<PAGE>
 
                                                                      EXHIBIT 21

                          SUBSIDIARIES OF THE COMPANY


Subsidiaries of the Company as of June 30, 1998, are as follows:

<TABLE>
<CAPTION>
                                                        State of                   PERCENTAGE OF VOTING
NAME OF COMPANY                                      Incorporation                   SECURITIES OWNED
---------------                                      -------------                 -------------------- 
<S>                                                   <C>                       <C>
Mississippi Phosphates Corporation                      Delaware                           100%
                                                                                           
NSI Land Corporation                                    Delaware                           100%
                                                                                           
Mississippi Chemical Management Company                 Delaware                           100%
                                                                                           
Mississippi Chemical Company, L.P.                      Delaware                           100%
                                                                                           
MCC Investments, Inc.                                   Delaware                           100%
                                                                                           
Mississippi Potash, Inc.                               Mississippi                         100%
                                                                                           
Eddy Potash, Inc.                                      Mississippi                         100%
 (a subsidiary of Mississippi Potash, Inc.)                                                
                                                                                           
Triad Nitrogen, Inc.                                    Delaware                           100%
                                                                                           
Triad Fertilizer, Inc.                                 Mississippi                         100%
 (a subsidiary of Triad Nitrogen, Inc.)                                                    
                                                                                           
TNI, Inc.                                              Mississippi                         100%
 (a subsidiary of Triad Nitrogen, Inc.)                                                    
                                                                                           
Triad Barge, Inc.                                      Mississippi                         100%
 (a subsidiary of Triad Nitrogen, Inc.)                                                    
                                                                                           
TNI Barge, Inc.                                         Delaware                           100%
 (a subsidiary of Triad Barge, Inc.)
</TABLE>