Nitrogen Cycle

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Soil Microbiology Nature of Soil Soil Habitats (Lithosphere) Microorganisms in Soil Decomposition of Organic Matter in Soil Bacteria in Soil Physiological Types of Bacteria in Different Soils Fungi in Soil Protozoa in Soil Algae in Soil Viruses in Soil Functions of Microorganisms in Soil Humus Functions of Humus Cycles of Elements Carbon Cycle Nitrogen Cycle

Nitrogen Cycle

	Nitrogen Cycle -Nitrogen is the most important structural element of all living organisms. There is a vast store of nitrogen in the air, but animals and the majority of plants are unable to fix atmospheric nitrogen. The nitrogen cycle is chiefly concerned with the incorporation of atmospheric gaseous nitrogen and organic nitrogen of dead plants and animals into the forms that are usable by higher plants.
The scarcity of suitable nitrogenous compounds is a major problem in the maintenance of soil fertility. For this reason the transformation of nitrogen has attracted considerable attention from soil microbiologists. Higher plants generally require nitrogen in the form of nitrates, although ammonia and some organic nitrogenous compounds are also utilized to a lesser extent.
The overall transformations in which microorganisms are involved range from elementary nitrogen to protein and other complex organic nitrogenous compounds, with a large number of intermediary substances. The distinctive processes of nitrogen cycle are ammonification of cellular nitrogen; nitrification, nitrate reduction, denitrification and nitrogen fixation.

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Sulphur Cycle Ammonification in Soil Nitrification in Soil Nitrate Reduction in Soil Denitrification in Soil Nitrogen Fixation Symbiotic Nitrogen Fixation Rhizobium Specificity of Bacteria and Legumes Non-Symbiotic Nitrogen Fixation Non-symbiotic Nitrogen Fixing Microorganisms Mechanism of Nitrogen Fixation Oxidation of Sulphur and Sulphur Compounds by Bacteria