Bio fertilizers/ Microbial Inoculants

'Microbial Inoculants ' is the appropiate name of Biofertilizer. 

It is defined as preparation containing live or latent cells of efficient strains of N- fixing , Po4 solublising or cellulolytic micro- organisms used for application of seed , soil or composting areas with the objective of increasing the number of such micro - organisms and accelerate certain microbial process to augment the extent of the availability of nutrients in a form which can be assimilated by plants .

Application:

a) Seed Inoculant : 20 g Rhizobium culture is required to treat 1 kg seed 

One packet of Rhizobium culture contains 200 g of Rhizobium culture.

1) For small seeded pulses like moong , Arhar , lentil , Berseem, Lucerne  kulthi , 500 g of Rhizobium culture is sufficient for seeds required to be sown in 1 ha 

2) For Groundnut 

1.5 kg of Rhizobium culture for 80-100 kg seeds for 1 ha 

3) For Soybean and Bengal gram 1 kg/ha 

B) Soil Inoculant: 

10 packets (2 kg/ ha of carrier based Azotobacter and Azospirillum culture is mixed with 25 kg FYM and 25 kg soil and is broadcasted in the field uniformly before transplanting 

Benefits:

1)Rhizobium Biofertilizer can fix 50-200 kg N/ha per year

2) Increases yield by 25-30 % and 40-80 kg N is left over the in the field useful for subsequent crop

3) BGA can add up to about 20-25 kg N/ha to rice field

4) BF like BGA , Azotobacter and Azospirillum also supply growth Regulator such as IAA, IBA , NAA GA1 to GA3 and vitamins.

5) Azotobacter and Azospirillum secrete antibiotic which act as pesticides so biofertilizers also act as ' Bio- Pesticides '

6) Azolla not only supplies N but also increase O.M inform of biomass and increases soil fertility

7) It incrases soil physical properties such as a soil structure, texture , chemical properties such as water holding capacity, cation exchange capacity of soil buffer capacity etc

8) It proliferates useful soil micro organism I e. biological properties of soil

9) It is ecological friendly, technologically feasible and socially acceptable input to the farmers

A list of common legumes and the Rhizobium strains by which they are inoculated

Fixation of Atmospheric Nitrogen:

     1) Physio- chemical 

e.g. Discharge of electricity in atomosphere

2) Bio- chemical by

1) Activity of certain saprophytic bacteria 

2) Activity of symbiotic bacteria

3) Activity of Blue green algae

Bio- chemical or Biological N- fixation is the natural process of fixation of Atmospheric N2 through the activity of soil micro - organisms 

Symbiotic N- fixation:

 a) Nodule forming:

1) With Legumes:

On the experimental basis Boussingault first proved that legumes use free N2 of air for their normal growth.

The bacterial symbiont is member of genus Rhizobium. 

Leghaemoglobin is the Oxygen carrier in the N- fixation in nodules and it also protects N- fixing enzyme 

Rhizobium bacteria is aerobic and heterotrophs .

Greengram fixes 20 kg /ha whereas Lucerne, even more than 250 kg/ha

With non legumes:

The  important group is angiosperms .

The roots of these plants inoculated by soil Actinomycetes of the genus Frankia and Casuarina alder lives in association with casuarina 

• Actinomycetes are in between true fungi and bacteria

Actinomycetes.   50-150 kgN/ha year

Legumes                150-250 kg Nper ha                                       per year

Beans                         30-50 kg N/ha/year

Pulses.                       30 kg N/ha/year

Factors affecting:

Nodule formation & N- fixation

1) pH: legumes fail to develop nodules when pH less than 5.0

2) N&P status of soil

Excess Moisture in soil- Since Rhizobia are aerobic , there is detrimental effect of excess moisture in soil.

b) Without Nodule:

The Blue green algae Anabena azollae is having a symbiotic association with water fern, Azolla pinnata 

 It fix 30-40 kg N/ha 

Opt temp: 20-30°C , pH : 5.5-7.0 

Nursery for Azolla culture: 4m× 2m × 30-40 cm raisedc, under shade

Azolla application rate @ 0.1 - 0.5 kg/ square metre.

For faster growth SSP@ 2.5 g/square metre and carbofuran granules @1.2 g/square metre to control leaf eating caterpillars are required

Azolla is applied in the main field as a green manure and dual crop

B) Non - Symbiotic N- fixation:

By  soil and water free living micro organisms

a) Fixation by Heterotrophs:

Several groups of bacteria and BGA 

1) Aerobic bacteria:

✓ Azotobacter chroccum and Azotobacter vinefandi:  Act in temperate zone soils ;Opt pH 6.5-8

2) Beijernckia :

In tropical soils

✓ Anaerobic bacteria:

Clostridium -

Tolerant to wider pH

Opt pH 5.0-9.0

The above bacteria fix the nitrogen @5-20 kg/ha/year.

These bacteria ate applied in the field by mixing 3-5 kg it's Inoculum with ,5 tonne FYM per hactare

b) Fixation by Autrotrops:

Certain photosynthetic bacteria viz. Rhodospirillum and Blue green algae

Azotobacter  is used for rice , cotton and sugarcane

Whereas Azospirillum for sorghum

• Saprophytes: Such microorganisms are calable of decomposing O.M. at a faster rate hence can be used as a fertilizer for quick release of nutrients e.g. Aspergillus, penicillium , Trichoderma are cellulolytic fungi

✍️ Agricos 🌱🌾 🌿

 Vaishnavi Nimkar