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  Section: General Biotechnology / Plant Biotechnology
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The Blue-Green Algae (Cyanobacteria)

Role of the blue-green algae (e.g. Aulosira, Anabaena, Cylindrospermum, Nostoc, Plectonema, Tolypothrix) in the paddy fields was realized much earlier (Singh, 1961). In water-logging condition, the cyanobacteria multiply, fix atmospheric N2 and release it into the surroundings in the form of amino acids, proteins and other growth promoting substances (Sewart, 1970). Recent works done at Central Rice Research Institute, (Cuttack), Indian Council of Agricultural Research (New Delhi) and other centres, e.g. Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi are of much importance.



It were Japanese workers (Watanabe and coworkers) who developed techniques for mass cultivation of blue-green algae to be used as biofertilizer in paddy fields. Venkataraman (1961) coined the term 'algalization' to denote the process of application of blue-green algal culture in field as biofertilizer. He initiated algalization technology in India and demonstrated the way how this technology could be transferred to farmer level who hold small lands (Vekataraman, 1972).


At present, algalization is being followed in Tamil Nadu and Uttar Pradesh, and tried in Jammu and Kashmir, Andhra Pradesh, Karnataka, Maharashtra and Haryana. Algalization is also being practiced in China, Egypt, Philippines and erstwhile U.S.S.R.






Mass cultivation






Azotobactors, azospirillum and phosphate solubilizers


Green Manuring

Blue green algae





Mass cultivation of blue-green algae


Azolla and biofertilizer



Mass cultivation of Azolla

Mycorrhizae as biofertilizer


Mechanism of Symbiosis


Types of Mycorrhizas


Methods of Inoculum Production and Inoculation


Benefits from Mycorrhizas to Plants

Benefits from biofertilizers

Producers of biofertilizers

In 1990, Department of Biotechnology, Government of India, New Delhi establishment four major centres in different paddy growing areas of the country for acceleration and extension of works on algal biofertilizers. The programme was launched under 'Technology Development and Demonstration Projects on Cyanobacterial Biofertilizers' in U.P. (Lucknow), Tamil Nadu (Madurai), West Bengal (Calcutta) and New Delhi. The main objectives of the programme were (i) to develop low cost indigenous technology for mass production of cyano bacteria, (ii) to isolate regional specific fast growing and better N2 - fixing strains, (iii) to develop starter inoculum, (iv) to demonstrate the farmers in field, and (v) to study the benefits on both economy and ecology. As a result of these studies cyanobacterial biofertilizer was found very useful, especially for small and marginal farmers of the country with the view point of both economy and ecology (Venkataraman, 1993).


Table 12.5. Contribution of nitrogen by some of the nodulated legumes when used as green manure/cover crop.


N2 fixing system

Amount of N contributed (q/ha)


Green manure legumes :



Sesbania aculeata – Rhizobium



Leucaena leucocephala - Rhizobium



Beans (broad beans / lupines /soybean / lentil, etc.) - Rhizobium



Fodders (Trifolium / Medicagol Melilotus, etc. ) - Rhizobium



Cover crop legumes :



Lablab purpureus - Rhizobium



Glycine jawanica - Rhizobium



Non-legumes :



Casuarina equisitifolia - Frankia



Alnus - Frankia



Others :



Azolla - Anabaena



Grasses - Azospirillium


Source : Ghai and Thomas (1989).


D.B.T. Centre of U.P. (Lucknow) has reported the increase in yield of paddy (about 12.5 q/ha) to be due to cyanobacterial biofertilizer. Moreover, its use continued with chemical fertilizer gave the best results. Because the cyanobacterial biofertilizer not only increase the productivity and quality of paddy, but also minimize the harmful effects of the chemical fertilizers.


Mass cultivation of cyanobacterial biofertilizers

For outdoor mass cultivation of cyanobacterial biofertilizers, the regional specific strains should be used. However, many germplasm collection laboratories have been established by the D.B.T. in different parts of the country for the development of starter inoculum. Mixture of 5 or 6 regional acclimatized strains of cyanobacteria, e.g. species of Anabaena, Aulosira, Cylindrospermum, Gloeotrichia, Nostoc, Plectonema, Tolypothrix are generally used for starter inoculum. The following four methods are used for mass cultivation : (i) cemented tank method., (ii) shallow metal troughs method, (iii) polythene lined pit method, and (iv) field method. The polythene lined pit method is most suitable for small and marginal farmers to prepared algal biofertilizer. In this method, small pits are prepared in field and lined with thick polythene sheets. Mass cultivation of cyanobacteria is done by using any of the four methods under the following steps:


Prepare the cemented tanks, shallow trays of iron sheets or polythene lined pits in an open area. Width of tanks or pits should not be more than 1.5 m. This will facilitate the proper handling of culture.


Transfer 2 -3 Kg soil (collected from open place for lm 2 area of the tank) and add 100 g of superphosphate. Water the pit to about 10 cm height. Mix lime to adjust the pH 7. Add 2 ml of insecticide e.g. malathion to protect the culture from mosquitoes. Mix well and allow to settle down soil particles.


When water becomes clear, sprinkle 100 g of starter inoculum on the surface of water.


When temperature remains between 35-40° during summer, optimum growth of cyanobacteria is achieved. Always maintain the water level to about 10 cm during this period,


After drying, the algal mat will get separated from the soil and forms flakes. During summer about 1 kg pure algal mat per m2 area is produced. These are collected, powdered, kept in sealed polythene bags and supplied to the farmers.


The algal flakes can be used as starter inoculum if the same process is repeated.


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