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Azotobacter biofertilizer

Azotobacter is a free-living, aerobic, gram-negative soil bacterium used as a biofertiliser inoculant for non-leguminous crops including paddy, wheat, maize, cotton, vegetables and sugarcane. Unlike Rhizobium, Azotobacter fixes atmospheric nitrogen in the bulk soil without forming root nodules, contributing supplementary nitrogen to the crop and producing plant-growth promoting metabolites.

Composition

  • Recommended species: Azotobacter chroococcum
  • Carrier types: lignite/peat-based powder or liquid formulation
  • FCO specification: pH 6.0-7.5, 35-40% moisture in carrier, no contamination at 10^5 dilution
  • Activity standard: minimum 10 mg N fixed per g sucrose utilised
  • Shelf life: approximately one year

The strain bank is maintained by ICAR institutes including NBAIM and NBAIR; commercial production is licensed through state biofertiliser units and private firms.

Mode of action

Azotobacter fixes 15-20 kg N per hectare per season under favourable soil moisture and organic-carbon conditions. Beyond N fixation, the bacterium produces indole-3-acetic acid (IAA), gibberellins and siderophores that promote root growth, and contributes modestly to phosphate solubilisation. It is sensitive to soil acidity, prolonged dryness and high salinity.

Target use and dose

Application is by seed treatment (10-25 g/kg seed), seedling root dip in paddy nurseries, or soil application with FYM at 2-4 kg/acre for powder formulations. It is most effective when combined with reduced (not eliminated) doses of Urea and adequate organic matter; full-rate chemical N suppresses Azotobacter populations.

Safety and regulatory status

Notified under Schedule III of the FCO biofertiliser specifications. Non-pathogenic to humans, animals and plants. Should be stored cool and dry and must not be mixed with chemical fungicides or hot fertilisers.

See also: Microbial Biofertilizers, Liquid Organic Biofertilizer Consortia, Vam Mycorrhiza, Waste Decomposer Ncof.

References

  1. BioBacter Liquid Azotobacter Biofertilizer. Office of the Principal Scientific Adviser, Government of India.
  2. Azotobacter Species for Crop Nutrition and Sustainable Agriculture. Frontiers in Microbiology.