Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
PERTZ DOUGLAS A
   2. Issuer Name and Ticker or Trading Symbol
MOSAIC CO [MOS] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
100 SOUTH SAUNDERS ROAD, SUITE 300		 3. Date of Earliest Transaction (Month/Day/Year)
07/18/2005
(Street)

LAKE FOREST, IL 60045		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 07/18/2005   M   172,206 A $ 10.19 238,168.52 D  
Common Stock 07/18/2005   M   277,200 A $ 10.76 515,368.52 D  
Common Stock 07/18/2005   S(1)   172,206 D $ 16.5878 343,162.52 D  
Common Stock 07/18/2005   S(1)   277,200 D $ 16.75 65,962.52 D  
Common Stock 07/19/2005   M   32,800 A $ 10.76 98,762.52 D  
Common Stock 07/19/2005   M   220,000 A $ 12.99 318,762.52 D  
Common Stock 07/19/2005   S(1)   32,800 D $ 16.75 285,962.52 D  
Common Stock 07/19/2005   S(1)   220,000 D $ 17 65,962.52 D  

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (right to buy) $ 18.1875             10/22/2004 08/28/2008 Common Stock 320,000   320,000 D  
Stock Option (right to buy) $ 18.1875             10/22/2004 08/28/2008 Common Stock 180,000   180,000 D  
Stock Option (right to buy) $ 14.3125             10/22/2004 10/01/2009 Common Stock 275,000   275,000 D  
Stock Option (right to buy) $ 15.0312             10/22/2004 02/22/2010 Common Stock 254,000   254,000 D  
Stock Option (right to buy) $ 15.0625             10/22/2004 03/30/2010 Common Stock 124,040   124,040 D  
Stock Option (right to buy) $ 13.55             10/22/2004 02/28/2011 Common Stock 325,000   325,000 D  
Stock Option (right to buy) $ 12.99 07/19/2005   M     220,000 10/22/2004 01/02/2012 Common Stock 440,000 $ 0 220,000 D  
Stock Option (right to buy) $ 10.76 07/18/2005   M     277,200 10/22/2004 01/02/2013 Common Stock 310,000 $ 0 32,800 D  
Stock Option (right to buy) $ 10.19 07/18/2005   M     172,206 10/22/2004 01/02/2014 Common Stock 172,206 $ 0 0 D  
Grant of Restricted Stock Units $ 0             11/30/2007   (2) Common Stock 3,452   3,452 D  
Stock Option (right to buy) $ 10.76 07/19/2005   M     32,800 10/22/2004 01/02/2013 Common Stock 32,800 $ 0 0 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
PERTZ DOUGLAS A
100 SOUTH SAUNDERS ROAD
SUITE 300
LAKE FOREST, IL 60045		   X      

Signatures

 s/Richard L. Mack Attorney in fact for Douglas A. Pertz   07/20/2005
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The sales reported in this Form 4 were effected pursurant to a Rule 10b5-1 trading plan adopted by the reporting person on February 1, 2005.
(2) Not Applicable.

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