Theoretical analyses of interactions between inorganic nitrogen and soil organic matter

Summary The organic matter of the soil has a large potential to retain inorganic nitrogen by means of both biotic (microbially mediated) and abiotic (chemical) reactions. We derive one equation with which we analyse the nitrogen retention due to these mechanisms in terms of organic matter properties. We first of all show how to separate gross mineralization from immobilization. We then show that our equation can reproduce studies of microbially–mediated or purely inorganic immobilization. We then apply the theory to soils of different characteristics (typical agricultural and forest soils) and find that the major factor determining the fraction of added inorganic nitrogen that is immobilized is the ratio between soil carbon and inorganic nitrogen concentration.