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The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes.
Nitrogen cycle. Nitrification is the biological oxidation of ammonia to nitrate via the intermediary nitrite.Nitrification is an important step in the nitrogen cycle in soil.The process of complete nitrification may occur through separate organisms [1] or entirely within one organism, as in comammox bacteria.
In excess, denitrification can lead to overall losses of available soil nitrogen and subsequent loss of soil fertility. However, fixed nitrogen may circulate many times between organisms and the soil before denitrification returns it to the atmosphere. The diagram above illustrates the nitrogen cycle.
The total nitrogen content depends largely on the soil organic matter content, which in turn depends on texture, climate, vegetation, topography, age and soil management. [40] Soil nitrogen typically decreases by 0.2 to 0.3% for every temperature increase by 10 °C. Usually, grassland soils contain more soil nitrogen than forest soils, because ...
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Nitrogen-15 (15 N) tracing is a technique to study the nitrogen cycle using the heavier, stable nitrogen isotope 15 N.Despite the different weights, 15 N is involved in the same chemical reactions as the more abundant 14 N and is therefore used to trace and quantify conversions of one nitrogen compound to another.
Whether nitrogen is mineralized or immobilized depends on the C/N ratio of the plant residues. [6] For example, incorporating materials high in carbon to nitrogen ratio such as saw dust and straw will stimulate soil microbial activity, increase demand for nitrogen, leading to immobilization. [7] This is known as priming effect. [8]
As part of the nitrogen cycle, it is essential for soil fertility and the growth of terrestrial and semiaquatic vegetations, upon which all consumers of those ecosystems rely for biomass. Nitrogen fixation is thus crucial to the food security of human societies in sustaining agricultural yields (especially staple crops ), livestock feeds ...