Read the following passage carefully and answer the given questions.
Biofertilisers
Biofertilisers are organisms that enrich the nutrient quality of the soil and their main sources 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 can fix atmospheric nitrogen into organic forms. Other bacteria can also fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter). Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter in to the soil and increase its fertility. Currently, in our country, a number of biofertilisers are available commercially in the market and farmers use these regularly in their fields to replenish soil nutrients and to reduce dependence on chemical fertilisers.
In organic farming, there is -
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Use of biofertilisers
Option (1) Overuse of chemical fertilisers — Incorrect. This is the very problem that organic farming tries to solve. Heavy use of chemical fertilisers pollutes the soil and water.
Option (2) Use of biofertilisers — Correct. Organic farming feeds the soil with living organisms in place of chemicals. Rhizobium, Azotobacter, Azospirillum, mycorrhizal fungi and cyanobacteria all add nutrients to the soil.
Option (3) No use of fertilisers — Incorrect. Organic farming does not leave the soil unfed. It replaces chemical fertilisers with biofertilisers, so fertilisers are still used.
Option (4) Only use of symbiotic bacteria — Incorrect. The word “only” makes this wrong. Biofertilisers also include free-living bacteria, fungi and cyanobacteria, not just symbiotic bacteria like Rhizobium.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Microbes as Biofertilisers – “… With our present day life styles environmental pollution is a major cause of concern. The use of the chemical fertilisers to meet the ever-increasing demand of agricultural produce has contributed significantly to this pollution. Of course, we have now realised that there are problems associated with the overuse of chemical fertilisers and there is a large pressure to switch to organic farming – the use of biofertilisers.”