Question

Which organisms can act like biofertilisers? Explain with examples.

Answer 1

Biofertilisers are living organisms that increase the availability of nutrients, particularly nitrogen, to plants. The main groups are bacteria, cyanobacteria and fungi.

1. Bacteria: Rhizobium fixes nitrogen in the root nodules of legumes. Free-living Azotobacter fixes nitrogen in soil, while Azospirillum forms a loose association with roots of grasses and crops such as rice and maize.
2. Cyanobacteria: Anabaena azollae lives in association with the fern Azolla and fixes nitrogen. Free-living Nostoc and Aulosira also fix nitrogen; Azolla is often grown in rice fields and enriches the soil as it decays.
3. Fungi: Mycorrhizal fungi, including Glomus, associate with plant roots. Their hyphae help plants absorb water and minerals, including phosphorus, while the plant supplies the fungus with food.

These organisms can improve soil fertility and reduce reliance on chemical fertilisers.