Main steps of nitrogen cycle
- Nitrogen fixation.
- Nitrification.
- Denitrification.
- Ammonification.
- Nitrogen assimilation.
Nitrogen fixation
Mainly two steps in nitrogen fixation; Biological N2 fixation (BNF) and Non-biological N2 fixation (NBNF).
Biological N2 fixation is mainly done by prokaryotes using nitrogenase enzyme complex; it catalyzes the N2 to NH3 and this process is energy consuming reaction. These enzyme complex is highly sensitive to oxygen. Nitrogenase is inhibited in air containing more than 2% oxygen level. Most of N2 fixation aerobic bacteria have very high rate of respiration rate therefore these cell can maintain the very low concentration of o2 level inside the microorganisms.
Examples for N2 fixation bacteria – Cyanobacteria, Clostridium, Rhizobium
Nitrification
Nitrification is the conversion of ammonia, ammonium into nitrate.
Examples for Nitrification : Nitrosomonas, Nitrobacter
Nitrate is highly soluble and therefore, it rapidly leach out from the soil therefore is not beneficial in agriculture. Although ammonia is positively charge it is strongly adsorbed to clay minerals.
Denitrification
which nitrate is converted to gaseous N2. This process in occurred in anaerobic environment. however this process is highly damaged by the human activities such as wastewater treatments and agricultural fertilizers.
Examples for Denitrification : Bacillus, Pseudomonas
Ammonification
Ammonification is the process of breakdown of the organic nitrogen compounds such as amino acids, proteins into ammonia by microbes such as bacteria and fungi. Ammonification depends on the temperature, moisture. High level of ammonification increases the soil pH. which is negative impacts for the pant growth.
Nitrogen assimilation
Plant and other organisms uptake nitrate and ammonia is incorporate.
Ammonia fluxes
Ammonia fluxes is the process of transportation of ammonia in the environment. Ammonia fluxes can also be released by anthropogenic activities agricultural fertilizer, combustion of fossil fuels. there are main importance of the understanding the ammonia fluxes; such as improve fertilizer management systems, reduce nutrient loss, reduce the negative impact on ammonia on the environment such as increase pH of the soil, eutrophication, reduce the greenhouse effect and global warming.
Impact of Nitrification on Ecosystems
- Positive impacts of the nitrification – make nitrogen available to plants
- Negative impacts of nitrification – Greenhouse gas emission, eutrophication, acid rains, acidification of the soil, water contaminations.
Nitrification & Bioremediation
Nitrification bacteria can remove the nitrogen containing pollutant from the environment such as removing of ammonia from contaminated water systems such as agricultural runoffs, wastewater.
Nitrification & agriculture
- Positive impacts nitrate which is important for plant growth.
- Negative impacts loss of nitrate the from leaching resulting the decreasing the soil fertility and reduced the yield, eutrophication, forming harmful algal booms
