What can be the impact of excessive/inappropriate use of nitrogenous fertilizers in agriculture? 1. Proliferation of nitrogen-fixing microorganisms in soil can occur. 2. Increase in the acidity of soil can take place. 3. Leaching of nitrate to the groundwater can occur. Select the correct answer using the code given below.

States that excessive use of chemical fertilizers reduces the population of soil-borne organisms and degrades soil structure.

A student could infer that adding large amounts of inorganic N might suppress or kill some soil microbes (including N-fixers) rather than promote their proliferation, and could check studies comparing microbial abundance under high vs low fertilizer regimes.

Says chemical fertilizers can kill bacteria and other microorganisms, leaving soil less fertile over time.

Combine this with the hypothesis that added N reduces the ecological niche for N-fixing microbes: if fertilizers kill microbes or remove the need for biological N fixation, their numbers may fall rather than rise.

Defines bio-fertilizers as preparations used to increase numbers of nitrogen-fixing microorganisms by deliberate application.

Shows that increases in N-fixer populations are normally achieved by adding live microbes, not by adding inorganic N; students could contrast effects of biofertilizer application versus inorganic N fertilizer on N-fixer abundance.

Explains that microorganisms (bacteria and blue‑green algae) are a primary natural route of nitrogen fixation, distinct from industrial fertilizers.

A student can use this to reason that industrial N addition is a separate source of plant-available N and might reduce selection pressure for biological N fixation, so one would predict less, not more, microbial fixation activity when inorganic N is abundant.

Notes neem-coated urea alters fertilizer behavior and even claims (as an option) increased nitrogen fixation via soil microorganisms when neem oil is released.

This example suggests that fertilizer formulation can affect microbial processes; a student could investigate whether some fertilizer treatments might indirectly favor or disfavor N-fixers (so effects are context-dependent).