PotashCorp Adopts Shareholder Rights Plan

SASKATOON, Canada, August 17, 2010 - Potash Corporation of Saskatchewan Inc. ("PotashCorp") today
announced that its Board of Directors has adopted a Shareholder Rights Plan,
subject to TSX acceptance.

The Rights Plan is intended to ensure that in the context of a
formal take-over bid, the Board of Directors of PotashCorp has sufficient
time to explore and develop alternatives to enhance shareholder value,
including competing transactions that might emerge.

In connection with the adoption of the Rights Plan, the Board
of Directors authorized the issuance of one share purchase right in respect
of each common share of PotashCorp outstanding as of the close of business on
August 16, 2010 (and each share issued thereafter, subject to the limitations
set out in the Rights Plan). Under the terms of the Rights Plan, the rights
will become exercisable if a person, together with its affiliates, associates
and joint actors, acquires or announces an intention to acquire beneficial
ownership of shares which, when aggregated with its current holdings, total
20% or more of PotashCorp's outstanding common shares, subject to the ability
of the Board of Directors to defer the time at which the rights become
exercisable and to waive the application of the Rights Plan.

Following the acquisition of more than 20% of the outstanding
common shares by any person (and its affiliates, associates and joint
actors), each right held by a person other than the acquiring person (and its
affiliates, associates and joint actors) would, upon exercise, entitle the
holder to purchase PotashCorp's common shares at a substantial discount to
their then prevailing market price.

The Rights Plan permits the acquisition of control of Potash
through a "permitted bid", a "competing permitted bid" or a negotiated
transaction. A permitted bid is one that, among other things, is made to all
holders of shares, is open for a minimum of 90 days and is supported by a
majority of PotashCorp's shareholders.

A more detailed summary of the rights plan is set out in
PotashCorp's Material Change Report and Current Report on Form 8-K which is
being filed with the Canadian securities regulatory authorities and the
United States Securities and Exchange Commission and will be available at
www.sedar.com and www.sec.gov. A full copy of the Rights Plan
will also be available at www.sedar.com and www.sec.gov in due
course.

This release contains forward-looking statements or
forward-looking information (forward-looking statements). These statements
are based on certain factors and assumptions including foreign exchange
rates, expected growth, results of operations, performance, business
prospects, evaluations and opportunities and effective income tax rates.
While the company considers these factors and assumptions to be reasonable
based on information currently available, they may prove to be incorrect.
Several factors could cause actual results to differ materially from those
expressed in the forward-looking statements, including, but not limited to:
future actions taken by BHP Billiton in connection with its unsolicited,
non-binding proposal; fluctuations in supply and demand in fertilizer,
sulfur, transportation and petrochemical markets; changes in competitive
pressures, including pricing pressures; the recent global financial crisis
and conditions and changes in credit markets; the results of sales contract
negotiations with China and India; timing and amount of capital expenditures;
risks associated with natural gas and other hedging activities; changes in
capital markets and corresponding effects on the company's investments;
changes in currency and exchange rates; unexpected geological or
environmental conditions, including water inflow; strikes and other forms of
work stoppage or slowdowns; changes in and the effects of, government policy
and regulations; and earnings, exchange rates and the decisions of taxing
authorities, all of which could affect our effective tax rates. Additional
risks and uncertainties can be found in our Form 10-K for the fiscal year
ended December 31, 2009 under captions "Forward-Looking Statements" and "Item
1A - Risk Factors" and in our other filings with the US Securities and
Exchange Commission and Canadian provincial securities commissions.
Forward-looking statements are given only as at the date of this release and
the company disclaims any obligation to update or revise the forward-looking
statements, whether as a result of new information, future events or
otherwise, except as required by law.

For further information please contact:

    Investors

    Denita Stann
    Senior Director, Investor Relations
    Phone: +1(847)849-4277
    Email: ir@potashcorp.com
    Media
    Bill Johnson
    Director, Public Affairs
    Phone: +1(306)933-8849
    Email: pr@potashcorp.com
    Eric Brielmann / Jamie Moser / Andrew
    Siegel
    Joele Frank, Wilkinson Brimmer Katcher
    Phone: +1(212)355-4449

Web Site: www.potashcorp.com

Investors, Denita Stann, Senior Director, Investor Relations, Phone: +1(847)849-4277, Email: ir at potashcorp.com, Media, Bill Johnson, Director, Public Affairs, Phone: +1(306)933-8849, Email: pr at potashcorp.com, Eric Brielmann / Jamie Moser / Andrew, Siegel, Joele Frank, Wilkinson Brimmer Katcher, Phone: +1(212)355-4449