THE NITROGEN CYCLE

THE NITROGEN CYCLE

Nitrogen cycle is the recycling of the nitrogen through the ground or soil organisms and the atmosphere.

 

PROCESSES THAT ADD NITROGEN TO THE SOIL

The ultimate source of nitrogen (N) used by plants in Nitrogen gas (N2), which constitutes 78% of the earth’s atmosphere. Higher plants cannot metabolize nitrogen gas (N2) and must be converted to ammonium (NH4+) in the soil by one of the following processes;

1.  1. Symbiotic nitrogen fixation

2.      2.  Non- symbiotic nitrogen fixation

3.       3. Putrefaction or Aminization

4.       4. Ammonification

5.       5. Nitrification

6.       6. Nitrogen fixation by Electric Discharge/ Lightening or Thunderstorm or Chemical Fixation

7.       7..Industrial nitrogen- fixation

8.      8.  Combustion of fossil fuel and Forest burning

 

 

PROCESSES THAT REMOVE NITROGEN FROM THE SOIL

 1. Denitrification

2. Anaerobic Ammonia Oxidation

3. Nitrate Reduction or Volatilization

4. Soil Erosion

5. Leaching

6. Drainage

7. Crop Removal

8. Immobilization

PROCESSES THAT CONTRIBUTE TO RETURN NITROGEN TO THE ATMOSPHERE IN THE NITROGEN CYCLE

 1. Denitrification

2. Anaerobic Ammonia Oxidation

3. Nitrate Reduction or Volatilization 

ORGANISMS INVOLVED IN THE NITROGEN CYCLE

1. Symbiotic nitrogen-fixing bacteria or Rhizobium leguminosarum

2. Non-symbiotic nitrogen-fixing bacteria or Azotobacter, Clostridium, and Beijerinkia

3. Nitrifying bacteria or Nitrosomonas or Nitrobacter

4. Putrefying bacteria

5. Denitrifying bacteria or Planococus, Pseudomonas, Clostridium

6. Blue-green algae or Nostoc puntiforme or Anabana vaiabilis

7. Lichens

Importance of nitrogen cycle to plants and animals

 

Lost nitrogen in the soil is replaced through the nitrogen cycle process. This improves the fertility of the soil. The availability of nitrogen in the soil means plants can easily get access to it for proper growth. Nitrogen, which is an important source of nutrient for animals as well, is passed on to animals from plants. This occurs when animals eat the plants that have absorbed nitrogen from the soil through their roots.

 

In a nutshell, nitrogen cycle is very important because:

 

1. It supplies plants with needed nitrogen (nitrate ions).

 

2. It improves the fertility of the soil.

 

3. It improves the productivity and structure of the soil and sustains the activities and growth of microbes.

 

4. It prevents the accumulation of worn- out plant and animals tissues in the soil.

 

5. It releases nitrogen which is stack-up in organisms.

 

6. Nitrogen is an important nutrient which helps plants to manufacture their food for the nourishment of other organisms.