Physiology and Distribution of Nitrogen in Soils

Abstract

One of the important element for plant growth and which signifies soil health is Nitrogen. Soil is majorly bound with inorganic (NO2−, NO3−, non-exchangeable (mineral-fixed) NH4+, exchangeable NH4+, nitrous oxide (N2O) and dinitrogen gas (N2)) and organic forms (amino acids, amino sugars and nucleic acid bases) of Nitrogen. Soil N amount depends upon N2 fixation through microorganisms, losses from leaching and crop removal, volatilization and Emission of N2O and N2. Initially NH+ conversion is processed through ammonification followed by the conversion of nitrite to nitrate through nitrification process. Further, NH+ and NO3− are utilised by microorganisms and plants by process immobilization and assimilation, respectively. In the end, the N cycle is completed with denitrification process i.e. N releases back to atmosphere. Soil N is vast and not only related to transformation and distribution of inorganic and organic N but also its interaction with biosphere and atmosphere. The following chapter gives an overview of soil N by keeping in mind to keep a detailed view of its distribution and physiology.