<PAGE>
 
                                 [TERRA LOGO]
                                        

                             CONVERSION STATEMENT

     Until March 31, 1997, holders of Senior Preference Units ("SPUs") of Terra
Nitrogen Company, L.P. ("TNCLP") have the right to convert SPUs into Common
Units of TNCLP.

      Conversion decision required - your consideration is very important

     Holders who fail to take action will, by default, remain SPU holders and be
subject to redemption at a price of $21.50 per SPU.  The rights and benefits of
Common Units are substantially similar to those that have existed for the SPUs,
although Common Units do not have any preference rights.  After December 31,
1996, SPUs are no longer entitled to participate in quarterly cash distributions
in excess of the minimum quarterly distribution ("MQD") of $0.605 per unit.  The
Common Units will receive cash distributions, if any, only after SPUs have been
paid the MQD. Holders must convert to Common Units in order to participate in
any cash distributions above the MQD.  (Cash distributions in excess of $0.605
per unit have been paid on SPUs and Common Units for twelve consecutive
quarters.)  The last reported sale of SPUs on the New York Stock Exchange
Composite Tape on December 20, 1996 was $45 per SPU.

     The Common Units are approved for listing on the New York Stock Exchange,
provided that a minimum level of elections to convert is satisfied.  The General
Partner currently anticipates that the thresholds for NYSE trading of the Common
Units will be satisfied.  If the Common Units cannot be listed on the NYSE,
despite TNCLP's good faith attempts, publicly held SPUs may not convert.

     These are your alternatives:

     1.  If you wish to remain a holder of SPUs, no action on your part is
         required.

     2.  If you want to convert to Common Units, either you or the nominee
         holding your SPUs must complete and deliver the Conversion
         Notice/Letter of Transmittal, along with your SPU certificates, as
         instructed on the form.

     This Conversion Statement provides you with detailed information about the
conversion process and the consequences of the decision you make.  We encourage
you to read this document carefully.  In addition, you may obtain information
about TNCLP from documents TNCLP has filed with the Securities and Exchange
Commission.

         THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE
          SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES
          COMMISSION, NOR HAS THE SECURITIES AND EXCHANGE COMMISSION
              OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
                    ACCURACY OR ADEQUACY OF THIS CONVERSION
                     STATEMENT.  ANY REPRESENTATION TO THE
                        CONTRARY IS A CRIMINAL OFFENSE.

This Conversion Statement is dated and mailed to SPU holders on December 31,
1996.
<PAGE>
 
                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
 
                                                                   Page
                                                                   ----
<S>                                                                <C>
 
     Conversion Q & A................................................3
     Summary.........................................................8
     Conversion Background..........................................13
     The Conversion.................................................13
     Certain Federal Income Tax Consequences........................16
     Market Price of Securities; Cash Distributions.................17
     Description of Units...........................................19
     Exchange Agent.................................................20
</TABLE>


                             AVAILABLE INFORMATION

     TNCLP is subject to the information requirements of the Securities Exchange
Act of 1934, as amended, and is required to file periodic reports and other
information with the Securities and Exchange Commission (the "Commission").
Reports and other information filed by TNCLP can be inspected and copied at the
public reference facilities maintained by the Commission at Room 1024, 450 Fifth
Street, N.W., Washington, D.C. 20549, and at the Regional Offices of the
Commission at 75 Park Place, New York, New York 10007 and at Northwestern Atrium
Center, 500 West Madison Street, Suite 1400, Chicago, Illinois 60661. The
Commission also maintains a Web site that contains reports and other information
regarding registrants, like TNCLP, that file electronically with the Commission
(site address http://www.sec.gov).  In addition, reports and other information
may be inspected, with respect to TNCLP, at the offices of the New York Stock
Exchange, 20 Broad Street, New York, New York 10005, upon which the units of
TNCLP are listed.

                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

     The following documents filed with the Commission (File No. 1-10877) are
incorporated herein by reference: (i) TNCLP's Annual Report on Form 10-K for the
fiscal year ended December 31, 1995; (ii) TNCLP's Quarterly Report on Form 10-Q
for the fiscal quarters ended March 31, 1996, June 30, 1996 and September 30,
1996; and (iii) the description of the Units, set forth in the Registration
Statement on Form 8-A dated September 27, 1991, as amended by Form 8 dated
October 16, 1991.

     All documents filed by TNCLP pursuant to Section 13(a), 13(c), 14 or 15(d)
of the Exchange Act subsequent to the date of this Conversion Statement and
prior to the termination of the conversion period contemplated hereby shall be
deemed to be incorporated by reference into this Conversion Statement and to be
a part hereof from the date of filing of such documents. Any statement contained
in a document incorporated or deemed to be incorporated by reference herein
shall be deemed to be modified or superseded for purposes of this Conversion
Statement to the extent that a statement contained herein or in any subsequently
filed document which also is or is deemed to be incorporated by reference herein
modifies or supersedes such statement. Any such statement so modified or
superseded shall not be deemed, except as so modified or superseded, to
constitute a part of this Conversion Statement.

                                       2
<PAGE>
 
     TNCLP will provide without charge to each person to whom this Conversion
Statement is delivered, upon the written or oral request of such person, a copy
of any or all of the documents incorporated herein by reference (other than
exhibits, unless such exhibits are specifically incorporated by reference in
such documents).  Written requests for such copies should be directed to
Corporate and Investor Relations, Terra Nitrogen, 600 Fourth Street, P.O. Box
6000, Sioux City, Iowa 51102-6000 (phone (712) 277-5438).

                               _________________

     No person is authorized in connection with this conversion to give any
information or to make any representations other than as contained or
incorporated by reference in this Conversion Statement, and, if given or made,
such information or representations must not be relied upon as having been
authorized by TNCLP or the General Partner.  This Conversion Statement does not
constitute an offer to sell or the solicitation or an offer to buy any of the
securities offered hereby to any person in any jurisdiction in which it is
unlawful to make such offer or solicitation. Neither the delivery of this
Conversion Statement nor any conversion effectuated hereunder shall, under any
circumstances, create any implication that the information contained herein is
correct as of any date subsequent to the date hereof.

                               _________________

                               CONVERSION Q & A

     The following summary is qualified in its entirety by reference to, and
should be read in conjunction with, the more detailed information appearing
elsewhere in this Conversion Statement or incorporated by reference herein.

------------------------------------------------------------------
What changed for Senior Preference Unitholders at the end of 1996?
------------------------------------------------------------------

     Starting December 31, 1996, holders of SPUs became limited in the amount of
quarterly cash distributions they can receive, as further described below.  In
addition, after April 1, 1997, SPUs can be redeemed by TNCLP for $21.50 per SPU.
These changes are in accordance with TNCLP's Partnership Agreement.

     Cash distributions to SPU holders will be no more than the minimum
quarterly distribution (MQD) of $0.605 per unit ($2.42 annually).  The MQD is
considerably less than cash distributions to SPU holders of $5.00 per SPU paid
in 1995 and $7.73 per SPU paid in 1996.  The redemption price of $21.50 per SPU
is also considerably less than the closing market price for SPUs of $45 on
December 20, 1996.

     SPU holders who want to retain their rights to participate in distributions
greater than the MQD and avoid having SPUs redeemed by TNCLP for $21.50 per SPU,
can elect to convert to "Common Units" of TNCLP before March 31, 1997. This
conversion is on a one-for-one basis and at no cost to the holder.  Although the
Common Units are not publicly traded at the current time, the New York Stock
Exchange has approved an application to list the Common Units, provided that a
minimum level of elections to convert is satisfied. (The General Partner
currently anticipates that the NYSE thresholds will be satisfied.)  If the

                                       3
<PAGE>
 
Common Units cannot be listed on the NYSE, despite TNCLP's good faith attempts,
publicly held SPUs may not convert.

-------------------------------------------------------------
What are the ramifications of converting to the Common Units?
-------------------------------------------------------------

     Quarterly distributions on the Common Units will be paid after the
nonconverted SPU holders have been paid the MQD.  Common Unitholders share on a
quarterly basis all the remaining Available Cash with the General Partner, which
could be more or less than the MQD on a per unit basis. (Cash distributions in
excess of the MQD have been made on SPUs and Common Units for twelve consecutive
quarters.)  The Common Units will not be subject to the redemption feature, but
can be called at a then-current market price by TNCLP, the General Partner or
its affiliates under certain circumstances as described on the next page.

-----------------------------------------------------------------------
What are the ramifications of remaining a Senior Preference Unitholder?
-----------------------------------------------------------------------

     Again, after December 31, 1996, nonconverting SPU holders will not receive
any distributions in excess of the MQD, although they will receive their MQD
before the Common Units are paid  A Reserve Amount equal to one year's MQD
payments will be maintained to support distributions on nonconverted SPUs.  If
the SPUs no longer meet the NYSE's listing requirements, the SPUs would be
subject to delisting.

     In addition, according to the Partnership Agreement, TNCLP has the right,
and currently expects, to redeem nonconverted SPUs at a price of $21.50 per SPU.

----------------------------------------------------------------------------
What is the effect of this conversion process on cash distributions normally
paid in February?
----------------------------------------------------------------------------

     The Partnership intends to distribute cash to unitholders at the end of
February 1997 equal to the MQD ($0.605 per unit). The excess of Available Cash
for the quarter ended December 31, 1996 over the amounts distributed in February
1997 will be paid to all partners other than nonconverting SPUs based on a
record date shortly after the expiration of the conversion period.  An
announcement concerning the amount and timing of the distribution is scheduled
for late January 1997.  Nonconverting SPU holders will not receive any cash
distributions in excess of the MQD.

-------------------------------------------------------------------------
Does the General Partner and its affiliates intend to convert their SPUs?
-------------------------------------------------------------------------

     The General Partner and its affiliates intend to convert their respective
SPUs into Common Units.  The General Partner and its affiliates currently own
6,974,900 SPUs and 5,172,414 Common Units.  The public owns 6,661,464 SPUs.

---------------------------------------
How long do I have to make my decision?
---------------------------------------

     You have 90 days to make your decision (until 5:00 p.m. Eastern (Daylight)
Time on March 31, 1997).  Failure to return 

                                       4
<PAGE>
 
a completed Conversion Notice/Letter of Transmittal, along with your SPU
certificates, within the 90 day time frame will cause your units to remain SPUs.

Can decisions to convert be withdrawn?

     Decisions to convert SPUs into Common Units that have been completed by
delivering a Conversion Notice/Letter of Transmittal may be withdrawn at any
time prior to 5:00 p.m. Eastern Standard (Daylight) Time on March 31, 1997 by
contacting the Exchange Agent, First Chicago Trust Company of New York, and
delivering a letter to that effect.

If I want to convert, what do I do?

     If you are the holder of record (a person to whom a certificate was
issued), you need to complete the Conversion Notice/Letter of Transmittal and
forward it along with your SPU certificate to the Exchange Agent.

     You are not the holder of record if your broker or another nominee holds
the SPUs on your behalf.  In these cases you need to instruct your broker or
other nominee to complete the conversion election on your behalf.

Will the SPUs convert to Terra Industries Inc. common stock (exchange symbol:
TRA)?

     No, the SPUs will have the option to convert to Common Units of TNCLP, not
common stock of Terra Industries.

Can the SPUs be redeemed?

     TNCLP may redeem any or all of the outstanding SPUs at any time upon at
least 30 but not more than 60 days notice.  If, after giving effect to an
anticipated redemption, fewer than 1.0 million SPUs would be held by non-
affiliates of the General Partner, TNCLP must redeem all such SPUs if it redeems
any SPUs.  The redemption price per SPU is $21.50. TNCLP currently expects that
it will seek to redeem all outstanding SPUs sometime after the conversion
process is completed.

Under what circumstances can the Common Units be called?

     If at any time not more than 25% of the issued and outstanding Common Units
are held by non-affiliates of the General Partner, either TNCLP, the General
Partner or its affiliates may call all such outstanding units held by non-
affiliated persons. TNCLP shall give at least 30 but not more than 60 days
notice of its decision to purchase the outstanding units of the class. The
purchase price per unit will be the greater of (1) the average of the previous
twenty trading days closing prices as of the date five days before the purchase
is announced or (2) the highest price paid by the General Partner or any of its
affiliates for any unit within the 90 days preceding the date the purchase is
announced.  In the event all SPUs owned by the General Partner and its
affiliates are converted, they will own 12.15 million Common Units.  If at least
4.05 million of the 6.66 million publicly held SPUs convert, the non-affiliated
persons will own more 

                                       5
<PAGE>
     
than 25% of the issued and outstanding Common Units (assuming the General
Partner and its affiliates do not acquire any additional Common Units).

How will future cash distributions be determined?

     Cash distributions will continue to be determined using the same
methodology as in the past.  The terms of the Partnership Agreement require
TNCLP to distribute 100% of its Available Cash.  Available Cash is largely
dependent on TNCLP earnings. The principal change in future cash distributions
is that nonconverted SPU holders are only entitled to the MQD.

What level of conversions is needed for listing Common Units on the NYSE?

     The Common Units are approved for listing on the NYSE if after conversion
there are at least 1.1 million publicly held Common Units, the aggregate market
value of the publicly held Common Units is at least $40 million and there are at
least 2,000 holders of "round lots" of Common Units. The General Partner
currently anticipates that the thresholds for NYSE trading of Common Units will
be satisfied.

If NYSE trading of Common Units is initiated, what will be the price of the
Common Units and how will it be determined?

     Currently there is no public trading market for the Common Units.  The
public market will determine the price.  Since this is a one-for-one conversion
of substantially similar securities, the Common Units will presumably be valued
substantially the same as the SPUs they will replace.  This value will depend
on, among other things, TNCLP performance, general market conditions and cash
distributions.  The closing market price of SPUs as of December 20, 1996 was
$45.

When will the Common Units begin trading on the NYSE?
 
     Assuming sufficient conversion elections are made, Common Units are
expected to begin trading on the NYSE on April 1, 1997 (the day following the
expiration of the conversion period). Beginning April 1, 1997, any trading of
Units on the NYSE is anticipated to be made under the symbol "TNH" for Common
Units and "TNH PR" for SPUs.

What happens if the Common Units cannot be listed on the NYSE?

     If the Common Units cannot be listed on the NYSE, despite TNCLP's good
faith attempts, only SPUs owned by the General Partner and its affiliates may be
converted into Common Units.  SPUs held by all others will remain SPUs, will no
longer participate in distributions in excess of the MQD and will be subject to
redemption at a price of $21.50.

After the conversion period is over, will there be a public market for the SPUs?

     After the conversion period, the SPUs will continue to trade on the NYSE

                                       6
<PAGE>
 
under the new symbol "TNH PR" separate from the Common Units only if the SPUs
continue to meet the exchange listing requirements and are not otherwise
redeemed.  If the SPUs do not continue to meet the NYSE listing requirements,
the SPUs would be subject to delisting.  It is entirely possible that there
would be an insufficient number of SPUs to provide a liquid secondary trading
market.

Will the General Partner continue to be entitled to incentive distributions?

     The General Partner will continue to be entitled to incentive
distributions. Nonconverted SPUs will receive only the MQD, and the balance of
Available Cash will be distributed to the Common Unitholders and to the General
Partner.  The General Partner's percentage interest in distributions increases
as distributions to the Common Unitholders exceed specified target levels (e.g.,
distributions of Available Cash exceeding $1.045 per Common Unit per quarter are
paid 50% to Common Unitholders and 50% to the General Partner).

If I convert an SPU into a Common Unit, what will be the tax basis of the Common
Unit and will the conversion generate a taxable transaction?

     Upon conversion of an SPU into a Common Unit, the holder of the SPU will
not recognize gain or loss and will have a basis and holding period in the
Common Unit equal to the basis and holding period of the converted SPU.

Will future distributions be supported by cash reserves held by TNCLP?
 
     TNCLP has been required to maintain cash reserves equal to one year's MQD
payments on outstanding SPUs.  This requirement would be ongoing for SPUs that
do not convert.  No reserves are required for Common Units.  It is anticipated
that any reduction in the Reserve Amount from its current level of $18.5 million
will be available for cash distributions in May 1997.

                                       7
<PAGE>
 
                                    SUMMARY

     The following summary is qualified in its entirety by reference to, and
should be read in conjunction with, the more detailed information and financial
statements appearing elsewhere in this Conversion Statement or incorporated by
reference herein.

                                  The Company

     Terra Nitrogen Company, L.P. ("TNCLP" or the "Company") is one of the
largest U.S. manufacturers and marketers of nitrogen fertilizer products.  The
Company produces ammonia, urea and urea ammonium nitrate solution ("UAN"), which
are used by farmers to provide crops with nitrogen, an essential nutrient for
plant growth.  The Company sells its products to dealers, distributors, other
fertilizer producers and traders for ultimate distribution principally in the
Central and Southern Plains, Cornbelt and Western regions of the United States
and areas served by the Mississippi, Missouri, Ohio and Illinois River systems.

     The Company's two nitrogen fertilizer plants are advantageously located
with ready access, via barge, rail and pipeline, to major farming areas in the
United States.  The Company's plant in Verdigris, Oklahoma is the largest
domestic UAN production facility, and its plant in Blytheville, Arkansas is one
of the largest domestic urea production facilities.  Both of the Company's
plants manufacture anhydrous ammonia (referred to as ammonia), the majority of
which is directly upgraded at the plants into UAN and urea.

     The U.S. nitrogen fertilizer business is both seasonal and volatile due to
a number of factors that affect U.S. and world supply and demand.  Although
there have historically been wide imbalances between world supply and demand for
nitrogen fertilizers, the Company believes that a more favorable balance has
developed in recent years, particularly in the U.S. market, which accounts for
over 95% of the Company's sales.  As a result, the Company and many other U.S.
producers have been operating at near-capacity rates.  Nitrogen fertilizer is a
global commodity, however, and the profitability and cash flow of nitrogen
fertilizer producers, including the Company, has been volatile in the past and
can be expected to be volatile in the future.

     The principal executive offices of the Company are located at 5100 East
Skelly Drive, Suite 800, Tulsa, Oklahoma 74135, and its telephone number is
(918) 660-0050.

                                       8
<PAGE>
 
                                  Risk Factors

     Limited partner interests are inherently different from capital stock of a
corporation. Current and prospective holders of SPUs or Common Units
(collectively, the "Units") should consider the following factors in evaluating
the Units:

     .  The markets for TNCLP's products are seasonal and volatile.
 
     .  TNCLP's business is highly competitive.
 
     .  TNCLP's profitability and cash flow are affected by the price and
        availability of natural gas, as well as the price of its nitrogen
        products.
        
     .  Voting rights of holders of Units are limited; pursuant to the terms of
        the Partnership Agreement, the General Partner manages and controls
        TNCLP.
 
     .  The General Partner and its affiliates may potentially have conflicts of
        interest with TNCLP and the holders of Units, although the General
        Partner has undertaken by written agreement to act fairly and reasonably
        in connection with TNCLP and the holders of Units. (The General Partner
        has also elected two independent directors to its board of directors who
        review potential conflict of interest situations in furtherance of such
        obligations.)
 
     .  The General Partner's liability to TNCLP and the holders of Units is
        limited by the Partnership Agreement.
 
     .  There is no established trading market for the Common Units and the
        trading market for the SPUs may be adversely affected as a result of the
        conversion.


                                 The Conversion
 
Terms                 Until March 31, 1997, SPU holders are being offered the
                      opportunity to elect to convert SPUs into Common Units of
                      TNCLP on a one-for-one basis at no conversion cost to the
                      holder. In the event that the Common Units cannot be
                      listed on the NYSE, despite TNCLP's good faith attempts,
                      only SPUs owned by the General Partner and its affiliates
                      may be converted into Common Units.
 
Distributions of      After December 31, 1996, SPUs are no longer entitled to
Available Cash        participate in quarterly cash distributions from 
(General)             "Available Cash" in excess of $0.605 per SPU ($2.42 per
                      SPU annually). Common Units will participate in quarterly
                      cash distributions from Available Cash, if any, only after
                      SPUs have been paid $0.605

                                       9
<PAGE>
 
                      per SPU. (Cash distributions from Available Cash in excess
                      of $0.605 per unit have been paid on SPUs and Common Units
                      for twelve consecutive quarters.) The ability of TNCLP to
                      make cash distributions will be largely dependent on TNCLP
                      earnings.

February 1997         TNCLP intends to distribute cash to unitholders at the end
Cash Distribution     of February 1997 equal to the minimum quarterly
                      distribution ("MQD") of $0.605 per unit. The excess of
                      Available Cash for the quarter ended December 31, 1996
                      over the amounts distributed in February 1997 will be paid
                      to all partners other than nonconverting SPUs based on a
                      record date shortly after the expiration of the conversion
                      period. An announcement concerning the amount and timing
                      of the distribution is scheduled for late January 1997.
                      Nonconverting SPU holders will not receive any cash
                      distributions in excess of the MQD.
 
Redemption            TNCLP has the right to redeem the nonconverted SPUs at a
                      price of $21.50 per SPU.
 
Procedure for         Depository receipts evidencing SPUs being converted, 
Conversion            together with a properly completed and duly executed
                      Conversion Notice/Letter of Transmittal, must be received
                      on or before 5:00 p.m. Eastern Standard (Daylight) Time on
                      March 31, 1997 by the Exchange Agent, First Chicago Trust
                      Company of New York.
 
Withdrawal            Elections to convert SPUs may be withdrawn by the
Rights                unitholder at any time prior to 5:00 p.m. Eastern Standard
                      (Daylight) Time on March 31, 1997 by contacting the
                      Exchange Agent, First Chicago Trust Company of New York,
                      and delivering a written notice of withdrawal.
 
Certain Federal       For a summary of certain federal income tax consequences 
Income Tax            relating to the conversion, see "Certain Federal Income 
Consequences          Tax Consequences" in this document, page 16.

Limited Call Right    If at any time not more than 25% of the issued and
                      outstanding Common Units are held by non-affiliates of the
                      General Partner, either TNCLP, the General Partner or its
                      affiliates may call all such outstanding units held by 
                      non-affiliated persons. TNCLP shall give at least 30 but
                      not more than 60 days notice of its decision to purchase
                      the outstanding units of the class. The

                                       10
<PAGE>
 
                      purchase price per unit will be the greater of (1) the
                      average of the previous twenty trading days closing prices
                      as of the date five days before the purchase is announced
                      or (2) the highest price paid by the General Partner or
                      any of its affiliates for any unit within the 90 days
                      preceding the date the purchase is announced. In the event
                      all SPUs owned by the General Partner and its affiliates
                      are converted, they will own 12.15 million Common Units.
                      If at least 4.05 million of the 6.66 million publicly held
                      SPUs convert, the non-affiliated persons will own more
                      than 25% of the issued and outstanding Common Units
                      (assuming the General Partner and its affiliates do not
                      acquire any additional Common Units).

Difference            For a summary of certain differences between SPUs and 
between SPUs and      Common Units, see "Description of Units" in this document,
Common Units          page 19.

                                       11
<PAGE>
 
                             SUMMARY FINANCIAL DATA

     The following table presents (i) summary consolidated financial data for
the years ended December 31, 1993, 1994 and 1995 derived from TNCLP's audited
consolidated financial statements, (ii) summary consolidated financial data for
the nine months ended September 30, 1995 and 1996 derived from TNCLP's unaudited
consolidated financial statements for such period and (iii) certain operational
information for the periods covered.  The following information should be read
in conjunction with "Management's Discussion and Analysis of Financial Condition
and Results of Operations," "Selected Financial and Operating Data" and the
consolidated financial statements of TNCLP and related notes thereto
incorporated by reference herein.
<TABLE>
<CAPTION>
 
(dollars in thousands, except                  Year Ended December 31,             Nine Months Ended September 30,
 per unit amounts)                        --------------------------------         -------------------------------
                                            1993        1994        1995             1995                   1996
                                          --------    --------    --------         --------               --------
<S>                                       <C>         <C>         <C>              <C>                    <C>
Income and Cash Flow Statement Data:
Total revenues........................    $259,782    $300,269    $373,325         $279,722               $277,943
Cost of goods sold....................     190,192     193,541     187,615          137,526                129,495
Operating expenses....................      17,645      20,000      16,840           13,604                  9,156
Operating income......................      53,004      87,638     169,724          128,592                139,292
Net income............................      49,729      86,545     172,468          130,662                143,563
Net income allocable to limited             
partners' interest....................      48,741      84,822     123,220           96,678                 94,654
Net income per limited partnership          
unit..................................        2.59        4.51        6.55             5.14                   5.03
Cash distributed per limited                  
partnership unit......................        2.48        2.64        6.25             4.34                   5.82
   
Summary Operating Data:
Sales volumes (thousands of tons)
Ammonia...............................         453         541         451              327                    311
Urea..................................         460         418         455              358                    312
UAN...................................       1,985       1,884       2,133            1,522                  1,731

Balance Sheet Data (at end of period):
Net property, plant and equipment.....    $184,629    $179,028    $177,358         $174,196               $172,827
Total assets..........................     286,355     316,645     338,123          317,090                301,412
Long term debt and capital lease           
obligations including current
maturities............................      38,418      42,450       5,702            6,263                  4,870
Partners' capital.....................     201,003     236,879     286,354          282,194                258,624
</TABLE>

                                       12
<PAGE>
 
                             CONVERSION BACKGROUND

     The conversion process described herein is expressly provided for in the
Partnership Agreement and was disclosed in the initial public offering of SPUs
in 1991.

     Section 5.5(c) of the Partnership Agreement provides as follows:

          "For a 90-day period commencing on the date the General Partner mails
     notice to the Unitholders that the Senior Conversion Date has occurred,
     Unitholders will have the right to elect to convert their Senior Preference
     Units into Common Units, effective as of the Senior Conversion Date, on a
     one-for-one basis, subject to adjustment, by delivering a Conversion Notice
     to the General Partner; provided, however, that any Units as to which a
     Conversion Notice is not received during such 90-day period shall remain
     Senior Preference Units; and provided further that in the event that the
     Common Units are not approved for listing on the New York Stock Exchange or
     the American Stock Exchange at such time, only those Senior Preference
     Units as to which a Conversion Notice has been delivered by the General
     Partner and its Affiliates shall be converted into Common Units and Senior
     Preference Units held by all other holders shall not be converted into
     Common Units, but shall remain Senior Preference Units.  On or before the
     Senior Conversion Date, the Partnership shall file an application to list
     the Common Units on the New York Stock Exchange or the American Stock
     Exchange and shall pursue such application in good faith; provided that
     upon termination of the 90-day conversion period the Partnership and its
     Common Units meet the applicable listing requirements."

     Consistent with the terms of the Partnership Agreement, the General Partner
has determined that the "Senior Conversion Date" occurred on December 31, 1996.


                                 THE CONVERSION
General
 
     SPU holders have, for a limited time, the right to elect to convert SPUs
into Common Units of TNCLP on a one-for-one basis and at no conversion cost to
the holder.

     TNCLP's obligation to issue Common Units to holders properly completing and
delivering the Conversion Notice/Letter of Transmittal is conditioned on the
Common Units being approved for listing on the New York Stock Exchange.  The
Common Units are approved for listing on the NYSE, provided that a minimum level
of elections to convert is satisfied.  See  "--Post Conversion Trading."

                                       13
<PAGE>
 
Conversion Period; Procedure for Electing to Convert

     The conversion period commenced on December 31, 1996 and expires at 5:00
p.m. Eastern Standard (Daylight) Time on March 31, 1997.  All appropriate
documentation must be received on or before 5:00 p.m. Eastern Standard
(Daylight) Time on March 31, 1997 by First Chicago Trust Company of New York
(the "Exchange Agent").  Failure to comply with the instructions set forth in
the Conversion Notice/Letter of Transmittal could result in rejection of the
conversion election.

     Holders of record seeking to convert must deliver their depository receipts
evidencing SPUs being converted, together with a properly completed and duly
executed Conversion Notice/Letter of Transmittal, and any other documents
required by the Conversion Notice/Letter of Transmittal, to the Exchange Agent
at the address set forth below under "Exchange Agent" prior to the expiration of
the conversion period.

     All beneficial owners of SPUs who wish to convert (but do not constitute
holders of record) should instruct the holder of record to complete and forward
the Conversion Notice/Letter of Transmittal on their behalf.  Nominees or other
record holders who hold SPUs for more than one beneficial owner are entitled to
make multiple elections pursuant to the Conversion Notice/Letter of Transmittal.

     All questions as to the validity, form, eligibility (including time of
receipt) and acceptance of any Conversion Notice/Letter of Transmittal will be
determined by TNCLP, in its sole discretion, whose determination will be final
and binding on all parties.  TNCLP reserves the absolute right, in its sole
discretion, to reject any and all conversion elections determined not to be in
proper form or not to be available for lawful acceptance.  TNCLP also reserves
the absolute right, in its sole discretion, to waive any of the conditions of
the Conversion Notice/Letter of Transmittal or any defect or irregularity in the
conversion elections of any SPUs.  No submission of a Conversion Notice/Letter
of Transmittal will be deemed to be properly made until all irregularities have
been cured or waived.  TNCLP's interpretation of the terms and conditions of the
Conversion Notice/Letter of Transmittal relating to the conversion will be final
and binding.  None of TNCLP, the General Partner, the Exchange Agent or any
other person will be under any duty to give notification of any defects or
irregularities in conversion elections or incur any liability for failure to
give any such notification.

Withdrawal Rights

     Conversion Notices/Letters of Transmittal submitted for conversion may be
withdrawn by the unitholder, upon written notice to the Exchange Agent, at any
time prior to 5:00 p.m. Eastern Standard (Daylight) Time on March 31, 1997.
Conversion Notices/Letters of Transmittal not timely withdrawn will become
irrevocable.

                                       14
<PAGE>
 
     To be effective, a written or facsimile transmission of a withdrawal letter
must (i) be timely received by the Exchange Agent at one of its addresses
specified herein, (ii) specify the name of the person who submitted the
Conversion Notice/Letter of Transmittal to be withdrawn, (iii) if depositary
receipts evidencing SPUs have been deposited with or otherwise identified to the
Exchange Agent, contain the description of the depositary receipts to be
withdrawn, indicate the certificate number shown on the certificates evidencing
such depositary receipts and the number of SPUs represented by such depositary
receipts and (iv) be signed by the holder of the depositary receipts in the same
manner as the original signature on the Conversion Notice/Letter of Transmittal.

Post Conversion Trading

     Nonconverted SPUs will continue to trade on the NYSE under the new symbol
"TNH PR" only if the SPUs continue to meet the exchange listing requirements and
are not otherwise redeemed.  It is entirely possible that there would be an
insufficient number of SPUs to provide a liquid secondary trading market.  TNCLP
currently expects that it will redeem all nonconverted SPUs sometime after the
conversion process is completed.

     The issuance of the Common Units upon conversion of the SPUs is exempt from
the registration requirements of the Securities Act of 1933 (the "Securities
Act"), pursuant to Section 3(a)(9) of the Securities Act.  As the issuance of
the SPUs was registered under the Securities Act, the Common Units issued upon
exchange of the SPUs will be freely tradable under federal law, without
compliance with prospectus delivery requirements; provided, however, that the
person holding the SPUs, or the Common Units issued upon exchange of the SPUs,
is not an affiliate of the Company.  If the person holding the SPUs is an
affiliate of the Company, the Common Units issuable upon exchange of the SPUs
may be sold only pursuant to an effective registration statement under the
Securities Act with respect to such Common Units or an exemption from
registration thereunder.

     Assuming that sufficient conversion elections are made to satisfy
thresholds for the listing of Common Units on the New York Stock Exchange, the
Common Units are expected to commence trading on the NYSE on April 1, 1997 (the
day following the expiration of the conversion period).  The Common Units are
approved for listing on the NYSE under the symbol "TNH" if after conversion
there are at least 1.1 million publicly held Common Units, the aggregate market
value of the publicly held Common Units is at least $40 million and there are at
least 2,000 holders of "round lots" of Common Units.

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<PAGE>
 
                    CERTAIN FEDERAL INCOME TAX CONSEQUENCES

          Upon the conversion of an SPU into a Common Unit, the holder of an SPU
will not recognize gain or loss and will have a tax basis and holding period in
the Common Unit received equal to the tax basis and holding period of the SPU so
converted.  If the holder of SPUs converts all SPUs, the holder's tax basis in
the Common Units will be equal to the tax basis in the SPUs converted and such
tax basis should be equally apportioned among the Common Units received.  If a
holder of SPUs decides to convert some, but not all, of the holder's SPUs, it is
unclear how the tax basis would be apportioned between the SPUs retained and the
Common Units received upon the conversion.

          The Internal Revenue Service has ruled that a partner who acquires
interests in a partnership in separate transactions must combine such interests
and maintain a single adjusted tax basis in a single partnership interest.  Upon
a sale or other disposition of less than all of such interest, a portion of such
tax basis must be allocated to the interests sold using an "equitable
apportionment" method.  The ruling is unclear as to how the holding period of
these interests is determined once they are combined.  If this ruling is
applicable to the holders of SPUs, a holder of SPUs who owns SPUs with differing
tax bases (generally as a result of acquiring them at different times) will be
unable to select high or low basis SPUs to convert as would be the case with
corporate stock.  It is not clear whether the ruling applies to TNCLP, because,
similar to corporate stock, limited partner interests in TNCLP are evidenced by
separate certificates. Accordingly, the effect of such ruling on the holders of
SPUs is unclear.  In addition, on March 19, 1996, certain tax legislation, known
as the Revenue Reconciliation Act of 1996, was presented to Congress that would
impact the taxation of certain financial products including partnership
interests.  Under one proposal contained in the Revenue Reconciliation Act of
1996, in the case of partnership interests in publicly traded partnerships which
are substantially identical, the basis of such interests and any adjustments to
tax basis, would be determined on an average basis and, for holding period
purposes, a taxpayer would be treated as selling such interests on a first-in,
first-out basis.  It is unclear how such proposed legislation, if enacted, would
impact (if at all) a holder of SPUs who converts some, but not all, of the
holder's SPUs.  A holder of SPUs seeking to convert less than all of such
holder's SPUs should consult a tax advisor as to the possible consequences of
such ruling and subsequent legislation.

                                       16
<PAGE>
 
                MARKET PRICE OF SECURITIES; CASH DISTRIBUTIONS

     SPUs (NYSE symbol: TNH) are traded on the NYSE.  The following table sets
forth the high and low closing sale prices for the SPUs and the amount of cash
distributed to each SPU and Common Unit in each calendar quarter since January
1, 1994.

<TABLE>
<CAPTION>
 
                                   SPU Closing Price         Cash Distributed to each
Period                             High          Low           SPU and Common Unit
------                             ----          ---           -------------------
<S>                                <C>           <C>           <C>

1996
----
Fourth quarter
  (through December 20, 1996)    $ 45.75       $ 41.50               $1.77
Third quarter                      46.25         37.50                2.42
Second quarter                     49.25         37.00                1.63
First quarter                      47.25         35.75                1.91

1995
----
Fourth quarter                   $38.875       $31.625               $1.47
Third quarter                      32.50         29.50                1.73
Second quarter                     32.25         28.50                1.14
First quarter                      30.50        24.125                0.66

1994
----
Fourth quarter                   $28.625       $22.125               $0.66
Third quarter                      29.50         24.50                0.66
Second quarter                     30.25        26.125                0.66
First quarter                      31.00         25.00                0.66
</TABLE>

     Currently there is no trading market for the Common Units.  The Common
Units will presumably be valued substantially consistent with the past valuation
of SPUs and will depend on, among other things, TNCLP performance, general
market conditions and cash distributions.

Quarterly Cash Distributions

     After December 31, 1996, SPUs are no longer entitled to participate in
quarterly cash distributions in excess of $0.605 per unit (the "minimum
quarterly distribution" or "MQD").  Holders must convert to Common Units in
order to participate in any cash distributions above this level, although the
Common Units will receive cash distributions, if any, only after SPUs have been
paid the MQD.

     TNCLP intends to distribute cash to unitholders at the end of February 1997
equal to only the MQD ($0.605 per unit).  The excess of the Available Cash for
the quarter ended December 31, 1996 over the amounts distributed in February
1997 will be paid to all partners other than 

                                       17
<PAGE>
 
nonconverting SPUs based on a record date shortly after the expiration of the
conversion period.  An announcement concerning the amount and timing of the
distribution is scheduled for late January 1997.  Nonconverting SPU holders are
not entitled to participate in cash distributions in excess of the MQD.

     Future cash distributions will continue to be based on Available Cash,
which will be determined using the same methodology as in the past.  Pursuant to
the terms of the Partnership Agreement, TNCLP is required to pay out 100% of
Available Cash.  Available Cash is largely dependent on TNCLP earnings and is
dependent on other factors, including working capital requirements and capital
expenditures.

     The General Partner will continue to be entitled to incentive
distributions.  The General Partner's percentage interest in distributions
increases as distributions to the Common Unitholders exceed specified target
levels (e.g., distributions of Available Cash from Operations exceeding $1.045
per Common Unit per quarter are paid 50% to Common Unitholders and 50% to the
General Partner).

Reserve Amount

     Cash reserves (or the "Reserve Amount") will be maintained in the amount
equal to four quarters of MQDs on all nonconverted SPUs.  No cash reserves are
required for Common Units.  In connection with the conversion process,
reductions in the Reserve Amount from its current level of $18.5 million will be
available for potential cash distributions in May 1997.

Distributions of Cash Upon Liquidation

     TNCLP will dissolve on December 31, 2041, unless sooner dissolved pursuant
to the terms of the Partnership Agreement.  In connection with the dissolution
and liquidation of TNCLP, the proceeds of such liquidation shall be applied,
first, in accordance with the provisions of the Partnership Agreement and
applicable law to the payment of creditors in the order of priority provided by
law and to the creation of a reserve of cash or other assets for contingent
liabilities in an amount, if any, determined by the liquidator to be appropriate
for such purposes.  Any remaining proceeds (or assets in kind) will be
distributed to Unitholders and the General Partner as set forth below.

     If cash (or other assets) to be distributed upon liquidation equals the
aggregate balances of the partners' capital accounts (before adjustment for
income and loss upon liquidation), such cash (or other assets) will be
distributed in proportion to such capital accounts.

     If cash (or other assets) to be distributed upon liquidation exceeds such
aggregate balance of the Partners' capital accounts, cash (or other assets)
equal to such aggregate balance will be distributed in proportion to capital
accounts and the excess will be distributed, first, 2% to the General partner
and 98% to the holders of the Senior Preference Units to the extent of

                                       18
<PAGE>
 
Unrecovered Capital plus accrued arrearages, if any, next, 2% to the General
Partner and 98% to the holders of the Common Units to the extent of Unrecovered
Capital plus accrued arrearages, if any, and thereafter to the General Partner
and to all holders of the Common Units, with the General Partner's percentage
interest increasing as distributions to the Common Unitholders exceed specified
targets.
                               
     Any loss or unrealized loss will be allocated to the General Partner and
the Unitholders, first, in proportion to the positive balances in such partners'
capital accounts until all such balances are reduced to zero, and second, to the
General Partner.

                             DESCRIPTION OF UNITS
General

     The Units are equity securities entitled to participate in such
distributions of Available Cash as may properly be made from time to time
(although the SPUs are only entitled to the MQD after December 31, 1996) and, in
the event of any liquidation on winding up of TNCLP, to share in any assets of
TNCLP remaining after satisfaction of TNCLP liabilities as provided in the
Partnership Agreement.

     Holders of Units do not have preemptive rights.  Holders of Units are
entitled to one vote per Unit at meetings of Limited Partners with respect to
matters as to which approvals may be solicited.  The General Partner does not
anticipate that any meeting of Limited Partners will be called in the
foreseeable future since the General Partner is authorized in general to perform
all acts deemed necessary to carry out the purposes of the Partnership and to
conduct the business of the Partnership.

Senior Preference Units

     The Senior Preference Units ("SPUs") are entitled to receive from Available
Cash a minimum quarterly distribution of $0.605 per SPU, aggregating $2.42 per
SPU on an annualized basis, plus any arrearages in the payment of the MQD for
prior quarters, before any distribution of Available Cash is made to holders of
Common Units for such quarter.  After payment of the MQD with respect to the
SPUs and Common Units, only the Common Units will participate in additional
quarterly distributions of Available Cash to the limited partners.

     For a 90-day period commencing on the mailing by the General Partner of
this Conversion Statement, the holders of SPUs will have the right to convert
their SPUs into Common Units on a one-for-one basis, if the Common Units are
approved for listing on the NYSE, subject to official notice of issuance.  In
the event that the Common Units cannot be listed on the NYSE, only SPUs owned by
the General Partner and its affiliates may be converted into Common Units, and
SPUs held by all other Unitholders will remain SPUs.

                                      19
<PAGE>
 
     Any or all of the SPUs may be redeemed at the option of TNCLP upon at least
30 but not more than 60 days notice at a price equal to Unrecovered Capital plus
accrued arrearages, if any. Unrecovered Capital, as further defined in the
Partnership Agreement, means an amount equal to the excess of (i) the initial
public offering price per SPU ($21.50) over (ii) the sum of all distributions
made in respect of an SPU out of Available Cash constituting Cash from Interim
Capital Transactions.  If after giving effect to an anticipated redemption,
fewer than 1.0 million SPUs would be held by non-affiliates of the General
Partner, TNCLP must redeem all such SPUs if it redeems any SPUs.  The SPUs are
entitled to a liquidation preference over the Common Units.

Common Units

     The holders of Common Units are entitled to receive distributions from
Available Cash only after TNCLP has distributed the MQD to holders of SPUs.
After the holders of SPUs have received the MQD for any quarter plus any
arrearages, only the Common Units will participate in distributions of Available
Cash to the limited partners.

     If at any time not more than 25% of the issued and outstanding Common Units
are held by non-affiliates of the General Partner, then TNCLP may call, or
assign to the General Partner or its affiliates its right to acquire, the
remaining publicly-held Units of such class at a purchase price equal to the
greater of (i) the highest cash price paid by the General Partner or its
affiliates for any Unit of such class purchased within the 90 days preceding the
date the General Partner mails notice of the election to call or acquire such
Units or (ii) the average of the last reported sales price per Unit on the
principal securities exchange on which the Units trade over the 20 trading days
preceding the date five days before the General Partner mails such notice.

                                 EXCHANGE AGENT

     First Chicago Trust Company of New York will act as Exchange Agent for the
conversion.  All correspondence in connection with the conversion and the
Conversion Notice/Letter of Transmittal should be addressed to the Exchange
Agent as follows:
<TABLE>
<CAPTION>
 
   By Overnight Courier:            By Hand:                   By Mail:
   ---------------------            --------                   --------
<S>                          <C>                        <C>
First Chicago Trust Company     First Chicago Trust       First Chicago Trust
        of New York             Company of New York       Company of New York
   Tenders and Exchanges       Tenders and Exchanges     Tenders and Exchanges
        Suite 4680             c/o Depository Trust            Suite 4660
      14 Wall Street,        55 Water Street, DTC TAD        P.O. Box 2565
       Eighth Floor              Vietnam Veterans           Jersey City, NJ
    New York, NY 10005            Memorial Plaza               07303-2565
                                New York, NY 10041
 
                   For Information:    Call: (201) 324-0137
                                        Fax: (201) 222-4720
</TABLE>

                                      20