Exhibit 4.6**AMENDMENT NO. 5 TO THE AMENDED AND RESTATED CREDIT AGREEMENT**          Amendment No. 5 (this “*Amendment*”), dated as of July 11, 2007, among TerraCapital, Inc., a Delaware corporation (“*Terra Capital*”), Terra Mississippi Holdings Corp.(f/k/a Mississippi Chemical Corporation), a Mississippi corporation (“*TMH*”), and TerraNitrogen (U.K.) Limited, a company incorporated in England and Wales (“*TerraUK*”) (Terra Capital, TMH and Terra UK each a “*Borrower*” and, collectively, the“*Borrowers*”), Terra Industries Inc., a Maryland corporation (“*Terra Industries*”),Terra Capital Holdings, Inc., a Delaware corporation (“*Terra Capital Holdings*”), theLenders party hereto and Citicorp USA, Inc., as administrative agent and collateral agentfor the Lenders and the Issuers (in such capacities, the “*Administrative Agent*”), amends certainprovisions of the Amended and Restated Credit Agreement, dated as of December 21, 2004 (asamended, supplemented or otherwise modified from time to time, including previous amendmentshereto, the “*Credit Agreement*”), amongthe Borrowers, Terra Industries, Terra CapitalHoldings, the financial institutions from time to time party thereto as lenders (the “*Lenders*”),the financial institutions from time to time party thereto as issuing banks (the “*Issuers*”) andCiticorp USA, Inc., as administrative agent and collateral agent for the Lenders and theIssuers (in such capacities, the “*Administrative Agent*”).W I T N E S S E T H:          WHEREAS, Terra Capital has informed the Administrative Agent of its intention to sell theproperties located at Highway 347, 77705 in the city of Beaumont, Jefferson county in the State ofTexas; and          WHEREAS, the Borrowers, Terra Industries and Terra Capital Holdings have requested, and theRequisite Lenders and the Administrative Agent have agreed to, certain amendments to the CreditAgreement to permit the sale of the Beaumont Properties (as defined below) and certain otheramendments set forth below.          NOW, THEREFORE, in consideration of the premises and the mutual covenants and provisionshereinafter contained, the parties hereto hereby agree as follows:          **1.****Defined Terms**. Capitalized terms used herein and not defined herein but definedin the Credit Agreement are used herein as defined in the Credit Agreement.          **2.****Amendments**. Upon the occurrence of the Fifth Amendment Effective Date (as definedin Section 4), the Credit Agreement is hereby amended as follows:          (a) *Section 1.1*of the Credit Agreement is hereby amended by inserting among the existingdefined terms therein in alphabetical order the following defined terms:     “*Beaumont Properties*” means all real and personal property owned by BMC Holdings,Inc. located at its facility at Highway 347, 77705 in the city of Beaumont, Jeffersoncounty in the State of Texas.          (b) *Section 8.3(e)*of the Credit Agreement is hereby amended by deleting “or” appearingimmediately before clause (iv) and inserting the following new clause at the end of clause (iv) toread as follows:     or (v) owing by or to Terra Canada to or from Terra (UK) Holdings.
 

 
          (c) *Section 8.4*of the Credit Agreement is hereby amended by (A) deleting the word “and”appearing at the end of *clause (f),*(B) deleting the “period” appearing at the end of *clause (g)*and inserting “; and” in lieu thereof, and (C) inserting a new *clause (h)*immediately after *clause(g)*to read as follows:     (h) an Asset Sale with respect to the Beaumont Properties for not less than FairMarket Value and provided that at least 75% of the consideration with respect theretoshall be in cash.          (d) The first sentence of *Section 6.11(a)*is hereby deleted in its entirety and replaced withthe following:     (a) The Borrowers shall furnish a Borrowing Base Certificate with respect to eachof them to the Administrative Agent no later than:     (1) 5 Business Days after the end of each fiscal month (calculated as of the lastday of such fiscal month) at any time when (i) no Revolving Loans are outstanding, (ii)Letter of Credit Obligations outstanding do not exceed $50,000,000 at such time, and(iii) no Default or Event of Default exists and is continuing, or     (2) Wednesday of each week (calculated as of the immediately preceding Friday) ormore frequently (calculated as of the third preceding Business Day) as may be requestedby the Administrative Agent if all of the above conditions in *clause (A)*above are notmet;     in each case, executed by a Responsible Officer of each Borrower together withreasonably detailed supporting information and documentation acceptable to theAdministrative Agent.          **3.****Waiver of Mandatory Prepayment****.**The Requisite Lenders waive the Borrowers’obligations to apply 100% of the proceeds of the sale of the Beaumont Properties (or provide cashcollateral in respect of Letters of Credit) as required under *Section 2.9(a)(i)*so long as (i) noDefault shall have occurred which is continuing and (ii) 100% of all proceeds arising from suchsale are deposited by Terra Capital in a Cash Collateral Account. Such proceeds may thereafter beused by the Borrowers for general corporate purposes in accordance with the Credit Agreement.          **4.****Conditions Precedent to the Effectiveness of this Amendment****.**This Amendment shallbecome effective on the date (the “*Fifth Amendment Effective Date*”) when the following conditionsprecedent have been satisfied:                (a) Certain Documents. The Administrative Agent shall have received on or before theFifth Amendment Effective Date, all of the following, each of which shall be in form and substancesatisfactory to the Administrative Agent:                    (i) this Amendment, executed by the Borrowers, Terra Industries, Terra Capital Holdings, theAdministrative Agent and the Requisite Lenders; and                    (ii) such additional documentation as the Administrative Agent or the Lenders may reasonablyrequire.               (b) Representations and Warranties. Each of the representations and warranties madeby the Borrowers or the Guarantors in or pursuant to the Credit Agreement, as amended
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hereby, and the other Loan Documents to which any of the Borrowers or the Guarantors is aparty or by which the Borrowers or the Guarantors are bound, shall be true and correct in allmaterial respects on and as of the Fifth Amendment Effective Date (other than representations andwarranties in any such Loan Document which expressly speak as of a specific date, which shall havebeen true and correct in all material respects as of such specific date).          (c) No Event of Default. No Default or Event of Default shall have occurred and becontinuing on the Fifth Amendment Effective Date.          (d) Fees and Expenses Paid. The Borrowers shall have paid to the Administrative Agentin accordance with Section 11.3 of the Credit Agreement, all outstanding costs and expenses of theAdministrative Agent, including the reasonable fees and out-of-pocket expenses of counsel for theAdministrative Agent incurred prior to or otherwise in connection with this Amendment to the extentinvoiced to the Borrowers.     **5. ****Representations and Warranties****.**On and as of the date hereof, and as of the FifthAmendment Effective Date, after giving effect to this Amendment, each Borrower, Terra Industriesand Terra Capital Holdings hereby represents and warrants to the Lenders as follows:          (a) Each of the representations and warranties contained in Article IV of the CreditAgreement, the other Loan Documents or in any certificate, document or financial or other statementfurnished at any time under or in connection therewith are true and correct in all materialrespects on and as of the date as if made on and as of such date, except to the extent that suchrepresentations and warranties specifically relate to a specific date, in which case suchrepresentations and warranties shall be true and correct in all material respects as of suchspecific date; *provided*, *however*, that references therein to the “*Credit Agreement*” shall be deemedto include this Amendment; and          (b) No Default or Event of Default has occurred and is continuing.     **6. ****Continuing Effect; No other Amendments****.**Except as expressly amended hereby orwaiver herein, all of the terms and provisions of the Credit Agreement and the other LoanDocuments are, and shall remain, in full force and effect. The amendments and consents containedherein shall not constitute an amendment or a waiver of any other provision of the CreditAgreement or the other Loan Documents or for any purpose except as expressly set forth herein.     **7. ****Loan Documents****.**This Amendment is deemed to be a “Loan Document” for the purpo**ses**of the Credit Agreement.     **8. ****Costs and Expenses****.**The Borrowers, Terra Industries and Terra Capital Holdingsagree to pay on demand all reasonable and documented out-of-pocket costs and expenses of theAdministrative Agent in connection with the preparation, execution and delivery of this Amendmentand other instruments and documents to be delivered pursuant hereto, including the reasonable anddocumented fees and