<PAGE>
 
                                                                     EXHIBIT 4.3



                    MISSISSIPPI BUSINESS FINANCE CORPORATION



                                       TO



                        DEPOSIT GUARANTY NATIONAL BANK,
                                   As Trustee



                           _________________________

                               INDENTURE OF TRUST
                           _________________________



                           Dated as of March 1, 1998



                                                                                
<PAGE>
 
                               INDENTURE OF TRUST

                    (This Table of Contents is not a part of
                    this Indenture of Trust and is only for
                           convenience of reference)

                               TABLE OF CONTENTS

                                                                            PAGE
                                                                            ----

Preamble..................................................................    1
Bond Form.................................................................    3

                                   ARTICLE I
                    DEFINITIONS AND RULES OF INTERPRETATION

Section 1.1.       Definitions.                                               13
Section 1.2.       Rules of Interpretation                                    16

                                   ARTICLE II
                                   THE BONDS

Section 2.1.       Authorized Amount of Bonds                                 16
Section 2.2.       Issuance of Bonds                                          16
Section 2.3.       Execution; Limited Obligation                              17
Section 2.4.       Authentication                                             18
Section 2.5.       Form of Bonds                                              18
Section 2.6.       Delivery of Bonds                                          18
Section 2.7.       Mutilated, Lost, Stolen or Destroyed Bonds                 19
Section 2.8.       Registration and Exchange of Bond; Persons Treated as
                    Owners                                                    19
Section 2.9.       Cancellation of Bonds                                      20
Section 2.10.      Book Entry System                                          20

                                  ARTICLE III
                      REDEMPTION OF BONDS BEFORE MATURITY

Section 3.1.      Redemption Dates and Prices                                 20
Section 3.2.      Notice of Redemption                                        22
Section 3.3.      Deposit of Funds                                            22
Section 3.4.      Partial Redemption of Bonds                                 23
Section 3.5.      Selection of Bonds for Redemption                           23
<PAGE>
 
                                   ARTICLE IV
                               GENERAL COVENANTS

Section 4.1.       Payment of Principal and Interest                          23
Section 4.2.       Performance of Covenants; Issuer                           23
Section 4.3.       Right to Payments under Agreement and Guaranty;              
                    Instruments of Further Assurance                          24
Section 4.4.       Recordation and Other Instruments                          24
Section 4.5.       Inspection of Project Books                                25
Section 4.6.       List of Bondholders                                        25
Section 4.7.       Rights Under Agreement and Guaranty                        25
Section 4.8.       Prohibited Activities                                      25

                                   ARTICLE V
                               REVENUES AND FUNDS

Section 5.1.       Source of Payment of Bonds                                 25
Section 5.2.       Creation of Bond Fund                                      25
Section 5.3.       Payments into Bond Fund                                    26
Section 5.4.       Use of Moneys in Bond Fund                                 26
Section 5.5.       Custody of Bond Fund                                       26
Section 5.6.       Construction Fund                                          26
Section 5.7.       Payments into Construction Fund; Disbursements             26
Section 5.8.       Completion of Project                                      27
Section 5.9.       Transfer of Construction Fund                              27
Section 5.10.      Creation of Refunding Fund                                 27
Section 5.11.      Payments into the Refunding Fund                           27
Section 5.12.      Use of Moneys in the Refunding Fund                        27
Section 5.13.      Non-presentment of Bonds                                   28
Section 5.14.      Moneys to be Held in Trust                                 28
Section 5.15.      Repayment to the Company from Bond Fund                    28
Section 5.16.      Additional Payments Under the Agreement                    28
Section 5.17.      Arbitrage Requirements                                     29
Section 5.18.      Rebate Fund; Tax Agreement                                 29

                                   ARTICLE VI
                              INVESTMENT OF MONEYS

Section 6.1.       Investment of Moneys                                       29

                                  ARTICLE VII
                               DISCHARGE OF LIEN

Section 7.1.       Discharge of Lien                                          30
<PAGE>
 
                                 ARTICLE VIII
           DEFAULT PROVISIONS AND REMEDIES OF TRUSTEE AND BONDHOLDERS

Section 8.1.       Defaults; Events of Default                                31
Section 8.2.       Acceleration                                               32
Section 8.3.       Other Remedies; Rights of Bondholders                      32
Section 8.4.       Right of Bondholders to Direct Proceedings                 32
Section 8.5.       Appointment of Receivers                                   33
Section 8.6.       Reserved                                                   33
Section 8.7.       Application of Moneys                                      33
Section 8.8.       Remedies Vested in Trustee                                 34
Section 8.9.       Rights and Remedies of Bondholders                         34
Section 8.10.      Termination of Proceedings                                 35
Section 8.11.      Waivers of Events of Default                               35
Section 8.12.      Notice of Defaults under Section 8.1(c); Opportunity of
                    the Issuer and the Company to Cure Such Defaults          36
Section 8.13.      Notice to Bondholders; Defaults; Acceleration              36

                                   ARTICLE IX
                                  THE TRUSTEE

Section 9.1.       Acceptance of Trusts                                       36
Section 9.2.       Fees, Charges and Expenses of the Trustee                  39
Section 9.3.       Trustee as Paying Agent and Registrar                      39
Section 9.4.       Intervention by the Trustee                                39
Section 9.5.       Successor Trustee                                          40
Section 9.6.       Resignation by the Trustee                                 40
Section 9.7.       Removal of the Trustee                                     40
Section 9.8.       Appointment of Successor Trustee by Bondholders or Issuer  40
Section 9.9.       Concerning Any Successor Trustee                           41
Section 9.10.      Appointment of Co-Trustee                                  41
Section 9.11.      Representations, Warranties and Covenants of the Trustee   42
Section 9.12.      Required Reporting to Issuer                               42

                                   ARTICLE X
                            SUPPLEMENTAL INDENTURES

Section 10.1.      Supplemental Indentures Not Requiring Consent of
                    Bondholders                                               43
Section 10.2.      Supplemental Indentures Requiring Consent of Bondholders   44
Section 10.3.      Consent of Company                                         44
Section 10.4.      Opinion of Bond Counsel                                    45
<PAGE>
 
                                   ARTICLE XI
                      AMENDMENT OF AGREEMENT AND GUARANTY
 
Section 11.1.       Amendments, etc., to Agreement and Guaranty Not
                     Requiring Consent of Bondholders                         45
Section 11.2.       Amendments, etc., to Agreement and Guaranty Requiring
                     Consent of Bondholders                                   45
Section 11.3.       Opinion of Bond Counsel                                   46

                                  ARTICLE XII
                                 MISCELLANEOUS

Section 12.1.      Consents, etc., of Bondholders                             46
Section 12.2.      Limitation of Rights                                       47
Section 12.3.      Severability                                               47
Section 12.4.      Notices                                                    47
Section 12.5.      Payments Due on Saturdays, Sundays and Holidays            48
Section 12.6.      Action by Company and Issuer                               48
Section 12.7.      Counterparts                                               48
Section 12.8.      Applicable Provisions of Law                               48
Section 12.9.      No Recourse                                                48
<PAGE>
 
                               INDENTURE OF TRUST

  THIS INDENTURE OF TRUST dated as of March 1, 1998, by and between the
MISSISSIPPI BUSINESS FINANCE CORPORATION, a public corporation created under the
laws of the State of Mississippi, including the Act, party of the first part
(hereinafter sometimes referred to as the "Issuer"), and DEPOSIT GUARANTY
NATIONAL BANK, a national banking association duly organized, existing and
authorized to accept and execute trusts of the character herein set out under
and by virtue of the laws of the United States, with its principal corporate
trust office located in Jackson, Mississippi, as trustee (hereinafter sometimes
referred to as the "Trustee"), party of the second part,

                              W I T N E S S E T H:

  WHEREAS, pursuant to the authority set forth in Section 57-10-201 et seq.,
Mississippi Code of 12972, as amended (the "Act"), and Indenture of Trust dated
as of July 1, 1997 (the "Series 1997A Indenture"), between the Issuer and the
Trustee, the Issuer has hitherto issued its Solid Waste Disposal Revenue Bonds
(Mississippi Phosphates Corporation Project) Series 1997A (the "Series 1997A
Bonds") in the principal amount of $6,000,000, the proceeds of which were loaned
to Mississippi Phosphates Corporation, a Delaware corporation (the "Company"),
and used to finance a portion of the costs of the Project (as hereinafter
defined); and

  WHEREAS, the proceeds of the Series 1997A Bonds were loaned to the Company
pursuant to the terms of a Loan Agreement dated as of July 1, 1997 (the "Series
1997A Loan Agreement") between the Issuer and the Company; and
 
  WHEREAS, pursuant to the Act and an Indenture of Trust dated as of July 1,
1997 (the "Series 1997B Indenture"), between the Issuer and the Trustee, the
Issuer has hitherto issued its Solid Waste Disposal Revenue Bonds (Mississippi
Phosphates Corporation Project) Series 1997B (the "Series 1997B Bonds") in the
principal amount of $8,500,000, the proceeds of which were loaned to the Company
and used to finance a portion of the costs of the Project; and

  WHEREAS, the proceeds of the Series 1997B Bonds were loaned to the Company
pursuant to the terms of a Loan Agreement dated as of July 1, 1997 (the "Series
1997B Loan Agreement") between the Issuer and the Company; and

  WHEREAS, the Issuer is authorized and empowered by the provisions of the Act
to issue its limited obligation revenue bonds in accordance with the Act and to
make secured or unsecured loans for the purpose of refunding the outstanding
Series 1997A Bonds and the Series 1997B Bonds (collectively, the "Series 1997
Bonds"), and to pledge the proceeds of any loan agreements as security for the
payment of the principal of, premium, if any, and interest on such revenue
bonds; and
<PAGE>
 
  WHEREAS, the Issuer is entering into a Loan Agreement of even date herewith
with the Company in which the Issuer has agreed to loan the proceeds of its
Solid Waste Disposal Revenue Refunding Bonds (Mississippi Phosphates Corporation
Project) Series 1998 (the "Bonds") to the Company to defray the cost of
refunding the outstanding principal amount of the Series 1997 Bonds and pursuant
to which the Company has agreed to repay the loan in an amount sufficient to pay
the principal of, premium, if any, and interest on the Bonds when due; and

  WHEREAS, the Issuer has determined that the Bonds in the aggregate principal
amount of $14,500,000 should be issued, sold and delivered pursuant to the Act
and this Indenture to provide proceeds for loan to the Company to provide for
the refunding of the Series 1997 Bonds;  and

  WHEREAS, the Issuer has contracted for the sale and delivery of the Bonds to
be issued in the aggregate principal amount of $14,500,000 as herein provided;
and

  WHEREAS, all Bonds issued under this Indenture will be secured by a pledge and
assignment of the aforesaid Loan Agreement (except as otherwise herein
provided); and

  WHEREAS, the Bonds and the Trustee's certificate of authentication to be
endorsed on the Bonds are to be in substantially the following form, with
appropriate variations, omissions and insertions as permitted or required by
this Indenture, to-wit:
<PAGE>
 
                                (FORM OF BONDS)

                            UNITED STATES OF AMERICA

                              STATE OF MISSISSIPPI

                    MISSISSIPPI BUSINESS FINANCE CORPORATION
                  SOLID WASTE DISPOSAL REVENUE REFUNDING BOND
                  (MISSISSIPPI PHOSPHATES CORPORATION PROJECT)
                                  SERIES 1998

Registered  Registered

No. R-__________  $_______________

Interest Rate:                        Maturity Date:  CUSIP No.:
-------------                         -------------   --------- 
   5.80%                              March 1, 2022  ________________

Registered Owner:

Principal Amount:

     KNOW ALL MEN BY THESE PRESENTS that the MISSISSIPPI BUSINESS FINANCE
CORPORATION (the "Issuer"), a public corporation created under the laws of the
State of Mississippi, for value received, promises to pay (but only out of the
sources and in the manner as hereinafter provided) to the Registered Owner
identified above, or registered assigns as hereinafter provided, on the Maturity
Date identified above, except as the provisions set forth in the Indenture with
respect to redemption prior to maturity may become applicable hereto, the
Principal Amount identified above, and in like manner to pay interest on said
Principal Amount from the date hereof at the Interest Rate per annum identified
above, payable semiannually on March 1 and September 1 of each year, commencing
September 1, 1998 (each, an "Interest Payment Date"), until said Principal
Amount is paid.  The principal of this Bond shall be payable in lawful money of
the United States of America at the principal corporate trust office of Deposit
Guaranty National Bank, a national banking association organized under the laws
of the United States, as Trustee, or its successor in trust (the "Trustee").
Payment of interest on any Interest Payment Date shall be made in lawful money
of the United States of America to the Registered Owner hereof as of the close
of business on the Record Date with respect to such Interest Payment Date and
shall be paid (i) by check or draft mailed to such Registered Owner at his
address as it appears on the registration books of the Issuer maintained by the
Trustee or (ii) at the option of any Registered Owner of at least $1,000,000 in
aggregate principal amount of the Bonds, by wire transfer or other means
acceptable to the Trustee at an address within the United States upon written
instructions filed by such Registered Owner with the Trustee not later than the
close of business on such Record Date (which instructions shall remain in effect
until revoked by subsequent written instructions).
<PAGE>
 
     THIS BOND AND THE OBLIGATION TO PAY INTEREST HEREON ARE LIMITED OBLIGATIONS
OF THE ISSUER, SECURED AS AFORESAID AND PAYABLE SOLELY OUT OF THE REVENUES AND
INCOME DERIVED FROM THE HEREINAFTER DEFINED AGREEMENT AND AS OTHERWISE PROVIDED
IN THE HEREINAFTER DEFINED INDENTURE AND AGREEMENT.  THIS BOND AND THE
OBLIGATION TO PAY INTEREST HEREON SHALL NOT BE DEEMED TO CONSTITUTE AN
INDEBTEDNESS OR AN OBLIGATION OF THE ISSUER, THE STATE OF MISSISSIPPI OR ANY
POLITICAL SUBDIVISION THEREOF WITHIN THE PURVIEW OF ANY CONSTITUTIONAL
LIMITATION OR PROVISION OR A CHARGE AGAINST THE GENERAL CREDIT OR TAXING POWERS,
IF ANY, OF ANY OF THEM.  THE ISSUER HAS NO TAXING POWER.  NO OWNER OF THIS BOND
SHALL HAVE THE RIGHT TO COMPEL ANY EXERCISE OF THE TAXING POWER, IF ANY, OF THE
ISSUER, THE STATE OF MISSISSIPPI OR ANY POLITICAL SUBDIVISION THEREOF TO PAY ANY
PRINCIPAL INSTALLMENT OF, OR INTEREST ON, THIS BOND.

                           _________________________

     REFERENCE IS HEREBY MADE TO THE FURTHER PROVISIONS OF THIS BOND SET FORTH
ON THE REVERSE HEREOF AND SUCH FURTHER PROVISIONS SHALL FOR ALL PURPOSES HAVE
THE SAME EFFECT AS IF SET FORTH AT THIS PLACE.

                           _________________________

     This Bond shall not be valid or become obligatory for any purpose or be
entitled to any security or benefit under the Indenture until the certificate of
authentication hereon shall have been manually executed by the Trustee.

     This Bond is issued with the intent that the laws of the State of
Mississippi will govern its construction.

     IT IS HEREBY CERTIFIED, RECITED AND DECLARED that all acts, conditions and
things required to exist, happen and be performed precedent to and in the
execution and delivery of the Indenture and the issuance of this Bond do exist,
have happened and have been performed in due time, form and manner as required
by law; and that the issuance of this Bond and the series of which it forms a
part does not exceed or violate any constitutional or statutory limitation.
<PAGE>
 
     IN WITNESS WHEREOF, the MISSISSIPPI BUSINESS FINANCE CORPORATION has caused
this Bond to be executed in its name by the manual or facsimile signature of its
Executive Director, and its corporate seal to be impressed or imprinted hereon,
attested by the manual or facsimile signature of its Secretary, all as of the
1st day of March, 1998.

                                       MISSISSIPPI BUSINESS FINANCE CORPORATION
 
 
                                       By: ____________________________________
                                                   Executive Director

ATTEST:

______________________
Secretary

[SEAL]



               [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

  This Bond is one of the Bonds of the issue described in the within mentioned
Indenture of Trust.

Date of Authentication:

                                        DEPOSIT GUARANTY NATIONAL BANK,
  as Trustee


  By: ______________________________
           Authorized Signatory


                           (FORM OF REVERSE OF BONDS)

  This Bond is one of an authorized series of Bonds in the aggregate principal
amount of $14,500,000 (the "Bonds") issued for the purpose of funding a loan by
the Issuer to Mississippi Phosphates Corporation, a Delaware corporation (the
"Company"), for the purpose of refunding those certain Mississippi Business
Finance Corporation Solid Waste Disposal Revenue Bonds (Mississippi Phosphates
Corporation Project) Series 1997A (the "Series 1997A Bonds") and those certain
Mississippi Business Finance Corporation Solid Waste Disposal Revenue Bonds
<PAGE>
 
(Mississippi Phosphates Corporation Project) Series 1997B (the "Series 1997B
Bonds"), the proceeds of which Series 1997A Bonds and Series 1997B Bonds
(collectively, the "Series 1997 Bonds") have been used to provide financing for
the cost of land, buildings and equipment to be acquired, constructed and
installed by the Company (the "Project") for the disposal of solid waste which
solid waste is generated by the Company's chemical fertilizer manufacturing
plant  in Jackson County, Mississippi (the "Plant").

  The Bonds are all issued under and are equally and ratably secured by and
entitled to the protection of an Indenture of Trust dated as of March 1, 1998
(which indenture, as from time to time amended and supplemented, is herein
referred to as the "Indenture"), duly executed and delivered by the Issuer to
the Trustee.  Reference is hereby made to the Indenture for a description of the
rights, duties and obligations of the Issuer, the Trustee and the owners of the
Bonds and the terms upon which the Bonds are issued and secured.  The terms and
conditions of the  loan of the proceeds of the Bonds to the Company to provide
for the refunding of the principal of the Series 1997 Bonds and to provide for
the payment of a portion of the costs of issuance of the Bonds, and the
repayment of said loan, are contained in a Loan Agreement dated as of March 1,
1998, between the Issuer and the Company (which agreement, as from time to time
amended and supplemented, is herein referred to as the "Agreement").  The
Project is not pledged as security for the Bonds.

  This Bond is issued pursuant to and in full compliance with the Constitution
and laws of the State of Mississippi, and particularly the Act, and pursuant to
a resolution duly adopted by the Issuer authorizing, among other things, the
execution and delivery of the Indenture.  The Bonds are limited obligations of
the Issuer payable solely from certain payments provided to be made by the
Company under the Agreement, which payments are designed to be sufficient to pay
the principal of, premium, if any  and interest on the Bonds as the same become
due and payable.  The Bonds are further secured by the unlimited guaranty of
Mississippi Chemical Corporation, the corporate parent of the Company, pursuant
to a Guaranty Agreement dated as of March 1, 1998.  The principal of, premium,
if any  and interest on the Bonds are payable solely from the funds pledged for
their payment in accordance with the proceedings authorizing their issuance and
the Indenture.  All payments under the Agreement are to be paid to the Trustee
for the account of the Issuer and deposited in a special trust fund created by
the Issuer, maintained by the Trustee and designated "Mississippi Business
Finance Corporation Solid Waste Disposal Revenue Refunding Bonds (Mississippi
Phosphates Corporation Project) Series 1998 Bond Fund," and, in addition, the
rights of the Issuer under the Agreement (except the right to receive certain
fee, expense and indemnification payments and to receive notices) have been
assigned and pledged to the Trustee to secure the payment of such principal and
interest under the Indenture.

  This Bond is transferable by the Registered Owner hereof in person or by his
attorney duly authorized in writing at the principal corporate trust office of
the Trustee, but only in the manner, subject to the limitations and upon payment
of the charges provided in the Indenture, and upon surrender and cancellation of
this Bond.  Upon such transfer a new registered Bond or Bonds of an Authorized
Denomination or Authorized Denominations, for the same aggregate principal
amount, will be issued to the transferee in exchange therefor.  Subject to the
limitations
<PAGE>
 
and upon payment of the charges provided in the Indenture, and upon surrender
and cancellation thereof, Bonds may be exchanged for a like aggregate principal
amount of Bonds of another Authorized Denomination or Authorized Denominations.
The Trustee shall not be required to transfer or exchange any Bond from the
fifteenth day of the month next preceding an Interest Payment Date and such
Interest Payment Date, nor to transfer or exchange any Bond after the mailing of
notice calling such Bond or a portion thereof for redemption, nor during the
period of fifteen days next preceding the giving of such notice of redemption.
The Issuer and the Trustee may deem and treat the Registered Owner hereof as the
absolute owner hereof for the purpose of receiving payment of or on account of
principal hereof and interest due hereon and for all other purposes and neither
the Issuer nor the Trustee shall be affected by any notice to the contrary.

  The Bonds are subject to extraordinary optional redemption at any time in
whole, but not in part, at a redemption price equal to 100% of the principal
amount thereof plus accrued interest, if any, to the redemption date, upon the
exercise by the Company of its option to prepay loan repayment installments
under the Agreement, if any of the following shall have occurred:

         (a)  The Project or the Plant shall have been damaged or destroyed
     (in whole or in part) by fire or other casualty to such extent that, in the
     opinion of the Company, it is not practicable or desirable to rebuild,
     repair or restore the Project or the Plant; or

         (b)  Title to, or the temporary use of, all or substantially all the
     Project or Plant shall have been taken under the exercise of the power of
     eminent domain by any governmental authority, or person, firm or
     corporation acting under governmental authority; or

         (c)  Changes in the economic availability of raw materials, operating
     supplies or facilities necessary for the operation of the Project or Plant
     shall have occurred or such technological or environmental or other changes
     shall have occurred which, in the Company's judgment, render the continued
     operation of the Project or Plant uneconomic.

  The Bonds are subject to optional redemption prior to maturity at the election
of the Corporation on March 1, 2008, and thereafter, either as a whole or in
part on any date from any moneys that may be made available for such purpose, at
the following redemption prices (expressed as a percentage of principal amount
or portion thereof to be redeemed), plus accrued interest to the redemption
date:

       Redemption Dates (Inclusive)                          Redemption Price
       ----------------------------                          ----------------
  March 1, 2008 through February 28, 2009                         102%
  March 1, 2009 through February 28, 2010                         101%
  March 1, 2010 and thereafter                                    100%
<PAGE>
 
  The Bonds are subject to mandatory redemption at any time in whole (or in the
case of the events stated in (b) or (c) of this paragraph, in whole or in part
as provided in the Indenture), at a redemption price equal to 100% of the
principal amount thereof plus accrued interest, if any, to the redemption date,
if any of the following shall have occurred:

         (a)  As a result of any changes in the Constitution of the State of
     Mississippi or the Constitution of the United States of America or of
     legislative or administrative action (whether state or federal) or by final
     decree, judgment or order of any court or administrative body (whether
     state or federal) the Agreement shall have become void or unenforceable or
     impossible to perform in accordance with the intent and purposes of the
     parties as expressed in the Agreement; or

         (b)  A final determination by the Internal Revenue Service or a court
     of competent jurisdiction as a result of a proceeding in which the Company
     participates to the degree it deems sufficient, which determination the
     Company, in its discretion, does not contest by an appropriate proceeding,
     that, as a result of failure by the Company to observe any covenant,
     agreement or representation by the Company in the Agreement, the interest
     payable on the Bonds or any of them is includable for federal income tax
     purposes in the gross income of any owner of a Bond (other than an owner
     who is a "substantial user" of the Project or a "related person" within the
     meaning of Section 147 of the Code and the applicable regulations
     thereunder); or

         (c)  Proceeds of the Series 1997 Bonds, including income from the
     investment thereof, in an amount equal to or greater than $100,000 shall
     remain after completion of the Project and the payment of all costs of the
     Project.

  In the event any of the Bonds or portions thereof (in Authorized
Denominations) are called for redemption as aforesaid, notice thereof
identifying the Bonds or portions thereof to be redeemed will be given by the
Trustee by mailing a copy of the redemption notice by first-class mail at least
thirty (30) days prior to the date fixed for redemption to the Registered Owner
of each Bond to be redeemed in whole or in part at the address shown on the
registration books; provided, however, that failure to give such notice by
mailing, or any defect therein, shall not affect the validity of any proceeding
for the redemption of any Bond with respect to which no such failure or defect
has occurred.  Any notice mailed in such manner shall be conclusively presumed
to have been duly given whether or not the Registered Owner receives such
notice.  If less than all of the Bonds are to be redeemed, Bonds or portions
thereof (in Authorized Denominations) shall be selected by lot in the manner
provided in the Indenture.  All Bonds or portions thereof so called for
redemption will cease to bear interest on and after the specified redemption
date provided funds for the redemption thereof are on deposit with the Trustee
at that time.

  The Registered Owner of this Bond shall have no right to enforce the
provisions of the Indenture or the Agreement or to institute action to enforce
the covenants therein, or to take any action with respect to any event of
default under the Indenture or the Agreement, or to institute,
<PAGE>
 
appear in or defend any suit or other proceedings with respect thereto, except
as provided in the Indenture. In certain events, on the conditions, in the
manner and with the effect set forth in the Indenture, the principal of all the
Bonds issued under the Indenture and then outstanding may become or may be
declared due and payable before the stated maturity thereof, together with
interest accrued thereon. The Indenture prescribes the manner in which it may be
discharged, including a provision that under certain circumstances the Bonds
shall be deemed to be paid if Governmental Obligations, maturing as to principal
and interest in such amounts and at such times as will, without reinvestment,
provide sufficient funds to pay the principal of, premium, if any and interest
on the Bonds, shall have been deposited with the Trustee, and all fees and
expenses of the Trustee and all other liabilities of the Company under the
Agreement are paid or provided for, after which the Bonds shall no longer be
secured by or entitled to the benefits of the Indenture or the Agreement, except
for purposes of exchange and transfer and payment from such Governmental
Obligations on the date or dates specified at the time of such deposit.

  The Indenture permits the amendment thereof and the modification of the rights
and obligations of the Issuer and the rights of the owners of the Bonds at any
time by the Issuer with the consent of the owners of not less than a majority,
or in certain instances 100%, in aggregate principal amount of the Bonds at the
time outstanding, as defined in the Indenture.  Any such consent or waiver by
the owner of this Bond shall be conclusive and binding upon such owner and upon
all future owners of this Bond and of any Bond issued upon the transfer or
exchange of this Bond, whether or not notation of such consent or waiver is made
upon this Bond.  The Indenture also contains provisions permitting the Trustee
to enter into certain supplemental indentures without the consent of the owners
of the Bonds and to waive certain past defaults under the Indenture and their
consequences.  No supplemental indenture will become effective without the
consent of the Company.

  No recourse shall be had for the payment of the principal of, premium, if any
and interest on any of the Bonds or for any claim based thereon or upon any
obligation, covenant or agreement in the Indenture or the Agreement contained,
against any past, present or future member, officer, agent or employee of the
Issuer, under any rule of law or equity, statute or constitution or by the
enforcement of any assessment or penalty or otherwise, and all such liability of
any such member, officer, employee, director or agent as such is hereby
expressly waived and released as a condition of and consideration for the
execution of the Indenture or the Agreement and the issuance of any of the
Bonds.

  Terms which are used herein as defined terms and which are not otherwise
defined herein shall have the meanings assigned to them in the Indenture.
<PAGE>
 
                              (FORM OF ASSIGNMENT)

  The following abbreviations, when used in the inscription on the face of this
Bond, shall be construed as though they were written out in full according to
applicable laws or regulations:

                                                UNIF GIFT MIN ACT--
TEN COM    __as tenants in common               _____________________________
TEN ENT    __as tenants by the                  (Custodian)
             entireties                         under Uniform Gifts to Minors 
JT TEN     __as joint tenants with right        Act of
             of survivorship and not as         _____________________________
             tenants in common                  (State)

  Additional abbreviations may also be used though not in the above list.

  FOR VALUE RECEIVED, the undersigned sells, assigns and transfers unto

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________
                         (Name and Address of Assignee)

the within Bond of the Mississippi Business Finance Corporation and does hereby
irrevocably constitute and appoint to transfer said Bond on the books kept for
registration thereof with full power of substitution in the premises.


Dated:  __________________


Signature Guaranteed:


__________________________

NOTICE: The signature to this assignment must correspond with the name as
it appears upon the face of the within Bond in every particular, without
alteration or enlargement or any change whatever; and

NOTICE: Signature(s) must be guaranteed by a member firm of the Securities
Transfer Agent Medallion Program.
<PAGE>
 
                             VALIDATION CERTIFICATE

  The issue of the Bonds of which this Bond is one has been validated and
confirmed by decree of the Chancery Court of the First Judicial District of
Hinds County, Mississippi, rendered on the ____day of _______, 1998.



                             (END OF FORM OF BONDS)
<PAGE>
 
  WHEREAS, all things necessary to make the Bonds, when authenticated by the
Trustee and issued as in this Indenture provided, the valid, binding and legal
obligations of the Issuer according to the import thereof, and to constitute
this Indenture a valid assignment and pledge of the amounts assigned and pledged
to the payment of the principal of, premium, if any and interest on the Bonds
and a valid assignment of certain rights of the Issuer under the Agreement have
been done and performed, and the creation, execution and delivery of this
Indenture, and the creation, execution and issuance of the Bonds, subject to the
terms hereof, have in all respects been duly authorized;

                                GRANTING CLAUSES

              NOW, THEREFORE, THIS INDENTURE OF TRUST WITNESSETH;

  That the Issuer in consideration of the premises and the acceptance by the
Trustee of the trusts hereby created and of the purchase and acceptance of the
Bonds by the owners thereof, and for other good and valuable considerations, the
receipt of which is hereby acknowledged, in order to secure the payment of the
principal of, premium, if any and interest on the Bonds according to their tenor
and effect and to secure the performance and observance by the Issuer of all the
covenants expressed or implied herein and in the Bonds, does hereby grant,
bargain, sell, convey, assign and pledge, and grant a security interest in, to
Deposit Guaranty National Bank, as Trustee, and its successors in trust and
assigns forever, to the extent provided in this Indenture:

                             GRANTING CLAUSE FIRST

  All of the rights and interest of the Issuer in and to the Loan Agreement
dated as of March 1, 1998, between the Issuer and Mississippi Phosphates
Corporation, except for the rights of the Issuer to receive notices thereunder
and the rights of the Issuer under Sections 4.2(c), 5.2 and 6.3 of said Loan
Agreement, and all rights of the Issuer in and to the Guaranty Agreement dated
as of March 1, 1998, delivered by Mississippi Chemical Corporation.

                             GRANTING CLAUSE SECOND

  All moneys and securities from time to time held by the Trustee under the
terms of this Indenture and any and all other real or personal property of every
name and nature from time to time hereafter by delivery or by writing of any
kind conveyed, mortgaged, pledged, assigned or transferred, as and for
additional security hereunder by the Issuer or by anyone in its behalf, or with
its written consent to the Trustee which is hereby authorized to receive any and
all such property at any and all times and to hold and apply the same subject to
the terms hereof.

  TO HAVE AND TO HOLD all and singular the Trust Estate, whether now owned or
hereafter acquired, unto the Trustee and its respective successors in said trust
and assigns forever:

  IN TRUST NEVERTHELESS, upon the terms and trusts herein set forth for the
equal and proportionate benefit, security and protection of all present and
future owners of the Bonds
<PAGE>
 
from time to time issued under and secured by this Indenture without privilege,
priority or distinction as to the lien or otherwise of any of the Bonds over any
of the other Bonds (except as herein otherwise expressly provided);

  PROVIDED, HOWEVER, that if the Issuer, its successors or assigns, shall well
and truly pay, or cause to be paid, the principal of, premium, if any  and
interest on the Bonds due or to become due, at the times and in the manner
mentioned in the Bonds according to the true intent and meaning thereof, and
shall cause the payments to be made on the Bonds as required under Article IV
hereof, or shall provide, as permitted hereby, for the payment thereof by
depositing with the Trustee the entire amount due or to become due thereon (or
Governmental Obligations sufficient for that purpose as provided in Article VII
hereof), and shall pay or cause to be paid to the Trustee all sums of money due
or to become due to it in accordance with the terms and provisions hereof, then
upon the final payment thereof or provision therefor this Indenture and the
rights hereby granted shall cease, determine and be void; otherwise this
Indenture to be and remain in full force and effect.

  THIS INDENTURE OF TRUST FURTHER WITNESSETH, and it is expressly declared that,
all Bonds issued and secured hereunder are to be issued, authenticated and
delivered and all property, rights and interest, including, without limitation,
the amounts hereby assigned and pledged, are to be dealt with and disposed of
under, upon and subject to the terms, conditions, stipulations, covenants,
agreements, trusts, uses and purposes as hereinafter expressed, and Issuer has
agreed and covenanted, and does hereby agree and covenant with the Trustee and
with the respective owners of the Bonds as follows (subject, however, to the
provisions of Section 2.3 hereof):


                                   ARTICLE I
                    DEFINITIONS AND RULES OF INTERPRETATION
                                        
  SECTION 1.1.  DEFINITIONS.  All words and phrases defined in the Recitals
hereof and in Article I of the Agreement shall have the same meaning in this
Indenture.  All words when capitalized herein but not defined shall have the
meaning provided in the Agreement.  In addition, the following words and phrases
shall have the following meanings:

  "Act" means the Mississippi Small Business Financing Act, appearing as Section
57-10-201 et seq., Mississippi Code of 1972, as amended.

  "Affiliate" means any person directly or indirectly controlling or controlled
by or under direct or indirect common control with another person.  For the
purposes of this definition, "control" when used with respect to a person means
the power to direct the management and policies of such person, directly or
indirectly, whether through the ownership of voting securities, by contract or
otherwise, and the terms "controlling" and "controlled" have meanings
correlative to the foregoing.

  "Agreement" means the Loan Agreement of even date herewith, between the Issuer
and the Company, and any amendments and supplements thereto.
<PAGE>
 
  "Authorized Denominations" means $100,000 and any integral multiple thereof.

  "Bondholder" or "holder" or "owner" means the Registered owner of any Bond.

  "Bonds" means the $14,500,000 aggregate principal amount of Bonds authorized
to be issued by the Issuer pursuant to the terms and conditions of Sections 2.1
and 2.2 hereof.

  "Default" or "event of default" means any occurrence or event specified in and
defined by Section 8.1 hereof.

  "Governmental Obligations" means noncallable direct general obligations of, or
obligations the payment of the principal and interest of which are
unconditionally guaranteed by, the United States of America.

  "Interest Payment Date" means March 1 and September 1 of each year, commencing
September 1, 1998.

  "Outstanding" or "Bonds outstanding" means all Bonds which have been
authenticated and delivered by the Trustee under this Indenture, except:

       (a) Bonds canceled after purchase or because of payment at, or redemption
     prior to, maturity;

       (b) Bonds or portions thereof (of Authorized Denominations) for the
     payment or redemption of which cash funds or Governmental Obligations shall
     have been theretofore deposited with the Trustee (whether upon or prior to
     the maturity or redemption date of any such Bonds or portions thereof);
     provided that, if such Bonds or portions thereof are to be redeemed prior
     to the maturity thereof, notice of such redemption shall have been given or
     arrangements satisfactory to the Trustee shall have been made therefor, or
     waiver of such notice satisfactory in form to the Trustee shall have been
     filed with the Trustee; and

       (c) Bonds in lieu of which others have been authenticated under Section
     2.7 hereof.

  If this Indenture shall have been discharged pursuant to the provisions of
Article VII hereof, no Bonds shall be deemed to be outstanding within the
meaning of this provision.

  "Paying Agent" means the Trustee.

  "Plant" means the chemical fertilizer manufacturing plant operated by the
Company in Pascagoula, Mississippi.
<PAGE>
 
  "Project" means the land and those items of machinery, equipment, structures
and related property purchased or to be purchased, acquired, constructed or
installed with proceeds from the sale of the Series 1997 Bonds or the proceeds
of any payment by the Company pursuant to Section 3.4 of the Agreement, as more
particularly described in Exhibit A to the Agreement.

  "Project Site" means the real property upon which the Company is constructing
its solid waste disposal facilities in Jackson County, Mississippi, as it may at
any time exist and as it currently exists.

  "Record Date" means the fifteenth day of the month next preceding an Interest
Payment Date.

  "Registered owner" shall mean the person or persons in whose name or names a
Bond shall be registered on books of the Issuer kept by the Trustee for that
purpose in accordance with the terms of this Indenture.

  "Registrar" means the Trustee.

  "Revenues" means all amounts payable pursuant to Section 4.2(a) of the
Agreement.

  "Series 1997A Bonds" means the Mississippi Business Finance Corporation Solid
Waste Disposal Revenue Bonds (Mississippi Phosphates Corporation Project) Series
1997A issued in the principal amount of $6,000,000.

  "Series 1997B Bonds" means the Mississippi Business Finance Corporation Solid
Waste Disposal Revenue Bonds (Mississippi Phosphates Corporation Project) Series
1997B issued in the principal amount of $8,500,000.

  "Series 1997A Indenture" means the Indenture of Trust dated as of July 1,
1997, between the Issuer and the Trustee pertaining to the Series 1997A Bonds.

  "Series 1997B Indenture" means the Indenture of Trust dated as of July 1,
1997, between the Issuer and the Trustee pertaining to the Series 1997B Bonds.

  "Tax Agreement" means the Tax Exemption Certificate and Agreement with respect
to the Bonds, dated the date of the delivery of the Bonds, among the Company,
the Issuer and the Trustee, as it may hereafter be amended or supplemented.

  "Trust Estate" means the property conveyed to the Trustee pursuant to the
Granting Clauses hereof.
<PAGE>
 
  "Trustee" means Deposit Guaranty National Bank and its successors and any
corporation resulting from or surviving any consolidation or merger to which it
or its successors may be a party and any successor trustee and/or co-trustee at
the time serving as such hereunder.

  "Underwriter" means BancAmerica ROBERTSON STEPHENS.

  SECTION 1.2.  RULES OF INTERPRETATION.  The following rules of interpretation
shall govern the interpretation of this Indenture unless the context clearly
indicates otherwise:

  The words "hereof", "herein", "hereunder" and other words of similar import
refer to this Indenture as a whole.

  References to Articles, Sections and other subdivisions of this Indenture are
to the designated Articles, Sections and other subdivisions of this Indenture as
originally executed.

  The plural includes the singular, and the singular includes the plural.

  The headings of this Indenture are for convenience only and shall not define
or limit the provisions hereof.


                                   ARTICLE II
                                   THE BONDS
                                        
  SECTION 2.1.  AUTHORIZED AMOUNT OF BONDS.  No Bonds may be issued under the
provisions of this Indenture except in accordance with this Article.  The total
principal amount of Bonds that may be issued is hereby expressly limited to
$14,500,000, except as provided in Section 2.7 hereof.

  SECTION 2.2.  ISSUANCE OF BONDS.  The Bonds shall be designated "Mississippi
Business Finance Corporation Solid Waste Disposal Revenue Refunding Bonds
(Mississippi Phosphates Corporation Project) Series 1998," and shall be issuable
only as fully registered Bonds without coupons in Authorized Denominations.
Unless the Issuer shall otherwise direct, the Bonds shall be numbered separately
from 1 upward.

  The Bonds shall be dated as of March 1, 1998 and shall mature, subject to
prior redemption, upon the terms and conditions hereinafter set forth, on March
1, 2022.  The Bonds shall bear interest at the rate of five and eight-tenths
percent (5.80%) per annum from and including the date thereof until payment of
the principal or redemption price thereof shall have been made or provided for
in accordance with the provisions hereof, whether at maturity, upon redemption
or otherwise.  Interest on the Bonds shall be computed upon the basis of a 360-
day year, consisting of twelve (12) thirty (30) day months.  Each Bond shall
bear interest on overdue principal and, to the extent permitted by law, on
overdue interest at the rate of interest borne by the Bonds.
<PAGE>
 
  The principal of the Bonds shall be payable in lawful money of the United
States of America at the principal corporate trust office of the Trustee.
Payment of interest on any Bond on any Interest Payment Date shall be made in
lawful money of the United States of America to the Registered owner as of the
close of business on the Record Date immediately prior thereto and shall be paid
(i) by check or draft mailed on the applicable Interest Payment Date to the
Registered owner at his address as it appears on the registration books of the
Issuer maintained by the Trustee or (ii) at the option of any Registered owner
of at least $1,000,000 in aggregate principal amount of the Bonds, by wire
transfer or other means acceptable to the Trustee at an address within the
United States upon written instructions filed by such Registered owner with the
Trustee not later than the close of business on the Record Date immediately
prior thereto (which instructions shall remain in effect until revoked by
subsequent written instructions).

  Interest on each Bond shall be computed from the Interest Payment Date to
which interest has been paid or duly provided for next preceding its date of
authentication, unless (i) such date shall be prior to the first Interest
Payment Date, in which case such interest shall be computed from the date of the
Bonds, or (ii) such date of authentication shall be an Interest Payment Date to
which interest on the Bonds has been paid in full or duly provided for, in which
case interest on such Bond shall be computed from such date of authentication;
provided, however, that if, as shown by the records of the Trustee, interest on
the Bonds shall be in default, interest on Bonds issued in exchange for Bonds
surrendered for transfer or exchange shall be computed from the last date to
which interest has been paid in full or duly provided for on the Bonds, or if no
interest has been paid or duly provided for on the Bonds, from the date thereof.

  SECTION 2.3.  EXECUTION; LIMITED OBLIGATION.  The Bonds shall be executed on
behalf of the Issuer with the manual or facsimile signature of its Executive
Director, and shall have impressed or imprinted thereon the official seal of the
Issuer or a facsimile thereof, attested by the manual or facsimile signature of
its Secretary.  All authorized facsimile signatures shall have the same force
and effect as if manually signed.  In case any official whose signature or a
facsimile of whose signature shall appear on the Bonds shall cease to be such
official before the delivery of such Bonds, such signature or such facsimile
shall nevertheless be valid and sufficient for all purposes, the same as if such
official had remained in office until delivery.  The Bonds may be signed on
behalf of the Issuer by such persons who, at the time of the execution of such
Bonds, are duly authorized or hold the appropriate offices of the Issuer,
although on the date of the Bonds such persons were not so authorized or did not
hold such offices.

  The Bonds, together with interest thereon, are limited obligations of the
Issuer payable solely from the Revenues (except to the extent paid out of moneys
attributable to the proceeds of the Bonds or the income from the temporary
investment thereof) and shall be a valid claim of the respective owners thereof
only against the Bond Fund and other moneys held by the Trustee and the
Revenues, which Revenues shall be used for no other purpose than to pay the
principal of, premium, if any  and interest on the Bonds, except as may be
otherwise expressly authorized in this Indenture or the Agreement.  The Bonds
and the obligation to pay interest thereon do not now and shall never constitute
an indebtedness or obligation of the Issuer, the State of Mississippi or any
political subdivision thereof, within the purview of any constitutional
<PAGE>
 
limitation or provision, or a charge against the general credit or taxing
powers, if any, of any of them, but shall be secured as aforesaid, and shall be
payable solely from the Revenues.  No owner of the Bonds shall have the right to
compel the exercise of the taxing power, if any, of the Issuer, the State of
Mississippi or any political subdivision thereof to pay the principal of,
premium, if any  or interest on the Bonds.  The Issuer has no taxing power.

  SECTION 2.4.  AUTHENTICATION.  No Bond shall be valid or obligatory for any
purpose or entitled to any security or benefit under this Indenture unless and
until a certificate of authentication on such Bond substantially in the form
hereinabove set forth shall have been duly executed by the Trustee, and such
executed certificate of the Trustee by duly authorized signatory upon any such
Bond shall be conclusive evidence that such Bond has been authenticated and
delivered under this Indenture.  The Trustee's certificate of authentication on
any Bond shall be deemed to have been executed by it if manually signed by an
authorized signatory of the Trustee, but it shall not be necessary that the same
signatory sign the certificate of authentication on all of the Bonds issued
hereunder.  The Trustee shall insert the date of authentication of each Bond in
the place provided for such purpose in the form of certificate of authentication
of the Trustee to appear on each Bond.

  SECTION 2.5.  FORM OF BONDS.  The Bonds issued under this Indenture shall be
substantially in the form hereinabove set forth with such variations, omissions
and insertions as are permitted or required by this Indenture.

  SECTION 2.6.  DELIVERY OF BONDS.  Upon the execution and delivery of this
Indenture, the Issuer shall execute and deliver to the Trustee and the Trustee
shall authenticate the Bonds and deliver them to the Underwriter as directed in
writing by the Issuer as hereinafter in this Section provided.

  Prior to the delivery by the Trustee of any of the Bonds there shall be filed
with the Trustee:

       (a) A copy, duly certified by the Secretary of the Issuer, of the
     proceedings of the Issuer authorizing the execution and delivery of the
     Agreement and this Indenture and the issuance of the Bonds.

       (b) Original executed counterparts of this Indenture, the Agreement, the
     Tax Agreement and the Guaranty.

       (c) A request and authorization to the Trustee on behalf of the Issuer
     and signed by its Executive Director to authenticate and deliver the Bonds
     to or as directed by the Underwriter upon payment to the Trustee, but for
     the account of the Issuer, of a sum specified in such request and
     authorization. The proceeds of such payment shall be deposited in
     accordance with Sections 5.3 and 5.7 hereof.
<PAGE>
 
  SECTION 2.7.  MUTILATED, LOST, STOLEN OR DESTROYED BONDS.  In the event any
Bond is mutilated, lost, stolen, or destroyed, the Issuer may execute and the
Trustee may authenticate a new Bond of like denomination as that mutilated,
lost, stolen or destroyed; provided that, in the case of any mutilated Bond,
such mutilated Bond shall first be surrendered to the Issuer, and in the case of
any lost, stolen or destroyed Bond, there shall be first furnished to the Issuer
and the Trustee and the Company evidence of such loss, theft or destruction
satisfactory to the Issuer, the Trustee and the Company, together with any
indemnity satisfactory to them.  In the event any such Bond shall have matured,
instead of issuing a duplicate Bond, the Issuer may pay the same without
surrender thereof.  The Issuer and the Trustee may charge the owner of such Bond
with their reasonable fees and expenses in this connection.

  SECTION 2.8.  REGISTRATION AND EXCHANGE OF BOND; PERSONS TREATED AS OWNERS.
The Issuer shall cause books for the registration and for the transfer of the
Bonds as provided in this Indenture to be kept by the Trustee which is hereby
constituted and appointed the Registrar of the Issuer.

  Upon surrender for transfer of any Bond at the principal corporate trust
office of the Trustee, duly endorsed for transfer or accompanied by an
assignment duly executed by the Registered owner or his attorney duly authorized
in writing, the Trustee shall authenticate and deliver in the name of the
transferee or transferees a new Bond or Bonds duly executed by the Issuer of an
Authorized Denomination or Authorized Denominations for a like aggregate
principal amount.

  Any Bond or Bonds may be exchanged at the principal corporate trust office of
the Trustee for a new Bond or Bonds of like principal amount of another
Authorized Denomination or  Authorized Denominations.  Upon surrender of any
Bond or Bonds for exchange, the Trustee shall authenticate and deliver a new
Bond or Bonds duly executed by the Issuer which the Bondholder making the
exchange is entitled to receive.

  The Trustee shall not be required to transfer or exchange any Bond during the
period of fifteen days next preceding any Interest Payment Date, nor to transfer
or exchange any Bond after the mailing of notice calling such Bond or portion
thereof for redemption has been given as herein provided, nor during the period
of fifteen days next preceding the giving of such notice of redemption.

  The person in whose name any Bond shall be registered shall be deemed and
regarded as the absolute owner thereof for all purposes, and payment of or on
account of the principal of, premium, if any or interest on any such Bond shall
be made only to or upon the written order of the Registered owner thereof or his
legal representative, but such registration may be changed as hereinabove
provided.  All such payments shall be valid and effectual to satisfy and
discharge the liability upon such Bond to the extent of the sum or sums so paid.
<PAGE>
 
  In each case the Trustee shall require the payment by the Bondholder
requesting exchange or transfer of any tax or other governmental charge required
to be paid with respect to such exchange or transfer, but otherwise no charge
shall be made to the Bondholder for such exchange or transfer.

  SECTION 2.9.  CANCELLATION OF BONDS.  Whenever any outstanding Bond shall be
delivered to the Trustee for cancellation pursuant to this Indenture, upon
payment of the principal amount represented thereby, or for replacement pursuant
to Section 2.7 hereof, such Bond shall be promptly canceled and destroyed by the
Trustee and counterparts of a certificate of destruction evidencing such
cancellation and destruction shall be furnished by the Trustee to the Issuer and
the Company.

  SECTION 2.10.  BOOK ENTRY SYSTEM.  The Trustee and the Issuer, at the
direction of the Company, may from time to time enter into, and discontinue, an
agreement with a "clearing agency" (securities depository) registered under
Section 17A of the Securities Exchange Act of 1934, as amended (the "Securities
Depository"), which is the owner of the Bonds, to establish procedures with
respect to the Bonds not inconsistent with the provisions of this Indenture;
provided, however, that any such agreement may provide:

       (a) that such Securities Depository is not required to present a Bond to
     the Trustee in order to receive a partial payment of principal;

       (b) that a legend shall appear on each Bond so long as the Bonds are
     subject to such agreement; and

       (c) that different provisions for notice to such Securities Depository
     may be set forth therein.

  So long as any such agreement with a Securities Depository is in effect, the
term "owner", as it appears in Section 3.1(b) and the second paragraph of
Article VII hereof (but not for any other provision of this Indenture, except
only as specifically provided herein) and in Sections 5.3 and 7.1(b) of the
Agreement, shall be deemed to include the Beneficial Owner.  "Beneficial Owner"
shall mean the owner of a Bond or portion thereof for federal income tax
purposes.

                                  ARTICLE III
                      REDEMPTION OF BONDS BEFORE MATURITY
                                        
  SECTION 3.1.  REDEMPTION DATES AND PRICES.  (a) The Bonds shall be subject to
extraordinary optional redemption at any time in whole, but not in part, at a
redemption price equal to 100% of the principal amount thereof plus accrued
interest, if any, to the redemption date, upon the exercise by the Company of
its option to prepay loan repayment installments under Section 7.2 of the
Agreement, if any of the following shall have occurred:
<PAGE>
 
       (1) The Project or the Plant shall have been damaged or destroyed (in
     whole or in part) by fire or other casualty to such extent that, in the
     opinion of the Company, it is not practicable or desirable to rebuild,
     repair or restore the Project or Plant; or

       (2) Title to, or the temporary use of, all or substantially all the
     Project or Plant shall have been taken under the exercise of the power of
     eminent domain by any governmental authority, or person, firm or
     corporation acting under governmental authority; or

       (3) Changes in the economic availability of raw materials, operating
     supplies or facilities necessary for the operation of the Project or Plant
     shall have occurred or such technological or environmental or other changes
     shall have occurred which, in the Company's judgment, render the continued
     operation of the Project or Plant uneconomic.

     (b) The Bonds are subject to optional redemption prior to maturity at the
election of the Corporation on March 1, 2008, and thereafter, either as a whole
or in part on any date from any moneys that may be made available for such
purpose, at the following redemption prices (expressed as a percentage of
principal amount or portion thereof to be redeemed), plus accrued interest to
the redemption date:

       Redemption Dates (Inclusive)                     Redemption Price
       ----------------------------                     ----------------
  March 1, 2008 through February 28, 2009                     102%
  March 1, 2009 through February 28, 2010                     101%
  March 1, 2010 and thereafter                                100%

       (c) The Bonds shall be subject to mandatory redemption at any time in
whole (or in the case of the events stated in (2) or (3) of this paragraph in
whole or in part as provided below), at a redemption price equal to 100% of the
principal amount thereof plus accrued interest, if any, to the redemption date,
if any of the following shall have occurred:

         (1) As a result of any changes in the Constitution of the State of
     Mississippi or the Constitution of the United States of America or of
     legislative or administrative action (whether state or federal) or by final
     decree, judgment or order of any court or administrative body (whether
     state or federal) the Agreement shall have become void or unenforceable or
     impossible to perform in accordance with the intent and purposes of the
     parties as expressed in the Agreement; or

         (2) A final determination by the Internal Revenue Service or a court of
     competent jurisdiction as a result of a proceeding in which the Company
     participates to the degree it deems sufficient, which determination the
     Company, in its discretion, does not contest by an appropriate proceeding,
     that, as a result of failure by the Company to observe any covenant,
     agreement or representation by the Company in the Agreement,
<PAGE>
 
     the interest payable on the Bonds or any of them is includable for federal
     income tax purposes in the gross income of any owner of a Bond (other than
     an owner who is a "substantial user" of the Project or a "related person"
     within the meaning of Section 147 of the Code and the applicable
     regulations thereunder); or

         (3) Proceeds of the Series 1997 Bonds, including income from the
     investment thereof, in an amount equal to or greater than $100,000 shall
     remain after completion of the Project and the payment of all costs of the
     Project.

Upon the occurrence of the event stated in Section 3.1(c)(2) hereof, the Bonds
will be redeemed in whole unless the Company delivers to the Trustee, at the
Company's expense, an opinion of Bond Counsel upon which the Trustee may rely to
the effect that redemption of a portion of the Bonds outstanding would have the
result that interest payable on the Bonds remaining outstanding after such
redemption would not be includable for federal income tax purposes in the gross
income of any owner of a Bond (other than an owner who is a "substantial user"
of the Project or a "related person" within the meaning of Section 147 of the
Code and the applicable regulations thereunder), and in such event the Bonds or
portions thereof (in Authorized Denominations) shall be redeemed at such times
and in such amounts as Bond Counsel shall so direct in such opinion.  Upon the
occurrence of the event stated in Section 3.1(c)(3) hereof, the principal amount
of the Bonds to be redeemed will be a principal amount equal to the highest
integral multiple of $100,000 equal to or less than the remaining proceeds of
the Bonds.  Any of such remaining proceeds which are not utilized for such
mandatory redemption of Bonds shall be applied to the debt service coming due on
the Bonds on the next Interest Payment Date.

  SECTION 3.2.  NOTICE OF REDEMPTION.  Upon receipt of written notice given by
the Company pursuant to Section 7.4 of the Agreement not less than forty (40)
days prior to the date of redemption (or such later date as is acceptable to the
Issuer and the Trustee), notice of the call for any redemption of Bonds or any
portions thereof pursuant to Section 3.1 hereof identifying the Bonds or
portions thereof to be redeemed, specifying the redemption date, the redemption
price, the place and manner of payment and that from the redemption date
interest will cease to accrue on the Bonds provided that funds for the
redemption thereof are on deposit with the Trustee, shall be given by the
Trustee by mailing a copy of the redemption notice by first-class mail at least
thirty (30) days prior to the date fixed for redemption to the Registered owner
of each Bond to be redeemed in whole or in part at the address shown on the
registration books; provided, however, that failure to duly give such notice, or
any defect therein, shall not affect the validity of any proceeding for the
redemption of Bonds with respect to which no such failure or defect occurred.
Any notice mailed as provided in this Section shall be conclusively presumed to
have been duly given, whether or not the Registered owner receives the notice.

  SECTION 3.3.  DEPOSIT OF FUNDS.  For the redemption of any of the Bonds, the
Issuer shall cause to be deposited in the Bond Fund out of the Revenues (or out
of maturing principal and interest, if any, of Governmental Obligations in which
Revenues for such purpose are required to be invested) moneys sufficient to pay
when due the principal of, premium, if any and interest on the Bonds or portions
thereof to be redeemed on
<PAGE>
 
the redemption date. Moneys in the Bond Fund which are available therefor shall
be credited against any moneys which the Issuer is required to cause to be so
deposited in the Bond Fund.

  SECTION 3.4.  PARTIAL REDEMPTION OF BONDS.  In case a Bond is of a
denomination larger than the minimum Authorized Denomination, all or a portion
of such Bond may be redeemed in an Authorized Denomination.  Upon surrender of
any Bond for redemption in part only, the Trustee shall authenticate and deliver
to the owner thereof, without cost to the owner, a new Bond or Bonds duly
executed by the Issuer of an Authorized Denomination or Authorized Denominations
in aggregate principal amount equal to the unredeemed portion of the Bond
surrendered.

  SECTION 3.5.  SELECTION OF BONDS FOR REDEMPTION.  If less than all of the
Bonds are called for redemption, the Trustee shall select the Bonds or portions
thereof (in Authorized Denominations) to be redeemed from the Bonds outstanding
not previously called for redemption by lot in such manner as the Trustee in its
discretion may deem proper, and each $100,000 of face value of each Bond shall
be treated as a separate Bond for the purpose of selection by lot.  If it is
determined that a portion but not all of the principal amount of any Bond is to
be called for redemption, then, upon notice of intention to redeem such portion,
the Registered owner of such Bond shall surrender such Bond to the Trustee for
(a) payment to such owner of the redemption price of the portion of principal
amount called for redemption, and (b) delivery to such owner of a new Bond or
Bonds in the aggregate principal amount of the unredeemed portion of the
principal amount of such Bond.  New Bonds representing the unredeemed portion of
the principal amount of such Bond shall be issued to the Registered owner
thereof without charge therefor.  If the Registered owner of any such Bond shall
fail to present such Bond to the Trustee for payment and exchange as aforesaid,
such Bond shall, nevertheless, become due and payable on the date fixed for
redemption to the extent of the portion of principal amount called for
redemption (and to that extent only) and interest with respect to such portion
will cease to accrue.

                                   ARTICLE IV
                               GENERAL COVENANTS
                                        
  SECTION 4.1.  PAYMENT OF PRINCIPAL, PREMIUM, AND INTEREST.  The Issuer
covenants that it will promptly pay the principal of, premium, if any  and
interest on, every Bond issued under this Indenture at the place, on the dates
and in the manner provided herein and in said Bonds according to the true intent
and meaning thereof.  The principal and interest are payable by the Issuer
solely from the Revenues (except to the extent paid out of moneys attributable
to the Bond proceeds or the income from the temporary investment thereof) and
nothing in the Bonds or this Indenture should be considered as assigning or
pledging any other funds or assets of the Issuer other than such Revenues and
the right, title and interest of the Issuer in the Agreement in the manner and
to the extent herein specified.

  SECTION 4.2.  PERFORMANCE OF COVENANTS; ISSUER.  The Issuer covenants that it
will faithfully perform on its part at all times any and all covenants,
undertakings, stipulations and provisions contained in this
<PAGE>
 
Indenture, in any and every Bond executed, authenticated and delivered hereunder
and in all of its proceedings pertaining thereto; provided, however, that except
for the matters set forth in Section 4.1 hereof, the Issuer shall not be
obligated to take any action or execute any instrument pursuant to any provision
hereof until it shall have been requested to do so by the Company or by the
Trustee, or shall have received the instrument to be executed, and at the
Issuer's option shall have received from the Company assurance satisfactory to
the Issuer that the Issuer shall be reimbursed for its reasonable expenses
incurred or to be incurred in connection with taking such action or executing
such instrument. The Issuer covenants that it is duly authorized under the
Constitution and laws of the State of Mississippi, including particularly the
Act and the resolution of the Issuer pursuant to which the Bonds were issued, to
issue the Bonds authorized hereby and to execute this Indenture, to grant the
security interest herein provided, to assign and pledge the Agreement (except as
otherwise provided herein) and the Guaranty (to the extent of its interest
therein) and to assign and pledge the amounts hereby assigned and pledged in the
manner and to the extent herein set forth; that all action on its part for the
issuance of the Bonds and the execution and delivery of this Indenture has been
duly and effectively taken, and that the Bonds in the hands of the owners
thereof are and will be valid and enforceable obligations of the Issuer
according to the terms thereof and hereof. Anything contained in this Indenture
to the contrary notwithstanding, it is hereby understood that none of the
covenants of the Issuer contained in this Indenture are intended to create a
general or primary obligation of the Issuer.

  SECTION 4.3.  RIGHT TO PAYMENTS UNDER AGREEMENT AND GUARANTY; INSTRUMENTS OF
FURTHER ASSURANCE.  The Issuer covenants that it will defend its right to the
payment of amounts due from the Company under the Agreement or the Guarantor
under the Guaranty (to the extent of its interest therein) to the Trustee for
the benefit of the owners of the Bonds against the claims and demands of all
persons whomsoever.  The Issuer covenants that it will do, execute, acknowledge
and deliver such indentures supplemental hereto and such further acts,
instruments and transfers as the Trustee may reasonably require for the better
assuring, transferring, conveying, pledging, assigning and confirming unto the
Trustee all and singular the rights assigned hereby and the amounts pledged and
assigned hereby to the payment of the principal of, premium, if any  and
interest on the Bonds.  The Issuer covenants and agrees that, except as herein
and in the Agreement provided, it will not sell, convey, mortgage, encumber or
otherwise dispose of any part of the Revenues or its rights under the Agreement.

  SECTION 4.4.  RECORDATION AND OTHER INSTRUMENTS.  The Trustee covenants that
it will cause, at the Company's expense and as provided in Section 5.13 of the
Agreement, and the Issuer, to the extent permitted by law, covenants that it
will cooperate with the Trustee in causing, such security agreements, financing
statements and all supplements thereto and other instruments as may be required
hereunder or under the Agreement from time to time to be kept, recorded and
filed in such manner and in such places as may be required by law in order to
fully preserve and protect the security of the Trustee on behalf of the owners
of the Bonds and the rights of Trustee hereunder, and to perfect the security
interest of the Trustee.
<PAGE>
 
  SECTION 4.5.  INSPECTION OF PROJECT BOOKS.  The Issuer and the Trustee
covenant and agree that all books and documents in their possession relating to
the Project and the Revenues shall at all reasonable times be open to inspection
by such accountants or other agencies as the other party may from time to time
designate in writing.

  SECTION 4.6.  LIST OF BONDHOLDERS.  The Trustee will keep on file a list of
the names and addresses of all registered owners of Bonds on the registration
books of the Issuer maintained by the Trustee as Registrar, together with the
principal amount and numbers of such Bonds.  At reasonable times and under
reasonable regulations established by the Trustee, said list may be inspected
and copied by the Company.

  SECTION 4.7.  RIGHTS UNDER AGREEMENT AND GUARANTY.  The Agreement and the
Guaranty, duly executed counterparts of which have been filed with the Trustee,
set forth the covenants and obligations of the Issuer, the Company and the
Guarantor, including provisions that subsequent to the issuance of Bonds and
prior to their payment in full or provision for payment thereof in accordance
with the provisions hereof the Agreement and the Guaranty may not be effectively
amended, changed, modified, altered or terminated without the written consent of
the Trustee, and reference is hereby made to the same for a detailed statement
of said covenants and obligations of the Company and the Guarantor thereunder,
and the Issuer agrees that the Trustee in its name or in the name of the Issuer
may enforce all rights of the Issuer and all obligations of the Company under
and pursuant to the Agreement or the obligations of the Guarantor under the
Guaranty for and on behalf of the Bondholders, whether or not the Issuer is in
default hereunder.

  SECTION 4.8.  PROHIBITED ACTIVITIES.  Subject to the limitations on its
liability as stated herein, the Issuer covenants and agrees that it has not
knowingly engaged and will not knowingly engage in any activities and that it
has not knowingly taken and will not knowingly take any action which might
result in its income becoming taxable to it or any interest on the Bonds
becoming includable in the gross income of the owners thereof for federal income
tax purposes.

                                   ARTICLE V
                               REVENUES AND FUNDS
                                        
  SECTION 5.1.  SOURCE OF PAYMENT OF BONDS.  The Bonds herein authorized and all
payments to be made by the Issuer hereunder are not general obligations of the
Issuer but are limited obligations payable solely from the Revenues (except to
the extent paid out of moneys attributable to the Bond proceeds or the income
from the temporary investment thereof), and as authorized by the Act and
provided in the Agreement, the Guaranty and in this Indenture.  The Revenues are
to be remitted directly to the Trustee for the account of the Issuer and
deposited in the Bond Fund (hereinafter created).  The entire amount of the
Revenues is hereby pledged and assigned to the payment of the principal of,
premium, if any  and interest on the Bonds.

  SECTION 5.2.  CREATION OF BOND FUND.  There is hereby created by the Issuer
and ordered established with the Trustee a trust fund to be
<PAGE>
 
designated "Mississippi Business Finance Corporation Solid Waste Disposal
Revenue Refunding Bonds (Mississippi Phosphates Corporation Project) Series 1998
Bond Fund," which is pledged and shall be used to pay the principal of, premium,
if any and interest on the Bonds.

  SECTION 5.3.  PAYMENTS INTO BOND FUND.  There shall be deposited into the Bond
Fund, as and when received, (a) accrued interest received upon the delivery of
the Bonds to the Underwriter; (b) any amount in the Construction Fund directed
to be paid into the Bond Fund under Section 5.8 or 5.9 hereof; (c) all Revenues;
and (d) all other moneys received by the Trustee under and pursuant to any of
the provisions of the Agreement or the Guaranty which are required or which are
accompanied by directions that such moneys are to be paid into the Bond Fund.
The Issuer hereby covenants and agrees that so long as any of the Bonds issued
hereunder are outstanding it will deposit, or cause to be paid to the Trustee
for deposit in the Bond Fund for its account, sufficient sums from revenues and
receipts derived from the Agreement promptly to meet and pay the principal of,
premium, if any  and interest on the Bonds as the same become due and payable.

  SECTION 5.4.  USE OF MONEYS IN BOND FUND.  Except as provided in Sections 5.18
and 9.2 hereof, moneys in the Bond Fund shall be used solely for the payment of
the principal of, premium, if any  and interest on the Bonds.

  SECTION 5.5.  CUSTODY OF BOND FUND.  The Bond Fund shall be in the custody of
the Trustee but in the name of the Issuer, and the Issuer hereby authorizes and
directs the Trustee to withdraw sufficient funds from the Bond Fund to pay the
principal of, premium, if any and interest on the Bonds as the same become due
and payable and to make payments and reimbursements pursuant to Section 9.2
hereof, which authorization and direction the Trustee hereby accepts.

  SECTION 5.6.  CONSTRUCTION FUND.  There is hereby created and established with
the Trustee a trust fund in the name of the Issuer to be designated "Mississippi
Business Finance Corporation Solid Waste Disposal Revenue Refunding Bonds
(Mississippi Phosphates Corporation Project) Series 1998 Construction Fund,"
which shall be expended in accordance with the provisions of the Agreement.

  SECTION 5.7.  PAYMENTS INTO CONSTRUCTION FUND; DISBURSEMENTS.  The Issuer
hereby notifies and directs the Trustee that amounts on deposit in the
Mississippi Business Finance Corporation Solid Waste Disposal Revenue Bonds
Construction Fund-Mississippi Phosphates Corporation Project-Series 1997A
established pursuant to the provisions of the Series 1997A Indenture and on
deposit in the Mississippi Business Finance Corporation Solid Waste Disposal
Revenue Bonds Construction Fund-Mississippi Phosphates Corporation Project-
Series 1997B established pursuant to the provisions of the Series 1997B
Indenture shall be transferred to and deposited in the Construction Fund.
Moneys in the Construction Fund shall be expended for the purposes set forth in
Section 3.3 of the Agreement pursuant to requisitions signed by an Authorized
Company Representative and delivered to the Trustee stating, with respect to
each payment to be made:
<PAGE>
 
  (a) The requisition number;

  (b) The name and address of the person, firm or corporation to whom payment is
      due or has been made, which may include the Company;

  (c) The amount to be or which has been paid; and

  (d) That each obligation mentioned therein has been properly incurred, is a
      proper charge against the Construction Fund in accordance with the
      provisions hereof and of the Agreement and has not been the basis of any
      previous requisition from the Construction Fund or from the proceeds
      (including investment income) of any other obligations issued by or on
      behalf of any state or political subdivision, including authorities,
      agencies, departments or other similar issuers.

  The Trustee is hereby authorized and directed to make the disbursement
pursuant to each such requisition and to issue its checks therefor.  In making
any such disbursement, the Trustee may rely on any such requisition.  The
Trustee shall keep and maintain adequate records pertaining to the Construction
Fund and all disbursements therefrom and shall provide monthly statements of
transactions and investments pertaining to the Construction Fund to the Company
so long as any Bonds remain outstanding.

  SECTION 5.8.  COMPLETION OF PROJECT.  The completion of the Project and
payment or provision made for payment of the full Cost of the Project shall be
evidenced by the filing with the Trustee of a certificate required by the
provisions of Section 3.4 of the Agreement.  Any balance remaining in the
Construction Fund on the Completion Date shall be used in accordance with
Section 3.4 of the Agreement.

  SECTION 5.9.  TRANSFER OF CONSTRUCTION FUND.  If all of the Bonds are paid or
deemed to be paid as herein provided, then, notwithstanding anything herein to
the contrary, any balance then remaining in the Construction Fund shall, without
further authorization, be deposited in the Bond Fund by the Trustee.

  SECTION 5.10.  CREATION OF REFUNDING FUND.  There is hereby created by the
Issuer and ordered established with the Trustee a trust fund to be designated
"Mississippi Business Finance Corporation Solid Waste Disposal Revenue Refunding
Bonds (Mississippi Phosphates Corporation Project) Series 1998 Refunding Fund."

  SECTION 5.11.  PAYMENTS INTO THE REFUNDING FUND.  There shall be deposited
into the Refunding Fund as and when received, $14,500,000 of the proceeds of the
sale of the Bonds.

  SECTION 5.12.  USE OF MONEYS IN REFUNDING FUND.  Of the amount deposited in
the Refunding Fund, $6,000,000 shall be transferred immediately to the trustee
under the Series 1997A Indenture and used and applied to the redemption, at the
earliest practicable time, of all of
<PAGE>
 
the Series 1997A Bonds, and $8,500,000 shall be transferred immediately to the
trustee under the Series 1997B Indenture and used and applied to the redemption,
at the earliest practicable time, of all of the Series 1997B Bonds. Payment of
interest on the Series 1997A Bonds and the Series 1997B Bonds shall be paid from
a draw on the respective Letters of Credit applicable to such Bonds.

  SECTION 5.13.  NON-PRESENTMENT OF BONDS.  In the event any Bond shall not be
presented for payment when the principal thereof becomes due, either at maturity
or otherwise, or at the date fixed for redemption thereof, or in the event any
check for the payment of interest shall not be cashed or any wire transfer for
interest shall be returned, then if funds sufficient to pay such Bond or
interest shall have been made available to the Trustee, all liability of the
Issuer for the payment of such Bond or interest shall forthwith cease, terminate
and be completely discharged, and thereupon it shall be the duty of the Trustee
to hold such funds uninvested, without liability for interest thereon, for the
benefit of the owner of such Bond, who shall thereafter be restricted
exclusively to such funds, for any claim of whatever nature on his part under
this Indenture or on, or with respect to, said Bond or interest.  The Trustee
shall hold such funds until required to pay such funds to the State Treasurer
under the Mississippi Uniform Disposition of Unclaimed Property Act.

  Thereafter, the Bondholders shall be entitled to look only to the State
Treasurer for payment, and then only to the extent of the amount so repaid, and
the State Treasurer shall not be liable for any interest thereon to the
Bondholders and shall not be regarded as a trustee of such money.

  SECTION 5.14.  MONEYS TO BE HELD IN TRUST.  All moneys required to be
deposited with or paid to the Trustee for account of the Bond Fund, the
Construction Fund and the Refunding Fund  under any provision of this Indenture
shall be held by the Trustee in trust, and except for moneys deposited with or
paid to the Trustee for the redemption of Bonds, notice of the redemption of
which has been duly given, and moneys referred to in Section 5.13 hereof held by
the Trustee for the payment of Bonds or interest, shall, while held by the
Trustee, constitute part of the Trust Estate and be subject to the lien or
security interest created hereby.

  SECTION 5.15.  REPAYMENT TO THE COMPANY FROM BOND FUND.  Any amounts remaining
in the Bond Fund after payment in full of the Bonds (or provision therefor
having been made in accordance herewith), the fees, charges and expenses
(including reasonable attorneys' fees and expenses) of the Trustee, and all
other amounts required to be paid hereunder or under the Agreement, shall be
paid to the Company as provided in Section 8.5 of the Agreement.

  SECTION 5.16.  ADDITIONAL PAYMENTS UNDER THE AGREEMENT.  Pursuant to Section
4.2(b) of the Agreement, the Company has agreed to pay as provided therein fees
and expenses (including reasonable attorneys' fees and expenses) of the Trustee
and to indemnify and hold harmless the Trustee for and against certain losses,
liabilities and expenses.  Such additional payments received by the Trustee
shall not be paid into the Bond Fund but shall be for the account of the
Trustee.
<PAGE>
 
  SECTION 5.17.  ARBITRAGE REQUIREMENTS.  Anything in the Agreement or this
Indenture to the contrary notwithstanding, the Trustee is hereby authorized to
deposit moneys in the Construction Fund, the Bond Fund and the Refunding Fund
and to withdraw moneys from such Funds upon the written direction of the Company
in order to comply with the provisions of the Tax Agreement.

  SECTION 5.18.  REBATE FUND; TAX AGREEMENT.  The Trustee agrees to establish a
trust fund to be designated the "Mississippi Business Finance Corporation Solid
Waste Disposal Revenue Refunding Bonds Rebate Fund - Mississippi Phosphates
Corporation Project - Series 1998", if so requested by the Issuer or the
Company, and will hold amounts in the Rebate Fund in trust as provided herein
and as directed by the Issuer and the Company pursuant hereto and pursuant to
the Tax Agreement.  Moneys in the Rebate Fund shall not be considered moneys
held under the Indenture and shall not constitute a part of the Trust Estate
held for the benefit of the Bondholders, or, except as otherwise provided herein
or as provided in the Tax Agreement, for the benefit of the Issuer or the
Company.  Moneys in the Rebate Fund (including earnings and deposits therein)
shall be held in trust by the Trustee and held for future payment to the United
States Government as required by Section148(f) of the Code and as contemplated
under the provisions of the Tax Agreement and shall be paid out by the Trustee
to such persons, in such amounts and at such times as shall be set forth in
written instructions delivered to the Trustee by an Authorized Company
Representative.  Notwithstanding anything in the Agreement or this Indenture to
the contrary, the Trustee is hereby authorized, at the written direction of an
Authorized Company Representative, to transfer moneys from the Rebate Fund to
the Construction Fund and the Bond Fund and to transfer moneys from the Bond
Fund to the Rebate Fund, in order to comply with the provisions of the Tax
Agreement.

                                   ARTICLE VI
                              INVESTMENT OF MONEYS
                                        
  SECTION 6.1.  INVESTMENT OF MONEYS.  Any moneys held as part of the
Construction Fund or the Bond Fund shall be invested and reinvested by the
Trustee in accordance with the provisions of Section 3.5 of the Agreement.  The
Trustee may make any and all such investments through its own or any of its
Affiliate's trust investment department.  Any such investments shall be held by
or under the control of the Trustee and shall be deemed at all times a part of
the fund for which they were made.  The interest accruing thereon and any profit
realized from such investments shall be credited to such fund, and any net loss
resulting from such investments shall be charged to such fund.  The Trustee
shall sell and reduce to cash a sufficient amount of such investments of the
Construction Fund whenever the cash balance in the Construction Fund is
insufficient to pay a requisition when presented or of the Bond Fund whenever
the cash balance in the Bond Fund is insufficient to pay the principal of,
premium, if any, and interest on the Bonds when due.  The Trustee shall have no
responsibility with respect to the compliance by the Company or the Issuer with
any covenant herein or in the Tax Agreement regarding the yield on investments
made in accordance with this Section, other than to use its best reasonable
efforts to comply with instructions from the Company regarding such investments
and the Trustee shall bear no responsibility for losses incurred from such
investments.  Since the investments permitted by this Section have been made
<PAGE>
 
at the request of the Company and the making of such investments from time to
time will be subject to the Company's direction, the Issuer and the Trustee
specifically disclaim any obligation to the Company for any loss arising from,
or tax consequences of, investments pursuant to the provisions of this Section.
The Trustee shall not be responsible for any depreciation of the value of any
investment made pursuant to this Section or for losses incurred in the
redemption, sale or other disposal of any investments made in accordance with
this Section.

                                  ARTICLE VII
                               DISCHARGE OF LIEN

  If the Issuer shall pay or cause to be paid, or there shall be otherwise paid
or provision for payment made to or for the owners of the Bonds, of the
principal and interest due or to become due on the Bonds at the times and in the
manner stipulated therein, and shall pay or cause to be paid to the Trustee all
sums of money due or to become due according to the provisions hereof, and if
all other liabilities of the Company under the Agreement shall have been paid or
the payment thereof provided for, then these presents and the estate and rights
hereby granted shall cease, determine and be void, whereupon the Trustee shall
cancel and discharge the lien of this Indenture and execute and deliver to the
Issuer such instruments in writing as shall be requisite to cancel and discharge
the lien hereof, and reconvey, release, assign and deliver unto the Issuer any
and all the estate, right, title and interest in and to any and all property
conveyed, assigned or pledged to the Trustee or otherwise subject to the lien of
this Indenture, except (i) amounts in the Bond Fund required to be paid to the
Company under Section 5.18 hereof and (ii) moneys or securities held by the
Trustee for the payment of the principal of, premium, if any  and interest on
the Bonds.

  Any Bond shall be deemed to be paid within the meaning of this Article when
payment of the principal of, premium, if any,  plus interest thereon to the due
date thereof (whether such due date be by reason of maturity or upon redemption
as provided in this Indenture, or otherwise), either (i) shall have been made or
caused to be made in accordance with the terms thereof, or (ii) shall have been
provided by irrevocably depositing with the Trustee, in trust and irrevocably
set aside exclusively for such payment, (1) moneys sufficient to make such
payment or (2) Governmental Obligations (provided that the Company delivers to
the Trustee, at the Company's expense, an opinion of Bond Counsel upon which the
Trustee may rely to the effect that all conditions with respect to such deposit
specified in this Article VIII have been satisfied or provision therefor made
and that such deposit will not cause interest on any of the Bonds to be
includable for federal income tax purposes in the gross income of any owner
thereof (other than an owner who is a "substantial user" of the Project or a
"related person" within the meaning of Section 147(a) of the Code and the
applicable regulations thereunder) or cause any of the Bonds to be classified as
arbitrage bonds (within the meaning of Section 148 of the Code and the
applicable regulations thereunder)) maturing as to principal and interest in
such amount and at such times as will, without reinvestment, provide sufficient
moneys to make such payment, as verified by a report prepared by a firm of
certified public accountants, and all necessary and proper fees, compensation
and expenses (including reasonable attorneys' fees and expenses) of the Trustee
pertaining to the Bonds with respect to which such deposit is made shall have
been paid or provided for to the satisfaction of the Trustee.  At such time as a
Bond shall be deemed to
<PAGE>
 
be paid hereunder, as aforesaid, it shall no longer be secured by or entitled to
the benefits of this Indenture, except for the purposes of transfer and exchange
and of payment from such moneys or Governmental Obligations on the date or dates
specified at the time of such deposit.

  Notwithstanding the foregoing, in the case of Bonds which by their terms may
be redeemed prior to the stated maturities thereof, no deposit under clause (ii)
of the immediately preceding paragraph shall be deemed a payment of such Bonds
as aforesaid until the deposit shall have been made under the terms of an escrow
deposit arrangement in form and substance satisfactory to the Trustee and
consistent herewith and until the Company, on behalf of the Issuer, shall have
given the Trustee, in form satisfactory to the Trustee, irrevocable instructions
in writing:

    (a) stating the date when principal of each such Bond is to be paid, whether
 at maturity or on a redemption date (which may be any redemption date permitted
 by this Indenture);

    (b) to call for redemption pursuant to the Indenture any Bonds to be 
 redeemed prior to maturity pursuant to (a) hereof; and

    (c) to mail, as soon as practicable, in the manner prescribed by Article III
 hereof, a notice to the owners of such Bonds that the deposit required by (ii)
 above has been made with the Trustee and that said Bonds are deemed to have 
 been paid in accordance with this Article and stating the maturity or 
 redemption date upon which moneys are to be available for the payment of the 
 principal or redemption price, as applicable, on said Bonds as specified in 
 (a) hereof.

  Anything in Article X hereof to the contrary notwithstanding, if moneys or
Governmental Obligations have been deposited or set aside with the Trustee
pursuant to this Article for the payment of Bonds and the interest thereon and
such Bonds and the interest thereon shall not have in fact been actually paid in
full, no amendment to the provisions of this Article shall be made without the
consent of the owner of each of the Bonds affected thereby.

                                  ARTICLE VIII
                   DEFAULT PROVISIONS AND REMEDIES OF TRUSTEE
                                AND BONDHOLDERS
                                        
  SECTION 8.1.  DEFAULTS; EVENTS OF DEFAULT.  If any of the following events
occur, it is hereby declared to constitute an "event of default":

  (a) Failure to pay interest on any Bond as and when such interest shall
have become due and payable, and the continuation of such failure for one
business day;

  (b) Failure to pay any principal of any Bond, as and when due, whether at
the stated maturity thereof or upon proceedings for redemption thereof, and
the continuation of such failure for one business day;
<PAGE>
 
  (c) Failure to perform or observe any other of the covenants, agreements
or conditions on the part of the Issuer in this Indenture or in the Bonds
contained and failure to remedy the same after notice thereof pursuant to
Section 8.12 hereof; or

  (d) The occurrence of an "Event of Default" under the Agreement or the
Guaranty.

       SECTION 8.2. ACCELERATION. Upon the occurrence of an event of default the
Trustee may, and upon the written request of the owners of not less than a
majority in aggregate principal amount of Bonds then outstanding shall, by
notice in writing delivered to the Issuer, declare the principal of all Bonds
then outstanding and the interest accrued thereon to the date of such
declaration immediately due and payable, and such principal and interest shall
thereupon become and be immediately due and payable. Upon any declaration of
acceleration hereunder the Trustee shall immediately declare an amount equal to
all amounts then due and payable on the Bonds to be immediately due and payable
under Section 4.2(a) of the Agreement.

       SECTION 8.3. OTHER REMEDIES; RIGHTS OF BONDHOLDERS. Upon the occurrence
of an event of default the Trustee may, in addition or as an alternative, pursue
any available remedy by suit at law or in equity to enforce the payment of the
principal of, premium, if any and interest on the Bonds then outstanding,
including making claim under or enforcing the Guaranty.

       If an event of default shall have occurred, and if requested so to do by
the owners of a majority in aggregate principal amount of Bonds then outstanding
and upon being indemnified as provided in Section 9.1(1) hereof, the Trustee
shall be obligated to exercise such one or more of the rights and powers
conferred by this Section 8.3 as the Trustee, being advised by counsel, shall
deem most expedient in the interests of the Bondholders. No remedy by the terms
of this Indenture conferred upon or reserved to the Trustee (or to the
Bondholders) is intended to be exclusive of any other remedy, but each and every
such remedy shall be cumulative and shall be in addition to any other remedy
given to the Trustee or to the Bondholders hereunder or now or hereafter
existing at law or in equity.

       No delay or omission to exercise any right or power accruing upon any
default or event of default shall impair any such right or power or shall be
construed to be a waiver of any such default or event of default or acquiescence
therein; and such right and power may be exercised from time to time as often as
may be deemed expedient.

       No waiver of any default or event of default hereunder, whether by the
Trustee or by the Bondholders, shall extend to or shall affect any subsequent
default or event of default or shall impair any rights or remedies consequent
thereon.

       SECTION 8.4.  RIGHT OF BONDHOLDERS TO DIRECT PROCEEDINGS.  Subject to the
provisions of Section 9.1(1) hereof, anything in this Indenture to the contrary
notwithstanding, the owners of a majority in aggregate principal amount of the
Bonds then outstanding shall have the right, at any time, by an instrument or
instruments in writing executed and delivered to the Trustee, to direct the
method
<PAGE>
 
and place of conducting all proceedings to be taken in connection with the
enforcement of the terms and conditions of this Indenture, or for the
appointment of a receiver or any other proceedings hereunder; provided, that
such direction shall not be otherwise than in accordance with the provisions of
law and of this Indenture.

  SECTION 8.5.  APPOINTMENT OF RECEIVERS.  Upon the occurrence of an event of
default, and upon the filing of a suit or other commencement of judicial
proceedings to enforce the rights of the Trustee and of the Bondholders under
this Indenture, the Trustee shall be entitled, as a matter of right, to the
appointment of a receiver or receivers of the Trust Estate and of the revenues,
earnings, income, products and profits thereof, pending such proceedings, with
such powers as the court making such appointment shall confer.

  SECTION 8.6.  RESERVED.

  SECTION 8.7.  APPLICATION OF MONEYS.  All moneys received by the Trustee
pursuant to any right given or action taken under the provisions of this Article
shall, after payment of the costs and expenses of the proceedings resulting in
the collection of such moneys and of the expenses, liabilities and advances
incurred or made by the Trustee, be deposited in the Bond Fund and, subject to
the provisions of Section 9.2 hereof, all moneys held or deposited in the Bond
Fund during the continuation of the Event of Default shall be applied as
follows:

       (a) Unless the principal of all the Bonds shall have become or shall have
   been declared due and payable, all such moneys shall be applied:

           FIRST - To the payment to the persons entitled thereto of all
     interest then due on the Bonds (other than interest due on Bonds for the
     payment of which moneys are held pursuant to the provisions of this
     Indenture), and, if the amount available shall not be sufficient to pay
     said amount in full, then to the payment ratably, according to the amounts
     due, to the persons entitled thereto, without any discrimination or
     privilege;

           SECOND - To the payment to the persons entitled thereto of the
     unpaid principal of any of the Bonds which shall have become due (other
     than Bonds matured or called for redemption for the payment of which moneys
     are held pursuant to the provisions of this Indenture), and, if the amount
     available shall not be sufficient to pay in full such unpaid principal,
     then to the payment ratably to the persons entitled thereto without any
     discrimination or privilege; and

           THIRD - To the payment to the persons entitled thereto of interest on
     overdue principal of any Bonds and, to the extent permitted by law,
     interest on overdue interest on any Bonds, without preference or priority
     as between principal or interest one over the others, or any installment of
     interest over any other installment of interest, or of any Bond over any
     other Bond, and if the amount available shall not be sufficient to pay such
     amounts in full, then ratably, without any discrimination or privilege.
<PAGE>
 
       (b) If the principal of all the Bonds shall have become due or shall have
   been declared due and payable, all such moneys shall be applied to the
   payment of the principal and interest then due and unpaid upon the Bonds
   (other than Bonds matured or called for redemption or interest due on Bonds
   for the payment of which moneys are held pursuant to the provisions of this
   Indenture), without preference or priority of principal or interest one over
   the other, or of any installment of interest over any other installment of
   interest, or of any Bond over any other Bond, ratably, according to the
   amounts due respectively for principal and interest, to the persons entitled
   thereto without any discrimination or privilege.

       (c) If the principal of all the Bonds shall have been declared due and
   payable, and if such declaration shall thereafter have been rescinded and
   annulled under the provisions of this Article then, subject to the provisions
   of Section 8.7(b) hereof in the event that the principal of all the Bonds
   shall later become due or be declared due and payable, the moneys shall be
   applied in accordance with the provisions of Section 8.7(a) hereof.

      Subject to the provisions of Section 9.2 hereof, whenever moneys are to be
applied pursuant to the provisions of this Section 8.7, such moneys shall be
applied at such times, and from time to time, as the Trustee shall determine,
having due regard to the amount of such moneys available for application and the
likelihood of additional moneys becoming available for such application in the
future.  Whenever the Trustee shall apply such funds, it shall fix the date
(which shall be an Interest Payment Date unless it shall deem another date more
suitable) upon which such application is to be made and upon such date interest
on the amounts of principal to be paid on such date shall cease to accrue.  The
Trustee shall give such notice as it may deem appropriate of the deposit with it
of any such moneys and of the fixing of any such date, and shall not be required
to make payment to the owner of any Bond until such Bond shall be presented to
the Trustee for appropriate endorsement or for cancellation if fully paid.

  Whenever the principal of, premium, if any  and interest on all Bonds has been
paid under the provisions of this Section 8.7 and all expenses, charges and fees
of the Trustee and the Issuer have been paid, any balance remaining in the Bond
Fund shall be paid to the Company as provided in Section 5.18 hereof.

  SECTION 8.8.  REMEDIES VESTED IN TRUSTEE.  All rights of action (including the
right to file proofs of claim) under this Indenture or under any of the Bonds
may be enforced by the Trustee without the possession of any of the Bonds or the
production thereof in any trial or other proceeding relating thereto and any
such suit or proceeding instituted by the Trustee shall be brought in its name
as Trustee without the necessity of joining as plaintiffs or defendants any
owners of the Bonds, and any recovery of judgment shall be for the equal and
ratable benefit of the owners of the outstanding Bonds.

  SECTION 8.9.  RIGHTS AND REMEDIES OF BONDHOLDERS.  No owner of any Bond shall
have any right to institute any suit, action or proceeding at law or in equity
for the enforcement of this Indenture or the Agreement or for the execution of
any trust hereof or for the appointment of a
<PAGE>
 
receiver or any other remedy hereunder or thereunder, unless also a default has
occurred of which the Trustee has been notified as provided in Section 9.1(h)
hereof, or of which by said subsection it is deemed to have notice, nor unless
also such default shall have become an event of default and the owners of a
majority in aggregate principal amount of Bonds then outstanding shall have made
written request to the Trustee and shall have offered it reasonable opportunity
either to proceed to exercise the powers hereinbefore granted or to institute
such action, suit or proceeding in its own name, nor unless also they have
offered to the Trustee indemnity as provided in Section 9.1(1), nor unless the
Trustee shall thereafter fail or refuse to exercise the powers hereinbefore
granted, or to institute such action, suit or proceeding in its own name; and
such notification, request and offer of indemnity are hereby declared in every
case at the option of the Trustee to be conditions precedent to the execution of
the powers and trusts of this Indenture, and to any action or cause of action
for the enforcement of this Indenture or the Agreement, or for the appointment
of a receiver or for any other remedy hereunder or thereunder; it being
understood and intended that no one or more owners of the Bonds shall have any
right in any manner whatsoever to affect, disturb or prejudice the lien of this
Indenture by its, his or their action or to enforce any right hereunder or
thereunder except in the manner herein provided, and that all proceedings at law
or in equity shall be instituted, had and maintained in the manner herein
provided and for the equal and ratable benefit of the owners of all Bonds then
outstanding.  However, nothing contained in this Indenture shall affect or
impair the right of any Bondholder to enforce the payment of the principal of,
premium, if any  and interest on any Bond at and after the maturity thereof, or
the obligation of the Issuer to pay the principal of, premium, if any  and
interest on each of the Bonds issued hereunder to the respective owners thereof
at the time, place, from the source and in the manner in the Bonds expressed.

  SECTION 8.10.  TERMINATION OF PROCEEDINGS.  In case the Trustee shall have
proceeded to enforce any right under this Indenture by the appointment of a
receiver or otherwise, and such proceedings shall have been discontinued or
abandoned for any reason, or shall have been determined adversely, then and in
every such case the Issuer, the Trustee and the Bondholders shall be restored to
their former positions and rights hereunder respectively with regard to the
property subject to this Indenture, and all rights, remedies and powers of the
Trustee shall continue as if no such proceedings had been taken.

  SECTION 8.11.  WAIVERS OF EVENTS OF DEFAULT.  The Trustee may, in its
discretion, waive any event of default hereunder and its consequences and
rescind any declaration of acceleration of principal, and shall do so upon the
written request of the owners of (1) a majority in principal amount of all the
Bonds then outstanding in respect of which default in the payment of principal
and interest, or either of them, exists, or (2) a majority in principal amount
of all Bonds then outstanding in the case of any other default; provided,
however, that there shall not be waived (a) any event of default in the payment
of the principal of any outstanding Bonds or (b) any default in the payment when
due of the interest on any such Bonds, unless prior to such waiver or rescission
all arrears of principal, with interest thereon as in the Bonds provided, and
all arrears of interest with interest thereon to the extent permitted by law as
in the Bonds provided, and all expenses of the Trustee in connection with such
default, shall have been paid or provided for, and in case of any such waiver or
rescission, or in case any proceeding taken by the Trustee on account of any
such default shall have been discontinued or abandoned or determined adversely,
<PAGE>
 
then and in every such case the Issuer, the Trustee and the Bondholders shall be
restored to their former positions and rights hereunder respectively, but no
such waiver or rescission shall extend to any subsequent or other default or
impair any right consequent thereon.

  SECTION 8.12.  NOTICE OF DEFAULTS UNDER SECTION 8.1(C); OPPORTUNITY OF THE
ISSUER AND THE COMPANY TO CURE SUCH DEFAULTS.  Anything herein to the contrary
notwithstanding, no default under Section 8.1(c) hereof shall constitute an
event of default until actual notice of such default by registered or certified
mail, return receipt requested, shall be given to the Issuer, the Company and
the Guarantor by the Trustee or by the owners of not less than a majority in
aggregate principal amount of all Bonds outstanding, and the Issuer, the Company
and the Guarantor shall have had thirty days after receipt of such notice to
correct said default or cause said default to be corrected within the applicable
period; provided, however, if said default be such that it cannot be corrected
within the applicable period, it shall not constitute an event of default if
corrective action is instituted within the applicable period and diligently
pursued until the default is corrected.

  With regard to any default concerning which notice is given to the Issuer, the
Company and the Guarantor under the provisions of this Section, the Issuer
hereby grants the Company and the Guarantor full authority for account of the
Issuer to perform any covenant or obligation alleged in said notice to
constitute a default, in the name and stead of the Issuer with full power to do
any and all things and acts to the same extent that the Issuer could do and
perform any such things and acts and with power of substitution.

  SECTION 8.13.  NOTICE TO BONDHOLDERS; DEFAULTS; ACCELERATION.  If a default
occurs of which the Trustee is by Section 9.1(h) hereof required to take notice
or if notice of default be given as therein provided, then the Trustee shall
promptly give written notice thereof by first-class mail to the owner of each
Bond.  If the Trustee declares the principal of all Bonds then outstanding and
the interest accrued thereon to the date of such declaration immediately due and
payable pursuant to Section 8.2 hereof, then the Trustee shall promptly give
written notice thereof by first-class mail to the owner of each Bond.

                                   ARTICLE IX
                                  THE TRUSTEE
                                        
  SECTION 9.1.  ACCEPTANCE OF TRUSTS.  The Trustee hereby accepts the trusts
imposed upon it by this Indenture, and agrees to perform said trusts, but only
upon and subject to the following express terms and conditions to which the
Issuer, the owners of the Bonds and the Company agree:

       (a) The Trustee, prior to the occurrence of an event of default and after
     curing of all events of default which may have occurred, undertakes to
     perform such duties and only such duties as are specifically set forth in
     this Indenture. In case an event of default has occurred (which has not
     been cured or waived) of which the Trustee has notice or is deemed to have
     notice, the Trustee shall exercise such of the rights and powers vested in
     it by this Indenture, and
<PAGE>
 
     use the same degree of care and skill in their exercise, as a prudent man
     would exercise or use under the circumstances in the conduct of his own
     affairs.

       (b) The Trustee may execute any of the trusts or powers hereof and
     perform any of its duties by or through Affiliates, attorneys, accountants
     and other experts, agents or receivers and shall not be answerable for the
     conduct of the same appointed in good faith in accordance with the standard
     specified above, and shall be entitled to advice of counsel concerning its
     duties hereunder, and may in all cases pay such reasonable compensation to
     all such attorneys, accountants and other experts, agents and receivers as
     may reasonably be employed in connection with the trusts hereof.

       (c) The Trustee shall not be responsible for any recital herein, or in
     the Bonds, or for the recording or filing of any instrument required to
     secure the Bonds, or for the validity of the execution by the Issuer of
     this Indenture, or of any instruments of further assurance, or for the
     sufficiency of the security for the Bonds issued hereunder or intended to
     be secured hereby; but the Trustee shall be responsible for the filing of
     any continuation statements which may from time to time be required to be
     filed under the Mississippi Uniform Commercial Code in order to continue
     the perfection of the lien of this Indenture and, in filing such
     continuation statements, the Trustee shall be entitled to rely on an
     opinion of counsel. The Trustee shall not be responsible for insuring the
     Project or collecting any insurance moneys, or for the validity of the
     execution by the Issuer of this Indenture or of any supplements thereto or
     instruments of further assurance, or for the sufficiency of documents
     relating to the security for the Bonds issued hereunder or intended to be
     secured hereby, and the Trustee shall not be bound to ascertain or inquire
     as to the observance or performance of any covenants, conditions or
     agreements on the part of the Issuer or on the part of the Company under
     the Agreement except as herein set forth.

       (d) The Trustee shall not be accountable for the use of any Bonds
     authenticated or delivered hereunder. The Trustee may become the owner of
     Bonds secured hereby with the same rights which it would have if not the
     Trustee.

       (e) The Trustee shall be protected in acting upon any notice, request,
     consent, certificate, order, affidavit, letter, telegram or other paper or
     document believed to be genuine and correct and to have been signed or sent
     by the proper person or persons. Any action taken by the Trustee pursuant
     to this Indenture upon the request or authority or consent of any person
     who at the time of making such request or giving such authority or consent
     is the owner of any Bond, shall be conclusive and binding upon all future
     owners of the same Bond and upon Bonds issued in exchange therefor or in
     place thereof.

       (f) As to the existence or non-existence of any fact or as to the
     sufficiency or validity of any instrument, paper or proceeding, the Trustee
     shall be entitled to rely upon a certificate signed by the Executive
     Director or an authorized officer of the Issuer or an Authorized Company
     Representative under the Agreement as sufficient evidence of the facts
     therein contained and prior to the occurrence of a default of which the
     Trustee has been notified as provided in Section 9.1(h) hereof, or of which
     by Section 9.1(h) it is deemed to have notice,
<PAGE>
 
     shall also be at liberty to accept a similar certificate to the effect that
     any particular dealing, transaction or action is necessary or expedient,
     but may at its discretion secure such further evidence deemed by it to be
     necessary or advisable, but shall in no case be bound to secure the same.
     The Trustee may accept a certificate of the Executive Director or an
     authorized officer of the Issuer under the seal of the Issuer to the effect
     that an authorization in the form therein set forth has been adopted by the
     Issuer as conclusive evidence that such authorization has been duly adopted
     and is in full force and effect.

       (g)  The permissive right of the Trustee to do things enumerated in this
     Indenture shall not be construed as a duty and it shall not be answerable
     for other than its negligence or willful default.

       (h) The Trustee shall not be required to take notice or be deemed to have
     notice of any default hereunder except failure by the Issuer to cause to be
     made any of the payments to the Trustee required to be made by Article IV
     hereof, unless the Trustee shall be specifically notified in writing of
     such default by the Issuer or by an owner of Bonds, and all notices or
     other instruments required by this Indenture to be delivered to the
     Trustee, must, in order to be effective, be delivered at the principal
     corporate trust office of the Trustee (or such other office designated in
     writing by the Trustee to the Issuer), and in the absence of such notice so
     delivered the Trustee may conclusively assume there is no default except as
     aforesaid.

       (i)  At any and all reasonable times the Trustee, and its duly authorized
     agents, attorneys, experts, engineers, accountants and representatives,
     shall have the right fully to inspect any and all of the property herein
     conveyed, including all books, papers and records of the Issuer pertaining
     to the Project and the Bonds, and to take such memoranda from and with
     regard thereto as may be desired.

       (j) The Trustee shall not be required to give any bond or surety in
     respect of the execution of the said trusts and powers or otherwise in
     respect of the premises.

       (k) Notwithstanding anything elsewhere in this Indenture with respect to
     the authentication of any Bonds, the withdrawal of any cash, the release of
     any property, or any action whatsoever within the purview of this
     Indenture, the Trustee shall have the right, but shall not be required, to
     demand any showings, certificates, opinions, appraisals or other
     information, or corporate action or evidence thereof, in addition to that
     by the terms hereof required as a condition of such action, by the Trustee
     deemed desirable for the purpose of establishing the right to the
     authentication of any Bonds, the withdrawal of any cash, or the taking of
     any other action by the Trustee.

       (l) Before taking any action referred to in Section 8.3, 8.4, 8.8 or 9.4
     hereof the Trustee may require that a satisfactory indemnity bond be
     furnished for the reimbursement of all expenses to which it may be put and
     to protect it against all liability, except liability which is adjudicated
     to have resulted from its failure to comply with the standard of care
     prescribed by Section 9.1(a) and (g) hereof by reason of any action so
     taken.
<PAGE>
 
       (m) All moneys received by the Trustee shall, until used or applied or
     invested as herein provided, be held in trust for the purposes for which
     they were received but need not be segregated from other funds except to
     the extent required by law.

       (n) The Trustee may rely upon advice of counsel chosen by the Trustee
     with due care and shall not be responsible for any loss or damage resulting
     from any action or non-action by it taken or omitted to be taken in good
     faith in reliance upon advice of such counsel. The permissive right of the
     Trustee to do things enumerated in this Indenture shall not be construed as
     a duty and the Trustee shall not be answerable for the exercise of any
     discretion or power under this Indenture or for anything whatsoever in
     connection with the trusts created hereby, except only for its own
     negligence or willful misconduct, including that of its directors, officer,
     employees or agents.

       (o) None of the provisions contained in this Indenture shall require the
     Trustee to expend or risk its own funds or otherwise to incur financial
     liability in the performance of any of its duties or the exercise of any of
     its rights or powers hereunder, except as expressly provided herein. The
     Trustee shall not be required to give any bond or surety in respect to the
     execution of its rights and obligations hereunder.

       SECTION 9.2. FEES, CHARGES AND EXPENSES OF THE TRUSTEE. The Trustee shall
be entitled to payment and reimbursement for reasonable fees for its services
rendered hereunder and all advances, counsel fees and expenses (including the
allocated costs and expenses of its in-house counsel and legal staff) and other
expenses reasonably made or incurred by the Trustee in connection with such
services and in connection with entering into this Indenture, including any such
fees and expenses incurred in connection with action taken hereunder. Upon an
event of default, but only upon an event of default, the Trustee shall have a
first lien with right of payment prior to payment on account of principal of,
premium, if any and interest on any Bond upon the Trust Estate for the foregoing
fees, charges and expenses incurred by it.

       SECTION 9.3. TRUSTEE AS PAYING AGENT AND REGISTRAR. The Trustee shall
also serve as the Paying Agent and the Registrar for the Bonds, and all
references to fees, charges and expenses of the Trustee in this Indenture,
including without limitation such references in Section 9.2 hereof, shall be
deemed also to refer to the fees, charges and expenses of the Paying Agent and
the Registrar.

       SECTION 9.4.  INTERVENTION BY THE TRUSTEE.  In any judicial proceeding to
which Issuer is a party which, in the opinion of the Trustee and its counsel,
has a substantial bearing on the interests of owners of the Bonds, the Trustee
may intervene on behalf of Bondholders and shall do so if requested in writing
by the owners of at least a majority of the aggregate principal amount of Bonds
then outstanding, provided that the Trustee shall first have been offered such
indemnification in accordance with Section 9.1(1) hereof against such liability
as it may incur in or by reason of such proceeding.  The rights and obligations
of the Trustee under this Section are subject to the approval of a court of
competent jurisdiction.
<PAGE>
 
  SECTION 9.5.  SUCCESSOR TRUSTEE.  Any corporation or association into which
the Trustee may be converted or merged, or with which it may be consolidated, or
to which it may sell or transfer its corporate trust business and assets as a
whole or substantially as a whole, or any corporation or association resulting
from any such conversion, sale, merger, consolidation or transfer, to which it
is a party, shall be and become successor trustee hereunder and vested with all
of the title to the Trust Estate and all the trusts, powers, discretions,
immunities, privileges and all other matters as was its predecessor, without the
execution or filing of any instrument or any further act, deed or conveyance on
the part of any of the parties hereto, anything herein to the contrary
notwithstanding.  Any such successor trustee shall give notice thereof to the
Issuer and the Company.

  SECTION 9.6.  RESIGNATION BY THE TRUSTEE.  The Trustee and any successor
trustee may at any time resign from the trusts hereby created by giving at least
thirty days written notice by registered or certified mail, return receipt
requested, to the Issuer, the Company and the owner of each Bond, and such
resignation shall take effect upon the appointment of a successor trustee
pursuant to the provisions of Section 9.8 hereof and the acceptance by the
successor trustee of such appointment.

  SECTION 9.7.  REMOVAL OF THE TRUSTEE.  The Trustee may be removed at any time,
by an instrument or concurrent instruments in writing delivered to the Trustee
at least thirty days prior to the successor trustee's acceptance of its
appointment, to the Issuer and to the Company, and signed by the owners of a
majority in aggregate principal amount of Bonds then outstanding, or (so long as
no event of default is then existing under Section 6.1(a), (b), (c) or (d) of
the Agreement) signed by the Company and delivered to the Trustee and the
Issuer, and such removal shall take effect upon the appointment of a successor
trustee pursuant to the provisions of Section 9.8 hereof and the acceptance by
the successor trustee of such appointment.

  SECTION 9.8.  APPOINTMENT OF SUCCESSOR TRUSTEE BY BONDHOLDERS OR ISSUER.  In
case the Trustee hereunder shall resign or be removed, or be dissolved, or shall
be in the course of dissolution or liquidation, or otherwise become incapable of
acting hereunder, or in case it shall be taken under the control of any public
officer or officers, or of a receiver appointed by a court, a successor may be
appointed by the Issuer (at the direction of the Company so long as no event of
default is then existing under Section 6.1(a), (b), (c) or (d) of the
Agreement), or if no successor trustee is so appointed by the Issuer, then by
the owners of a majority in aggregate principal amount of Bonds then
outstanding, by an instrument or concurrent instruments in writing signed by
such owners, or by their duly authorized attorneys in fact, a copy of which
shall be delivered personally or sent by registered mail, return receipt
requested, to the Issuer and the Company; provided, that if a successor trustee
is not so appointed and accepts such appointment within thirty days of such
resignation, removal or other action, then the Trustee may petition a court of
competent jurisdiction for the appointment of a successor trustee.  Every such
Trustee appointed pursuant to the provisions of this Section shall be a trust
company or bank in good standing having a reported capital and surplus of not
less than $100,000,000, if there be such an institution willing, qualified and
able to accept the trust upon customary terms, and (unless the Company shall
then be in default under Section 6.1(a), (b), (c) or (d) of the Agreement) shall
be satisfactory to the Company.
<PAGE>
 
  SECTION 9.9.  CONCERNING ANY SUCCESSOR TRUSTEE.  Every successor trustee
appointed hereunder shall execute, acknowledge and deliver to its or his
predecessor and also to the Issuer and the Company an instrument in writing
accepting such appointment hereunder and thereupon such successor, without any
further act, deed or conveyance, shall become fully vested with all the estates,
properties, rights, powers, trust, duties and obligations of its predecessors;
but such predecessor shall, nevertheless, on the written request of the Issuer,
or of its successor, execute and deliver an instrument transferring to such
successor all the estates, properties, rights, powers and trusts of such
predecessor hereunder; and every predecessor Trustee shall deliver all
securities and moneys held by it as Trustee hereunder to its successor.  Should
any instrument in writing from the Issuer be required by any successor trustee
for more fully and certainly vesting in such successor the estate, rights, power
and duties hereby vested or intended to be vested in the predecessor, any and
all such instruments in writing shall, on request, be executed, acknowledged and
delivered by the Issuer.  The resignation of any Trustee and the instrument or
instruments removing any Trustee and appointing a successor hereunder, together
with all other instruments provided for in this Article, shall be filed or
recorded by the successor trustee in each recording office, if any, where the
Indenture shall have been filed or recorded.

  SECTION 9.10.  APPOINTMENT OF CO-TRUSTEE.  It is the purpose of this
Indenture that there shall be no violation of any law of any jurisdiction
(including particularly the law of Mississippi) denying or restricting the right
of banking corporations or associations to transact business as Trustee in such
jurisdiction.  It is recognized that in case of litigation under this Indenture
or the Agreement, and in particular in case of the enforcement of either on
default, or in case the Trustee deems that by reason of any present or future
law of any jurisdiction it may not exercise any of the powers, rights or
remedies herein granted to the Trustee or hold title to the properties, in
trust, as herein granted, or take any other action which may be desirable or
necessary in connection therewith, it may be necessary that the Trustee appoint
an additional individual or institution as a separate or co-trustee.  The
following provisions of this Section 9.10 are adapted to these ends.

  In the event that the Trustee appoints an additional individual or institution
as a separate or co-trustee, each and every remedy, power, right, obligation,
claim, demand, cause of action, immunity, estate, title, interest and lien
expressed or intended by this Indenture to be imposed upon, exercised by or
vested in or conveyed to the Trustee with respect thereto shall be imposed upon,
exercisable by and vest in such separate or co-trustee but only to the extent
necessary to enable such separate or co-trustee to exercise such powers, rights
and remedies and every covenant and obligation necessary to the exercise thereof
by such separate or co-trustee shall run to and be enforceable by either of
them.  Such separate or co-trustee shall deliver an instrument in writing
acknowledging and accepting its appointment hereunder to the Issuer, the Trustee
and the Company.

  Should any instrument in writing from the Issuer be required by the separate
trustee or co-trustee so appointed by the Trustee for more fully and certainly
vesting in and confirming to him or it such properties, rights, powers, trusts,
duties and obligations, any and all such instruments in writing shall, on
request, be executed, acknowledged and delivered by the Issuer.
<PAGE>
 
In case any separate trustee or co-trustee, or a successor to either, shall die,
become incapable of acting, resign or be removed, all the estates, properties,
rights, powers, trusts, duties and obligations of such separate trustee or co-
trustee, so far as permitted by law, shall vest in and be exercised by the
Trustee until the appointment of a new trustee or successor to such separate
trustee or co-trustee.

  The appointment of a co-trustee hereunder shall not in any way change the
Trustee's fiduciary duties and obligations hereunder.

  SECTION 9.11.  REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE TRUSTEE.  All
federal, state and local governmental, public and regulatory authority
approvals, consents, notices, authorizations, registrations, licenses,
exemptions, and filings that are required to have been obtained or made by
Trustee with respect to the authorization, execution, delivery and performance
by, or the enforcement against or by, the Trustee of this Indenture have been
obtained and are in full force and effect and all conditions of such approvals,
consents, notices, authorizations, registrations, licenses, exemptions, and
filings have been fully complied with.

  The Trustee is qualified to do business in the State of Mississippi.  The
Trustee has a combined capital and surplus of at least $50,000,000 or,
alternatively, a liability policy having the type of coverage and in an amount
acceptable to the Issuer and the Company.  The Trustee has an operations group
of at least four experienced trust officers, with primary responsibility for
municipal bond issues.  The Trustee administers at least 25 municipal bond
indentures aggregating at least $25,000,000 under its administration.

  SECTION 9.12.  REQUIRED REPORTING TO ISSUER.  The Trustee shall keep, or cause
to be kept, proper books of record and account in which complete and accurate
entries shall be made of all funds and accounts established by or pursuant to
this Indenture, which shall at all reasonable times be subject to the inspection
by the Issuer or the owners (or a designated representative thereof) of not less
than 10% in aggregate principal amount of the Bonds then outstanding.

  If requested in writing by the Issuer, the Trustee shall furnish to the Issuer
within five days after each date on which principal of, premium, if any  or
interest on, any of the Bonds is due, a written certificate setting forth the
following:

   (i) the designated name of the Bonds;

   (ii) the date on which such interest on any of the Bonds was due, the rate of
   interest borne by such Bonds and the amount of such interest due;

   (iii) the date on which such interest on any of the Bonds was paid and the
   amount of such interest paid;

   (iv) the date on which such principal of any of the Bonds was due (whether at
   maturity, upon call for redemption or acceleration) and the amount of such
   principal due;
<PAGE>
 
   (v) the date on which such principal of any of the Bonds was paid and the
   amount of such principal paid; and

   (vi)  the name of the Trustee.

  Not later than 30 days after the end of each calendar year commencing with the
calendar year 1998, the Trustee will prepare and file with the Issuer a
statement setting forth, with respect to the preceding year, (l) amounts
withdrawn from and deposited in each fund and account relating to the Bonds
hereunder, (2) the balance on deposit in each such fund or account relating to
the Bonds at the end of each year for which such statement is prepared, (3) a
brief description of all obligations held as investments in each such fund or
account relating to the Bonds, (4) the amount, if any, applied to the redemption
of the Bonds, a description of the Bonds or portions of Bonds so redeemed, and
an accounting of the Bonds of each maturity outstanding, and (5) any other
information that the Issuer may reasonably request or that the Trustee may from
time to time deem appropriate.


                                   ARTICLE X
                            SUPPLEMENTAL INDENTURES
                                        
  SECTION 10.1.  SUPPLEMENTAL INDENTURES NOT REQUIRING CONSENT OF BONDHOLDERS.
The Issuer and the Trustee may, without consent of, or notice to, any of the
Bondholders enter into an indenture or indentures supplemental to this Indenture
for any one or more of the following purposes:

       (a) To cure any ambiguity or formal defect or omission in this Indenture;

       (b) To grant to or confer upon the Trustee for the benefit of the
   Bondholders any additional rights, remedies, powers or authority that may
   lawfully be granted to or conferred upon the Bondholders or the Trustee;

       (c) To evidence the appointment of a separate trustee or a co-trustee or
   the succession of a new trustee hereunder;

       (d) To provide for an uncertificated book-entry system of registration
   for the Bonds;

       (e) To preserve the tax exempt status of interest on the Bonds as
   required in an opinion of Bond Counsel delivered to the Trustee;

       (f) To obtain or maintain an appropriate rating or ratings on the Bonds;
   and

       (g) To make any other change which, in the judgment of the Trustee, is
   not to the prejudice of the Bondholders.
<PAGE>
 
  SECTION 10.2.  SUPPLEMENTAL INDENTURES REQUIRING CONSENT OF BONDHOLDERS.
Exclusive of supplemental indentures covered by Section 10.1 hereof and subject
to the terms and provisions contained in this Section, and not otherwise, the
owners of not less than a majority in aggregate principal amount of the Bonds
then outstanding shall have the right, from time to time, anything contained in
this Indenture to the contrary notwithstanding, to consent to and approve the
execution by the Issuer and the Trustee of such other indenture or indentures
supplemental hereto as shall be deemed necessary and desirable by the Issuer for
the purpose of modifying, altering, amending, adding to or rescinding, in any
particular, any of the terms or provisions contained in this Indenture or in any
supplemental indenture; provided, however, that nothing in this Section or in
Section 10.1 hereof contained shall permit, or be construed as permitting,
without the consent of the owners of 100% in aggregate principal amount of the
Bonds then outstanding, (a) an extension of the maturity (or mandatory
redemption date) of the principal of, or the interest on, any Bond issued
hereunder, or (b) a reduction in the principal amount of, or rate of interest
on, any Bond issued hereunder, or (c) a privilege or priority of any Bond or
Bonds over any other Bond or Bonds, or (d) a reduction in the aggregate
principal amount of the Bonds the owners of which are required to consent to
such supplemental indenture, or (e) the creation of any lien ranking prior to or
on a parity with the lien of this Indenture on the Trust Estate or any part
thereof, or (f) deprivation of the owner of any Bond then outstanding of the
lien hereby created on the Trust Estate.

  If at any time the Issuer shall request the Trustee to enter into any such
supplemental indenture for any of the purposes of this Section, the Trustee
shall, upon being satisfactorily indemnified with respect to expenses, cause
notice of the proposed execution of such supplemental indenture to be mailed by
first class mail to all Bondholders.  Such notice shall briefly set forth the
nature of the proposed supplemental indenture and shall state that copies
thereof are on file at the corporate trust office of the Trustee for inspection
by all Bondholders.  If, within sixty days or such longer period as shall be
prescribed by the Issuer following the mailing of such notice, the owners of not
less than a majority or 100%, as the case may be, in aggregate principal amount
of the Bonds then outstanding shall have consented to and approved the execution
thereof as herein provided, no owner of any Bond shall have any right to object
to any of the terms and provisions contained therein, or the operation thereof,
or in any manner to question the propriety of the execution thereof, or to
enjoin or restrain the Trustee or the Issuer from executing the same or from
taking any action pursuant to the provisions thereof. Upon the execution of any
such supplemental indenture as in this Section permitted and provided, this
Indenture shall be and be deemed to be modified and amended in accordance
therewith.

  SECTION 10.3.  CONSENT OF COMPANY.  Anything herein to the contrary
notwithstanding, a supplemental indenture under this Article shall not become
effective unless and until the Company shall have consented to the execution and
delivery of such supplemental indenture.  In this regard, the Trustee shall
cause notice of the proposed execution of any such supplemental indenture
together with a copy of the proposed supplemental indenture to be mailed by
certified or registered mail, return receipt requested, to the Company at least
fifteen days prior to the proposed date of execution and delivery of any such
supplemental indenture.  The Company shall be deemed to have consented to the
execution and delivery of any such supplemental indenture if
<PAGE>
 
the Trustee does not receive a letter of protest or objection thereto signed by
or on behalf of the Company by an Authorized Company Representative on or before
4:30 o'clock P.M. local time at the principal corporate trust office or other
designated corporate trust office of the Trustee, on the fifteenth day after the
mailing of said notice.

  SECTION 10.4.  OPINION OF BOND COUNSEL.  The Trustee may require that the
Company deliver to the Trustee at the Company's expense an opinion of Bond
Counsel upon which the Trustee may rely to the effect that a supplemental
indenture is permitted by applicable law and will not adversely affect the tax-
exempt status of the interest on the Bonds and that such supplemental indenture
complies with the terms and provisions of this Indenture.

                                   ARTICLE XI
                      AMENDMENT OF AGREEMENT AND GUARANTY
                                        
  SECTION 11.1.  AMENDMENTS, ETC., TO AGREEMENT AND GUARANTY NOT REQUIRING
CONSENT OF BONDHOLDERS.  The Trustee shall without the consent of or notice to
the Bondholders consent to any amendment, change or modification of the
Agreement or the Guaranty which does not adversely affect the Bondholders (i) as
may be required by the provisions of the Agreement, the Guaranty or this
Indenture, (ii) for the purpose of curing any ambiguity or formal defect or
omission therein, (iii) to describe more fully or to amplify or correct the
description of any property financed under the Agreement or intended so to be,
(iv) to preserve the tax exempt status of interest on the Bonds, (v) to obtain
or maintain an appropriate rating or ratings on the Bonds, or (vi) in connection
with any other change therein which, in the judgment of the Trustee, is not to
the prejudice of the Bondholders.

  SECTION 11.2.  AMENDMENTS, ETC., TO AGREEMENT AND GUARANTY REQUIRING CONSENT
OF BONDHOLDERS.  Except for the amendments, changes or modifications as provided
in Section 11.1 hereof, the Trustee shall not consent to any other amendment,
change or modification of the Agreement or the Guaranty without the giving of
notice and the written approval or consent of the owners of not less than a
majority in aggregate principal amount of the Bonds at the time outstanding
given as in this Section provided; provided, however, that nothing in this
Section or in Section 11.1 herein contained shall permit or be construed as
permitting, without the consent of the owners of 100% in aggregate principal
amount of the Bonds then outstanding, (a) an extension of time for the payment
of an amount due pursuant to Section 4.2(a) of the Agreement or an extension of
time for an amount due under the Guaranty, (b) a reduction in the total amount
due pursuant to Section 4.2(a) of the Agreement or under the Guaranty, (c) a
reduction in the aggregate principal amount of the Bonds the owners of which are
required to consent to such amendment, change or modification of the Agreement
or the Guaranty, or (d) any release or modification of the obligation of a
Guarantor under the Guaranty.  If at any time the Issuer, the Company or the
Guarantor shall request the consent of the Trustee to any such proposed
amendment, change or modification of the Agreement or Guaranty, the Trustee
shall, upon being satisfactorily indemnified with respect to expenses, cause
notice of such proposed amendment, change or modification to be given in the
same manner as provided by Section 10.2 hereof with
<PAGE>
 
respect to supplemental indentures. Such notice shall briefly set forth the
nature of such proposed amendment, change or modification and shall state that
copies of the instrument embodying the same are on file at the principal
corporate trust office of the Trustee for inspection by all Bondholders.

  SECTION 11.3.  OPINION OF BOND COUNSEL.  The Trustee may require that the
Company deliver to the Trustee at the Company's expense an opinion of Bond
Counsel upon which the Trustee may rely to the effect that any amendment, change
or modification of the Agreement is permitted by applicable law and will not
adversely affect the tax-exempt status of interest on the Bonds and that such
amendment, change or modification complies with the terms and provisions of the
Agreement and this Indenture.


                                  ARTICLE XII
                                 MISCELLANEOUS
                                        
  SECTION 12.1.  CONSENTS, ETC., OF BONDHOLDERS.  Any consent, request,
direction, approval, objection or other instrument required by this Indenture to
be signed and executed by the Bondholders may be in any number of concurrent
documents and may be executed by such Bondholders in person or by agent
appointed in writing.  Proof of the execution of any such consent, request,
direction, approval, objection or other instrument or of the writing appointing
any such agent and of the ownership of Bonds, if made in the following manner,
shall be sufficient for any of the purposes of this Indenture, and shall be
conclusive in favor of the Trustee with regard to any action taken by it under
such request or other instrument, namely:

       (a) The fact and date of the execution by any person of any such writing
   may be proved by the certificate of any officer in any jurisdiction who by
   law has power to take acknowledgments within such jurisdiction that the
   person signing such writing acknowledged before him the execution thereof, or
   by an affidavit of any witness to such execution.

       (b) The fact of ownership of Bonds and the amount or amounts, numbers and
   other identification of such Bonds, and the date of owning the same shall be
   proved by the registration books of the Issuer maintained by the Trustee
   pursuant to Section 2.8 hereof.

       For all purposes of this Indenture and of the proceedings for the
enforcement hereof, such person shall be deemed to continue to be the owner of
such Bond until the Trustee shall have received notice in writing to the
contrary.

       In determining whether the owners of the requisite principal amount of
Bonds outstanding have given any request, demand, authorization, direction,
notice, consent or waiver under this Indenture, Bonds owned by the Company or
any affiliate of the Company shall be disregarded and deemed not to be
Outstanding under this Indenture, except that in determining whether the Trustee
shall be protected in relying upon any such request, demand, authorization,
direction, notice, consent or waiver, only Bonds which the Trustee knows to be
so owned shall
<PAGE>
 
be so disregarded. For purposes of this paragraph (a) an "affiliate" means any
person directly or indirectly controlling or controlled by or under direct or
indirect common control with the Company; and for the purposes of this
definition (b) "control", means the power to direct the management and policies
of such person, directly or indirectly, whether through the ownership of voting
securities, by contract or otherwise. Notwithstanding the foregoing, Bonds so
owned which have been pledged in good faith shall not be disregarded as
aforesaid if the pledgee establishes to the satisfaction of the Trustee the
pledgee's right so to act with respect to such Bonds and that the pledgee is not
the Company or any affiliate of the Company.

  Notwithstanding the foregoing paragraph, Bonds owned by the Company or any
affiliate of the Company shall be deemed to be Outstanding under the Indenture
if all the Bonds Outstanding at the time are owned by the Company or an
affiliate of the Company; provided, however, that in such event the Company or
such affiliate may not consent to any supplement to this Indenture that would
affect the validity of the Bonds or the tax-exempt status of the interest on the
Bonds; and provided further that if a supplement to this Indenture is executed
at a time when the Company or any affiliate is the owner of all the Outstanding
Bonds, Bond Counsel shall render an opinion that the execution of the supplement
to this Indenture does not adversely affect the validity of the Bonds or the
tax-exempt status of the interest thereon.

  SECTION 12.2.  LIMITATION OF RIGHTS.  With the exception of rights herein
expressly conferred, nothing expressed or mentioned in or to be implied from
this Indenture or the Bonds is intended or shall be construed to give to any
person or company other than the parties hereto and the Company, the Guarantor
and the owners of the Bonds, any legal or equitable right, remedy or claim under
or with respect to this Indenture or any covenants, conditions and provisions
herein contained; this Indenture and all of the covenants, conditions and
provisions hereof being intended to be and being for the sole and exclusive
benefit of the parties hereto and the Company, the Guarantor and the owners of
the Bonds as herein provided.

  SECTION 12.3.  SEVERABILITY.  If any provisions of this Indenture shall be
held or deemed to be or shall, in fact, be illegal, inoperative or
unenforceable, the same shall not affect any other provision or provisions
herein contained or render the same invalid, inoperative, or unenforceable to
any extent whatever.

  SECTION 12.4.  NOTICES.  Unless otherwise specifically provided herein, any
notice, request, complaint, demand, communication or other paper shall be
sufficiently given and shall be deemed given (i) on the fourth day following the
day on which the same has been mailed by first class mail, postage prepaid, or
(ii) when the same are delivered, in each case to the parties at the following
addresses: if to the Issuer, at Mississippi Business Finance Corporation, 1300
Walter Sillers Building, P.O. Box 849, Jackson, Mississippi 39205-0849
Attention: Executive Director; if to the Trustee, at Deposit Guaranty National
Bank, One Deposit Guaranty Plaza-DGP#8, P.O. Box 23100, Jackson, Mississippi
39225-3100 Attention: Corporate Trust Department; if to the Company, at
Mississippi Phosphates Corporation, c/o Mississippi Chemical Corporation, 3622
Highway 49 East, Yazoo City, Mississippi 39199-0388 Attention: Chief
<PAGE>
 
Financial Officer; and if to the Guarantor at Mississippi Chemical Corporation,
3622 Highway 49 East, Yazoo City, Mississippi 39199-0388 Attention: Chief
Financial Officer. A duplicate copy of each notice, certificate or other
communication given hereunder by either the Issuer, the Guarantor or the Company
shall also be given to the Trustee. The Issuer, the Company, the Guarantor and
the Trustee may, by notice given hereunder, designate any further or different
addresses to which subsequent notices, certificates or other communications
shall be sent.

  SECTION 12.5.  PAYMENTS DUE ON SATURDAYS, SUNDAYS AND HOLIDAYS.  In any case
where the date of maturity of interest on or principal of the Bonds or the date
fixed for redemption of any Bonds shall be at the principal corporate trust
office of the Trustee, a Saturday, a Sunday or a legal holiday or a day on which
banking institutions are required or authorized by law to close (and the
principal corporate trust office of the Trustee is in fact closed), then payment
of principal or interest need not be made on such date but may be made on the
next succeeding business day with the same force and effect as if made on the
date of maturity or the date fixed for redemption.

  SECTION 12.6.  ACTION BY COMPANY AND ISSUER.  Wherever it is herein provided
or permitted for any action to be taken by the Company, such action may be taken
by an Authorized Company Representative under the Agreement unless the context
clearly indicates otherwise.  Whenever it is herein provided or permitted for
any action to be taken by the Issuer, such action may be taken by an Authorized
Issuer Representative under the Agreement unless the context clearly indicates
otherwise.

  SECTION 12.7.  COUNTERPARTS.  This Indenture may be simultaneously executed in
several counterparts, each of which shall be an original and all of which shall
constitute but one and the same instrument.

  SECTION 12.8.  APPLICABLE PROVISIONS OF LAW.  This Indenture shall be governed
by and construed in accordance with the laws of the State of Mississippi
applicable to contracts performed wholly therein.

  SECTION 12.9.  NO RECOURSE.  No recourse shall be had for the payment of the
principal of, premium, if any  and interest on any of the Bonds or for any claim
based thereon or upon any obligation, covenant or agreement contained in this
Indenture or the Agreement against any past, present or future member, officer,
agent or employee of the Issuer, or any incorporator, member, officer, employee,
director or  trustee of any successor corporation, as such, either directly or
through the Issuer or any successor corporation, under any rule of law or
equity, statute or constitution or by the enforcement of any assessment or
penalty or otherwise, and all such liability of any such incorporator, member,
officer, employee, director, agent or trustee as such is hereby expressly waived
and released as a condition of and consideration for the execution of this
Indenture or the Agreement and the issuance of the Bonds.


                  [Remainder of page left intentionally blank]
<PAGE>
 
   IN WITNESS WHEREOF, the Mississippi Business Finance Corporation and Deposit
Guaranty National Bank, have caused this Indenture of Trust to be executed in
their respective corporate names and the Mississippi Business Finance
Corporation has caused its corporate seal to be hereunto affixed and attested by
its duly authorized officer, all as of the day first above written.

                                  MISSISSIPPI BUSINESS FINANCE CORPORATION


                                  By:  ______________________________
                                            Executive Director

ATTEST:

By:  ________________________
            Secretary

(SEAL)


                                  DEPOSIT GUARANTY NATIONAL BANK,
                                  as Trustee


                                  By:  ______________________________
                                             Authorized Officer

ATTEST:

By:  _______________________
            Title: