Change set
Pick exam & year, then Go.
Question map
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.
Explanation
The correct answer is option C (statements 2 and 3 only).
**Statement 1 is incorrect**: Excessive nitrogenous fertilizers do not cause proliferation of nitrogen-fixing microorganisms. In fact, excessive use of chemical fertilizers reduces the population of soil-borne organisms[1]. When external nitrogen is abundantly available, nitrogen-fixing organisms have no competitive advantage, so they don't proliferate.
**Statement 2 is correct**: Excessive use of chemical fertilizers made the soil acidic[2], which is why it can be treated with lime, which is a base[2]. This acidification negatively affects plant growth and soil health.
**Statement 3 is correct**: Excess fertilizers may reach the ground water by leaching[3]. This contamination is serious, as high nitrate contamination in groundwater is believed to cause blue baby syndrome, resulting from leaching of nitrate generated from fertilizer used in agricultural lands[4].
Therefore, only statements 2 and 3 are correct impacts of excessive nitrogenous fertilizer use.
Sources- [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > iii. Fertilizers and manurest > p. 79
- [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 2: Exploring Substances: Acidic, Basic, and Neutral > 2.3 Neutralisation in Daily Life > p. 18
- [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 3) Agricultural sources: > p. 74
- [4] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > d) Blue baby syndrome > p. 416
PROVENANCE & STUDY PATTERN
Guest previewThis is a classic 'Green Revolution fallout' question. Statements 2 and 3 are direct lifts from basic NCERT/Shankar texts on pollution. Statement 1 requires 'Ecological Logic' rather than a specific book line: Nature is efficient; if you provide free nitrogen, microbes stop fixing it energetically. Don't just memorize 'pollution is bad'; understand the biological feedback loops.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
Web source
Presence: 4/5
"the reduction of nitrogen inputs in freshwater lakes is ineffective when it leads to an increase in nitrogen-fixing organisms (such as cyanobacteria)."
Why this source?
- Explicitly states that reductions in nitrogen inputs can lead to increases in nitrogenâfixing organisms (implying the oppositeâhigh N inputs do not promote them).
- Gives an example (cyanobacteria) showing nitrogenâfixers proliferate under lower N availability, which counters the claim that excessive fertiliser increases them.
Web source
Presence: 3/5
"Corals are adapted to thrive in the sun-lit, nutrient-poor waters of tropical oceans13 thanks to their intimate relationship with microscopic algae and nitrogen-fixing microbes (called diazotrophs)."
Why this source?
- Describes nitrogenâfixing microbes (diazotrophs) as part of systems adapted to nutrientâpoor (lowâN) environments, implying they are associated with low nitrogen availability rather than high.
- Supports the inference that adding excess inorganic N would not promote, and may suppress, diazotroph proliferation.
- Explicitly states that reductions in nitrogen inputs can lead to increases in nitrogenâfixing organisms (implying the oppositeâhigh N inputs do not promote them).
- Gives an example (cyanobacteria) showing nitrogenâfixers proliferate under lower N availability, which counters the claim that excessive fertiliser increases them.
- Describes nitrogenâfixing microbes (diazotrophs) as part of systems adapted to nutrientâpoor (lowâN) environments, implying they are associated with low nitrogen availability rather than high.
- Supports the inference that adding excess inorganic N would not promote, and may suppress, diazotroph proliferation.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > iii. Fertilizers and manurest > p. 79
Strength: 5/5
âr Chemical fertilizers are added to the soil for increasing crop yield. Excessive use of chemical fertilizers reduces the population of soil-borne organism and the crumb structure of the soil, productivity of the soil and increases salt content of the soil.â
Why relevant
States that excessive use of chemical fertilizers reduces the population of soil-borne organisms and degrades soil structure.
How to extend
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.
Economics, Class IX . NCERT(Revised ed 2025) > Chapter 1: The Story of Village Palampur > Suggested Activity > p. 6
Strength: 5/5
âsoil for long. They may escape from the soil and pollute groundwater, rivers and lakes. Chemical fertilizers can also kill bacteria and other microorganisms in the soil. This means some time after their use, the soil will be less fertile than ever before....(Source: Down to Earth, New Delhi) .....The consumption of chemical fertilizers in Punjab is highest in the country. The continuous use of chemical fertilizers has led to degradation of soil health. Punjab farmers are now forced to use more and more chemical fertilizers and other inputs to achieve the same production level. This means cost of cultivation is rising very fast.....(Source: The Tribune, Chandigarh)â
Why relevant
Says chemical fertilizers can kill bacteria and other microorganisms, leaving soil less fertile over time.
How to extend
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.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Bio-fertilizers > p. 364
Strength: 4/5
âo Bio-fertilizers are the preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulolytic microorganisms used for application to seed or composting areas with the objective of increasing the numbers of such micro-organisms and accelerating those microbial processes which augment the availability of nutrients that can be easily assimilated by plantsâ
Why relevant
Defines bio-fertilizers as preparations used to increase numbers of nitrogen-fixing microorganisms by deliberate application.
How to extend
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.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > c) The Nitrogen Cycle > p. 19
Strength: 4/5
â(c) The Nitrogen Cycle 0000 00 Nitrogen is an essential constituent of protein and is a basic building block of all living tissue. It constitutes nearly 16% by weight of all the proteins. There is an inexhaustible supply of nitrogen in the atmosphere but the elemental form cannot be used directly by most of the living organisms. Nitrogen needs to be 'fixed', that is, converted to ammonia, nitrites or nitrates, before it can be taken up by plants. Nitrogen fixation on Earth is accomplished in three different ways: ⢠(i) By microorganisms (bacteria and blue-green algae) ⢠(ii) By man using industrial processes (fertilizer factories) and ⢠(iii) To a limited extent by atmospheric phenomenon such as thunder and lighting Certain microorganisms are capable of fixing atmospheric nitrogen into ammonium ions.â
Why relevant
Explains that microorganisms (bacteria and blueâgreen algae) are a primary natural route of nitrogen fixation, distinct from industrial fertilizers.
How to extend
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.
Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 9: Agriculture > 2016 > p. 361
Strength: 3/5
â⢠24. Why does the Government of India promote the use of 'neem-coated urea' in agriculture? ⢠(a) Release of Neem oil in the soil increases nitrogen fixation by the soil microorganisms. ⢠(b) Neem coating slows down the rate of dissolution of urea in the soil. ⢠(c) Nitrous oxide, which is a greenhouse gas, is not at all released into atmosphere by crop fields. ⢠(d) It is a combination of a weedicide and a fertilizer for particular crops. 25â
Why relevant
Notes neem-coated urea alters fertilizer behavior and even claims (as an option) increased nitrogen fixation via soil microorganisms when neem oil is released.
How to extend
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).
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 blueâgreen 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).
This tab shows concrete study steps: what to underline in books, how to map current affairs, and how to prepare for similar questions.
Login with Google to unlock study guidance.
Discover the small, exam-centric ideas hidden in this question and where they appear in your books and notes.
Login with Google to unlock micro-concepts.
Access hidden traps, elimination shortcuts, and Mains connections that give you an edge on every question.
Login with Google to unlock The Vault.