Biofertilizer contains living microorganisms which, when applied to soil, colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the availability of primary nutrients to the host plant.
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| Classification of Biofertilizers (Cover) |
Types of Biofertilizers
The various types of biofertilizers which help the plant to grow at different levels of its growth are:
1. Nitrogen Fixing Biofertilizers
2. Phosphate Biofertilizers
a. Phosphorous Solubilizing Biofertilizers
b. Phosphorus Mobilizing Biofertilizers
3. Biofertilizers for Micro-nutrients
4. Plant Growth Promoting Rhizobacteria
5. Compost
1) Nitrogen Fixing Biofertilizers
i. Increase soil nitrogen level ii. Fixes the atmospheric nitrogen in the soil and make it available to the plants
Examples: Azotobacter, Nostoc, Rhizobium, Azospirillum
a) Azobacter
i. Free living N-fixing bacterium
ii. Non-leguminous plants
b) Cyanobacteria
i. Nostoc/Blue green algae
ii. Free-living as well as symbiotic
iii. Fix atmospheric nitrogen to soil
c) Rhizobium
i. Symbiotic N-fixing bacterium
ii. Leguminous plants
d) Azospirillum
i. Associative symbiotic N-fixing bacteriumii. Graminaceous plants
a) Azobacter
i. Free living N-fixing bacterium
ii. Non-leguminous plants
b) Cyanobacteria
i. Nostoc/Blue green algae
ii. Free-living as well as symbiotic
iii. Fix atmospheric nitrogen to soil
c) Rhizobium
i. Symbiotic N-fixing bacterium
ii. Leguminous plants
d) Azospirillum
i. Associative symbiotic N-fixing bacteriumii. Graminaceous plants
2) Phosphate Biofertilizers
a. Phosphorous Solubilizing Biofertilizersb. Phosphorus Mobilizing Biofertilizersa) Phosphorus Solubilizing Biofertilizers
i. Solubilize the insoluble phosphate from organic and inorganic phosphate sources
ii. Releases insoluble phosphorus in soil and fix in clay minerals
iii. Secrete organic acids and lower the pH to dissolve bound phosphates in soil
Examples: Species of Bacillus, Pseudomonas, Penicillium, Aspergillus
b) Phosphorus Mobilising Biofertilizers
Transfer phosphorus from the soil to the root cortex
Examples: Arbuscular Mycorrhiza (AM fungi)
i.Fungus penetrates the cortical cells of the roots
ii. Increase surface area of roots
iii.Displace of absorption equilibrium of phosphate ions which increases the transfer of P ions
iv. Stimulate metabolic processes
v. Arbuscles absorb these nutrients into the root system
3) Biofertilizers for Micro-nutrients
i. Bacterial species are Silicate and Zinc solubilizers
ii. Degrade silicates and aluminium silicates in soil
iii. Help in silicate weathering
Example: Bacillus sp.
4) Plant Growth Promoting Rhizobacteria (PGPRs)
i. Act as both Biofertilizer and Biopesticides
ii. Promote growth by:
a) Improved Nutrient Availability (Biofertilizers)
b) Suppression of Plant Disease (Bioprotectants)
c) Phytohormones Production (Biostimulants)
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| Roles of PGPR |
Examples: Pseudomonas sp., Bacillus sp.
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| PGPR Action |
5) Compost Biofertilizers
i. Utilize animal dung to enrich soil with microorganisms
ii. Eco-friendly organic fertilizer
iii. Consists of nitrogen, phosphate solubilizing bacteria and various decomposing fungi
iv. Microorganisms breaks down organic matter (dead plants, farm yard waste, cattle waste etc.)
Examples: Cellulolytic fungi, Azotobacter
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| Compost Biofertilizers [Uses (Left) and mode of action(Right)] |
Liquid Biofertilizers
i. Liquid biofertilizers are suspensions having agriculturally useful microorganisms, which fix atmospheric nitrogen and solubilize insoluble phosphates and make it available for the plant
ii. Reduces the use of chemical fertilizer by 15-40%
iii. Long shelf life
iv. More temperature tolerant and contamination free
v. Easy to produce and apply
vi. Help to produce organic crops so as to compete in the global market
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Post by:Saman Riaz(M.Phil Scholar)
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