Question

What are the 5 stages of the nitrogen cycle?

Answer 1

Nitrogen cycle:

1. The earth's atmosphere contains approximately 78% nitrogen which is in inert form.
2. As a result, plants and animals cannot directly use it.
3. Plants use nitrogen by converting atmospheric nitrogen to nitrates, nitrites, and ammonia compounds through a process known as the nitrogen cycle.
4. Animals derive their nitrogen requirements from plants.

Stages of the Nitrogen Cycle:

Nitrogen fixation

1. Nitrogen fixation is a chemical process that converts atmospheric nitrogen into ammonia, which is absorbed by organisms.
2. This process can only be carried out by certain species of free-living saprophytic bacteria like Azobacter and Clostridium.
3. Industrial Nitrogen Fixation: This is a man-made alternative in which atmospheric nitrogen is converted into ammonia and then into nitrates in various fertilizers via Haber's process.

Nitrification

1. This happens in two steps.
2. The first step involves converting NH₃/NH₄₊ to NO_3- (nitrates).
3. Nitrosomonas and Nitrococcus bacteria found in soil convert NH₃ to NO_2-, while Nitrobacter bacteria convert NO₂- to NO₃-.
4. These bacteria gain energy through these conversions.

Nitrogen assimilation

1. It is the process by which nitrate and ammonia are utilized to form organic compounds.
2. Nitrogen from the soil is absorbed by plants in the form of nitrates and ammonium ions.
3. Plants absorb ammonium ions and nitrates via their respective transporters.
4. After absorption, nitrate is transported to the leaves and converted to ammonia.
5. Ammonia is also converted into amine groups of different amino acids.

Ammonification

1. Natural nitrogen compounds are converted into NH₃ and NH₄₊.
2. Some bacteria in the soil break down the organic remains of plants and animals, releasing ammonia into the soil.
3. These microorganisms feed on dead and decaying matter, releasing ammonia into the soil.

Denitrification

1. It is the inverse of nitrification.
2. It occurs in the deep layers of soil and involves bacteria converting NO₃-to N₂ and other gaseous compounds like NO₂.
3. Because oxygen is not available in deep layers of soil, soil bacteria use nitrogen compounds instead of oxygen.