Biofertilizers are defined as preparations containing living cells or latent cells of efficient strains of microorganisms that help crop plants’ uptake of nutrients by their interactions in the rhizosphere* when applied through seed or soil.
They accelerate certain microbial processes in the soil which augment the extent of availability of nutrients in a form easily assimilated by plants.
Use of biofertilizers is one of the important components of integrated nutrient management, as they are cost effective and renewable source of plant nutrients to supplement the chemical fertilizers for sustainable agriculture.
Several microorganisms and their association with crop plants are being exploited in the production of biofertilizers. They can be grouped in different ways based on their nature and function.
| S. No. | Groups | Examples |
| N2 fixing Biofertilizers | ||
| 1. | Free-living | Azotobacter, Beijerinkia, Clostridium, Klebsiella, Anabaena, Nostoc, |
| 2. | Symbiotic | Rhizobium, Frankia, Anabaena azollae |
| 3. | Associative Symbiotic | Azospirillum |
| P Solubilizing Biofertilizers | ||
| 1. | Bacteria | Bacillus megaterium var. phosphaticum, Bacillus subtilis Bacillus circulans, Pseudomonas striata |
| 2. | Fungi | Penicillium sp, Aspergillus awamori |
| P Mobilizing Biofertilizers | ||
| 1. | Arbuscular mycorrhiza | Glomus sp.,Gigaspora sp.,Acaulospora sp., Scutellospora sp. & Sclerocystis sp. |
| 2. | Ectomycorrhiza | Laccaria sp., Pisolithus sp., Boletus sp., Amanita sp. |
| 3. | Ericoid mycorrhizae | Pezizella ericae |
| 4. | Orchid mycorrhiza | Rhizoctonia solani |
| Biofertilizers for Micro nutrients | ||
| 1. | Silicate and Zinc solubilizers | Bacillus sp. |
| Plant Growth Promoting Rhizobacteria | ||
| 1. | Pseudomonas | Pseudomonas fluorescens |
(*The rhizosphere is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil. The rhizosphere contains many bacteria that feed on sloughed-off plant cells, termedrhizodeposition, and the proteins and sugars released by roots.)
Source :-
1. http://agritech.tnau.ac.in/org_farm/orgfarm_biofertilizertechnology.html
2. http://en.wikipedia.org/wiki/Rhizosphere
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