**EXHIBIT 4.5****AMENDMENT NO. 4 TO THE AMENDED AND RESTATED CREDIT AGREEMENT**          Amendment No. 4 (this “*Amendment*”), dated as of February 2, 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 issue certainsenior unsecured notes in an aggregate principal amount of approximately $375,000,000, the proceedsof which will be used by Terra Capital to purchase, redeem, defease or otherwise satisfy all of theexisting Senior Secured Notes and Senior Second Lien Notes and to discharge all of its obligationsthereunder (the “*Refinancing Transaction*”);          WHEREAS, Terra Capital has informed the Administrative Agent that Terra Industries has enteredinto a memorandum of understanding dated as of October 19, 2006 with Kemira GrowHow Oyi (OMXsymbol: KGH1V) (“*Kemira*”) pursuant to which Terra Industries and Kemira have agreed to establish ajoint venture (to be held 50% by Terra Industries and 50% by Kemira) for purposes of operatingfertilizer and associated process chemicals business (the “*New Joint Venture*”); and          WHEREAS, Terra Industries intends that all or substantially all of the assets and/or capitalstock of Terra UK to be contributed to the New Joint Venture and therefore requests that theAdministrative Agent and the Lenders consent to (A) the establishment of the New Joint Venture, (B)the Investment of the assets and/or capital stock of Terra UK as described above and (C) releaseTerra UK from all of its obligations under the Credit Agreement and the other Loan Documents and toterminate any Liens granted by Terra UK in favor of the Administrative Agent;          WHEREAS, the Borrowers, Terra Industries and Terra Capital Holdings have requested, and theLenders and the Administrative Agent have agreed to, certain amendments to the Credit Agreement topermit the occurrence of the Refinancing Transaction, to extend the Scheduled Termination Date, andcertain other amendments 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 Fourth Amendment Effective Date (asdefined in Section 5), the Credit Agreement is hereby amended as follows:          (a) *Section 1.1*of the Credit Agreement is hereby amended as follows:               (i) The grid appearing in the definition of “Applicable Margin” is hereby deleted in itsentirety and inserting the following in lieu thereof:           **Base Rate** **Eurodollar****Leverage Ratio** **Loans** **Rate Loans**Greater than 4.0 to 1  0.75%  2.00%Less than or equal to 4.0 to 1  0.50%  1.75%               (ii) The definition of “Indentures” is hereby amended by (x) deleting the word “and”immediately before clause (d) thereof and replacing it with a “,” and (y) inserting at the end ofsuch definition the following:          and (e) the Senior Unsecured Note (2007) Indenture.               (iii) The definition of “Scheduled Termination Date” is hereby deleted in its entirety and thefollowing is inserted in lieu thereof:          “*Scheduled Termination Date*” means January ___, 2012.          (b) *Section 1.1*of the Credit Agreement is hereby amended by inserting among the existingdefined terms therein in alphabetical order the following defined terms:     “*Amendment No. 4 to the Credit Agreement*” means that certain Amendment No. 4 to theCredit Agreement, dated as of January ___, 2007, entered into among the Borrowers, theAdministrative Agent and the Lenders party thereto.     “*New Joint Venture*” has the meaning specified in Amendment No. 4 to the CreditAgreement.     “*Senior Unsecured Note (2007) Documents*” means the Senior Unsecured Note (2007)Indenture and the Senior Unsecured Notes (2007) and all related documents.     “*Senior Unsecured Note (2007) Indenture*” means the indenture, dated on or aboutFebruary 2, 2007 between Terra Capital and the Senior Unsecured Note (2007) Trustee.     *“Senior Unsecured Notes (2007)*” means the 7.0 % senior unsecured notes due 2017issued or to be issued by Terra Capital pursuant to the Senior Unsecured Note (2007)Indenture.     *“Senior Unsecured Note (2007) Trustee*” means the trustee, together with itssuccessors and assigns in such capacity, appointed in accordance with the provisions ofthe
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Senior Unsecured Note (2007) Indenture to act for the benefit of the holders of theSenior Unsecured Notes (2007).          (c) *Section 5.2*of the Credit Agreement (*Capital Expenditures and Joint Venture Investments*)is hereby deleted in its entirety and the following is inserted in lieu thereof:     **Section 5.2****Capital Expenditures and Joint Venture Investments****.**TerraIndustries will not permit (a) Capital Expenditures (excluding any Capital Expendituresfinanced by insurance proceeds to the extent permitted hereunder) to be made or incurredduring each period set forth below and (b) the cash Investments in joint ventures madeduring such period permitted under *Section 8.3(l*), in aggregate to be in excess of themaximum amount set forth below, for such period:     Fiscal Year Maximum AmountFiscal Year ended December 31, 2006 $58,000,000 Fiscal Year ended December 31, 2007 and each Fiscal Yearthereafter $75,000,000           (d) *Clause (l)*in *Section 8.1*of the Credit Agreement is hereby amended by (x) inserting “(i)”at the beginning of such clause and (y) inserting at the end thereof:     and (ii) Indebtedness in respect of the Senior Unsecured Notes (2007); *provided*,*however*, that the aggregate principal amount of such Indebtedness pursuant to thisclause (ii) shall (x) not exceed at any time $375,000,000 and (y) be directly appliedupon issuance thereof in the refinancing, purchase, redemption, defeasance or othersatisfaction of the Indebtedness described in subclause (i) of this clause (l);          (e) *Clause (j)*in *Section 8.2*of the Credit Agreement is hereby amended by inserting at theend thereof:     , *provided*, *however*, that all such Liens shall be permanently released anddischarged upon the issuance of the Senior Unsecured Notes (2007) and Terra Industriesshall promptly following such issuance deliver to the Administrative Agent copies ofdocuments reasonably satisfactory to the Administrative Agent evidencing such releaseand discharge;          (f) *Sub-clause (ii)*of *Section 8.3 (b)*of the Credit Agreement is hereby amended by deletingthe text “$50,000,000 for more than 5 consecutive Business Days;” and inserting the following inlieu thereof:     $75,000,000 for more than 10 consecutive Business Days;          (g) *Section 8.3*of the Credit Agreement is hereby amended by deleting “.” at the end ofsub-clause “(n)” and inserting in lieu thereof “; and” and thereafter the following new sub-clause:          (o) Investments in the New Joint Venture consisting of the capital stock and/orassets of Terra UK; *provided*, *however*, that (i) there shall not exist any Default orEvent of Default
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immediately prior to or after giving effect to such Investments and (ii) theAdministrative Agent shall have executed and delivered a release of all Terra UK’sobligations and all Liens granted by Terra UK pursuant to the Credit Agreement and theother Loan Documents, (iii) Terra UK shall not have outstanding any Loans or Letters ofCredit for its account under the Credit Agreement and (iv) neither Terra Industries norany of its direct or indirect Subsidiaries (which are not Subsidiaries of Terra UK)shall contribute any of its assets to Terra UK, or otherwise make Investments in TerraUK or its Subsidiaries except to the extent (x) not made in contemplation of thetransactions described in this paragraph (o) and (y) otherwise permitted by thisAgreement.          (h) *Section 8.(4)(f)*of the Credit Agreement is hereby amended by inserting “(i)” immediatelybefore “the aggregate” appearing on the second line of that sub-clause and inserting the followingbefore “;” at the end of such sub-clause:               or (ii) to the extent constituting Investments permitted under *Section 8.3(o)*; and     (i) *Clause (x)*of *Section 8.12*of the Credit Agreement is hereby amended by deleting theentire subclause (1) thereof and inserting the following in lieu thereof:          (1) the purchase, redemption, repayment, defeasance or other satisfaction of theSenior Second Lien Notes and the Senior Secured Notes directly with proceeds of theissuance by Terra Capital of the Senior Unsecured Notes (2007),          **3.****Waiver of Mandatory Prepayment****.**Upon the occurrence of the RefinancingTransaction, the Administrative Agent and the Requisite Lenders waive, solely in connection withthe issuance of the Senior Unsecured Notes (2007), the Borrowers’ obligations to apply 100% of theproceeds of the Senior Unsecured Notes (2007) to the prepayment of outstanding Loans (or providecash collateral in respect of Letters of Credit) as required under Section 2.9(a)(i).          **4.****Consent to Release Terra UK**. Pursuant to *Section 11.1(a)(ix)*of the CreditAgreement, the Lenders hereby authorize the Administrative Agent to execute such releases andamendments and take such other actions as may be required in connection therewith to release (uponconsummation of the New Joint Venture and contribution therein of the capital stock and/or assetsof Terra UK) all of the obligations of Terra UK under the Credit Agreement and the other LoanDocuments (including its obligations as a Guarantor under the Guaranty) and the termination of allLiens granted by Terra UK in favor of the Administrative Agent. The Lenders hereby furtherauthorize the Administrative Agent to prepare and file any release document that may be necessaryto effectuate the foregoing releases including the termination of any filed UCC financingstatements.          **5.****Conditions Precedent to the Effectiveness of this Amendment****.**This Amendment shallbecome effective on the date (the “*Fourth Amendment Effective Date*”) when the following conditionsprecedent have been satisfied:               (a) Certain Documents. The Administrative Agent shall have received on or before theFourth 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 all Lenders;
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                         (ii) a fully executed Amendment No. 2 to the TNLP Credit Agreement providing for the extensionof the Scheduled Termination Date thereunder until January ___, 2012;                         (iii) certified copies of the Senior Unsecured Note (2007) Documents and each other documentand instrument executed and delivered in connection therewith (including all material tender offerdocuments and all related material documents with respect to the satisfaction and discharge of allIndebtedness and Liens with respect to the Senior Secured Notes and Senior Second Lien Notes), dulyexecuted by the parties thereto and each in form and substance reasonably satisfactory to theAdministrative Agent, together with a certificate of the Secretary or an Assistant Secretary ofTerra Capital that, as at the Fourth Amendment Effective Date, such Senior Unsecured Note (2007)Documents and other documents and instruments of which are attached thereto (A) are true andcomplete copies of the originals thereof and (B) are in full force and effect and have not beenmodified or amended from such attached copies; and                         (iv) 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 hereby, andthe other Loan Documents to which any of the Borrowers or the Guarantors is a party or by which theBorrowers or the Guarantors are bound, shall be true and correct in all material respects on and asof the Fourth Amendment Effective Date (other than representations and warranties in any such LoanDocument which expressly speak as of a specific date, which shall have been true and correct in allmaterial respects as of such specific date).               (c) No Event of Default. No Default or Event of Default shall have occurred and becontinuing on the Fourth Amendment Effective Date.               (d) Fees and Expenses Paid. The Borrowers shall have paid to the Administrative Agent(i) the amendment fee referred to in *Section 9*and (ii) in accordance with Section 11.3 of theCredit Agreement, all outstanding costs and expenses of the Administrative Agent, including thereasonable fees and out-of-pocket expenses of counsel for the Administrative Agent incurred priorto or otherwise in connection with this Amendment.          **6.****Representations and Warranties****.**On and as of the date hereof, and as of theFourth Amendment Effective Date, after giving effect to this Amendment, each Borrower, TerraIndustries and 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.
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          **7.****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.          **8.****Loan Documents****.**This Amendment is deemed to be a “Loan Document” for the purpo**ses**of the Credit Agreement.          **9.****Amendment Fees**. As consideration for the execution of this Amendment, theBorrowers agree to pay on the Fourth Amendment Effective Date to the Administrative Agent, for theaccount of each Lender signatory to this Amendment, an amendment fee equal to 0.10% of suchLender’s Revolving Credit Commitment then in effect.          **10.****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 out-of-pocket expenses of counsel for the Administrative Agent with respectthereto.          **11.****Governing Law; Counterparts; Miscellaneous****.**               (a) This Amendment shall be governed by, and construed and interpreted in accordance with, thelaw of the State of New York.               (b) This Amendment may be executed in any number of counterparts and by the different partieson separate counterparts, each of which counterparts when executed and delivered shall be anoriginal, but all of which shall together constitute one and the same instrument.               (c) Section captions used in this Amendment are for convenience only and shall not affect theconstruction of this Amendment.               (d) From and after the Fourth Amendment Effective Date, all references in the Credit Agreementto the “Agreement” shall be deemed to be references to such Agreement as modified hereby and thisAmendment and the Credit Agreement shall be read together and construed as a single instrument.[signature pages follow]
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          IN WITNESS WHEREOF, the undersigned parties have executed this Amendment No. 4 to the Amendedand Restated Credit Agreement to be effective for all purposes as of the Fourth Amendment EffectiveDate.      Borrowers