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Write an essay on Biofertilizers.

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Biofertilizers:

  • These days, scientists are cultivating the microbes which can fix atmospheric nitrogen at commercial scale. The microbes which enrich the soil in nutrients by their biological activities are called as biofertilizers.
  • The biofertilizers also accelerate the process of mineralization, in addition, to the increase in soil fertility.
  • Some of the examples of biofertilizers are Bacteria, Cyanobacteria, Fungi etc. 

These biofertilizers are mainly of six types: 

1. Symbiotic bacterium – Rhizobium: 

  • These bacteria are found in the root nodules of leguminous plants and obtain nutrition from the plant. They fix (trap) atmospheric nitrogen and convert it into ammonia and liberate it outside, which in turn is consumed by the plant.
  • Rhizobium can fix atmospheric nitrogen at a rate of 50 to 150 kg per hectare per year.
  • The use of these bacteria as biofertilizer can increase production up to 15 – 20%. Even the next crop grown after its application will yield more because of increased soil fertility. 

2. Non-symbiotic Bacteria: 

  • Non-symbiotic bacteria such as Azotobactor, Azospirillum, Clostridium etc. can also fix the nitrogen present in the soil and make it available to the plant. These bacteria absorb the free nitrogen of soil and convert it into organic nitrogenous compounds.
  • After the death of these bacteria, the nitrogenous compounds contained in these are decomposed by decomposing bacteria and the ammonia is released. The released ammonia is converted into nitrite and finally into nitrate which is finally used by the plants.
  • Azotobactor is used as biofertilizer during rice, maize, cotton cultivation. The production is increased up to 20%. 

3. Blue-Green Algae or Cyanobacteria:

  • Cyanobacteria such as Anabaena, Nostoc, Plectonema and other non-symbiotic prokaryotes perform nitrogen fixation. 
  • Cyanobacteria have special cells called heterocyst. The Nif gene present in these cells does nitrogen fixation. 
  • Rice fields are ideal for the growth of blue-green algae, hence use of blue-green algae in paddy fields increases the production of rice. Nowadays, one aquatic pteridophyte called Azolla is also used along with blue-green algae as algal biofertilizer in Southern and South-East Asia. 
  • The Azolla is a floating aquatic fern. Leaves of Azolla contain blue-green algae Anaebaen Azolla which fixes atmospheric nitrogen. Anabaena pinata is also a good biofertilizer. When it is used in combination with Azolla, it can increase rice production by 50%.
  • Anabaena Azolla is commercially produced at Central Rice Research Institute, Cuttack. 

4. Mycorrhiza: Symbiotic association of fungi with roots of higher plants is called Mycorrhiza. The fungus absorbs nutrients from the soil and provides to host plant and in turn host plant provides nutrition to the fungus. 

5. Phosphate dissolving Bacteria: Some bacteria such as Pseudomonas, Microbacterium, Bacillus etc. Convert non-available inorganic phosphate into available organic phosphate which is easily absorbed by plants. 

6. Organic manure: In India organic waste products are available in large amount in the form of domestic wastes, urban waste, sewage, remains of crops, animal excreta, bone powder etc. These wastes can be converted into organic manure by microbial degradation and can be used by plants.

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