Question

Which one of the following is useful in rice fields?

• A. Rhizobium
• B. Clostridium
• C. Anabaena
• D. Ferrobacterium

Hint:

Important nitrogen-fixing organisms: \[ \textit{Rhizobium} \rightarrow \text{Leguminous plants} \] \[ \textit{Anabaena} \rightarrow \text{Rice (paddy) fields} \] \[ \textit{Anabaena} + \textit{Azolla} \rightarrow \text{Important biofertilizer for paddy cultivation} \] A common NCERT fact frequently asked in CUET and NEET examinations.

Answer 1

The Correct Option is C

Step 1: Recall the biofertilizers used in rice cultivation. Rice fields are waterlogged environments where certain nitrogen-fixing cyanobacteria grow abundantly. These organisms enrich the soil by converting atmospheric nitrogen into usable forms.

Step 2: Examine the given options.
• Rhizobium forms symbiotic associations with leguminous plants, not rice. \(\times\)
• Clostridium is a free-living anaerobic bacterium but is not commonly used as a biofertilizer in rice fields. \(\times\)
• Anabaena is a nitrogen-fixing cyanobacterium widely used in paddy fields. \(\checkmark\)
• Ferrobacterium is not used as a biofertilizer in rice cultivation. \(\times\)

Step 3: Identify the correct answer. Anabaena fixes atmospheric nitrogen and improves soil fertility in rice fields. Therefore, \[ \boxed{\text{Anabaena}} \] is the correct answer. Hence, \[ \boxed{\text{(C)}} \]