Overview
Previous Year UPSC-CSE Questions By the end you will be able to draft model answers for the following UPSC questions. Each question carries a collapsible framework showing how to approach it in the exam.
- UPSC Prelims 2017Which of the following practices can help in water conservation in agriculture?
- Reduced or zero tillage of the land
- Applying gypsum before irrigating the field
- Allowing crop residue to remain in the field Select the correct answer using the code given below:
How to approach this Prelims question
Approach: Evaluate each statement against the water-conservation purpose. Reduced tillage limits soil disturbance and evaporative losses. Crop residue mulches the surface and slows evaporation. Gypsum supplies calcium to displace sodium on clay-exchange sites in sodic soils, a chemistry intervention unrelated to water conservation.
Trap to watch: Tempting to include gypsum because it appears in irrigation contexts; the correct framing is that gypsum addresses soil chemistry while tillage and residue address water economy.
Key facts to recall:
- Gypsum (CaSO4) is for sodic-soil reclamation via Ca-for-Na exchange
- Reduced tillage and crop residue retention reduce evaporation
- Saline-soil reclamation = gypsum, drainage, and salt-tolerant crops
- Water-conservation toolkit = tillage choice, mulching, and drip irrigation
Answer signal: Correct answer is (c): 1 and 3 only (NOT gypsum).
- UPSC Prelims 2016Which of the following is/are the advantage/advantages of practising drip irrigation?
- Reduction in weed
- Reduction in soil salinity
- Reduction in soil erosion Select the correct answer using the code given below:
How to approach this Prelims question
Approach: Drip irrigation feeds water in small, targeted volumes to the root zone. It limits weed germination in the dry inter-row spaces and reduces soil erosion by eliminating the overland flow that flood irrigation creates. The UPSC key does not credit reduction in soil salinity as an advantage, so Statement 2 is excluded.
Trap to watch: Statement 2 (reduction in soil salinity) reads plausible, but the UPSC key excludes it. The credited advantages are Statement 1 (weed reduction) and Statement 3 (soil-erosion reduction).
Key facts to recall:
- Drip irrigation limits inter-row weed germination by wetting only the root zone
- Drip irrigation reduces soil erosion by removing overland flow and runoff
- Reduction in soil salinity is NOT the UPSC-credited advantage in this question
- PMKSY per-drop-more-crop component promotes micro-irrigation including drip
Answer signal: Correct answer is (c): 1 and 3 only.
Saline and Alkaline Soils, traditionally called Usara in ancient Indian classification, are the salt-laden soils that develop where poor drainage combines with high evaporation to concentrate soluble salts in the upper horizons. Two sub-types are recognised. Saline soils (Solonchak) carry excess soluble salts (sodium, magnesium, potassium chlorides and sulphates) and show white efflorescence after dry spells. Alkaline soils (Solonetz, also called sodic) carry excess exchangeable sodium adsorbed on clay particles, producing a dispersed, structureless profile with high pH. Both sub-types are infertile in their native state and require active reclamation. The principal Indian distribution covers western Gujarat (Rann and Saurashtra), the east-coast deltas, the Sundarbans of West Bengal, and canal-irrigated Punjab-Haryana tracts where over-irrigation has driven secondary salinization.
Background and Historical Context
Saline and Alkaline Soils underlie a documented national land-degradation challenge. The ICAR estimates that around 6.7 million hectares of Indian land carry salt-affected soils, with the share rising under canal-irrigation expansion and sea-level-rise pressure on coastal tracts. UPSC Prelims has tested saline-soil management directly.
What is the significance of mastering saline-alkaline geography? Three operational dimensions follow. The Solonchak-Solonetz distinction is the analytical foundation: Solonchak (saline) carries soluble salts that leach out with good-quality water plus drainage; Solonetz (sodic) carries adsorbed sodium that requires gypsum to displace via calcium-for-sodium cation exchange. The primary-versus-secondary causation explains the policy menu: primary salinity in Rann of Kachchh and coastal deltas is geomorphological and inherits sea-water history; secondary salinity in canal-command Punjab-Haryana is anthropogenic and reflects irrigation mismanagement. The climate-change amplification via sea-level rise and storm-surge intensity threatens to expand coastal salt-affected tracts faster than reclamation can keep pace, especially in the Sundarbans and the east-coast deltas.
The ICAR-Central Soil Salinity Research Institute (CSSRI) at Karnal coordinates Indian saline-soil research; Rashtriya Krishi Vikas Yojana funds salinity reclamation; the Coastal Aquaculture Authority regulates brackish-water shrimp farming on saline coastal tracts; the Soil Health Card identifies salinity-affected villages and prescribes gypsum-and-drainage protocols. Climate-adaptation policy intersects with the National Action Plan on Climate Change and the Mission for Sustainable Agriculture on saline-tolerant cropping systems including dhaincha (Sesbania) green manure, salt-tolerant rice varieties, and bio-drainage using eucalyptus and casuarina species.
Introduction: Usara Soils and the Salt-Affected Belt
Two sub-types, national extent, ancient classification
Saline and Alkaline Soils were grouped under the ancient Indian classification name Usara (literally infertile) alongside the fertile Urvara soils covered in Soils Part 1. Modern pedology divides the Usara group into two operationally distinct sub-types: Solonchak (saline) soils dominated by soluble salt accumulation, and Solonetz (alkaline or sodic) soils dominated by exchangeable-sodium adsorption on clay particles. The distinction matters because the reclamation technology diverges.
The national extent is large. Indian Council of Agricultural Research estimates that around 6.7 million hectares of land carry salt-affected soils. The principal distribution covers western Gujarat (Rann of Kachchh, Saurashtra coast), the east-coast deltas (Mahanadi, Godavari-Krishna, Cauvery), the Sundarbans of West Bengal, and secondary-salinized canal-command tracts across Punjab, Haryana, and parts of western Uttar Pradesh.
Sub-Types: Solonchak (Saline) versus Solonetz (Alkaline)
Three distinguishing features of the two sub-types
The Solonchak-Solonetz distinction is the analytical foundation for saline-alkaline soil management. Solonchak soils carry soluble salts that leach out with good-quality irrigation water plus drainage. Solonetz soils carry sodium adsorbed on clay-exchange sites and require calcium-for-sodium cation displacement (typically via gypsum) before leaching can succeed. Treating one as the other wastes reclamation effort and can worsen the profile.
| Property | Solonchak (saline) | Solonetz (alkaline-sodic) |
|---|---|---|
| Dominant problem | Excess soluble salts | Excess exchangeable sodium on clay |
| Diagnostic threshold | Electrical conductivity above 4 dS/m | Exchangeable sodium percentage above 15 |
| Soil reaction (pH) | 7.5 to 8.5 (mildly alkaline) | 8.5 to 10.5 (strongly alkaline) |
| Physical structure | Reasonable structure (Ca and Mg stabilise clay) | Dispersed, structureless, dense B horizon |
| Surface signature | White salt efflorescence after dry spells | Dark organic staining from mobilised humus |
| Reclamation route | Leach with good water plus sub-surface drainage | Apply gypsum first, then leach the freed sodium |
- (i) Salt chemistry: Solonchak carries excess soluble salts (sodium chloride, sodium sulphate, magnesium and calcium salts); Solonetz carries excess exchangeable sodium on the clay-cation-exchange complex but lower soluble-salt concentration.
- (ii) Physical structure: Solonchak retains reasonable structure because divalent calcium and magnesium stabilise the clay; Solonetz shows dispersed, structureless clay because monovalent sodium causes deflocculation, producing a dense impermeable B horizon.
- (iii) pH and surface signature: Solonchak is moderately alkaline (pH 7.5 to 8.5) with white salt efflorescence after dry spells; Solonetz is strongly alkaline (pH 8.5 to 10.5) and may show dark organic surface staining from sodium-mobilised humus.
Distribution: Primary Geomorphological and Secondary Anthropogenic
Four belts and the primary-versus-secondary causation distinction
How primary geomorphology and secondary anthropogenic causation diverge. Primary salinity is a geomorphological inheritance: the Rann of Kachchh evaporite basin, the east-coast delta tidal-flat margins, the Sundarbans mangrove tidal flats. Secondary salinity is an anthropogenic consequence of canal-irrigation seepage, fertiliser overuse, and inadequate field drainage on otherwise non-saline land. The policy lever and the responsible institution differ across the two causation categories.
- Western Gujarat (primary): Rann of Kachchh evaporite tract; Saurashtra coastal saline patches; common salt commercially harvested from saline groundwater.
- East-coast deltas (primary): Mahanadi, Godavari-Krishna, Cauvery delta margins carry tidal salinization where the river system meets the Bay of Bengal.
- Sundarbans (primary and climate-amplified): Mangrove tidal flats at the Hooghly-Brahmaputra delta margin; Cyclone Aila 2009 documented salinity intensification; ongoing sea-level rise amplifies vulnerability.
- Punjab and Haryana and western UP canal-command (secondary): Anthropogenic salinization from canal-water seepage plus fertiliser overuse on Indo-Gangetic alluvial soil; Soil Health Card flags affected villages.
- Indo-Gangetic Usar patches (mixed): Uttar Pradesh and Bihar saline-sodic patches in flood-prone tracts; documented Usar belt of central UP.
Reclamation: Gypsum Chemistry, Drainage, Salt-Tolerant Cropping
Three operational outcomes of the reclamation programme
Observable outcomes of the reclamation toolkit. Three operational outcomes follow from the gypsum-drainage-crop triad applied across Indian salt-affected tracts.
- (a) Gypsum chemistry for sodic Solonetz: Calcium sulphate (CaSO4) supplies calcium that displaces exchangeable sodium on clay-exchange sites; the released sodium then leaches out with irrigation water; this is the standard Soil Health Card recommendation for canal-command sodic tracts.
- (b) Drainage engineering: Sub-surface tile drains and surface field drains lower the water table and carry leachate away; vertical wells and tube drains are used in deep saline-water-table tracts; the drainage outlet must lead to a saline-disposal channel that does not contaminate fresh-water sources downstream.
- (c) Salt-tolerant cropping: ICAR-CSSRI Karnal has bred salt-tolerant rice varieties including CSR-30, salt-tolerant wheat KRL-19 and KRL-210, and salt-tolerant barley; dhaincha (Sesbania) green manure is the standard bio-reclamation crop; bio-drainage using eucalyptus and casuarina plantation lowers the water table on the perimeter of salt-affected fields.
Contemporary Policy and Climate-Change Amplification
ICAR-CSSRI architecture and sea-level-rise vulnerability
The ICAR-Central Soil Salinity Research Institute (CSSRI) at Karnal coordinates Indian saline-alkaline soil research; the institute's regional centres at Lucknow, Bharuch, and Canning Town extend the operational reach to the Indo-Gangetic Usar belt, the Gujarat saline tracts, and the Sundarbans coastal tract respectively. Rashtriya Krishi Vikas Yojana funds salinity-reclamation under the state-implementation framework; the Soil Health Card identifies salinity-affected villages and prescribes gypsum-and-drainage protocols.
- ICAR-CSSRI Karnal: Central Soil Salinity Research Institute; coordinates research and breeds salt-tolerant crop varieties (CSR-30 rice, KRL-19/210 wheat).
- Coastal Aquaculture Authority: Regulates brackish-water shrimp farming on saline coastal tracts; balances aquaculture revenue with mangrove and rice ecosystem protection.
- Sundarbans Aila 2009 episode: Tropical Cyclone Aila documented severe storm-surge salinization of Sundarbans paddy fields; recovery extended over several years; informed coastal-resilience policy.
- IPCC AR6 sea-level rise: Roughly one metre global mean sea-level rise projected by 2100 under high-emission scenarios threatens to expand coastal salinization across the Sundarbans, the east-coast deltas, and the Saurashtra coast.
- Bio-drainage and salt-tolerant cropping: Eucalyptus and casuarina plantation lower the water table, dhaincha green manure rebuilds organic carbon, and salt-tolerant rice and barley sustain production while the soil heals.
Prelims MCQ practice
Each question below tests one specific concept on the topic. Click to reveal the answer and a full option-wise explanation.
Q1. Consider the following statements about saline and alkaline soils:
- Saline soils have high concentration of soluble salts (sodium chloride, sulphate) but neutral pH around 7-8.
- Alkaline soils have high exchangeable sodium (sodicity) and high pH typically above 8.5.
- Saline and alkaline soils are agronomically identical and require identical reclamation treatments.
Which of the statements given above are correct?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Show answer and explanation
Answer: 1 and 2 only
Explanation.
Correct: a (1 and 2 only). Statement 1 is correct: saline soils have high soluble-salt concentration with near-neutral pH. Statement 2 is correct: alkaline (sodic) soils have high exchangeable sodium and high pH above 8.5. Statement 3 is wrong: saline and alkaline soils have DIFFERENT chemistry AND require DIFFERENT reclamation treatments. Saline soils need leaching with good-quality water; alkaline soils need calcium amendment (gypsum) to replace exchangeable sodium.
Q2. Consider the following statements about reclamation of alkaline (sodic) soils:
- Gypsum (calcium sulphate) is the standard amendment for reclaiming sodic soils because calcium ions replace exchangeable sodium on the soil-exchange complex.
- Sodium leaches out after the calcium-replacement step when good-quality irrigation water is applied.
- Sodic soils can be reclaimed by simply adding urea fertiliser without any calcium amendment.
Which of the statements given above are correct?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Show answer and explanation
Answer: 1 and 2 only
Explanation.
Correct: a (1 and 2 only). Statement 1 is correct: gypsum is the standard sodic-soil amendment; calcium replaces exchangeable sodium on the exchange complex. Statement 2 is correct: sodium leaches out after calcium-replacement with good-quality water. Statement 3 is wrong: urea fertilisation does NOT reclaim sodic soils; calcium amendment (gypsum) is essential.
Q3. Consider the following statements about saline-alkaline soil research in India:
- ICAR-CSSRI (Central Soil Salinity Research Institute) at Karnal, Haryana, is the principal national institute for saline-alkaline soil research and reclamation.
- ICAR-CSSRI develops salt-tolerant crop varieties as part of its reclamation research mandate.
Which of the statements given above is/are correct?
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Show answer and explanation
Answer: Both 1 and 2
Explanation.
Correct: c (Both 1 and 2). Statement 1 is correct: ICAR-CSSRI at Karnal is the principal institute for saline-alkaline soil research. Statement 2 is correct: CSSRI develops salt-tolerant crop varieties (CSR rice series, salt-tolerant wheat) as part of its reclamation-research mandate.
Q4. Consider the following statements about the geographic distribution of saline-alkaline soils in India:
- Saline-alkaline soils are found in parts of Uttar Pradesh, Punjab, Haryana, Rajasthan, Gujarat (Kutch and Saurashtra), and the coastal tracts of West Bengal.
- Total area affected by salinity and alkalinity in India is approximately 6-7 million hectares.
- Saline-alkaline soils are absent from coastal regions because of the rainfall regime.
Which of the statements given above are correct?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Show answer and explanation
Answer: 1 and 2 only
Explanation.
Correct: a (1 and 2 only). Statement 1 is correct: salt-affected soils are in UP, Punjab, Haryana, Rajasthan, Gujarat, and coastal West Bengal among other tracts. Statement 2 is correct: total salt-affected area is around 6-7 million hectares. Statement 3 is wrong: coastal regions HAVE saline soils due to sea-water intrusion and tidal influence (the Sundarbans, parts of Kerala backwaters, AP and TN coastal tracts).
Q5. Consider the following statements about the causes of secondary salinity in India:
- Secondary salinity in irrigated tracts often results from waterlogging and capillary rise of saline groundwater under poor drainage.
- Canal-irrigation expansion without adequate drainage in parts of Punjab and Haryana has contributed to secondary salinity development.
Which of the statements given above is/are correct?
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Show answer and explanation
Answer: Both 1 and 2
Explanation.
Correct: c (Both 1 and 2). Statement 1 is correct: secondary salinity results from waterlogging plus capillary rise of saline groundwater under poor drainage. Statement 2 is correct: canal irrigation expansion in Punjab and Haryana without adequate drainage infrastructure has contributed to secondary salinity in some command-area tracts.
Q6. Consider the following statements about salt-tolerant crop cultivation:
- Salt-tolerant rice varieties developed at ICAR-CSSRI enable cultivation on moderately-saline soils.
- Barley, mustard, and sugar beet show relatively higher salt tolerance than most other crops.
Which of the statements given above is/are correct?
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Show answer and explanation
Answer: Both 1 and 2
Explanation.
Correct: c (Both 1 and 2). Statement 1 is correct: ICAR-CSSRI has released salt-tolerant rice varieties (CSR series) for cultivation on moderately-saline soils. Statement 2 is correct: barley, mustard, and sugar beet are among the relatively salt-tolerant crops in standard agronomic salt-tolerance rankings.
Sources
- NCERT Class 11 India Physical Environment, Chapter 6 (Soils), pp 75-76
- Indian Council of Agricultural Research (ICAR)
- ICAR-Central Soil Salinity Research Institute (CSSRI), Karnal
- National Bureau of Soil Survey and Land Use Planning (NBSS&LUP), Nagpur
- USDA Natural Resources Conservation Service: Aridisols (salic horizon)
- Ministry of Agriculture and Farmers Welfare, Soil Health Card
- United Nations Food and Agriculture Organization (FAO): Salt-affected soils
- Wikipedia: Saline soil
- Wikipedia: Sundarbans
- Wikipedia: Soils of India
Disclaimer
This article is prepared for UPSC preparation by Digitally Learn's editorial team. Key concepts and named institutions are cross-verified with NCERT and the authoritative sources listed below.
