Which of the following is/are used as bio-fertilisers? Select the correct answer from the codes given below:

1. Azolla
2. Blue Green Algae
3. Alfalfa
4. Nitrolim

Codes:

Detailed Solution:

The correct answer is “1 and 2”.

1) Azolla: Azolla is a floating aquatic fern that forms a symbiotic relationship with nitrogen-fixing cyanobacteria. It is used as a bio-fertilizer in rice fields.

2) Blue Green Algae: Blue-green algae, also known as cyanobacteria, are nitrogen-fixing bacteria that can be used as bio-fertilizers.

3) Alfalfa: Alfalfa is a plant used as fodder and cover crop. While it improves soil fertility through nitrogen fixation, it is not typically considered a bio-fertilizer itself.

4) Nitrolin is not a recognized bio-fertilizer.