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12   The Chemistry and Fertility of Soils under Tropical Weeds




                                                              2-
                                                            SO 4
                                                           NUTRIENTS

                                          SOIL MICROORGANISMS           PLANTS
                                           (DECOMPOSERS)              (PRODUCERS)


                                                  ARYLSULPHATASE



                                                                        ANIMALS
                                            ORGANIC S
                                                                      (CONSUMER I)

                                                          ANIMALS
                                                         (CONSUMER II)


                                           Fig. 1.8. The cycle of S in the soil – plant system
                                                       (Salam, 2014).


                                       N 2

                                                            NH 3
                                                           NH 4 +
                                                                         NO 2 -


                                     (Fixation/Decomposition)
                                         Microorganisms                      NO 3 -
                                                     PROTEASE
                                                     S
                                                                             Plants
                                        Organic N



                                                 (Protein)      (Proteins)
                                                 Animals/         Plants
                                                 Humans


                                          Fig. 1.9.  The N Cycle (Adapted from Salam, 2014).

                           Abdul Kadir Salam and Nanik Sriyani – 2019
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