INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO

§ 240.13d-2(a)

(Amendment No. 4)*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box o.

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See § 240.13d-7 for other parties to whom copies are to be sent.

(Continued on following pages)

(Page 1 of 9 Pages)

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (the “Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

1 Based on 99,825,840 shares of common stock, without par value, of the Company outstanding as of October 9, 2009, as set forth in the Company’s Definitive Proxy Statement on Schedule 14A, filed with the Securities and Exchange Commission on October 13, 2009.

2 Based on 99,825,840 shares of common stock, without par value, of the Company outstanding as of October 9, 2009, as set forth in the Company’s Definitive Proxy Statement on Schedule 14A, filed with the Securities and Exchange Commission on October 13, 2009.

3 Based on 99,825,840 shares of common stock, without par value, of the Company outstanding as of October 9, 2009, as set forth in the Company’s Definitive Proxy Statement on Schedule 14A, filed with the Securities and Exchange Commission on October 13, 2009.

This Amendment No. 4 (this “Amendment No. 4”) amends and supplements the Schedule 13D originally filed with the Securities and Exchange Commission (the “SEC”) on September 28, 2009 (the “Original Statement”), as amended by Amendment No. 1 filed with the SEC on November 3, 2009, Amendment No. 2 filed with the SEC on November 13, 2009 and Amendment No. 3 filed with the SEC on November 23, 2009 (the Original Statement and such amendments, together with this Amendment No. 4, are collectively referred to herein as the “Statement”), by CF Industries Holdings, Inc., a Delaware corporation (“CF Holdings”), CF Industries, Inc., a Delaware corporation and wholly-owned subsidiary of CF Holdings (“CF Industries”), and CF Composite, Inc., a New York corporation and wholly-owned subsidiary of CF Industries (“CF Composite” and, together with CF Holdings and CF Industries, the “Reporting Persons”).  Except as set forth in this Amendment No. 4, all information set forth in the Statement remains unchanged and capitalized terms used but not defined in this Amendment No. 3 shall have the meanings ascribed to such terms in the Original Statement.

Item 4.                    Purpose of Transaction.

Item 4 of the Statement is hereby amended and supplemented by adding the following at the end of the section entitled “CF Holdings’ Proposals and Actions Related to a Business Combination with the Company”:

On December 4, 2009, CF Holdings delivered a letter to the Board containing a revised proposal to acquire the Company for consideration per Company Share of 0.1034 CF Shares and $36.75 in cash (including the $7.50 per Company Share special dividend declared by the Company on October 29, 2009 and payable on December 11, 2009). A copy of CF Holdings’ letter to the Board, dated December 4, 2009, is filed as Exhibit 14 hereto and incorporated herein by reference.

Also on December 4, 2009, CF Holdings delivered a presentation relating to the revised proposal to the Board.  A copy of the presentation is filed as Exhibit 15 hereto and incorporated herein by reference.

Item 4 of the Statement is hereby amended and supplemented by adding the following at the end of the section entitled “Election of Directors at the Company’s 2009 Annual Meeting of Stockholders”:

On December 1, 2009, the Company announced that CF Holdings’ Nominees were elected and qualified to serve on the Board until the Company’s 2012 annual meeting of stockholders.

Item 6.                    Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer.

Item 6 of the Statement is hereby amended and supplemented by adding the following after the second paragraph:

On December 6, 2009, CF Holdings entered into a commitment letter (the “New Commitment Letter”), pursuant to which Morgan Stanley Senior Funding, Inc. committed to provide financing for CF Holdings’ acquisition of Terra. The New Commitment Letter provides for a senior secured term loan facility of up to $1.3 billion, a senior secured revolving credit facility of up to $300 million and a senior secured bridge facility of up to $1.2 billion.  Unless CF Holdings and Terra enter into a merger agreement by December 31, 2009, the New Commitment Letter would expire.  A copy of the New Commitment Letter is filed as Exhibit 16 hereto and incorporated herein by reference.

Item 7.                    Material to be Filed as Exhibits.

Item 7 of the Statement is hereby amended and supplemented by adding the following Exhibits:

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date:  December 7, 2009

EXHIBIT INDEX

(1) Previously filed as an Exhibit to the Original Statement.

(2) Previously filed as an Exhibit to Amendment No. 1 to the Original Statement, filed with the SEC on November 3, 2009.

(3) Previously filed as an Exhibit to Amendment No. 2 to the Original Statement, filed with the SEC on November 13, 2009.

(4) Previously filed as an Exhibit to Amendment No. 3 to the Original Statement, filed with the SEC on November 23, 2009.