Q.Why are cyanobacteria considered useful in paddy fields?
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Start your 14-day free trial to unlock the full solution →Cyanobacteria, particularly species like Anabaena and Nostoc, fix atmospheric nitrogen in paddy fields, enriching the soil naturally and reducing the need for chemical fertilizers.
Paddy cultivation presents a unique agricultural environment—waterlogged fields that create anaerobic conditions in the soil. This setting turns out to be ideal for certain microorganisms that can perform a remarkable service: capturing nitrogen from the air and converting it into forms that rice plants can absorb. Cyanobacteria, often called blue-green algae, are among the most valuable of these biological helpers.
The central reason cyanobacteria matter in paddy fields is their ability to fix atmospheric nitrogen. Nitrogen is essential for plant growth—it's a building block of proteins, chlorophyll, and nucleic acids—but most plants cannot use the abundant nitrogen gas (N2) in the atmosphere directly. Cyanobacteria possess specialized cells called heterocysts that house the enzyme nitrogenase, which breaks the strong triple bond in nitrogen gas and converts it into ammonia. This ammonia then becomes available to the rice plants, either directly or after further conversion by soil bacteria into nitrates.
In traditional and organic farming systems across India, farmers have long recognized the value of these organisms, even if they didn't know the biochemistry. When paddy fields flood, cyanobacteria multiply rapidly in the standing water and on the soil surface, forming visible blue-green mats. As they grow, die, and decompose, they release fixed nitrogen into the soil, effectively acting as a living fertilizer factory.
Common nitrogen-fixing cyanobacteria in Indian paddy fields include Anabaena, Nostoc, and Oscillatoria. Anabaena species are particularly efficient because of their well-developed heterocysts.
The practical benefits extend beyond just nitrogen enrichment:
- Cost reduction: Farmers can reduce their dependence on expensive synthetic nitrogen fertilizers, which also require significant energy to manufacture.
- Soil health: Unlike chemical fertilizers that can degrade soil structure over time, cyanobacteria add organic matter as they decompose, improving soil texture and water-holding capacity. …
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