Q. Which one of the following statements is correct?
A) Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants.
B) Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and for plant nutrition in soil
C) At present it is not possible to grow maize without chemical fertilizers
D) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.
Explanation
[Solution from source] Fertiliser run-off adds nitrates and phosphates to lakes and ponds, causing algal blooms and eutrophication. Azotobacter is free-living and does not form root nodules, and Anabaena and Nostoc fix nitrogen rather than mobilising phosphate (that is done by mycorrhizal fungi such as Glomus). Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.