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You are Here :: Organic Farming :Biofertilizers


1. Biofertilizers
Biofertilizers are defined as preparations containing living cells or latent cells of efficient strains of microorganisms that help crop plants’ uptake of nutrients by their interactions in the rhizosphere when applied through seed or soil. They accelerate certain microbial processes in the soil which augment the extent of availability of nutrients in a form easily assimilated by plants.

Very often microorganisms are not as efficient in natural surroundings as one would expect them to be and therefore artificially multiplied cultures of efficient selected microorganisms play a vital role in accelerating the microbial processes in soil.

Use of biofertilizers is one of the important components of integrated nutrient management, as they are cost effective and renewable source of plant nutrients to supplement the chemical fertilizers for sustainable agriculture. Several microorganisms and their association with crop plants are being exploited in the production of biofertilizers. They can be grouped in different ways based on their nature and function.

S. No. Groups Examples
N2 fixing Biofertilizers
1 Free-living Azotobacter, Beijerinkia, Clostridium, Klebsiella, Anabaena, Nostoc,
2 Symbiotic Rhizobium, Frankia, Anabaena azollae
3 Associative Symbiotic Azospirillum
P Solubilizing Biofertilizers
1 Bacteria Bacillus megaterium var. phosphaticum, Bacillus subtilis Bacillus circulans, Pseudomonas striata
2 Fungi Penicillium sp, Aspergillus awamori
P Mobilizing Biofertilizers
1 Arbuscular mycorrhiza Glomus sp.,Gigaspora sp.,Acaulospora sp., Scutellospora sp. & Sclerocystis sp.
2 Ectomycorrhiza Laccaria sp., Pisolithus sp., Boletus sp., Amanita sp.
3 Ericoid mycorrhizae Pezizella ericae
4 Orchid mycorrhiza Rhizoctonia solani
Biofertilizers for Micro nutrients
1 Silicate and Zinc solubilizers Bacillus sp.
Plant Growth Promoting Rhizobacteria
1 Pseudomonas Pseudomonas fluorescens

2. Different types of biofertilizers

1. Rhizobium is a soil habitat bacterium, which can able to colonize the legume roots and fixes the atmospheric nitrogen symbiotically. The morphology and physiology of Rhizobium will vary from free-living condition to the bacteroid of nodules. They are the most efficient biofertilizer as per the quantity of nitrogen fixed concerned. They have seven genera and highly specific to form nodule in legumes, referred as cross inoculation group. Rhizobium inoculant was first made in USA and commercialized by private enterprise in 1930s and the strange situation at that time has been chronicled by Fred (1932).

Initially, due to absence of efficient bradyrhizobial strains in soil, soybean inoculation at that time resulted in bumper crops but incessant inoculation during the last four decades by US farmers has resulted in the build up of a plethora of inefficient strains in soil whose replacement by efficient strains of bradyrhizobia has become an insurmountable problem.

2. Azotobacter - Of the several species of Azotobacter, A. chroococcum happens to be the dominant inhabitant in arable soils capable of fixing N2 (2-15 mg N2 fixed /g of carbon source) in culture media.

The bacterium produces abundant slime which helps in soil aggregation. The numbers of A. chroococcum in Indian soils rarely exceeds 105/g soil due to lack of organic matter and the presence of antagonistic microorganisms in soil.

3. Azospirillum lipoferum and A. brasilense (Spirillum lipoferum in earlier literature) are primary inhabitants of soil, the rhizosphere and intercellular spaces of root cortex of graminaceous plants. They perform the associative symbiotic relation with the graminaceous plants.

The bacteria of Genus Azospirillum are N2 fixing organisms isolated from the root and above ground parts of a variety of crop plants. They are Gram negative, Vibrio or Spirillum having abundant accumulation of polybetahydroxybutyrate (70 %) in cytoplasm.

Five species of Azospirillum have been described to date A. brasilense, A.lipoferum, A.amazonense, A.halopraeferens and A.irakense. The organism proliferates under both anaerobic and aerobic conditions but it is preferentially micro-aerophilic in the presence or absence of combined nitrogen in the medium.

Apart from nitrogen fixation, growth promoting substance production (IAA), disease resistance and drought tolerance are some of the additional benefits due to Azospirillum inoculation.

4. Cyanobacteria - Both free-living as well as symbiotic cyanobacteria (blue green algae) have been harnessed in rice cultivation in India. A composite culture of BGA having heterocystous Nostoc, Anabaena, Aulosira etc. is given as primary inoculum in trays, polythene lined pots and later mass multiplied in the field for application as soil based flakes to the rice growing field at the rate of 10 kg/ha. The final product is not free from extraneous contaminants and not very often monitored for checking the presence of desiredalgal flora.

Once so much publicized as a biofertilizer for the rice crop, it has not presently attracted the attention of rice growers all over India except pockets in the Southern States, notably Tamil Nadu. The benefits due to algalization could be to the extent of 20-30 kg N/ha under ideal conditions but the labour oriented methodology for the preparation of BGA biofertilizer is in itself a limitation. Quality control measures are not usually followed except perhaps for random checking for the presence of desired species qualitatively.

5. Azolla - Azolla is a free-floating water fern that floats in water and fixes atmospheric nitrogen in association with nitrogen fixing blue green alga Anabaena azollae. Azolla fronds consist of sporophyte with a floating rhizome and small overlapping bi-lobed leaves and roots. Rice growing areas in South East Asia and other third World countries have recently been evincing increased interest in the use of the symbiotic N2 fixing water fern Azolla either as an alternate nitrogen sources or as a supplement to commercial nitrogen fertilizers. Azolla is used as biofertilizer for wetland rice and it is known to contribute 40-60 kg N/ha per rice crop.

Liquid Biofertilizers
Biofertilizers are such as Rhizobium, Azospirillum and Phosphobacteria provide nitrogen and phosphorous nutrients to crop plants through nitrogen fixation and phosphorous solubilization processes. These Biofertilizers could be effectively utilized for rice, pulses, millets, cotton, sugarcane, vegetable and other horticulture crops.

Biofertilizers is one of the prime input in organic farming not only enhances the crop growth and yield but also improves the soil health and sustain soil fertility.

At present, Biofertilizers are supplied to the farmers as carrier based inoculants. As an alternative, liquid formulation technology has been developed in the Department of Agricultural Microbiology, TNAU, Coimbatore which has more advantages than the carrier inoculants.

The advantages of Liquid Bio-fertilizer over conventional carrier based Bio-fertilizers are listed below:

• Longer shelf life -12-24 months.

• No contamination.

• No loss of properties due to storage upto 45º c.

• Greater potentials to fight with native population.

• High populations can be maintained more than 109 cells/ml upto 12 months to 24 months.

• Easy identification by typical fermented smell.

• Cost saving on carrier material, pulverization, neutralization, sterilization, packing and transport.

• Quality control protocols are easy and quick.

• Better survival on seeds and soil.

• No need of running Bio-fertilizer production units through out the year.

• Very much easy to use by the farmer.

• Dosages is 10 time less than carrier based powder Bio-fertilizers.

• High commercial revenues.

• High export potential.

• Very high enzymatic activity since contamination is nil.

3. Application of Biofertilizers
1. Seed treatment or seed inoculation

2. Seedling root dip

3. Main field application

Seed treatment
One packet of the inoculant is mixed with 200 ml of rice kanji to make a slurry. The seeds required for an acre are mixed in the slurry so as to have a uniform coating of the inoculant over the seeds and then shade dried for 30 minutes. The shade dried seeds should be sown within 24 hours. One packet of the inoculant (200 g) is sufficient to treat 10 kg of seeds.

Seedling root dip
This method is used for transplanted crops. Two packets of the inoculant is mixed in 40 litres of water. The root portion of the seedlings required for an acre is dipped in the mixture for 5 to 10 minutes and then transplanted.

Main field application
Four packets of the inoculant is mixed with 20 kgs of dried and powdered farm yard manure and then broadcasted in one acre of main field just before transplanting.

For all legumes Rhizobium is applied as seed inoculant.

In the transplanted crops, Azospirillum is inoculated through seed, seedling root dip and soil application methods. For direct sown crops, Azospirillum is applied through seed treatment and soil application.

Inoculated through seed, seedling root dip and soil application methods as in the case of Azospirillum. Combined application of bacterial biofertilizers.

Phosphobacteria can be mixed with Azospirillum and Rhizobium. The inoculants should be mixed in equal quantities and applied as mentioned above.

Points to remember
• Bacterial inoculants should not be mixed with insecticide, fungicide, herbicide and fertilizers.

• Seed treatment with bacterial inoculant is to be done at last when seeds are treated with fungicides.

Biofertilizers recommendation (one packet - 200 g)
Crop Seed Nursery Seedling dip Main field Total requirement of packets per ha
Rice 5 10 5 10 30
Sorghum 3 - - 10 13
Pearl millet 3 - - 10 13
Ragi 3 - 5 10 18
Maize 3 - - 10 13
Cotton 3 - - 10 13
Sunflower 3 - - 10 13
Castor 3 - - 10 13
Sugarcane 10 - - 36 (3 split) 46
Turmeric - - - 24 (2 split) 24
Tobacco 1 3 - 10 g/pit 14
Papaya 3 - - 10 13
Cotton 2 - - 10 -
Mandarin Orange 2 - - 10 g/pit -
Tomato 1 - - 10 14
Banana - - 5 10 g/pit 5

Rhizobium (only seed application is recommended)
Crop Total requirement of packets per ha
Soybean 5
Groundnut 5
Bengalgram 5
Blackgram 3
Greengram 3
Redgram 3
Cowpea 3

The recommended dosage of Azospirillum is adopted for phosphobacteria inoculation; for combined inoculation, both biofertilizers as per recommendations are to be mixed uniformly before using.

4. Azolla – The best feed for cattle and poultry
Azolla is a free floating water fern that floats in water and fixes nitrogen in association with the nitrogen fixing blue green algae, Anabaena azollae. Azolla is considered to be a potential biofertilizer in terms of nitrogen contribution to rice. Long before its cultivation as a green manure, Azolla has been used as a fodder for domesticated animals such as pigs and ducks. In recent days, Azolla is very much used as a sustainable feed substitute for livestock especially dairy cattle, poultry, piggery and fish.

Azolla contains 25 – 35 per cent protein on dry weight basis and rich in essential amino acids, minerals, vitamins and carotenoids including the antioxidant b carotene. Cholorophyll a, chlorophyll b and carotenoids are also present in Azolla, while the cyanobiont Anabaena azollae contains cholorophyll a, phycobiliproteins and carotenoids. The rare combination of high nutritive value and rapid biomass production make Azolla a potential and effective feed substitute for live stocks.

Inputs required
Azolla fronds, Polythene sheet, Super phosphate and Cow dung.

The area selected for Azolla nursery should be partially shaded. The convenient size for Azolla is 10 feet length, 2 feet breadth and 1 feet depth. The nursery plot is spread with a polythene sheet at the bottom to prevent water loss. Soil is applied to a depth of 2 cm and a gram of super phosphate is applied along with 2 kg of vermicompost or cow dung in the nursery for quick growth. Azolla mother inoculum is introduced @ 5 kg/plot.

The contents in the plot are stirred daily so that the nutrients in the soil dissolve in water for easy uptake by Azolla. Azolla is harvested fifteen days after inoculation at the rate of 50-80 kg / plot. One third of Azolla should be left in the plot for further multiplication. Five kg cow dung slurry should be sprinkled in the Azolla nursery at ten days intervals. Neem oil can be sprayed over the Azolla at 0.5 5 level to avoid pest incidence.

Animal Dosage / day
Adult cow , Buffalo, Bullock 1.5-2 kg
Layer, Broiler birds 20 – 30 grams
Goat 300 – 500 grams
Pig 1.5 – 2.0 kg
Rabbit 100 gram

Value of the technology
The egg yield is increased in layer birds due to Azolla feeding. The Azolla fed birds register an overall egg productivity of 89.0 per cent as against 83.7 per cent recorded by the birds fed with only concentrated feed. The average daily intake of concentrated feed is considerably low (106.0 g) for birds due to Azolla substitution as against 122.0 g in the control birds. More impotantly Azolla feeding shows considerable amount of savings in the consumption of concentrated feed (13.0 %) leading to reduced operational cost. By considering the average cost of the concentrated feed as Rs. 17/ Kg, a 13.0 % saving in the consumption ultimately leads to a feed cost savings of 10.0 paise /day/ bird and hence a layer unit maintaining 10,000 birds could cut down its expense towards feed to a tune of rs.1000/day.

The Azolla feeding to layer birds increase egg weight, albumin, globulin and carotene contents. The total protein content of the eggs laid by the Azolla fed birds is high and the total carotene content of Azolla eggs(440 g 100 g-1 of edible portion)is also higher than the control. The rapid biomass production due to the high relative growth rate, increased protein and carotene contents and good digestability of the Azolla hybrid Rong ping favour its use as an effective feed supplement to poultry birds.

Effect of Azolla hybrid Rong Ping on the nutritional value of egg
Parameters Azolla egg Control percentage increase over control
Egg weight (g) 61.20 57.40 6.62
Albumin (g /100 g of edible portion) 3.9 3.4 14.70
Globulin (g /100 g of edible portion) 10.1 9.5 6.31
Total protein (g/ 100 g of edible portion) 14.0 12.9 8.52
Carotenes (µg / 100 g of edible portion) 440 405 8.64

In Indian conditions, agriculture is very much coupled with poultry farming. Azolla is an important low cost input, which plays a vital role in improving soil quantity in sustainable rice farming. The twin potentials as biofertilizer and animal feed make the water fern Azolla as an effective input to both the vital components of integrated farming, agricultural and animalo husbandry.

Azolla is a water fern and requires a growth temperature of 35-38º C. The multiplication of Azolla is affected under elevated temperature. Hence adopting this technology in dry zones where the temperature exceeds 40ºc is difficult.

5. Constraints in Biofertilizer Technology
Though the biofertilizer technology is a low cost, ecofriendly technology, several constraints limit the application or implementation of the technology the constraints may be environmental, technological, infrastructural, financial, human resources, unawareness, quality, marketing, etc. The different constraints in one way or other affecting the technique at production, or marketing or usage.

Technological constraints
• Use of improper, less efficient strains for production.

• Lack of qualified technical personnel in production units.

• Unavailability of good quality carrier material or use of different carrier materials by different producers without knowing the quality of the materials.

• Production of poor quality inoculants without understanding the basic microbiological techniques

• Short shelf life of inoculants.

Infrastructural constraints
• Non-availability of suitable facilities for production

• Lack of essential equipments, power supply, etc.

• Space availability for laboratory, production, storage, etc.

• Lack of facility for cold storage of inoculant packets

Financial constraints
• Non-availability of sufficient funds and problems in getting bank loans

• Less return by sale of products in smaller production units.

Environmental constraints
• Seasonal demand for biofertilizers

• Simultaneous cropping operations and short span of sowing/planting in a particular locality

• Soil characteristics like salinity, acidity, drought, water logging, etc.

Human resources and quality constraints
• Lack of technically qualified staff in the production units.

• Lack of suitable training on the production techniques.

• Ignorance on the quality of the product by the manufacturer

• Non-availability of quality specifications and quick quality control methods

• No regulation or act on the quality of the products

• Awareness on the technology

• Unawareness on the benefits of the technology

• Problem in the adoption of the technology by the farmers due to different methods of inoculation.

• No visual difference in the crop growth immediately as that of inorganic fertilizers.

Awareness on the technology
• Unawareness on the benefits of the technology.

• Problem in the adoption of the technology by the farmers due to different methods of inoculation.

• No visual difference in the crop growth immediately as that of inorganic fertilizers.

• Unawareness on the damages caused on the ecosystem by continuous application of inorganic fertilizer.

Marketing constraints
• Non availability of right inoculant at the right place in right time.

• Lack of retain outlets or the market network for the producers.

6. Cost and availability of Biofertilizers
Name of Biofertilizers Cost of Biofertilizers Availabilty
Azospirillum Rs.40/Kg Professor and Head
Department of Agricultural Microbiology Tamil Nadu Agricultural University Coimbatore - 641 003
Phone: 91-422-6611294
Fax: 91-422-2431672
Phosphobacteria Rs.40/Kg
Rhizobium Rs.40/Kg
Azotobacter Rs.40/Kg
VAM Rs.30/Kg