.03 (Early Redemption Date), the above reference to the last 30 trading days of
the Performance Cycle shall be substituted by the last 30 trading days up to the date of
the Entitled Executives retirement, disability, death or involuntary termination, as the
case may be.
 
 2.11
    
    Index Dividends
 Index Dividends means a cumulative amount derived from the return on dividends paid
and reinvested by the companies in the Index, during the Performance Cycle or, in the case
of an Entitled Executive for whom an early redemption date applies pursuant to paragraph (a)
of Section 6.03 (Early Redemption Date), a cumulative amount derived from the return on
dividends paid and reinvested by the companies in the Index, during the Performance Cycle up
to the date of the Entitled Executives retirement, disability, death or involuntary
termination, as the case may be.
 
 2.12
    
    Index Opening Price
 Index Opening Price means the average closing value of the Index, as reported by
the Dow Jones Company, for the last thirty trading days of 2005. Such value has been
determined as U.S. $204.230.
 
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2.13
    
    Index TSR
 Index TSR means the total shareholder return of the Index in the Performance Cycle,
expressed as a percentage, and determined as follows:
 (i)
    
    Index Closing Price
 MINUS
 Index Opening Price
 PLUS
 Index Dividends
 DIVIDED BY
 (ii)
    
    Index Opening Price
 MULTIPLIED BY
 (iii)
    
    100
 
 2.14
    
    Index TSR Award Units
 Index TSR Award Units means, in respect of an Entitled Executive, one half of the
Award Units allocated to the Entitled Executive pursuant to Section 4 (Allocation of Award
Units).
 
 2.15
    
    Just Cause
 Just Cause has such meaning as determined by the Committee from time to time,
consistent with the regular policies of the Corporation.
 
 2.16
    
    PCS Inc. Opening Share Price
 PCS Inc. Opening Share Price means the average closing price of the common stock of
PCS Inc. as reported on the New York Stock Exchange, for the last thirty trading days of
2005. Such price has been determined as U.S. $77.970.
 
 2.17
    
    PCS Inc. Closing Share Price
 PCS Inc. Closing Share Price means the average closing price of the common stock of
PCS Inc. as reported on the New York Stock Exchange, for the last 30 trading days of the
Performance Cycle or, in the case of an Entitled Executive for whom an early redemption date
applies pursuant to paragraph (a) of Section 6.03 (Early Redemption Date), the above
reference to the last 30 trading days of the Performance Cycle shall be substituted by
the last 30 trading days up to the date of the Entitled Executives retirement, disability,
death or involuntary termination, as the case may be.
 
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2.18
    
    PCS Inc. Dividends
 PCS Inc. Dividends means the cumulative amount of dividends paid by PCS Inc. on a
common share of PCS Inc. during the Performance Cycle or, in the case of an Entitled
Executive for whom an early redemption date applies pursuant to paragraph (a) of Section
6.03 (Early Redemption Date), the cumulative amount of dividends paid by PCS Inc. on a
common share of PCS Inc. during the Performance Cycle up to the date of the Entitled
Executives retirement, disability, death or involuntary termination, as the case may be.
 
 2.19
    
    Performance Cycle
 Performance Cycle means January 1, 2006 to December 31, 2008 inclusive.
 
 2.20
    
    Permanent Disability or Permanently Disabled
 Permanent Disability or Permanently Disabled means the permanent incapacity of an
Entitled Executive, as determined in accordance with the disability plan to which the
Entitled Executive is eligible to belong.
 
 2.21
    
    Plan
 Plan means this Medium-Term Incentive Plan, as amended from time to time.
 
 2.22
    
    Salary
 Salary means, in respect of an Entitled Executive, the Entitled Executives annual
base salary in effect as of the date the Entitled Executive commenced participation in the
Plan. However, if the Entitled Executive is promoted into a new Tier Group during the
Performance Cycle or if the annual base salary of the Entitled Executive is significantly
adjusted during the Performance Cycle as a result of a promotion, Salary for purposes of
paragraph (b) of Section 4.02 (Promotion to a New Tier Group or Other Promotion) shall be
the annual base salary in effect as of the date the Entitled Executive was promoted into a
new Tier Group or otherwise promoted.
 
 2.23
    
    Target Percentage
 Target Percentage means the target percentage applicable to an Entitled Executive
according to the Tier Group in which the Entitled Executive participates, as described in
Section 4.04 (Target Percentage).
 
 2.24
    
    Tier Group
 Tier Group means, in respect of an Entitled Executive, the Tier Group in which the
Entitled Executive participates, for purposes of this Plan, as described in section 4.04
(Target Percentage).
 
 2.25
    
    Vested Percentage
 Vested Percentage means the vested percentage of an Entitled Executives Corporate
TSR Units and Index TSR Units, as the case may be, as described in Section 5(Vesting of
Award Units).
 
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Section 3Participation
 
 
 3.01
    
    Initial Participation
 Participation in the Plan is limited to Entitled Executives.
 Each Entitled Executive shall participate in the Plan as of the first day of the Performance
Cycle, or on the date on which the Entitled Executive becomes an Entitled Executive, if
later.
 
 3.02
    
    Continued Participation
 Each Entitled Executive shall continue participation in the Plan throughout the
Performance Cycle, or until the Entitled Executives employment terminates for any reason,
the Entitled Executive becomes Permanently Disabled, or upon the Entitled Executive no
longer being designated as an Entitled Executive as recommended by the CEO and approved by
the Committee, whichever first occurs.
 
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Section 4Allocation of Award Units
 
 
 4.01
    
    Allocation
 Each person who is an Entitled Executive as of the Effective Date or who becomes an
Entitled Executive during the Performance Cycle but after the Effective Date shall be
allocated Award Units. The number of Award Units shall be equal to:
 (a)
    
    the Entitled Executives Salary as of the Effective Date or the date the
Entitled Executive commences participation in the Plan, whichever is later
 MULTIPLIED BY
 (b)
    
    the number of years and completed months (expressed as fractions of a year, to
two decimal places) from the Effective Date or the date the Entitled Executive
commences participation in the Plan, whichever is later, to the end of the Performance
Cycle
 MULTIPLIED BY
 (c)
    
    the Target Percentage applicable to the Entitled Executive, as described in
Section 4.04 below
 DIVIDED BY
 (d)
    
    the PCS Inc. Opening Share Price
 
 4.02
    
    Promotion to New Tier Group or Other Promotion
 In the event an Entitled Executive is promoted to a new Tier Group during the
Performance Cycle or if the Salary of the Entitled Executive is significantly adjusted
during the Performance Cycle as a result of a promotion, additional Award Units shall be
allocated to the Entitled Executive reflecting the incremental effect of the Entitled
Executives participation in the new Tier Group or new Salary, as the case may be, from the
date such changes occurred to the end of the Performance Cycle.
 
 4.03
    
    Corporate TSR Award Units and Index TSR Award Units
 One half the Award Units allocated pursuant to Sections 4.01 and 4.02 above shall be
Corporate TSR Award Units and one half shall be Index TSR Award Units.
 
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4.04
    
    Target Percentage
 The Target Percentage applicable to an Entitled Executive for purposes of this Plan
shall be determined by the Tier Group in which the Entitled Executive participates, as
follows:
 Tier Group
    
    Positions
    
    Target Percentage1
    
    Corporation
President and Chief Executive Officer
    
    70%2
    
    Executive
Vice President and Chief Operating Officer; Executive Vice
President and Chief Financial Officer
    
    45%3
    
    Selected
Corporate Senior Vice Presidents (Administration; Corporate
Relations); and Subsidiary Presidents
(Potash; Phosphate; Sales)
    
    40%4
    
    Selected
Senior Vice Presidents (IT; General Counsel, Fertilizer); Corporate
Vice Presidents; Selected Subsidiary
Vice Presidents
    
    30%5
    
    Selected
Subsidiary Vice PresidentsSelected Corporate Executive
Employees
Selected Operations General Managers
    
    25%6
    
    Selected
Operations General Managers
Selected Subsidiary Vice Presidents
Selected Senior Directors
    
    20%
  
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Section 5Vesting of Award Units
 
 
 5.01
    
    Vested Percentages
 The following Vested Percentages shall be used to determine the redemption of an
Entitled Executives Corporate TSR Award Units and Index TSR Award Units pursuant to
paragraphs (a) and (b) respectively of Section 6.02 (Value of Award Units).
 (a)
    
    Corporate TSR Vested Percentage
 Corporate TSRCorporate TSR
    
    Vested Percentage0% or less
    
    0%10%
    
    50%20%
    
    75%30%
    
    100%40%
    
    125%50% or more
    
    150%
 (b)
    
    Index TSR Vested Percentage
 Corporate TSR
    
    Index TSRminus Index TSR
    
    Vested PercentageLess than 0%
    
    0%0%
    
    50%5%
    
    100%10% or more
    
    150%
 All Corporate TSR and Corporate TSR minus Index TSR performances between the percentages in
the above tables will be interpolated in the manner adopted by the Corporation from time to
time.
 
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Section 6Redemption of Award Units
 
 
 6.01
    
    Redemption Date
 Subject to the provisions of Section 6.03 below, the Award Units of each Entitled
Executive shall be redeemed and paid out by the Corporation in a lump sum cash payment. This
payment shall occur as soon as practicable following the end of the Performance Cycle, or
following the date of the Entitled Executives retirement, permanent disability, death or
involuntary termination, if applicable, but in no event later than 2 1/2 months after the end
of the year in which such Award Units first become payable.
 
 6.02
    
    Value of Award Units
 The value of an Entitled Executives Award Units shall be equal to the sum of the
values of the Entitled Executives Corporate TSR Award Units and Index TSR Award Units, as
follows:
 (a)
    
    Corporate TSR Award Units
 The value of an Entitled Executives Corporate TSR Award Units shall be equal to:
 (i)
    
    the number of Corporate TSR Award Units granted to the Entitled
Executive, subject to the reduction or forfeiture of units described in Section
6.03, if applicable
 MULTIPLIED BY
 (ii)
    
    the Corporate TSR Vested Percentage
 MULTIPLIED BY
 (iii)
    
    PCS Inc. Closing Share Price, subject, however, to a maximum
value of three times the PCS Inc. Opening Share Price
 (b)
    
    Index TSR Award Units
 The values of an Entitled Executives Index TSR Award Units shall be equal to:
 (i)
    
    the number of Index TSR Award Units granted to the Entitled
Executive, subject to the reduction or forfeiture of units described in Section
6.03, if applicable
 MULTIPLIED BY
 (ii)
    
    the Index TSR Vested Percentage
 MULTIPLIED BY
 (iii)
    
    the PCS Inc. Closing Share Price, subject, however, to a
maximum value of three times the PCS Inc. Opening Share Price
 
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6.03
    
    Early Redemption Date
 (a)
    
    Retirement, Permanent Disability, Death or Involuntary Termination Without Just
Cause
 In the event an Entitled Executive Retires, becomes Permanently Disabled or dies
prior to the end of the Performance Cycle or in the event the Entitled Executives
employment is involuntarily terminated by the Corporation without Just Cause, the
number of Award Units allocated to the Entitled Executive pursuant to Section 4
(Allocation of Award Units) shall be reduced such that the calculation of years and
completed months of participation as described in paragraph (b) of Section 4.01
(Allocation) shall end as of the date of the Entitled Executives retirement,
Permanent Disability, death or involuntary termination, as the case may be.
 One half the Award Units reduced shall be Corporate TSR Award Units and one half
shall be Index TSR Award Units.
 An Entitled Executive shall be required to provide at least 30 days prior written
notice of retirement to the Corporation. In the event an Entitled Executive
provides less than 30 days prior written notice of retirement, the value of award
units calculation per Section 6.02 shall be performed as of the Entitled Executives
retirement date and the date that is 30 days following the date the Entitled
Executive provided written notice of retirement to the Corporation, and the
Corporation shall provide the lower valued award to the Entitled Executive as
determined by such two calculations.
 (b)
    
    Voluntary Termination or Involuntary Termination With Just Cause
 In the event an Entitled Executive Retires voluntarily terminates employment prior
to the end of the Performance Cycle or in the event the Entitled Executives
employment is involuntarily terminated by the Corporation with Just Cause, the
allocation of Award Units to the Entitled Executive pursuant to Section 4
(Allocation of Award Units) shall be forfeited as of the date of such termination of
employment and the Entitled Executive shall not be entitled to any payment under
this Plan.
 
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Section 7Administration of the Plan
 
 
 7.01
    
    Powers of the Committee
 The Committee shall have the discretionary power and authority to determine who shall
be Entitled Executives, approve Target Percentages and generally administer the Plan. The
Committee shall conclusively interpret the provisions of this Plan and decide all questions
of fact arising in the application thereof. To the extent applicable, the Plan shall be
interpreted so as to avoid the imposition of penalties pursuant to Section 409A of the U.S.
Internal Revenue Code.
 
 7.02
    
    Notification to Entitled Executives
 The Corporation will prepare a written notice to each Entitled Executive specifying
his or her Target Percentage, the number of Award Units allocated and the terms of the Plan.
 
 7.03
    
    Calculation of Award Payments
 Management of the Corporation shall provide a report to the Committee within 30 days
of the end of the Performance Cycle showing the calculations for determining award payments
including the calculation of the Corporate TSR and Index TSR. Such calculations shall be
subject to the review and confirmation of the Committee.
 
 7.04
    
    Delegation of Duties
 The Committee and/or the Board may delegate to any director or directors or any
officer or officers of the Corporation such administrative duties and powers as it may see
fit with respect to the Plan.
 
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Section 8General Provisions
 
 
 8.01
    
    Assignment or Alienation
 Except as required by applicable laws, the right of an Entitled Executive to Award
Units under this plan shall not be given as security, be subject to transfer, anticipation,
commutation, alienation, sale, assignment, encumbrance, charge, pledge, or hypothecation, or
be subject to execution, attachment, levy or similar process or assignment by operation of
law, and any attempt to effect any such action will be null and void and of no effect.
 
 8.02
    
    Amendment or Termination
 This Plan may be amended in whole or in part from time to time or terminated by the
Corporation. Any amendment or termination will be binding on the Corporation, Entitled
Executives and their respective beneficiaries. Notice of termination or amendment will be
provided to Entitled Executives and in the case of deceased Entitled Executives, their
respective beneficiaries. However, no amendment or termination of any provision of this
Plan shall directly or indirectly deprive any Entitled Executive or beneficiary of all or
any portion of Award Units allocated to the date of the amendment or termination.
 
 8.03
    
    No Enlargement of Contractual Rights
 This Plan shall not give any Entitled Executive the right to be retained in the
service of the Corporation nor will it interfere with the right of the Corporation to
terminate the employment of the Entitled Executive. Participation in this Plan will not
give any Entitled Executive any right or claim to any benefit, except to the extent provided
in this Plan.
 
 8.04
    
    Withholding of Taxes
 The Corporation will withhold all applicable taxes from any amounts paid pursuant to
this Plan.
 
 8.05
    
    Binding on Successors
 This Plan will be binding on any successor or successors of the Corporation whether
by merger, consolidation or otherwise.
 
 8.06
    
    Currency
 The Award Units redeemed pursuant to this Plan will be paid in the same currency as
the Entitled Executive receives his or her Salary. If the Salary of an Entitled Executive is
paid in more than one currency during a Performance Cycle, the currency of his or her Award
Payment for that Performance Cycle shall be determined by the Senior Vice-President,
Administration.
 
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8.07
    
    Certain Adjustments
 In the event that, at any time during the Performance Cycle, there is any variation
in the common shares of PCS Inc. or of any corporation within the Index by reason of (i) a
stock split, reverse of stock split, stock dividend or other increase or decrease in the
number of outstanding common shares, (ii) a merger, consolidation, recapitalization,
amalgamation, plan of arrangement or similar statutory or corporate transaction or (iii)
other event that the Committee determines, such as a sale of all or substantially all of any
such corporations assets, the Committee shall make such adjustments to the Index Opening
Price, PCS Inc. Opening Share Price, Index Closing Price or PCS Inc. Closing Share Price or
to the calculation of the Corporate TSR or Index TSR with respect to such corporation and,
in the case of any such event affecting the common shares of PCS Inc. the number of then
outstanding Award Units as it deems necessary or appropriate to reflect such event.
 
 8.08
    
    Governing Law
 This Plan shall be governed by the laws of the Province of Saskatchewan. Section
headings are for convenience only and shall not be considered provisions of the Plan. Words
in the singular shall included the plural, and vice versa, unless qualified by the context.
 January
1,
2006
 
 
 
 14