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Q82 (IAS/2018) Environment & Ecology › Ecology & Ecosystem Basics › Soil characteristics Official Key

With reference to agricultural soils, consider the following statements : 1. A high content of organic matter in soil drastically reduces its water holding capacity. 2. Soil does not play any role in the sulphur cycle. 3. Irrigation over a period of time can contribute to the salinization of some agricultural lands. Which of the statements given above is/are correct ?

Result
Your answer: —  ·  Correct: B
Explanation

The correct answer is option B (Statement 3 only).

**Statement 1 is incorrect**: The addition of organic matter to the soil usually increases the water holding capacity of the soil.[1] In fact, for each 1-percent increase in soil organic matter, the available water holding capacity in the soil increased by 3.7 percent.[2] This is because organic matter binds soil particles into aggregates and improves the water holding capacity of soil.[3]

**Statement 2 is incorrect**: The sulphur reservoir is in the soil and sediments where it is locked in organic and inorganic deposits, and it is released by weathering of rocks, erosional runoff and decomposition of organic matter.[4] This clearly shows soil plays a crucial role in the sulphur cycle.

**Statement 3 is correct**: Intensive irrigation and excessive use of water has led to the emergence of twin environmental problems of waterlogging and soil salinity.[5] Additionally, a large tract of agricultural land has lost its fertility due to alkalisation and salinisation of soils and waterlogging.[6]

Sources
  1. [1] https://openknowledge.fao.org/3/a-a0100e.pdf
  2. [2] https://openknowledge.fao.org/3/a-a0100e.pdf
  3. [3] https://openknowledge.fao.org/3/a-a0100e.pdf
  4. [4] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > b) Sulphur Cycle > p. 21
  5. [5] INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 6: Planning and Sustainable Development in Indian Context > Indira Gandhi Canal (Nahar) Command Area > p. 72
  6. [6] INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 3: Land Resources and Agriculture > Degradation of Cultivable Land > p. 39
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. With reference to agricultural soils, consider the following statements : 1. A high content of organic matter in soil drastically reduce…
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 6.7/10 · 3.3/10

This question rewards 'First Principles' thinking over rote memorization. It combines basic physical geography (salinization) with core ecology (nutrient cycles). If you simply understand why farmers add manure (to retain moisture), Statement 1 is eliminated instantly, cracking the whole question.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
In agricultural soils, does a high content of organic matter drastically reduce the soil's water-holding capacity?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"for each 1-percent increase in soil organic matter, the available water holding capacity in the soil increased by 3.7 percent."
Why this source?
  • Direct quantitative evidence that increasing organic matter raises available water-holding capacity (contradicts 'drastically reduce').
  • Shows a clear measured relationship: each 1% increase in organic matter increases available water holding capacity by 3.7%.
Web source
Presence: 5/5
"The addition of organic matter to the soil usually increases the water holding capacity of the soil. This is because the addition of organic matter increases the number of micropores and macropores in the"
Why this source?
  • States explicitly that adding organic matter usually increases water-holding capacity (opposite of a drastic reduction).
  • Provides a mechanism: organic matter increases micropores and macropores, which hold more water.
Web source
Presence: 5/5
"organic matter ... binds soil particles into aggregates and improves the water holding capacity of soil."
Why this source?
  • Notes organic matter binds particles into aggregates and improves water-holding capacity, supporting that higher organic matter enhances — not reduces — water retention.
  • Specifies this in the context of agricultural soils ('Most soils contain 2–10 percent organic matter').

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > EilUI RONMEf.IT'' /7=X x4 > p. 362
Strength: 5/5
“:EilUI RONMEf.IT'' /7=X x4 I l • Organic Fertilizers: Improves soil texture, adds organic nitrogen, and stimulates beneficial bacterial and fungi. Inorganic Fertilizer: Lowers oxygen content of the soil thereby keeping fertilizer from being taken up efficiently. • Organic Fertilizers: Improves water-holding capacity of soil.”
Why relevant

Explicitly states that organic fertilizers improve the water-holding capacity of soil (a general rule linking organic matter additions to increased water retention).

How to extend

A student could combine this with basic knowledge that organic fertilizers increase soil organic matter to infer that higher organic matter tends to increase, not drastically reduce, water-holding capacity.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Role of manures > p. 363
Strength: 5/5
“• r. Organic manures bind the sandy soil and improve its water holding capaciry. • z. They open the clayey soil and help in aerati6h better root growth. • 3. They add plant nutrients in small percentage and also add micro nutrients which are essential for plant growth. The microbial activity is increased, which helps in releasing plant nutrients available for e.g. A11 Rights Reserved. No part of this material nay be reproduced in anv ibrrl or b,v atry means, lvithout Permission in 1\'riting. rc$”
Why relevant

Says organic manures bind sandy soil and improve its water holding capacity and that they open clayey soil improving aeration—showing organic matter modifies texture and retention properties.

How to extend

Using standard facts about sandy soils having low retention and clay high retention, a student could infer organic matter raises retention in coarse soils and can change porosity in fine soils rather than drastically reducing it.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 5: Geomorphic Processes > Biological Activity > p. 45
Strength: 4/5
“The vegetative cover and organisms that occupy the parent materials from the beginning and also at later stages help in adding organic matter, moisture retention, nitrogen etc. Dead plants provide humus, the finely divided organic matter of the soil. Some organic acids which form during humification aid in decomposing the minerals of the soil parent materials. Intensity of bacterial activity shows up differences between soils of cold and warm climates. Humus accumulates in cold climates as bacterial growth is slow. With undecomposed organic matter because of low bacterial activity, layers of peat develop in subarctic and tundra climates. In humid tropical and equatorial climates, bacterial growth and action is intense and dead vegetation is rapidly oxidised leaving very low humus content in the soil.”
Why relevant

Notes humus (organic matter) contributes to moisture retention and other soil properties—linking organic matter directly to increased moisture-holding function.

How to extend

A student could use this rule plus general soil-water relationships to judge that more humus generally supports greater moisture retention.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Advantages of Zero tillage > p. 356
Strength: 4/5
“• Zero tilled soils are homogenous in structure with more number of earthworms • Organic matter content increases due to less mineralization • Surface runoff is reduced due to presence of mulch”
Why relevant

States zero tillage increases organic matter and reduces surface runoff due to mulch—suggesting organic matter on surface reduces loss of water from soil.

How to extend

Combining this with a map/field knowledge of rainfall/runoff, a student could infer higher organic cover/matter helps retain water rather than drastically lowering water-holding capacity.

Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > Activity 12.10: Let us survey > p. 206
Strength: 3/5
“What inference do you draw from your interactions with farmers? Synthetic fertilisers and pesticides have played a vital role in improving crop production and helped countries like India become food secure. However, their long-term use can affect the environment and soil health. Overuse of synthetic fertilisers may reduce soil fertility by decreasing friendly microorganisms in soil and lowering organic matter (humus), which helps bind soil particles. Without enough humus, soil becomes prone to erosion. Also, it reduces the population of natural predators which ultimately increase the population of pests (Fig. 12.18). Heavy irrigation and repeated ploughing can also disturb soil organisms like earthworms and snails, which are important for maintaining ecological balance.”
Why relevant

Explains that humus helps bind soil particles and that lack of humus makes soil prone to erosion—implying humus stabilizes soil structure which influences water retention.

How to extend

A student could extend this by noting stable, aggregated soils (from humus) typically have better infiltration and moisture-holding characteristics versus degraded soils.

Statement 2
Does soil play any role in the sulfur cycle in agricultural ecosystems?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > b) Sulphur Cycle > p. 21
Presence: 5/5
“(b) Sulphur Cycle The sulphur reservoir is in the soil and sediments where it is locked in organic (coal, oil and peat) and inorganic deposits (pyrite rock and sulphur rock) in the form of sulphates, sulphides and organic sulphur. It is released by weathering of rocks, erosional runoff and decomposition of organic matter and is carried to terrestrial and aquatic ecosystems in salt solution. The sulphur cycle is mostly sedimentary except two of its compounds, hydrogen sulphide (H,S) and sulphur dioxide (SO,) add a gaseous component to its normal sedimentary cycle. Sulphur enters the atmosphere from several sources, including volcanic eruptions, combustion of fossil fuels, from the surface of ocean and from gases released by decomposition.”
Why this source?
  • Explicitly identifies the sulphur reservoir as being in soil and sediments.
  • Lists chemical forms of sulphur present in soil (sulphates, sulphides, organic sulphur).
  • Describes release pathways (weathering, decomposition) that mobilize sulphur from soil to ecosystems.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > BiogEochEmical cyclEs. > p. 18
Presence: 4/5
“Te cycling, at various scales, of minerals and compounds through the ecosystem is known as biogeochemical cycle. Te cycles (carbon cycle and nitrogen cycle) involve phases of weathering of rocks, uptake and storage by organisms and return to the pool of the soil, the atmosphere or ocean sediments. Te biogeochemistry of carbon has attracted particular attention because of the concern of global warming and greenhouse efects.”
Why this source?
  • Describes biogeochemical cycles as involving weathering, uptake, storage and return to the soil pool.
  • Frames soil as a key compartment in elemental cycling, implying soil participation in cycling elements like sulphur.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > sEdimEntary cyclEs. > p. 25
Presence: 3/5
“Te oxygen, carbon, and nitrogen cycles are all referred to as gaseous cycles because they possess a gaseous phase in which the element involved is present in signifcant quantities in the atmosphere. Many other elements move in sedimentary cycles, that is, from the land to ocean in running water, returning after millions of years as uplifted terrestrial rock. Tese elements are not present in the atmosphere except in small quantities as blowing dust or condensation nuclei in precipitation. An illustration of sedimentary cycle has been shown in Fig.1.13. Tis fgure shows how some important macronutrients move in sedimentary cycles. Within a large box representing the lithosphere, are smaller compartments representing the parent matter of the soil and the soil itself.”
Why this source?
  • Explains sedimentary cycles and shows soil (within the lithosphere) as a compartment for macronutrient movement.
  • Indicates elements move via land–soil–ocean pathways, consistent with soil's role in element cycles.
Statement 3
Can prolonged irrigation lead to salinization of agricultural lands?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 3: Land Resources and Agriculture > Degradation of Cultivable Land > p. 39
Presence: 5/5
“One of the serious problems that arises out of faulty strategy of irrigation and agricultural development is degradation of land resources. This is serious because it may lead to depletion of soil fertility. The situation is particularly alarming in irrigated areas. A large tract of agricultural land has lost its fertility due to alkalisation and salinisation of soils and waterlogging. Excessive use of chemicals such as insecticides and pesticides has led to their concentration in toxic amounts in the soil profile. Leguminous crops have been displaced from the cropping pattern in the irrigated areas and duration of fallow has substantially reduced owing to multiple cropping.”
Why this source?
  • Explicitly states irrigated areas have lost fertility due to salinisation and alkalisation.
  • Links faulty irrigation strategy and intensive irrigation to land degradation and waterlogging.
Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > iv) Saline and Alkaline Soils > p. 19
Presence: 5/5
“(iv) Saline and Alkaline Soils Soil salinity and alkalinity are found in the relatively less rainfall recording areas where the rate of evaporation is generally higher than the rate of precipitation. They also develop in the Khadar lands and the canal irrigated areas. Under such conditions, the ground water level rises and saline and alkaline efflorescence consisting of salts of sodium, calcium, and manganese appear on the surface as a layer of white salt through capillary action. According to one estimate, about 80 lakh hectares (2.4% of the country's reporting area) has been adversely affected by saline and alkaline formations.”
Why this source?
  • Explains that saline and alkaline soils develop in canal-irrigated areas where groundwater rises.
  • Describes capillary action bringing salts to the surface, a direct mechanism for salinization.
INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 6: Planning and Sustainable Development in Indian Context > Indira Gandhi Canal (Nahar) Command Area > p. 72
Presence: 5/5
“This has also helped in reducing wind erosion and siltation of canal systems. But the intensive irrigation and excessive use of water has led to the emergence of twin environmental problems of waterlogging and soil salinity. Introduction of canal irrigation has brought about a perceptible transformation in the agricultural economy of the region. Soil moisture has been a limiting factor in successful growing of crops in this area. Spread of canal irrigation has led to increase in cultivated area and intensity of cropping. The traditional crops sown in the area, gram, bajra and jowar have been replaced by wheat, cotton, groundnut and rice.”
Why this source?
  • Case example: intensive/excessive irrigation in the Indira Gandhi Canal area produced waterlogging and soil salinity.
  • Shows real-world transformation of cropping patterns associated with irrigation-driven salinity.
Pattern takeaway: UPSC creates traps using 'Scientific Inversions' (stating the exact opposite of a known function, like organic matter reducing water) and 'Absolutist Negatives' (does not play *any* role). Trust basic functional logic over complex data.
How you should have studied
  1. [THE VERDICT]: Sitter. Pure static concepts found in NCERT Geography Class XI/XII and Shankar IAS Environment.
  2. [THE CONCEPTUAL TRIGGER]: Soil Health & Biogeochemical Cycles (Sedimentary vs Gaseous).
  3. [THE HORIZONTAL EXPANSION]: 1. Phosphorus Cycle (strictly sedimentary, no atmospheric release). 2. Gypsum (CaSO4·2H2O) cures Alkaline/Saline soils; Lime (CaCO3) cures Acidic soils. 3. Nitrogen Fixation: Rhizobium (symbiotic) vs Azotobacter (free-living). 4. Capillary Action: The mechanism behind salinization in arid regions.
  4. [THE STRATEGIC METACOGNITION]: Don't just memorize cycle diagrams. Classify them: Gaseous (N, C) vs Sedimentary (P, S). For soil properties, ask 'Functional Questions': Why do we add X? (e.g., Organic matter acts like a sponge, not a drain).
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Organic matter & soil water-holding capacity
💡 The insight

Several references explicitly link organic matter/humus to improved moisture retention rather than reduction, directly addressing the statement's claim.

High-yield for UPSC: questions often probe how soil properties affect agriculture and water management. Mastering this clarifies MCQs and mains answers on soil fertility, irrigation efficiency, and land management. It connects to topics on organic amendments, crop resilience, and sustainable practices.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > EilUI RONMEf.IT'' /7=X x4 > p. 362
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Role of manures > p. 363
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 5: Geomorphic Processes > Biological Activity > p. 45
🔗 Anchor: "In agricultural soils, does a high content of organic matter drastically reduce ..."
📌 Adjacent topic to master
S1
👉 Role of organic manures in soil structure
💡 The insight

References describe organic manures binding sandy soils and improving water-holding, and opening clayey soils to improve aeration—key mechanisms by which organic matter alters water behaviour.

Useful for questions on soil management and organic farming vs chemical inputs. Understanding these mechanisms helps in answering application-based questions (soil conservation, zero-till, mulch) and links agronomy with ecology and agrarian policy.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Role of manures > p. 363
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Advantages of Zero tillage > p. 356
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > Activity 12.10: Let us survey > p. 206
🔗 Anchor: "In agricultural soils, does a high content of organic matter drastically reduce ..."
📌 Adjacent topic to master
S1
👉 Humus formation, decomposition & climatic control
💡 The insight

Evidence links humus (organic matter) to moisture retention and notes climatic/biological factors (decomposition, oxidation) that control humus levels and thus influence soil moisture properties.

Important for conceptual clarity on why organic content varies regionally and how that affects soil behaviour; aids answers on regional soil fertility differences, peat/peatlands, and management strategies across climates.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 5: Geomorphic Processes > Biological Activity > p. 45
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > Soil Air > p. 3
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > Soil Water > p. 4
🔗 Anchor: "In agricultural soils, does a high content of organic matter drastically reduce ..."
📌 Adjacent topic to master
S2
👉 Soil as a reservoir in sedimentary element cycles
💡 The insight

Reference [1] names soil/sediments as the sulphur reservoir; [9] situates soil within sedimentary cycles moving macronutrients.

High-yield for ecology and agriculture questions — explains long-term storage and release of elements (e.g., sulphur) and helps answer questions on nutrient availability and anthropogenic impacts. Links to topics on rock weathering, soil fertility, and element cycling; useful for questions comparing gaseous vs sedimentary cycles and for evaluating soil management policies.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > b) Sulphur Cycle > p. 21
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > sEdimEntary cyclEs. > p. 25
🔗 Anchor: "Does soil play any role in the sulfur cycle in agricultural ecosystems?"
📌 Adjacent topic to master
S2
👉 Biogeochemical cycling: weathering, uptake and return to soil
💡 The insight

Reference [3] defines biogeochemical cycles as including weathering, organismal uptake and return to the soil pool — mechanisms relevant to sulphur movement.

Core concept for UPSC ecology papers — mastering the cycle phases lets aspirants explain nutrient flow in ecosystems, design answers on soil fertility and agricultural nutrient management, and tackle comparative cycle questions (carbon, nitrogen, sulphur). Practice mapping each phase to real-world processes (weathering, decomposition, runoff).

📚 Reading List :
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > BiogEochEmical cyclEs. > p. 18
🔗 Anchor: "Does soil play any role in the sulfur cycle in agricultural ecosystems?"
📌 Adjacent topic to master
S2
👉 Decomposition and organic matter as nutrient sources in soil
💡 The insight

References [6] and [7] show decomposition returns nutrients to soil and that soil contains organic materials from dead organisms — pathways that mobilize and store sulphur in agricultural soils.

Frequently tested in conservation, agriculture and environment sections — understanding decomposition links soil health to crop nutrition and nutrient cycles; helps in writing balanced answers on sustainable farming, soil management and nutrient replenishment strategies.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > 12.6 What Happens to Waste in Nature? > p. 201
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > 25.13. SOIL > p. 366
🔗 Anchor: "Does soil play any role in the sulfur cycle in agricultural ecosystems?"
📌 Adjacent topic to master
S3
👉 Irrigation-induced salinization
💡 The insight

Multiple references link intensive or faulty irrigation directly to soil salinity and alkalisation in irrigated/canal areas.

High-yield topic for environment/agriculture questions: explains a common anthropogenic cause of land degradation, connects to water resources and agricultural productivity, and appears in policy/impact questions. Master by studying mechanism, examples, and mitigation measures.

📚 Reading List :
  • INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 3: Land Resources and Agriculture > Degradation of Cultivable Land > p. 39
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > iv) Saline and Alkaline Soils > p. 19
  • INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 6: Planning and Sustainable Development in Indian Context > Indira Gandhi Canal (Nahar) Command Area > p. 72
🔗 Anchor: "Can prolonged irrigation lead to salinization of agricultural lands?"
🌑 The Hidden Trap

Cation Exchange Capacity (CEC). Just as Organic Matter increases water holding capacity, it also drastically increases CEC (the soil's ability to hold nutrients). Clay and Humus have high CEC; Sand has low CEC. Expect a question linking CEC to fertilizer efficiency.

⚡ Elimination Cheat Code

The 'Ecological Web' Rule. In Ecology, almost nothing plays 'no role'. Statement 2 says soil plays 'no role' in the sulphur cycle. This is an extreme negative in a highly interconnected system—eliminate it immediately. Statement 1 contradicts the basic logic of composting (we add compost to keep soil moist). Eliminate 1. Answer is B.

🔗 Mains Connection

Mains GS-3 (Agriculture): Link Statement 3 (Salinization) to the 'Green Revolution Crisis' in Punjab/Haryana. Excessive flood irrigation caused waterlogging and salinity. The solution links to PMKSY (Per Drop More Crop) and the shift toward crop diversification (away from water-guzzling paddy).

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SIMILAR QUESTIONS

IAS · 2023 · Q63 Relevance score: 1.89

Consider the following statements : Statement-I : The soil in tropical rain forests is rich in nutrients. Statement-II : The high temperature and moisture of tropical rain forests cause dead organic matter in the soil to decompose quickly. Which one of the following is correct in respect of the above statements?

IAS · 2019 · Q41 Relevance score: 1.15

Consider the following statements : 1. Agricultural soils release nitrogen oxides into environment. 2. Cattle release ammonia into environment. 3. Poultry industry releases reactive nitrogen compounds into environment. Which of the statements given above is/are correct?

CDS-I · 2020 · Q118 Relevance score: 0.75

Which one of the following soils is characterized by very high content of organic matter?

CDS-II · 2016 · Q45 Relevance score: 0.55

Which of the following statements regarding soil is/are correct? 1. Alluvial soils are rich in nitrogen content. 2. Black soils are rich in iron and lime but deficient in nitrogen. 3. Laterite soils are rich in iron and aluminium but deficient in nitrogen and potassium. Select the correct answer using the code given below.

CAPF · 2025 · Q103 Relevance score: 0.34

Consider the following statements: 1. The circulation of nitrogen from the inorganic compounds in the soil to form protein in plants and animals and back again is known as the nitrogen cycle. 2. The preparation of ammonia by Haber process is an endothermic reaction. 3. Urea is synthetically made by the action of ammonia and carbon dioxide under high temperature and high pressure. Which of the statements given above is/are **not** correct?