Question

Which biofertilizer system is particularly significant for rice cultivation in paddy fields?

Options

• Legume–Rhizobium symbiosis exclusively

• Azolla–Anabaena symbiosis and cyanobacteria

• Frankia associations with legumes

• Phosphate-solubilizing bacteria alone

Answer 1

The Azolla–Anabaena symbiosis and cyanobacteria are widely used in paddy fields because they significantly increase rice yield. Anabaena, a nitrogen-fixing cyanobacterium, lives in association with the water fern Azolla, and this combination enriches paddy field soil with biologically fixed nitrogen, making it ideal for rice cultivation.