Denitrification- Detailed Analysis

To make the nitrogen available for use by higher organisms, atmospheric nitrogen must be made accessible with the help of microorganisms in the surroundings. 

• To be readily taken up by the primary producers (plants), soil microbes use the denitrification process to metabolically reduce nitrate compounds to gases like dinitrogen (N₂), nitrous oxide (N₂O), etc.
• Denitrification usually occurs in the soil when the pores are filled with water causing an anoxic condition.
• This anoxic condition (low supply of oxygen) leads to the bacteria seeking out the oxygen in the nitrates as an electron acceptor in the respiration process.

Denitrification Hotspots

Since the denitrification process is carried out by the microbial species which are present greatly in the topsoil layer, hence higher denitrification activity can be observed here. Beneath the topsoil layer, denitrification is carried out with the aid of plant roots, as they take up oxygen via root cells and water via evapotranspiration. In a study, it’s been observed that denitrification is highest around decomposing living entities. They can also be seen in places with an extended dry period followed by a single rainstorm. Several factors such as the random placement of crop residues, aggregation of organic matter, and distribution of fertilizers influence and stimulate denitrification.

Denitrification Limiting Factors

• Nitrate Concentration – Denitrification process is only carried out in the presence of nitrate compounds, so a lower concentration of nitrate reduces denitrification and supports healthy plant growth. Also, the use of nitrification inhibitors in nitrogen fertilizers limits denitrification.
• Temperature – Optimal denitrifying activity can be observed at 20-35 degree Celsius.
• Soil Moisture – To trigger denitrification, the lower availability of oxygen in the water-logged soil provides a suitable condition, leading to the release of dinitrogen gas into the surroundings.
• Dissolved Carbon Availability – For maximum microbial activity for denitrification, carbon sources such as compost, crop residues, manure, etc, should be readily available to the microorganisms to reduce nitrate to dinitrogen. Lower concentrations of carbon sources lead to the production of nitrous oxide from nitrate as the end product.