THEORETICAL ANALYSES OF INTERACTIONS BETWEEN INORGANIC NITROGEN AND SOIL ORGANIC-MATTER

The organic matter of the soil has a large potential to retain inorgan ic nitrogen by means of both biotic (microbially mediated) and abiotic (chemical) reactions. We derive one equation with which we analyse th e nitrogen retention due to these mechanisms in terms of organic matte r properties. We first of all show how to separate gross mineralizatio n from immobilization. We then show that our equation can reproduce st udies of microbially-mediated or purely inorganic immobilization. We t hen apply the theory to soils of different characteristics (typical ag ricultural and forest soils) and find that the major factor determinin g the fraction of added inorganic nitrogen that is immobilized is the ratio between soil carbon and inorganic nitrogen concentration.