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Bacterial Biofertilzers

This is a continuing series of articles on Biofertilizers. This is part 2 of the series.

Read part 1 

RhizobiumBacterial Biofertilzers- Help in increasing the fertility of soil by adding nutrients to the soil. Help in fixing nitrogen as a result of their biological activities. They are either symbiotic (Rhizobium, Frankia, Xanthomonas, Mycobacterium) or Free living.

Free living can be saprophytic (Azotobacter, Clostridium) or Photosynthetic (Rhodospirillum, Rhodopseudomonas).

Of these, the symbiotic bacteria form mutually beneficial associations with plants and both parties are benefit as a result of the association. The association between Rhizobium and legumes is well known.


  • Gram negative, aerobic, rod shaped.
  • Soil bacterial species and exists in roots of legumes.
  • Forms nodules in roots and helps by fixing nitrogen, N2 to NH3.
  • Rhizobium is highly recommended as a biofertilizer as it can fix large quantities of N2.


  • Gram negative, non symbiotic.
  • Aerobic, present in large numbers in Rhizosphere soils.
  • Fixes N2.
  • It also secretes hormones such as IAA, Giberellic acid, and vitamins that help to promote plant growth.
  • Recommended as a biofertilizer for rice, cotton, millets, vegetables, mustard, and sunflower.

Some important Azotobacter species

1. Azotobacter vinelandii

2. Azotobacter beijerinckii

3. Azotobacter chrooocum

4. Azotobacter paspali

5. Azotobacter haplophilus

6. Azotobacter mischelhius

Read part 1


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