TERMS AGREEMENT Debt Securities

Exhibit 1(a)

POTASH CORPORATION OF SASKATCHEWAN INC.

TERMS AGREEMENT

Debt Securities

April 28, 2009

To: The Underwriters identified herein

Ladies and Gentlemen:

          The undersigned Potash Corporation of Saskatchewan Inc. (the “ Company ”) agrees to sell to the several Underwriters named in Schedule A hereto for their respective accounts, on and subject to the terms and conditions of the Underwriting Agreement attached hereto as Exhibit I (the " Underwriting Agreement ”), the following securities (the “ Offered Securities ”) on the following terms:

           Title: 5.25% Notes due May 15, 2014 (the “ 2014 Notes ”); 6.50% Notes due May 15, 2019 (the " 2019 Notes ”)

           Principal Amount: $500,000,000 aggregate principal amount of 2014 Notes; $500,000,000 aggregate principal amount of 2019 Notes

           Interest: 5.25% per annum from May 1, 2009 in the case of the 2014 Notes and 6.50% per annum from May 1, 2009 in the case of the 2019 Notes, in each case payable semiannually on May 15 and November 15, commencing November 15, 2009, to holders of record on the preceding May 1 or November 1, as the case may be

           Maturity: May 15, 2014 in the case of the 2014 Notes; May 15, 2019 in the case of the 2019 Notes

           Optional Redemption: The Offered Securities of each series will be redeemable, in whole or in part, at the option of the Company at any time and from time to time at a redemption price equal to the greater of (i) 100% of the principal amount of the Offered Securities to be redeemed and (ii) the sum of the present values of the remaining scheduled payments discounted to the date of redemption on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the adjusted treasury rate plus 50 basis points in the case of the 2014 Notes and 50 basis points in the case of the 2019 Notes, together with, in each case, accrued interest on the principal amount of the Offered Securities to be redeemed to the date of redemption, as more fully described in the Company’s final prospectus supplement, dated April 29, 2009 (the “ Final Prospectus Supplement ”)

           Listing: None

           Delayed Delivery Contracts: None

           Lock-up Period (pursuant to Section 4(j) of the Underwriting Agreement) : From the date hereof through May 1, 2009

           Underwriting Fee: 0.600% of the principal amount in the case of the 2014 Notes; 0.650% of the principal amount in the case of the 2019 Notes

           Payment by Underwriters: 99.157% of the principal amount, plus accrued interest, if any, from May 1, 2009 in the case of the 2014 Notes; 99.266% of the principal amount, plus accrued interest, if any, from May 1, 2009 in the case of the 2019 Notes

           Expected Reoffering Price: 99.757% of the principal amount in the case of the 2014 Notes and 99.916% of the principal amount in the case of the 2019 Notes, in each case subject to change by the Representatives

           Applicable Time: 3:45 p.m. (Eastern Time) on the date of this Terms Agreement

           Final Term Sheet: The Company will prepare and file a final term sheet relating to the Offered Securities as contemplated in Section 4(c) of the Underwriting Agreement

           Closing: 8:30 a.m. (Eastern Time) on May 1, 2009, at the offices of Jones Day, 77 West Wacker, Chicago, Illinois, in Federal (same day) funds

           Settlement and Trading: Book-Entry only via DTC

           Lead Underwriter: Banc of America Securities LLC

           Representatives: Banc of America Securities LLC, HSBC Securities (USA) Inc. and RBC Capital Markets Corporation

          The respective principal amounts of the Offered Securities to be purchased by each of the Underwriters are set forth opposite their names in Schedule A hereto.

          The provisions of the Underwriting Agreement form a part hereof.

          For purposes of Sections 2, 5 and 7 of the Underwriting Agreement, the only information furnished to the Company by any Underwriter for use in the General Disclosure Package (as defined in the Underwriting Agreement) or the Final Prospectus Supplement consists of the following information in the Company’s preliminary prospectus supplement, dated April 28, 2009 (the “ Preliminary Prospectus Supplement ”), and the Final Prospectus Supplement:

          If the foregoing is in accordance with your understanding of our agreement, kindly sign and return to the Company one of the counterparts hereof, whereupon it will become a binding agreement between the Company and the several Underwriters in accordance with its terms.

The foregoing Terms Agreement is hereby confirmed
and accepted as of the date first above written.

SCHEDULE A TO TERMS AGREEMENT

SCHEDULE B TO TERMS AGREEMENT

(referred to in Sections 2 and 5 of the Underwriting Agreement)

1. Base Prospectus, dated December 12, 2007, as supplemented by the Preliminary Prospectus Supplement

“General Use Issuer Free Writing Prospectus” includes each of the following documents:

1. Final term sheet, dated April 28, 2009, a copy of which is attached hereto

          The use of each of the following Issuer Free Writing Prospectuses has been consented to by the Company and the Representatives pursuant to Section 5(a)(iii) of the Underwriting Agreement:

          1. Electronic road show

FINAL TERM SHEET

A securities rating is not a recommendation to buy, sell or hold securities and may be subject to revision or withdrawal at any time.

The Issuer has filed a Registration Statement on Form S-3 (including a base prospectus dated December 12, 2007, as supplemented by a preliminary prospectus supplement, dated April 28, 2009, the “Prospectus”) with the SEC for the offering to which this communication relates. Before you invest, you should read the Prospectus and the documents incorporated therein by reference that the Issuer has filed with the SEC for more complete information about the Issuer and this offering. You may obtain these documents for free by visiting EDGAR on the SEC website at

www.sec.gov. Alternatively, the Issuer, any underwriter or any dealer participating in the offering will arrange to send you the Prospectus and any document incorporated by reference in the Prospectus if you request it by calling toll-free 1-800-294-1322, or you may e-mail a request to dg.prospectus_distribution@bofasecurities.com.

          Any legends, disclaimers or other notices that may appear below are not applicable to this communication and should be disregarded. Such legends, disclaimers or other notices have been automatically generated as a result of this communication having been sent via Bloomberg or another system.

EXHIBIT I

POTASH CORPORATION OF SASKATCHEWAN INC.
UNDERWRITING AGREEMENT

Debt Securities

     1.  Introductory. Potash Corporation of Saskatchewan Inc., a corporation continued and existing under the laws of Canada (the “ Company ”), proposes to issue and sell from time to time certain of its unsecured debt securities (the “ Registered Securities ”) registered under the registration statement referred to in Section 2(a). The Registered Securities will be issued under an indenture, dated as of February 27, 2003 (the “ Indenture ”), between the Company and The Bank of Nova Scotia Trust Company of New York, as trustee, in one or more series, which series may vary as to interest rates, maturities, redemption provisions, selling prices and other terms, with all such terms for any particular series of the Registered Securities being determined at the time of sale. Particular series of the Registered Securities will be sold pursuant to a Terms Agreement referred to in Section 3, for resale in accordance with terms of offering determined at the time of sale.

          The Registered Securities involved in any such offering are hereinafter referred to as the “ Offered Securities ”. The firm or firms that agree to purchase the Offered Securities are hereinafter referred to as the “ Underwriters ” of such securities, and the representative or representatives of the Underwriters, if any, specified in a Terms Agreement referred to in Section 3 are hereinafter referred to as the “ Representatives ”; provided , however , that if the Terms Agreement does not specify any representative of the Underwriters, the term “Representatives”, as used in this Agreement (other than in Sections 2(b), 5(c) and 7 and the second sentence of Section 3), shall mean the Underwriters.

     2.  Representations and Warranties of the Company . The Company, as of the date of each Terms Agreement referred to in Section 3, represents and warrants to, and agrees with, each Underwriter that:

          (a) Registration Statement Effective . An “automatic shelf registration statement” as defined under Rule 405 under the Securities Act of 1933, as amended (the “ Securities Act ”), on Form S-3 (File No. 333-148023) in respect of the Offered Securities has been filed with the Securities and Exchange Commission (the “ Commission ”); such registration statement, and any post-effective amendment thereto, became effective on filing; and no stop order suspending the effectiveness of such registration statement or any part thereof has been issued and no proceeding for that purpose has been initiated or threatened by the Commission (the base prospectus filed as part of the Registration Statement, in the form in which it has been most recently filed with the Commission on or prior to the date of any Terms Agreement referred to in Section 3, is hereinafter called the “ Base Prospectus ”; any preliminary prospectus (including any preliminary prospectus supplement) relating to the Offered Securities filed with the Commission pursuant to and in accordance with Rule 424(b) under the Securities Act prior to the filing of the Prospectus is hereinafter called a “ Preliminary Prospectus ”; the various parts of such registration statement, including all exhibits thereto but excluding the Form T-1 and including any information in a prospectus or prospectus supplement relating to the Offered Securities that is filed with the Commission and deemed or retroactively deemed by virtue of Rule 430B under the Securities Act to be part of such registration statement (“ 430B Information ”), each as amended at the time such part of the registration statement became effective, are hereinafter collectively called the “ Registration Statement ”; the Base Prospectus, as amended and supplemented (including by a Preliminary Prospectus) immediately prior to the Applicable Time (as defined in any Terms Agreement referred to in Section 3), is hereinafter called the “ Statutory Prospectus ”; the form of the final prospectus relating to the Offered Securities that discloses the public offering price and other 430B Information and other final terms of the Offered Securities and otherwise satisfies the requirements of Section 10(a) of the Securities Act, filed with the

Commission pursuant to Rule 424(b) under the Securities Act in accordance with Section 4(a) hereof is hereinafter called the “ Prospectus ”; any reference herein to the Base Prospectus, the Statutory Prospectus, any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated by reference therein pursuant to Item 12 of Form S-3 under the Securities Act, as of the date of such prospectus; any reference to any amendment or supplement to the Base Prospectus, any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include any post-effective amendment to the Registration Statement, any prospectus supplement relating to the Offered Securities filed with the Commission pursuant to Rule 424(b) under the Securities Act and any documents filed under the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), and incorporated therein, in each case after the date of the Base Prospectus, such Preliminary Prospectus, or the Prospectus, as the case may be; any reference to any amendment to the Registration Statement shall be deemed to refer to and include any annual report of the Company filed pursuant to Section 13(a) or 15(d) of the Exchange Act after the effective date of the Registration Statement that is incorporated by reference in the Registration Statement; any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being so specified in Schedule B to the Terms Agreement is hereinafter referred to as a “ General Use Issuer Free Writing Prospectus ”; any “issuer free writing prospectus”, as defined in Rule 433 under the Securities Act, relating to the Offered Securities in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g) under the Securities Act is hereinafter referred to as a “ Issuer Free Writing Prospectus ”; and any Issuer Free Writing Prospectus that is not a General Use Issuer Free Writing Prospectus is hereinafter referred to as a “ Limited Use Issuer Free Writing Prospectus ”.

          (b) Registration Statement and Prospectus Not Misleading . No order preventing or suspending the use of any Preliminary Prospectus or any Issuer Free Writing Prospectus has been issued by the Commission, and (i) each Preliminary Prospectus, at the time of filing thereof, conformed in all material respects to the requirements of the Securities Act and the Trust Indenture Act of 1939, as amended (“ Trust Indenture Act ”), and the rules and regulations of the Commission thereunder and did not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, and (ii) at the Applicable Time, the Registration Statement conforms, and any further amendments to the Registration Statement will conform, in all material respects to the requirements of the Securities Act, the Trust Indenture Act and the rules and regulations of the Commission thereunder, and does not and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein, not misleading and (iii) the Prospectus, and any further amendments or supplements to the Prospectus will conform (A) on its date, (B) at the time of filing the Prospectus pursuant to Rule 424(b) and (C) on the closing date with respect to the Offered Securities, in all material respects to the requirements of the Securities Act, the Trust Indenture Act and the rules and regulations of the Commission thereunder, and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the foregoing does not apply to statements in or omissions from any of such documents based upon written information furnished to the Company by any Underwriter through the Representatives, if any, specifically for use therein.

          (c) General Disclosure Package . For the purposes of this Agreement, the “Applicable Time” is the time set forth in the applicable Terms Agreement referred to in Section 3; as of the Applicable Time, neither (i) the General Use Issuer Free Writing Prospectus(es) issued at or prior to the Applicable Time, the Statutory Prospectus identified in Schedule B to the Terms Agreement attached hereto (which is the most recent Statutory Prospectus distributed to investors generally) and any other documents listed or information stated in Schedule B to the Terms Agreement attached hereto to be included in the General Disclosure Package, all considered together (collectively, the “ General Disclosure Package ”) or (ii) any

individual Limited Use Issuer Free Writing Prospectus, when considered together with the General Disclosure Package, included any untrue statement of a material fact or omitted to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading; and each Issuer Free Writing Prospectus does not conflict with the information contained in the Registration Statement, the Statutory Prospectus or the Prospectus and each such Issuer Free Writing Prospectus, as supplemented by and taken together with the General Disclosure Package as of the Applicable Time, did not include any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading; provided , however , that this representation and warranty shall not apply to statements or omissions made in the General Disclosure Package or an Issuer Free Writing Prospectus in reliance upon and in conformity with information furnished in writing to the Company by an Underwriter through the Representatives expressly for use therein.

          (d) Documents Incorporated by Reference . The documents incorporated by reference in the Statutory Prospectus and the Prospectus, when they became effective or were filed with the Commission, as the case may be, conformed in all material respects to the requirements of the Securities Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder, and none of such documents included any untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading; any further documents so filed and incorporated by reference in the Prospectus or any further amendment or supplement thereto, when such documents become effective or are filed with the Commission, as the case may be, will conform in all material respects to the requirements of the Securities Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder and will not include any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading; except that the foregoing does not apply to statements in or omissions from any of such documents based upon written information furnished to the Company by any Underwriter through the Representatives, if any, specifically for use therein; and no such documents were filed with the Commission since the Commission’s close of business on the business day immediately prior to the date of this Agreement and prior to the execution of this Agreement.

          (e) Taxation . Subject to the assumptions, limitations, qualifications and conditions set forth therein, the statements made in the General Disclosure Package and the Prospectus under the headings “United States Federal Income Tax Considerations”, insofar as they relate to matters of United States federal income tax law, and “Canadian Federal Income Tax Considerations”, insofar as they relate to matters of Canadian federal income tax law, constitute a fair summary of the matters so discussed and applicable to the holders of Offered Securities described therein.

          (f) Incorporation of the Company . The Company has been continued and is an existing corporation under the laws of Canada, with power and authority (corporate and other) to own its properties and conduct its business as described in the General Disclosure Package and the Prospectus; and the Company is duly qualified or registered to do business in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification or registration, except where the failure to be so qualified or registered would not individually or in the aggregate have a material adverse effect on the financial condition, business, properties or results of operations of the Company and its subsidiaries taken as one enterprise (a “ Material Adverse Effect ”).

          (g) Organization of Subsidiaries . Each material subsidiary of the Company is set forth on Schedule A hereto (each, a “ Subsidiary ”). Each Subsidiary is a corporation or limited partnership duly incorporated or organized, as the case may be, existing in good standing under the laws of the jurisdiction of its incorporation or organization, with power and authority (corporate and other) to own its properties

and conduct its business as described in the General Disclosure Package and the Prospectus; and each Subsidiary is duly qualified or registered to do business as a foreign corporation or limited partnership in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification or registration, except where the failure to be so qualified or registered would not individually or in the aggregate have a Material Adverse Effect; all of the issued and outstanding capital stock of each Subsidiary has been duly authorized and validly issued and is fully paid and nonassessable; and the capital stock of each Subsidiary is owned directly or indirectly by the Company free from liens, encumbrances and defects incurred or arising otherwise than in the ordinary course of business.

          (h) Authorization of Indenture and Offered Securities . The Indenture has been duly authorized, executed and delivered and has been duly qualified under the Trust Indenture Act; the Offered Securities have been duly authorized; and when the Offered Securities are delivered and paid for pursuant to the Terms Agreement on the Closing Date (as defined below) or pursuant to Delayed Delivery Contracts (as defined below), such Offered Securities will have been duly executed, authenticated, issued and delivered, will conform in all material respects to the description thereof contained in the General Disclosure Package, the Prospectus and the Indenture, and such Offered Securities will constitute valid and legally binding obligations of the Company, enforceable in accordance with their terms, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles.

          (i) No Consents . No consent, approval, authorization, or order of, or filing with, any governmental agency or body or any court is required for the consummation by the Company of the transactions contemplated by the Terms Agreement (including the provisions of this Agreement) in connection with the issuance and sale of the Offered Securities by the Company, except such as have been obtained and made under the Securities Act and the Trust Indenture Act and such as may be required under state securities laws or the securities laws of any jurisdiction outside the United States in which the Offered Securities are offered and sold.

          (j) No Breach or Default . The execution, delivery and performance by the Company of the Indenture, the Terms Agreement (including the provisions of this Agreement) and any Delayed Delivery Contracts and the issuance and sale of the Offered Securities and compliance with the terms and provisions thereof by the Company will not conflict with or result in a breach or violation of any of the terms and provisions of, or constitute a default or acceleration of payment under, any statute, any rule, regulation or order of any governmental agency or body or any court, domestic or foreign, having jurisdiction over the Company or any Subsidiary or any of their properties, or any material agreement or instrument to which the Company or any Subsidiary is a party or by which the Company or any Subsidiary is bound or to which any of the properties of the Company or any Subsidiary is subject, or the charter or by-laws of the Company or any Subsidiary.

          (k) Authorization of Terms Agreement . The Terms Agreement (including the provisions of this Agreement) and any Delayed Delivery Contracts have been duly authorized, executed and delivered by the Company.

          (l) Properties . Except as disclosed in the General Disclosure Package and the Prospectus, the Company and the Subsidiaries have good and marketable title to all real properties and all other properties and assets described in the General Disclosure Package and the Prospectus as being owned by them, in each case free from liens, encumbrances and defects that would materially affect the value thereof or materially interfere with the use made or to be made thereof by them, except to the extent that the failure to hold any such title would not have a Material Adverse Effect; and, except as disclosed in the General Disclosure Package and the Prospectus, the Company and the Subsidiaries hold any leased real or

personal property described in the General Disclosure Package and the Prospectus as being leased by them under valid and enforceable leases with no exceptions that would materially interfere with the use made or to be made thereof by them, except to the extent that the failure so to hold any such leased property would not individually or in the aggregate have a Material Adverse Effect.

          (m) Permits . Except as disclosed in the General Disclosure Package and the Prospectus, the Company and the Subsidiaries possess adequate certificates, approvals, licenses, franchises, authorizations or permits (collectively, “ Permits ”) issued by appropriate governmental agencies or bodies necessary to conduct the business now operated by them, except where the failure to have any such Permit would not individually or in the aggregate have a Material Adverse Effect; and, except as disclosed in the General Disclosure Package and the Prospectus, the Company and the Subsidiaries have not received any notice of proceedings relating to the revocation or modification of any Permit that, if determined adversely to the Company or any of the Subsidiaries, would individually or in the aggregate have a Material Adverse Effect.

          (n) Labor . No labor dispute with the employees of the Company or any Subsidiary exists or, to the knowledge of the Company, is threatened that would have a Material Adverse Effect.

          (o) Intellectual Property . The Company and the Subsidiaries own, possess or can acquire on reasonable terms, adequate trademarks, trade names and other rights to inventions, know-how, patents, copyrights, confidential information and other intellectual property (collectively, “ Intellectual Property Rights ”) presently employed by them or necessary to conduct the business now operated by them, and have not received any notice of infringement of or conflict with asserted rights of others with respect to any Intellectual Property Rights that, if determined adversely to the Company or any of the Subsidiaries, would individually or in the aggregate have a Material Adverse Effect.

          (p) Environmental Laws . Except as disclosed in the General Disclosure Package and the Prospectus, neither the Company nor any of the Subsidiaries is in violation of any statute, rule, regulation, decision or order of any governmental agency or body or any court, domestic or foreign, relating to the use, disposal or release of hazardous or toxic substances or relating to the protection or restoration of the environment or human exposure to hazardous or toxic substances (collectively, “ Environmental Laws ”), owns or operates any real property contaminated with any substance required to be remediated under any Environmental Laws, or, to the Company’s knowledge, is liable for any off-site disposal or contamination pursuant to any Environmental Laws or is subject to any claim under any Environmental Laws, which violation, contamination, liability or claim would individually or in the aggregate have a Material Adverse Effect; and, except as disclosed in the General D