Microbial Inoculants

7/27/2019 Microbial Inoculants

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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 microaerophilic 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 microaerophilic 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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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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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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Microbial Inoculants