Nitrogen Cycles | Definition, Importance, Process

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Hello, welcome to this blog on the topic: Nitrogen cycles: definition, the importance of nitrogen cycle, ways and process of formation.

Table Of Contents

  1. MEANING of nitrogen cycle
  2. Importance of nitrogen cycle
  3. Ways by which nitrogen is added to the soil in the nitrogen cycle.
  4. Ways by which soil nitrogen is lost from the soil
  5. Process that lead to the formation of nitrate from organic matter in the nitrogen cycle.

Nutrient cycles

Nutrient cycle refers to the circulation of certain nutrients like nitrogen, carbon and water in nature.

Nitrogen Cycle

Nitrogen cycles involves the complex process by which nitrogen is naturally added and removed from the soil. It is a sequence of reaction, indicating the various means by which nitrogen is added to and removed from the atmosphere and the soil.

Importance of Nitrogen Cycles

Nitrogen cycle is nature’s Way of regulating the amount of nitrogen in the soil and air.

Nitrogen fixation process involves soil organisms which add reasonable amount of nitrogen to the soil.

Ways by which nitrogen is added to the soil in the nitrogen cycles

These are the ways by which nitrogen is added to the soil in the nitrogen cycle:

  1. Direct fixation by lightning during rainfall (electrical discharge).
  2. Incorporation into the soil by free living bacteria or non symbiotic bacteria.
  3. Nitrogen fixing bacteria in the root modules.
  4. Decomposition of organic matter
  5. Application of nitrogenous fertilizers.
  6. Ammonification
  7. Nitrification

Soil can gain nitrogen through the following ways:

Symbiotic nitrogen fixation: Some bacteria, such as rhzobium leguminosarum, which live in the root modules of leguminous plants can fix atmospheric nitrogen directly in to the plant. The plants supplies carbohydrates for use by the bacteria which combined nitrogen.

Electrical discharge: Nitrogen can also be fixed into the soil during lightning. Nitrogen in the air combines with oxygen to form nitric oxide which further undergoes oxidation to form nitrogen dioxide. The nitrogen dioxide will dissolve in rainwater to form nitrous and nitric acid which later dissociates to form nitrate in the soil.

Non symbiotic nitrogen fixation: Some bacteria such as azotobacter and clostridium also live freely in the soil and can fix atmospheric nitrogen into the soil either aerobically and anaerobically.

Ammonification and nitrification: The process involving the formation of ammonium compounds from dead and decaying plants and animals are their waste products like urine and feaces is called ammonification. A further reaction known as nitrification involves the conversion of ammonium compound first to nitrite by nitrosomonas. These nitrites by another bacterium called nitrobacter. Plants can only absorb nitrates from the soil.

Application of organic manure and nitrogen fertilizers: These also add or supply nitrogen to the soil.

Ways by which soil nitrogen is lost from the soil

  1. By denitrification: This process involves the conversion of nitrates to nitrogen gas by certain bacteria. The nitrogen gas escapes into the air.
  2. Soil erosion
  3. Leaching
  4. Soil pH
  5. Bush burning
  6. Crop remover
  7. Volatilization
  8. Oxidation reaction
  9. Reduction reaction.

Processes that lead to the formation of nitrate from organic matter in the Nitrogen cycle

  1. Putrefaction
  2. Amminization
  3. Ammonification/mineralization
  4. Nitrification

1. Putrefaction: Decay of plant and animal remains into simpler nitrogenous compound by micro-organisms.

2. Amminization: Products from Putrefaction reaction converted to simple amino compounds and amines.

3. Ammonification: Conversion of amino compounds and amines into ammonium (NH+) compounds.

4. Nitrification: Oxidation of ammonium compounds into nitrites and nitrates.

Revision Questions

  1. What is the definition of nitrogen cycle?
  2. What are the ways by which nitrogen is added to the soil in the nitrogen cycle?
  3. State nine ways by which soil nitrogen is lost from the soil.
  4. State the importance of nitrogen cycle
  5. What are the processes that lead to the formation of nitrates from organic matter in the nitrogen cycle?

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