write a short note on nitrogen cycle ?

The atmosphere contains mainly nitrogen. in fact, the percentage of nitrogen in the air is 78%. 
1) atmospheric nitrogen is converted into nitrates in the soil by nitrogen fixing bacteriapresent in the root nodules of leguminous plants
2)nitrogen fixing bacteria present freely in the soil convert atmospheric nitrogen into ammonia in the soil
3)nitrates in the soil are assimilated (absorbed or taken up) by plants
4) plants are eaten by animals
5) when plants and animals die or excrete, the nitrates and ammonia go back into the soil 
6) denitrifying bacteria converts nitrates in the soil back into atmospheric nitrogen and thus the cycle continues
7)NOTE- atmospheric nitrogen can also be converted into nitrates in the soil by lightening storms. lightening creates so much energy in the atmosphere that the atmospheric nitrogen reacts and enters the soil as nitrates.

The atmosphere contains mainly nitrogen. in fact, the percentage of nitrogen in the air is 78%. 
1) atmospheric nitrogen is converted into nitrates in the soil by nitrogen fixing bacteria present in the root nodules of leguminous plants 
2)nitrogen fixing bacteria present freely in the soil convert atmospheric nitrogen into ammonia in the soil 
3)nitrates in the soil are assimilated (absorbed or taken up) by plants 
4) plants are eaten by animals 
5) when plants and animals die or excrete, the nitrates and ammonia go back into the soil 
6) denitrifying bacteria converts nitrates in the soil back into atmospheric nitrogen and thus the cycle continues 
7)NOTE- atmospheric nitrogen can also be converted into nitrates in the soil by lightening storms. lightening creates so much energy in the atmosphere that the atmospheric nitrogen reacts and enters the soil as nitrates.

In the atmosphere, the concentration of nitrogen is about 78%. It is essential for plants. Nitrogen forms a structural component of many important molecules such as DNA, RNA, and other vitamins. Plants cannot absorb nitrogen from the atmosphere. Certain forms of bacteria are able to convert atmospheric nitrogen into usable forms such as nitrates and nitrites. Such nitrogen fixing bacteria are commonly found in the roots of legumes (plants of pulses) inside special structures called root nodules. These usable forms of nitrogen are absorbed by plants to produce many compounds such as amino acids, which in turn form proteins. When an animal feeds on plants, nitrogen enters its body.When plants and animals die, they start decomposing after some time. During this process, proteins are converted into nitrates and nitrites by the action of decomposing bacteria. Certain other forms of bacteria convert nitrates and nitrites into elemental nitrogen. Thus, nitrogen flows between the various components of the biosphere in a cyclical manner. There are basically 5 steps of nitrogen cycle that help in fixing atmospheric nitrogen: * Nitrogen Fixation (N ₂ to NO ₃ - or NH ₄ ) * Nitrification (NH ₃ to NO ₃ - ) * Assimiliation (here the NH ₃ and NO ₃ - are incorporated into the biological tissues) * Ammonification (organic nitrogen compounds to NH ₃ ) * Denitrification (NO ₃ - to N ₂ )

Hope this helps!!!

n the atmosphere, the concentration of nitrogen is about 78%. It is essential for plants. Nitrogen forms a structural component of many important molecules such as DNA, RNA, and other vitamins. Plants cannot absorb nitrogen from the atmosphere. Certain forms of bacteria are able to convert atmospheric nitrogen into usable forms such as nitrates and nitrites. Such nitrogen fixing bacteria are commonly found in the roots of legumes (plants of pulses) inside special structures called root nodules. These usable forms of nitrogen are absorbed by plants to produce many compounds such as amino acids, which in turn form proteins. When an animal feeds on plants, nitrogen enters its body.When plants and animals die, they start decomposing after some time. During this process, proteins are converted into nitrates and nitrites by the action of decomposing bacteria. Certain other forms of bacteria convert nitrates and nitrites into elemental nitrogen. Thus, nitrogen flows between the various components of the biosphere in a cyclical manner. There are basically 5 steps of nitrogen cycle that help in fixing atmospheric nitrogen: * Nitrogen Fixation (N₂to NO₃- or NH₄) * Nitrification (NH₃to NO₃- ) * Assimiliation (here the NH₃and NO₃- are incorporated into the biological tissues) * Ammonification (organic nitrogen compounds to NH₃) * Denitrification (NO₃- to N₂)

our atmosphere contains 78% of nitrogen. But all this nitrogen cannot be taken up directly by plants and animals. As studied earlier, certain bacteria and blue-green algae fix the atmospheric nitrogen into soil and convert it into compounds of nitrogen.Rhizobiumis one such bacterium which does this. It converts the atmospheric nitrogen into usable form, which is then taken up by plants through their roots. This nitrogen is then utilized by plants to synthesize proteins and other such compounds. Nitrogen is then transferred to animals in the form of proteins when they feed on plants.

Thenitrogen cycleis the process by whichnitrogenis converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle includefixation,ammonification,nitrification, anddenitrification. The majority ofEarth's atmosphere(78%) isnitrogen,^[1]making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest toecologistsbecause nitrogen availability can affect the rate of key ecosystem processes, includingprimary productionanddecomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramaticallyaltered the global nitrogen cycle^{[citation needed]}.

Thenitrogen cycleis the process by whichnitrogenis converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle includefixation,ammonification,nitrification, anddenitrification. The majority ofEarth's atmosphere(78%) isnitrogen,^[1]making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest toecologistsbecause nitrogen availability can affect the rate of key ecosystem processes, includingprimary productionanddecomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramaticallyaltered the global nitrogen cycle^{[citation needed]}.

diagram of nitrogen cycle :-

i am sure it will help you in exam!!so give me thumbups please

Diagram of nitrogen cycle