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Denitrification is the final stage of the nitrogen fixation.

Denitrification is the final stage of the nitrogen fixation.

Denitrification is the process during which the nitrogen compound is released back into the atmosphere by converting nitrate (NO 3 -) into gaseous nitrogen (N). The process of denitrification is carried out during the absence of oxygen by Thiobacillus species such as Clostridium and Pseudomonas bacteria present in the soil. In this process, the genus of  Gram-negative bacteria  degrades nitrate compounds present in the soil and aquatic systems into nitrous oxide (N 2 O)and nitrogen gas, which are eventually released into the atmosphere. In this process, a large range of microorganisms is involved; therefore, it is also called the microbial process. This biogeochemical process is one of the main responses to changes in the oxygen (O 2 ) concentration in the environment. Denitrification is a universal process for both terrestrial and  aquatic ecosystems , which occurs naturally under the extreme concentrations in managed ecosystems – marine and freshwater environments, in tropical and temperate soils, in wastewater treatment plants, in aquifers, in manure stores, etc.

The denitrification is the last step in the  nitrogen cycle . It is a naturally occurring, microbially mediated process, where nitrate is used as a form of energy for denitrifiers. In this process, soil bacteria convert plant-available soil nitrate (NO 3 – ) into nitrogen (N) gases that are lost from the soil. Denitrification produces several gases: nitric oxide (NO), nitrous oxide (N 2 O), dinitrogen (N 2 ). The flowchart of the denitrification process is: Nitrite  →  Nitric Oxide  →   Nitrous oxide  →  Nitrogen gas.

Denitrification is a microbial process of removing valuable nitrogen from the soil and releasing the greenhouse gas nitrous oxide (N 2 O), and the tropospheric pollutant nitric oxide (NO). The biological cycle of denitrification involves a cascade of different enzymes, which reduces nitrate to dinitrogen. Also Read :  Biogeochemical Cycles

When the oxygen (O 2 ) supply in the soil becomes limited, a variety of bacteria use the oxygen instead of nitrate for respiration. Denitrification most commonly occurs in wet, moist or the soil flooded with water where the supply of oxygen for respiration is reduced or limited. Some fungi can denitrify, but they are not considered significant.

Denitrification is more active in the regions where water-filled pore space in the soil exceeds 60 per cent. The end-product gas depends on the soil conditions and the microbial community. As the deficiency of oxygen increases, microbes perform its functions by converting more of the nitrate to dinitrogen (N 2 ) gas. For the purposes of nutrient management, denitrification results in a loss of valuable nitrogen (N), but the impact in the atmosphere will vary.

The complete process of denitrification is influenced by the following factors: The main factor which influences the process of denitrification is the organic content in the soil. The organic matter available within the soil is the only source of nutrition for the bacteria. Therefore, the soil bacteria require a source of readily available organic matter, either from the plants, from the soil or from other additional sources. Other factors include:

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