BIO-FERTILIZERS - A BOON FOR SOIL HEALTH

Simerjeet Kaur*, Rajan Bhatt, Gurdeep Singh and Manoj Sharma

Krishi Vigyan Kendra, Kapurthala

Fertilizer is one of the major contributors to increased crop production but the

continuous and imbalanced use of chemical fertilizer is causing unsustainable environmental

penalties like soil health deterioration, contamination of surface water, nitrate pollution of

ground water and atmospheric pollution etc. The problems like leaching, volatilization,

de-nitrification of nitrogen and deposition of non-available phosphorus in soils are also due

to more use of chemical fertilizers. Fertilizer use efficiency in India is 30-50 % for Nitrogen,

15-20% for Phosphorus and 70-80 % for Potassium. Above all, the production of inorganic

fertilizers is energy intensive, depending upon fossil fuel and hence becoming costly day by

day. To cope with the above situation, Indian agricultural scientists are constantly stressing

upon the use of bio-fertilizers. During 2001-2002, the production and distribution of bio-

fertilizers in the country was roughly 10,000 metric tones, where the production of

Rhizobium, Azotobactor, Azospirillum, Acetobactor and PSB were 1603, 1553, 1258, 166

and 4088 metric tones, respectively. Among the other bio-fertilizers, compost accelerators

like cellulose/ lignin decomposers have got considerable importance.

Bio-fertilizers:

Bio-fertilizers are living microorganisms, which contribute nutrients to plants through

microbial activity. These microbial culture fix atmospheric nitrogen, solublize both native and

applied sparingly soluble Phosphate to increase soil fertility. In addition to these, plants

increase the surface area of the root system for better absorption of nutrients. Fungi,

bacteria and actinomycetes have the ability to accelerate the process of composting to

improve soil fertility and hence plant growth.

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* Assistant Professor ( Agronomy) Department of Agronomy, PAU.,Ludhiana

Benefits of Bio-fertilizers:

Enrich soil with nitrogen by biological nitrogen fixation.

Increase crop yield by 15-20 %.

Increase germination potential of seeds.

Develops resistance against disease in crops, suppress soil borne diseases as some of

the inoculants produce antibiotics.

Improves soil properties and sustain soil fertility.

Help in mineralization of plant nutrients, solublize unavailable phosphate and sulfur in the

soil converting them in available form.

Bio-fertilizers release certain hormones, which increase crop growth.

Save fertilizer consumption by nearly 15%.

Bio-fertilizers are cheap, handy, eco-friendly, pollution free and easy to transport.

Use of Bio-fertilizers in commercial crops:

1. Rhizobium All Leguminous crops

2. Azotobacter

Food crops Wheat, Barley, Maize, Oat and Paddy

Oil seeds Mustard, Sunflower, Linseed, Cotton and Coconut

Vegetables Potato, Onion, Cauliflower, Cabbage, Okra, Brinjal, Tomato, Chilly etc.

Flowers Dahlia, Chrysanthemum, Marigold, Rose, Gladiolus, Tuberose etc.

Fruits Mango, Guava, Banana, Papaya, Grapes, Mulberry, Cashew nut, Tea, Coffee,

Citrus, Apple, Litchi.

Forest All forest plants

3. Azospirillum Fruits, vegetables, ornamental plants, coffee, tea etc.

4. PSB For all crops

5. BGA Paddy

6. Azolla Paddy

Types of Biofertilizers:

Mainly there are two types of bio-fertilizers:

A. N-fixing bio-fertilizers

a. Symbiotic N-fixing bio-fertilizers e.g. Rhizobium, Actinomycetes

b. Non-symbiotic N-fixing bio-fertilizers e.g. Azotobacter, Azospirillum , Blue green algae

and Azolla

B. P-mobilizing bio-fertilizers

a. P-solubilizing bio-fertilizers e.g. Bacillus, Pseudomonas, Fungi

b. P-absorbing bio-fertilizers e.g. VAM

1. Rhizobium:

Rhizobium is the oldest and most widely used bio-fertilizer. Rhizobium has the

capacity to fix nitrogen in leguminous crops. Leguminous crops have nodules in their roots

where Rhizobium fixes atmospheric nitrogen with the help of nitrogenase enzyme. Number

and size of nodules directly affect the amount of nitrogen fixed by Rhizobium. Different crops

require different species of Rhizobia. Rhizobium can fix 50-200 Kg Nitrogen/hectare in

leguminous crops, which helps in saving nitrogen requirement for next crop.

Rhizobium species suitable for different crops:

Rhizobium Sp. Name of the Crop

R. leguminosarum Peas ( Pisum sp. ), Lathyrus sp., Vicia sp., lentil ( Lens sp. )

R. Tripoli Berseem ( Trifolium sp. )

R. phaseoli Kidney bean ( Phaseolus sp. )

R. lupini Lupinus, Ornithopus

R. japonicum Soybean ( Glycine sp.)

R. meliloti Melilotus, Lucerne ( Medicago ), Fenugreek ( Trigonella )

Cowpea miscellany Cowpea, Clusterbean, Green Gram, Black Gram, Red Gram,

Groundnut, Mothbean, Dhaincha, Sunhemp, Glyricidia, Acacia,

Prosopis, Dalbergia , Albizzia, Indigofera, Tephrosia, Atylosia, Stylo.

Inoculum Application:

a. Seed Treatment: Depending on the seed rate, the required quantity of jaggery is boiled

in water and cooled. Rhizobium inoculum (1.5 Kg/ha) is mixed in the jaggery solution and

sprinkled over the seeds. Then the seeds are thoroughly mixed to spread the inoculum over

the entire surface of the seeds. Seed are dried under shade and sown immediately.

c. Soil Treatment: The Rhizobium inoculum is mixed with soil and spread over the

field.

d. Soil Application: If Rhizobium inoculum is not available. Under such situation, 200 Kg

of surface soil (2-10 cm depth) can be collected from the field where that particular

leguminous crop was grown luxuriantly during last time and this soil can be broadcasted

over the field where the crop is to be sown for the first time.

2. Azotobacter:

Azotobacter is useful in fixing N in non-leguminous crops like cereals, fodder crops,

fruits and vegetables. Azotobacter bacteria fix nearly 20-25 Kg N/ha. Apart from fixing N,

these bacteria also release certain hormones, which help in plant growth. Azotobacter

bacteria are very fast growing and increase the crop yield by 10-20 %. It can be applied by

seed inoculation, seedling dip or by soil application. The inoculum required is 3-5 Kg /ha.

Application of 5 ton/ha of FYM helps in better growth of Azotobacter.

A study conducted to see the effect of Azotobacter on N economy in Maize Var.

Partap-1 at Krishi Vigyan Kendra, Kapurthala during Kharif-2001 revealed that seed

treatment with Azotobacter increased the grain yield, cob length and plant height. At

recommended level of N, Azotobacter application increased grain yield by 0.60 qt./ha.,

whereas, Azotobacter + Rec. N treatment gave the highest yield i.e. 38.35 qt./ha. followed

by Azotobacter+3/4 Rec. N treatment (38.05 qt./ha.).

3. Azospirillum:

Azospirillum is a non-symbiotic micro aerophillic bacterium that thrives well in soil

and rhizosphere of plants. This develops well utilizing the sugars and organic acids present

in the root exudates of plants. As there is no specificity, it can be used to a variety of crop

plants like cereals, millets, cotton, sugarcane etc. It is commonly found in association with

roots of horticultural crops has received great interest as a bio-fertilizer. Its useful characters

include high Nitrogen fixation capacity, low energy requirement and tolerance to high soil

temperature for its suitability under tropical conditions.

4. Blue-green algae and Azolla (Algal bio-fertilizer):

These are mainly used for low land rice cultivation. Among algal bio-fertilizers, major

strains are Tolypothrix, Nostoc, Anabaena, Aulosira, and Cylindrospermum. The amount of

Nitrogen fixed by Blue Green Algae ranges from 15-45 N kg/ha. Standing water of 2 to10 cm

in the field is a pre-requisite for the growth of blue-green algae. It can grow at a temperature

range of 25 to 450C. Bright sunshine increases the growth rate while rains and cloudiness

slows growth rate. It grows well in a pH range of 7- 8 and in soils with high organic matter.

Blue Green algae inoculum is applied after transplantation of rice crop in the main field. The

inoculum required is 10 Kg/ha. For higher nitrogen fixation, 3-4 ton/ha of farmyard manure

and 200kg/ha of Super phosphate are applied.

There are other benefits due to BGA growth in paddy fields. It produces organic

acids that solublizes phosphorus, precipitates Calcium that ameliorates the soil, growth

promoting substances and vitamins that favours rice growth and oxygenates the field

impounded water that prevents accumulation of reduced iron and sulphides that are injurious

to root growth. BGA also has a property of reducing hardness of water. This is particularly

helpful when rice raised with tubewell water. The biomass of BGA contains lot of water that

covers the soil, when there is no water in the field protecting the soil from rapid desiccation.

Among Azolla bio-fertilizers the important species are Azolla caroliniana, A. nilotica,

A. filiculoides, A. mexicana, A. microphylla and A. Pinnata, out of which Azolla pinnata is

most commonly used strain in India. It fixes nitrogen due to Anabaena species of BGA

present in the lobes of azolla leaves. A thick mat of azolla supplies 30-40 Kg nitrogen /ha.

Unlike blue green algae it thrives well at low temperature. Normal growth of Azolla occurs in

the temperature range of 20-30 0C. It grows better during monsoon season with frequent

rains and cloudiness. Suitable soil pH is 5.5 to 7.0. Nursery area should be under the shade

of trees. Azolla is applied at 0.1- 0.5 Kg/m2 in watered plots. For faster growth of nursery,

Superphosphate at the rate of 2.5 gm/m2 is applied. Carbofuran granules at 1.2 gm/m2 are

applied to control leaf eating caterpillars and other pests.

Mainly there are two methods of Azolla application:

1. as green manure before transplanting of rice.

2. by dual cropping with rice when Azolla grows side by side with rice

As green manure crop, azolla is allowed to grow on the flooded fields for 2-3 weeks

before transplanting. Later, water is drained and Azolla is incorporated by ploughing . As a

dual crop 1000 to 5000 Kg/ha of Azolla is applied to the soil one week after transplanting.

When a thick mat forms, it is incorporated by trampling. The left over Azolla develops again

which is trampled in as a second crop. For better growth of Azolla, 25-50 Kg /ha of

Superphosphate is applied and standing water of 5-10 cm is maintained continuously in the

rice field.

5. P-solubilising biofertilizer:

Phosphorus availability and phosphorus fertilizer use efficiency can be increased with

phosphate solubilizing bacteria and fungi. These include soil bacteria like Pseudomonas and

Bacillus and fungi like Penicillium and Aspergillus. Phosphorus is present in the soil in the

form of calcium phosphate, iron phosphate, aluminium phosphate, manganese phosphate

and zinc phosphate which are not available to plants. These have the ability to bring

insoluble phosphate present in soil into soluble forms by secreting organic acids like formic,

acetic, propionic and lactic acid etc. The acids lower down the pH of soil and bring the

dissolution of bound forms of phosphate. Among phophatic biofertilizers, Bacillus

megatherium termed as Phopho bacteria are prepared and used commercially.

6. Vesicular-Arbuscular Mycorrhizae (VAM):

Mycorrhiza is the symbiotic association of fungi with roots of vascular plants. The

main advantage of mycorhizae lies in extension of the penetration zone of root-fungus

system in the soil, and facilitating an increased efficiency of water and nutrient uptake by the

host plant. VAM has important effects on plant phosphorus uptake and availability of other

elements like Zn++, Cu++, K+, S-, Al+++, Mn++, Mg++, Fe++, etc.

Precautions:

Avoid direct contact of bio-fertilizers with sunlight and heat.

Store them in cool and dry place.

Never mix bio-fertilizer with chemical fertilizer.

Use bio-fertilizer before the expiry date mentioned on the packet.

Use only recommended bio-fertilizer for particular crop.

Bio-fertilizers are not the substitute for inorganic fertilizers but surely can help in

reducing the use of chemical fertilizers. These are eco-friendly, low cost inputs, which can be

used by small and marginal farmers to reduce their chemical fertilizer bills and to sustain the

soil health.