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 Mains 2020 GS-IThe process of desertification does not have climate boundaries. Justify with examples.
How to structure the answer in the exam
Introduction: State that desertification, as defined by the United Nations Convention to Combat Desertification, is land degradation in arid, semi-arid, and dry sub-humid regions, and that Indian evidence shows it is not confined to any single climate boundary.
Body (sub-themes to develop):
- Hot-arid leakage: the Thar dune fields spread eastward across the Aravali break into semi-arid southern Haryana and western Uttar Pradesh under overgrazing and deforestation.
- High-rainfall surface stripping: laterite and red-soil tracts of central and peninsular India degrade into barren surfaces after forest clearance, despite generous monsoon rainfall.
- Cold-arid degradation: the cold deserts of Ladakh and Lahaul-Spiti lose alpine pasture to gravel barrens under overgrazing and unregulated tourism.
- Policy linkage: India's Land Degradation Neutrality target for 2030 and the Desertification and Land Degradation Atlas of India by the Space Applications Centre, ISRO, map the spread.
Conclusion: Conclude that because degradation appears in hot arid, high-rainfall, and cold-arid settings alike, climate boundaries do not contain it, which is why the national response is framed around Land Degradation Neutrality rather than desert-margin control alone.
Arid Soil, also called Desert Soil, is the sandy red-to-brown soil that dominates the Thar Desert of western Rajasthan and extends into semi-arid Haryana, Punjab, and the Saurashtra-Kachchh belt of Gujarat. The soil is aeolian in origin, deposited as wind-blown sand under low-rainfall conditions over geological time. It is characterised by high salinity, low organic matter, poor moisture-holding capacity, and a distinctive Kankar (calcareous concretion) layer in the lower horizons that restricts deep water percolation. In the ICAR-USDA Soil Taxonomy it maps to the Aridisols order.
Background and Historical Context
Arid Soil covers nearly 4 per cent of India's land surface and underwrites the agricultural geography of one of the country's most water-stressed regions. The soil is the canvas on which the Indira Gandhi Canal wrote the country's largest arid-zone irrigation reclamation story, turning parts of Bikaner, Jaisalmer, and Sri Ganganagar into cotton and wheat tracts. UPSC Mains GS-I has tested the desertification dimension, while Prelims has tested adjacent UNCCD and conservation-agriculture themes.
What is the significance of mastering the arid-soil landscape? Three operational dimensions follow. The aeolian-origin chemistry fingerprint explains the sandy texture, the calcium-carbonate accumulation, and the salinity profile that distinguish Aridisols from every other Indian soil order. The moisture-management problem drives the entire agricultural strategy: without external irrigation the soil supports only drought-resistant bajra, jowar, and pulses; with canal irrigation it transforms into a cotton-wheat-citrus belt. The desertification dynamic explains the eastward leakage of Thar conditions across the Aravali break and into semi-arid Haryana and western Uttar Pradesh, a process amplified by overgrazing, deforestation, and climate-change-driven rainfall variability.
The Indira Gandhi Canal Pariyojana, India's largest canal-irrigation project conceived in 1948 and progressively commissioned since the 1960s, remains the principal reclamation lever; Phase I covered Suratgarh and Anupgarh, Phase II extended into Bikaner and Jaisalmer with documented secondary salinity from canal-seepage. India is party to the United Nations Convention to Combat Desertification (UNCCD) and has committed to Land Degradation Neutrality by 2030 under the Sustainable Development Goals. The ICAR-Central Arid Zone Research Institute (CAZRI) at Jodhpur coordinates Indian arid-zone research; the National Action Programme to Combat Desertification and the Desertification and Land Degradation Atlas of India published by the Space Applications Centre, ISRO, provides the operational map.
Introduction: Sandy Aeolian Soil of the Thar Desert
Definition, colour-texture profile, geographic extent
Arid Soil is the dominant soil of the Thar Desert and the semi-arid belt that wraps around it. The soil colour grades from red to brown depending on iron content and the depth of weathering; the texture is overwhelmingly sandy, reflecting the aeolian deposition that built it. The organic matter content is low because the dry climate suppresses biomass accumulation and accelerates decomposition; the moisture-holding capacity is poor for the same reason.
The soil covers roughly 4 per cent of India (about 1.42 lakh square kilometres), dominating western Rajasthan (Bikaner, Jaisalmer, Barmer, Jodhpur, Sri Ganganagar), extending into southern Haryana (Mahendragarh, Rewari) and southern Punjab (Bhatinda, Mansa, Fazilka), and including the Saurashtra-Kachchh arid fringe of Gujarat. The Aravali break separates the eastward semi-arid leakage from the deeper desert core.
Formation: Aeolian Deposition and Salinity Accumulation
Wind transport, evaporation salinity, Kankar precipitation
Wind is the principal geomorphic agent in the Thar region. Sand transported eastward from the Indus floodplain and locally from weathered rock surfaces accumulates as dunes (barchans, longitudinal ridges, transverse fields) and as inter-dune sandy plains; the soil typically runs 90 to 95 per cent sand with only 5 to 10 per cent clay.
The dry climate concentrates dissolved salts near the surface through capillary rise and evaporation. In some tracts the salt content is high enough that common salt is harvested by evaporating saline groundwater.
- (i) Aeolian sand transport: Westerly winds during the dry season carry fine to medium sand grains eastward; dune-building is active on unvegetated tracts; the Aravali break is the eastern edge of the major dune fields.
- (ii) Evaporation-driven salinity: Capillary rise plus surface evaporation concentrate sodium, calcium, and magnesium salts in the upper soil; the saline horizon often shows white efflorescence after rainfall and drying.
- (iii) Kankar (calcareous concretion) layer: Calcium carbonate precipitates as nodules in the lower horizons; the Kankar layer is harder than the surrounding matrix and restricts vertical water percolation, sometimes trapping a shallow saline water table.
The combined effect is a sandy, saline, low-humus profile with a poorly-permeable lower horizon. Without irrigation, the soil supports only drought-resistant grasses and shrubs.
Distribution: Thar Desert Core and Semi-Arid Eastward Leakage
Western Rajasthan core; Haryana-Punjab leakage; Kachchh fringe
The Thar Desert sits in the lee of the Aravali range, which intercepts the south-west monsoon and produces a deep rain-shadow over western Rajasthan. The rain-shadow plus the westerly wind regime together produce the Aridisol belt. Eastward of the Aravali break the semi-arid leakage runs across southern Haryana and southern Punjab; westward the fringe reaches Kachchh.
- Thar core (western Rajasthan): Bikaner, Jaisalmer, Barmer, Jodhpur, Sri Ganganagar; deep aeolian sand-dune fields and inter-dune sandy plains.
- Aravali break leakage: Sikar, Jhunjhunu, Mahendragarh, Rewari, Bhiwani extend semi-arid Aridisols into southern Haryana.
- Southern Punjab semi-arid fringe: Bhatinda, Mansa, Fazilka carry shallow Aridisols transitioning to alluvial soils eastward.
- Saurashtra-Kachchh arid belt: Western Gujarat carries Aridisols with high salinity; the Rann of Kachchh is a distinctive salt-flat sub-environment.
Characteristics: Salinity, Low Humus, Drought-Limited Fertility
Three observable outcomes for agriculture and policy
Observable outcomes of the aeolian-arid weathering regime. Three properties of Aridisols shape every agricultural decision and every reclamation programme on this soil.
- (a) Texture and water economy: Sandy texture drains rapidly; poor moisture-holding capacity; reliable cropping requires either rain-fed drought-resistant species or external irrigation; the Kankar layer beneath restricts deep percolation and can trap shallow saline water.
- (b) Chemistry and salinity: Alkaline pH (generally 7.5 to 9.0); high soluble-salt concentration (sodium, calcium, magnesium); white efflorescence common after rain-dry cycles; in extreme tracts the salt content is high enough that common salt is commercially harvested from groundwater evaporation.
- (c) Nutrient profile and crop choice: Low nitrogen, low organic matter, moderate phosphorus, adequate potash; rain-fed cropping is restricted to bajra (pearl millet), jowar, moth bean, cluster bean (guar), and sea buckthorn on the cold-arid Himalayan fringe; with irrigation the soil supports wheat, cotton, mustard, and citrus.
The crop-choice gradient (rain-fed bajra-jowar versus irrigated cotton-wheat) is the principal distinction between unreclaimed Aridisols and the canal-irrigated Indira Gandhi command areas. The table below sets the two regimes side by side.
| Parameter | Rain-fed (unreclaimed) | Canal-irrigated (Indira Gandhi command) |
|---|---|---|
| Water source | Erratic monsoon, under 250 mm in the core | Sutlej-Beas water via the Harike Barrage |
| Texture and salinity | Sandy, 90 to 95 per cent sand, salt-prone | Same soil, but seepage can raise secondary salinity |
| Typical crops | Bajra, jowar, moth bean, cluster bean (guar) | Cotton, wheat, mustard, citrus |
| Districts | Bikaner, Jaisalmer, Barmer interior | Sri Ganganagar, Suratgarh, Anupgarh command |
| Main risk | Crop failure in drought years | Waterlogging and salinity without field drainage |
IGNP Reclamation, Desertification, and Contemporary Policy
Indira Gandhi Canal, UNCCD, CAZRI
The Indira Gandhi Canal, formerly the Rajasthan Canal, is the country's largest arid-zone irrigation reclamation project and, at about 837 kilometres, the longest canal in India. Conceived in 1948 and progressively commissioned since the 1960s, it begins at the Harike Barrage where the Sutlej and Beas meet, and carries that water southwest into the Thar.
Phase I (Suratgarh and Anupgarh in Sri Ganganagar district) brought commercial cotton, wheat, mustard, and citrus into cultivation. Phase II extended into Bikaner and Jaisalmer, but with documented secondary salinity from canal seepage and inadequate field drainage.
- IGNP Phase I: Suratgarh, Anupgarh, Sri Ganganagar; cotton-wheat-mustard rotation; the showcase of arid-zone reclamation.
- IGNP Phase II: Bikaner, Jaisalmer; mixed results; salinity rise from over-irrigation plus inadequate field drainage.
- UNCCD and LDN 2030: India is a party to the United Nations Convention to Combat Desertification and has committed to Land Degradation Neutrality by 2030 under SDG Target 15.3.
- ICAR-CAZRI Jodhpur: The Central Arid Zone Research Institute coordinates Aridisol agronomy, sand-dune stabilisation via grass-and-shrub plantation, and drought-resistant crop breeding.
- Desertification Atlas of India: Space Applications Centre, ISRO maps the eastward leakage of Thar conditions across the Aravali break; informs the National Action Programme to Combat Desertification.
Sustainability concerns dominate the contemporary agenda. Secondary salinity from canal-seepage on IGNP Phase II tracts, eastward desertification leakage across the Aravali break into southern Haryana and western Uttar Pradesh, and climate-change-driven rainfall variability that intensifies dust-storm frequency together set the policy agenda for Aridisols in the present decade.
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 arid and desert soils in India:
- Arid and desert soils are concentrated in the western part of Rajasthan, parts of Haryana, Punjab, and Gujarat (Kutch).
- These soils are typically sandy in texture due to aeolian (wind-driven) deposition.
- Arid soils are highly fertile and support intensive paddy cultivation without any irrigation.
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: arid and desert soils dominate western Rajasthan (Thar Desert), parts of Haryana, Punjab, and Gujarat Kutch. Statement 2 is correct: they are typically sandy due to aeolian deposition. Statement 3 is wrong: arid soils are LOW IN FERTILITY (low organic matter, high salinity in places) and are NOT suited to intensive paddy without irrigation; they support hardy millets like bajra under rainfed conditions.
Q2. Consider the following statements about the formation of arid soils:
- Aeolian processes (wind transport and deposition) are the dominant soil-forming control in the Thar Desert.
- Salinity and alkalinity issues are common in arid soils due to high evaporation and low rainfall.
- Arid soils are formed exclusively through glacial sediment deposition under cold-climate conditions.
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: aeolian processes dominate Thar Desert soil formation. Statement 2 is correct: high evaporation plus low rainfall causes salt accumulation, leading to salinity and alkalinity issues. Statement 3 is wrong: arid soils are AEOLIAN (wind-deposited), NOT glacial; glacial soils characterise high-altitude Himalayan tracts, not arid lowlands.
Q3. Consider the following statements about the agronomic properties of arid soils:
- Arid soils have low organic matter and humus content.
- Calcium carbonate accumulation (calcrete or kankar layer) is common in the subsoil of arid Indian soils.
- Arid soils are agronomically suitable for cultivation of bajra (pearl millet) and other drought-tolerant crops under appropriate management.
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, 2 and 3
Explanation.
Correct: d (1, 2 and 3). All three statements are correct. Arid soils have low organic matter; calcrete (kankar) accumulates in the subsoil under low-rainfall conditions; and bajra plus drought-tolerant crops (mustard, jowar, pulses) grow on them under managed irrigation or rainfed conditions.
Q4. Consider the following statements about arid-zone agricultural research in India:
- The Central Arid Zone Research Institute (CAZRI) at Jodhpur is the principal national institute for arid-zone agricultural research.
- CAZRI was established in 1972 as the first institute set up under the Indian Council of Agricultural Research.
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: 1 only
Explanation.
Correct: a (1 only). Statement 1 is correct: CAZRI at Jodhpur is the principal national institute for arid-zone agricultural research (soil-water management, sand-dune stabilisation, drought-tolerant cropping). Statement 2 is wrong on two counts: CAZRI was established in 1959, not 1972, and it grew out of the earlier Desert Afforestation Research Station (1952); it was brought under the Indian Council of Agricultural Research in 1966 and was not the first ICAR institute.
Q5. Consider the following statements about irrigation in the Thar Desert tract:
- The Indira Gandhi Canal (formerly the Rajasthan Canal) draws water from the Harike Barrage at the Sutlej-Beas confluence and carries it to the Thar desert tract of Rajasthan.
- The Indira Gandhi Canal Project has enabled cultivation of crops including wheat, cotton, and mustard in areas that were previously largely uncultivated arid land.
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: the Indira Gandhi Canal begins at the Harike Barrage, where the Sutlej and Beas meet, and carries that water across northwestern Rajasthan to the Thar tract. Statement 2 is correct: the canal-irrigated tracts now support wheat, cotton, and mustard cultivation; the desert greening visible in northwestern Rajasthan traces to this canal infrastructure.
Q6. Consider the following statements about desertification in India:
- India is a signatory to the United Nations Convention to Combat Desertification (UNCCD).
- The Space Applications Centre of ISRO produces the Desertification and Land Degradation Atlas of India, which quantifies the degraded-land share of the country.
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: India ratified the UNCCD in 1996. Statement 2 is correct: the Space Applications Centre of ISRO, at Ahmedabad, produces the Desertification and Land Degradation Atlas of India, which places the degraded-land share at around 29 to 30 per cent of the total geographical area in recent editions.
Sources
- NCERT Class 11 India Physical Environment, Chapter 6 (Soils), p 75
- Indian Council of Agricultural Research (ICAR)
- ICAR-Central Arid Zone Research Institute (CAZRI), Jodhpur
- National Bureau of Soil Survey and Land Use Planning (NBSS&LUP), Nagpur
- USDA Natural Resources Conservation Service: Aridisols
- Ministry of Agriculture and Farmers Welfare, Soil Health Card
- United Nations Convention to Combat Desertification (UNCCD)
- Wikipedia: Arid soil
- Wikipedia: Indira Gandhi Canal
- Wikipedia: Thar Desert
Disclaimer
This article is prepared for UPSC preparation by Digitally Learn's editorial team. Key facts and named institutions are cross-verified with NCERT and the authoritative sources listed in the Sources block below.
