11/20/2024
Nitrogen is an essential macronutrient for plant growth and development. But Nitrogen can be one of the most challenging nutrients to manage in crops. The largest challenge is that a sufficient amount of plant available nitrogen is provided to the crop all while reducing the loss of nitrogen to the environment. A grower’s profitability is highly dependent on this balancing act of nitrogen as a large amount of their cost of production goes into nitrogen management. I cover the role of Nitrogen in the plant, factors affecting the availability of Nitrogen, deficiency symptoms and some Loveland Product, Inc. options for Nitrogen supplementation and stabilization in the below recorded presentation (both MP4 and ppt). But one thing I did not cover was the nitrogen cycle. Below you will find a hopefully good refresher on the different steps of the nitrogen cycle. 1. Nitrogen Fixation Process (N2 to NH3/ NH4+ or NO3-)
Nitrogen Fixation is the initial step of the nitrogen cycle. Here, Atmospheric nitrogen (N2) which is primarily available in an inert form, is converted into the usable form -ammonia (NH3).
During the process of Nitrogen fixation, the inert form of nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation.
The entire process of Nitrogen fixation is completed by symbiotic bacteria, which are known as Diazotrophs. Azotobacter and Rhizobium also have a major role in this process. These bacteria consist of a nitrogenase enzyme, which has the capability to combine gaseous nitrogen with hydrogen to form ammonia.
Nitrogen fixation can occur either by atmospheric fixation- which involves lightening, or industrial fixation by manufacturing ammonia under high temperature and pressure conditions. This can also be fixed through man-made processes, primarily industrial processes that create ammonia and nitrogen-rich fertilizers.
Types of Nitrogen Fixation
Atmospheric fixation: A natural phenomenon where the energy of lightning breaks the nitrogen into nitrogen oxides, which are then used by plants.
Industrial nitrogen fixation: It is a man-made alternative that aids in nitrogen fixation using ammonia. Ammonia is produced by the direct combination of nitrogen and hydrogen. Later, it is converted into various fertilizers such as urea.
Biological nitrogen fixation: We already know that nitrogen is not used directly from the air by plants and animals. Bacteria like Rhizobium and blue-green algae transform the unusable form of nitrogen into other compounds that are more readily usable. These nitrogen compounds get fixed in the soil by these microbes.
2. Nitrification (NH3 to NO2- to NO3-)
In this process, the ammonia is converted into nitrate by the presence of bacteria in the soil. Nitrites are formed by the oxidation of ammonia with the help of Nitrosomonas bacteria species. Later, the produced nitrites are converted into nitrates by Nitrobacter. This conversion is very important as ammonia gas is toxic for plants.
The reaction involved in the process of Nitrification is as follows:
2NH3 + 3O2 → 2NO2– + 2H+ + 2H2O
2NO2– + O2 → 2NO3–
3. Assimilation (incorporation of NH3, NO2- and NO3- into biological tissues)
Primary producers – plants take in the nitrogen compounds from the soil with the help of their roots, which are available in the form of ammonia, nitrite ions, nitrate ions or ammonium ions and are used in the formation of the plant and animal proteins. This way, it enters the food web when the primary consumers eat the plants.
4. Ammonification (nitrogenous organic compounds to NH3)
When plants or animals die, the nitrogen present in the organic matter is released back into the soil. The decomposers, namely bacteria or fungi present in the soil, convert the organic matter back into ammonium. This process of decomposition produces ammonia, which is further used for other biological processes.
5.Denitrification (NO3- to N2)
Denitrification is the process in which the nitrogen compounds make their way back into the atmosphere by converting nitrate (NO3-) into gaseous
nitrogen (N). This process of the nitrogen cycle is the final stage and occurs in the absence of oxygen. Denitrification is carried out by the denitrifying
bacterial species- Clostridium and Pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen gas as a byproduct.
