Nitrogen Clrcle B Ludhiana

Prepared By:Monika Science Mistress G . S. S. School, Samrala.

Nitrogen is present in the Air in its free state. Its ratio in air remains constant around 78% by volume. Importance of Nitrogen :- Nitrogen is a component of proteins and nucleic acids, which are essential structural and functional parts of living system but free nitrogen, cannot be assimilated by the living cells.

Source of Nitrogen :- The nitrate ions (NO3-) of soil and water are main source of nitrogen for green plants. Following processes participating in the cycle

Nitrogen Fixation Decay Nitrification Denitrification

Nitrogen Fixation Three processes are responsible for Nitrogen Fixation

3) Atmospheric Fixation 4) Biological Fixation 5) Industrial Fixation

Atmospheric Fixation

By Lightning:-

In the soil nitrates are formed by the action of nitric acid on the minerals present in the soil. Nitric acid is formed by reaction between nitrogen and oxygen when the lighting strikes.

Nitric acid comes to the earth along with rainwater reacts with minerals to form Nitrates.

Industrial Fixation

Under great pressure and Temp. atmospheric nitrogen and hydrogen can be combined to form ammonia which can be used fertilizer

 Manures and fertilizers are also the sources of nitrogen to the soil under great pressure and temperature atmospheric nitrogen and hydrogen can be combined to form ammonia which can be used directly as fertilizers.  On death and decay of all living organisms turn nitrogen present in their bodies to soil.

Biological Fixation  Certain nitrogen fixing bacteria found in the soil can convert atmospheric nitrogen directly into nitrates.  These bacteria have nitrogenous enzyme that combines atmospheric nitrogen with hydrogen to produce ammonia, which further converted by the bacteria to make organic compounds. Some nitrogen fixing bacteria as Rhizobium, live in the root nodules of Legumes (such as Peas or Beans). The leguminous plants.

e.g., Beans have bacteria present in the nodules on their roots, which directly convert atmospheric nitrogen in to nitrates.. Many legumes in addition to fixing atmospheric nitrogen, also perform nitrification

Nitrification The source of ammonia is the decomposition of dead organic matter by bacteria called decomposers which produce ammonium ions. Which convert into nitrite ions Then into nitrate ions. This conversion is known as Nitrification.

Decay The proteins made by plants enter and pass through food webs. At each level organic nitrogen compounds return to the environment by microorganisms which break down the molecules into Ammonia.

Denitrification All the processes discussing above remove nitrogen from the atmosphere and pass it through ecosystems. Denitrification reduces nitrates to nitrogen gas and completing the nitrogen cycle. Once again bacteria are the agents. They live deep in soil and are Anaerobic. They use nitrates for their Respiration. Thus they close the Nitrogen Cycle.