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MICROBIAL
INOCULANTS
(Biofertilizers)Beneficial microbes
N2 fixers
PO4Solubilizers
Organic Matter Decomposers
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What are Biofertilizers-1?
Biofertilizers are natural and organic fertilizers.
Biofertilizers are preparations containing cells of
microorganisms which may be nitrogen fixers,
phosphorus solublizers, sulphur oxidizers or organic
matter decomposers.
They are called as bioinoculants - bacterium or fungiwhich on supply to plant improve their growth and
yield. 2
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What are Biofertilizers-2?
These bioinoculants can reside on the surface of the
plant or form endophytic association or else
interacts with other microbes in the rhizosphere or
phyllosphere thereby influencing the plant growth.
Microbes are cost effective, ecofreindly with the
simple methodology of production and thereby no
hazard to the agro ecosystem
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Most Important nutrients: N, P & K
Biological N fixers:Types
Symbiotic N2 fixers
Non symbiotic N2 fixers
Free living N2 Fixers
Sources of K: Potassium chloride
Plant ash
Phosphate solubilizingbacteria
Formation of solubleinorganic phosphate:
easy absorption byplants
Reduce the phosphatedose by 50%
Cheaper Bacillus
Pseudomonas 5
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Symbiotic N fixers
Rhizobia: Most exploited Infect legumes
Rhizobia hostcompatibility
importantCyanobacteria:
Anabaena azollae :
azolla
flooded soil condition;wide adaptability
Increase availability ofmicronutrients;
Frankia: inoculum infectivity
customisation of target
area and target species
Cyanobacteria: Anabaena azollae :
azolla
Increased Nitrogen,
yield Great potential: very
important for Rice6
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Rhizobia-1
The best known and most exploited symbiotic N2 fixing
bacteria belonging to family Rhizobiacea include the
genera such as Rhizobium, Bradyrhizobium etc.
These bacteria infect legumes and have global
distribution. However N2 fixing capability of Rhizobia
varies greatly depending on the host plant species.
Therefore selection of best strains must take
Rhizobia host compatibility for selection of Biofertilizers
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Rhizobia-2
Legumes (such as beans, soybean, chickpea) inoculation
is an old practice that has been carried out especiallywhen local / resident rhizobial population in the soil are
low.
Rhizobial inoculum can be produced and applied in
numerous ways such as granular, liquid or powderformulation.
However the success depends upon strain and
environmental condition.
Therefore it is essential to evaluate inoculationprogramme, type depending on field experiments,
microbiological assays and cost benefit analysis.8
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Cyanaobacteria-1:
Cyanaobacteria are ecologically important in N2
fixing organisms especially in rice cultivation.
Anabaena azollae is a symbiotic heterocyst
nitrogen fixing Cyanaobacteria which lies in fronds
in the pores of the Azolla. Exploitation of azolla as a biofertilizer is a practical
possibility in flooded soil condition. It is used as
both green manure before planting and
intercropped with rice after planting. The latterpractice has wide adaptability and is more
economical as Azolla decomposes within two
weeks releasing about 67% of Its N.9
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Cyanaobacteria-2:
The increase in grain yield due to Azollagreen manuring is about 0.5-2 tonnes perhectare. Thereby cyanobacteria should beseriously considered as biofertilizer with a
great potential as these cyanobacterial(especially immobilized) have resulted inhigher heterocyst frequency growth,nitrogenase activity and increased
ammonia excretion and have alsoincreases availability of micronutrients likeiron. manganese in the soil. 10
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Frankia
Frankia is the genus of N2 fixing actinomyctes capable of
fixing N2 similar to rhizobial symbiosis. Frankia can fix N2 atnormal O2concentration at the rate sufficient to support its
growth N2 fixation is accompanied by the development of
terminal swelling known as vesicles in which nitrogenase
enzyme are protected by restricting O2 diffusion.
In addition to symbiotic properties of strain characteristics
such as age of the inoculum, cellular concentration and the
method of preservation greatly effect the inoculum
infectivity.
Since a universal strain adapted to different environmental
host genotype does not exist, best plant Frankia combination
should be selected and customized for a target area and
target species.11
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Non-Symbiotic N fixers-1
Azospirillum Wide host range
Tolerance to high soil temperature
Produce Plant growth promoting substance
Form Cyst under stress Great promise as a growth promoting N2 fixing
biofertilizer
Acetobacter
Is a non symbiotic associated with sugarcane crop Difficult to isolate
Grow artificially12
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Azospirillum-1
This genus includes spirally curved bacteria which not
only lives in rhizosphere of grasses but can also enter
root cortex. It is an associative micro- aerophilic Nitrogen
fixer which not only colonizes root mass and fixes N2 in
close association with plant in an environment of low O2
tension.
These bacteria induce plant roots to secrete mucilage
substances which creates low O2 environment and helps
to fix atmospheric Nitrogen.
It has a wide host range, high N2 fixation capacity, lowenergy requirement, tolerance to high soil temperature
thereby makes these suitable for tropical condition.13
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Azospirillum-2
The positive aspect of this inoculant is that theyproduce plant growth promoting substance in
addition to fixing the Nitrogen and has ability to
differentiate into cyst under stress that enables
its persistence for a long time in field condition.
Azospirillum bears great promise as a growth
promoting Nitrogen fixing biofertilizer.
It has been recorded that Azospirilluminoculation may be used as biofertilizer for
wheat ,rice thereby reducing use of
urea N by approximately 20%.14
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Non-Symbiotic N fixers-2
Klebsiella
Fix N2 under anaerobic
condition, microaerophilic condition
Require several field trailsBacillus
Increased chlorophyll, Phosphorus , N2
content Produce IAA, Giberrelic acid
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Klebsiella:
They fix N2 under anaerobic condition as these have
no means of protecting nitrogenase enzyme from
O2.
These organisms have flexibility to grow under both
aerobic and anaerobic environment. In the
laboratory Klebsiella has been shown to reproduce
Nitrogen under micro- aerophilic condition.
Therefore use ofKlebsiella as a biofertilizer will
require several field trials and future research.16
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Bacillus
Nitrogen fixing Bacillus Polymyxa and Bacillus
macerans were isolated from cotton phylloplane.Thesebacteria show an increase in yield of cotton due to its
ability to fix nitrogen produce Indole Acetic Acid and
Gibberelic acid production.
The foliar spray on this phylloplane bacteria wasshowing an increased growth, yield, increased
Nitrogen fixation and an increased chlorophyll ,
nitrogen, phosphorus content.
Similarly Bacillus subtilis inoculation on chilli plant
through the phyllosphere have resulted in increase in
chlorophyll content , photosynthetic quotient and
eventually increased growth.17
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Free living N bacteria
Azotobacter
Promotes plant growth by N2 fixation
Growth promoting substances
Fungi static substances
Improves seed germination and plant
growth
Thrives in alkaline soil
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Azotobacter-1
This is a group of bacteria which are free living nitrogen
fixer.
Sufficient research work has been carried out on the role
ofAzotobacterculture in sugarcane cultivation.
The result in general have indicated that application of
Azotobacterat the rate of 5kg per hectare helps in
reducing nitrogen dose by 50kg per hectare with increase
in yield of cane by 5 to 10 %.
The mechanism by which plants inoculated with
Azotobacterderive its benefits such as increased biomass ,Nitrogen uptake is attributed to increase in nitrogen input
by Biological nitrogen fixation.19
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Azotobacter-2
Plants inoculated withAzotobacter also derive its
benefits such as development and branching of
roots ,production of plant growth hormones,
vitamins, enhancement in uptake of nitrate,
ammonium orthophosphate, potassium and ironimproved water status of the plant and antifungal
compounds.
If environmental conditions allow nodulating
bacterial symbionts (ex Frankia) of plant roots canalso fix N2 when not in symbiotic association.
Estimation of Nitrogen fixation by free-living
bacteria is difficult.20
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Fungi as biofertilizer
Vesicular Arbuscular Mycorrhizae: obligatesymbiont.
Increased immobile nutrient uptake, water
Heavy metal tolerant
Disease resistance
Reduces stress response
Micro-propagation
Saves phosphate fertilizer
But limited Field application?
On farm Production21
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Phosphorus solubilizing bacteria-1
Phosphorus is the second most limiting plant nutrient
required for better crop yield. Indian soil contains on anaverage 0.05% Phosphorus which constitutes 0.2 % dry
weight.
Most of the soil Phosphorus pool is not in forms available
for plant uptake or the soil might contain insufficientamount of available phosphate to support plant growth. As
a result of application of phosphatic fertilizer is therefore
essential for optimum crop yield.
However the main problem concerning phosphaticfertilizer is that its fixation with soil complexes within a
very short period of application rendering more than two
third unavailable. 22
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Phosphorus solubilizing bacteria-2
Many organisms possess the ability to bring sparingly
soluble/insoluble inorganic and organic Phosphorus into
soluble forms by secreting organic acids. These organic acids
lower soil pH and in turn brings about dissolution of
unavailable forms of soil Phosphorus making it available for
plant growth and development. Some of the hydroxyl acidsmay chelate calcium, Aluminium, Iron and Magnesium
resulting in effective availability in soil.
Use of Phosphate solubilizing bacteria as bioinoculants could
reduce the phosphate dose by 50% and could be applied in
the form of Rock phosphate which is cheaper source ofPhosphorus.
The most commonly tested organisms of this group belong to
the genera Bacillus and and Pseudomonas.23
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Phosphorus solubilizing bacteria-3
There were two method of phosphobactrium applicationi.e. seed treatment (500ginoculum per hectare) and soil
application (200g per hectare).
Pretreatment of seeds of cereals with phosphobactrium
has been reported to help in reducing fertilizer
phosphate requirement of the crop and increasing its
grain yield.
Potential use as Biopesticide: Although extensive
research has been made on utilization of Phosphorus
solubilizing bacteria
in order to provide soluble forms of phosphate to plants
while some of them were found to release antifungal
compounds.
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Bacteria like Pseudomonas striata (P-27) have a high
P solubilzation activity and high anti fungal activity.
Use of several such bioinoculants with combinedattribute of fertilization and antipathogenic activity
can provide long-lasting effective solutions for
sustainable agriculture.
Combined treatment with Phosphobacteria andmychorhizal fungi in several agriculturally important
crops ex chillies, brinjal resulted in an increase in
plant height, root length, biomass as well as total
nitrogen and phosphorus content.Combined inoculation of Azospirillum and VAM
increased growth yield, nutrient uptake of plant
than with no bacterium added extraneously.
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Co inoculation of Rhizobia and Phosphate
solubilizing microorganisms is synergistic and
results in better phosphate utilization and higheryield. Some of the Phosphate solubilizing
microorganisms increase the uptake of nitrogen
too.
Thus right kind of bacteria and fungi in root zonefix nitrogen, release minerals and provide
protection against disease causing organisms too.
Thus multiple inoculation has a very important
role in the future of biofertilizers to develop
Integrated Nutrient Management package for
various crops thereby reducing our dependence on
synthetic chemical fertilizers.
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How to apply biofertilizer?
Seed treatment.
Soil Application.
Seedling root dip.
Other general techniques.
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Response may be poor when
the following are not OK
Quality of product
Proper Storage
Correct Usage
Soil and Environment
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How to get good
response ?
Right combination of Biofertilizers
Use suggested method of application at
appropriate time For problematic soils :use corrective
methods like lime or gypsum
Use for specified crop only
Care in storage31
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Prospect s for Emerging Biofertilizers In Global
Market/India:
One of the challenges of globalization and green revolutionis not only to increase the yield but is also to improve the
nutritional quality of product so that it matches global
standards. The world is undergoing a shift from inorganic
conventional farming towards organic eco - friendlyfarming methods. This not only requires the isolation of
bioinoculants with high potential for use as biofertilizers
but also several other factors right from proper application
procedures to correct marketing practices also being made
economically cheaper.
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