Algae as Bio-Fertilisers

Algae as Bio-Fertilisers

Algae as Bio-fertilisers
Another group of free-living nitrogen fixers are the cyanobacteria commonly called the blue-green algae (BGA). More than a hundred species of BGA can fix nitrogen.

Nitrogen fixation takes place in specialised cells called the heterocysts (large, thick walled and metabolically inactive cells) which depend on vegetative cells for energy to fix nitrogen while the fixed nitrogen is utilised by the vegetative cells for growth and development. BGA are very common in the rice fields (the micro-aerophilic condition and alkalinity are conducive to the algal population).

If no chemical fertilisers are added, inoculation of the algae can result in 10-14 % increase in crop yields. Unlike Azotobacter, the BGA are not inhibited by the presence of chemical fertilisers.

On the other land, presence of inorganic minerals (superphosphate) accelerates their growth. They are easy to produce and usually they are mass produced in cement tanks filled with fresh-water. Since they do not require any processing, they are quite cheap. Cost of 10 kg may be only Rs.30-40. Algal effect can be seen in subsequent years without the use of fresh inoculants. Examples of some algal bio-fertilisers are Anabaena, Nostoc and Oscillatoria. Algae have proved beneficial in the case of certain crops like vegetables, cotton and sugarcane when added along with chemical fertilisers.

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