Biofertilizers enrich the nutrient quality of the soil. Which of the…

The correct answer is Option (3) → Baculoviruses

Option (1) Bacteria — A source of biofertiliser. Rhizobium, Azotobacter, Azospirillum.

Option (2) Mycorrhiza — A source of biofertiliser. Fungi such as Glomus help plants absorb phosphorus.

Option (3) Baculoviruses — Not a source of biofertiliser. They kill insects and are used as biocontrol agents.

Option (4) Cyanobacteria — A source of biofertiliser. They fix nitrogen, especially in paddy fields.

NCERT Extract:
Microbes as Biofertilisers – “… Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria. You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient.”
Microbes as Biofertilisers – “… Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant.”