Q20. What effect can salinisation have when irrigation water evaporates and leaves salts in soil?
[UPSC CSE Preliminary (2011)]
- (A) It sharply increases crop yields
- (B) It can make some soils impermeable
- (C) It necessarily raises groundwater
- (D) It always fills soil pores with water
Answer: (B) It can make some soils impermeable
Explanation: Evaporating irrigation water can leave salts that accumulate in the root zone. In some affected soils, structural deterioration reduces water movement and infiltration. Salinisation also creates osmotic stress, making it difficult for crops to take up water.
Q19. Which soil texture contains particles of sand, silt and clay together?
[53rd–55th BPSC Preliminary (2011)]
- (A) Sand alone
- (B) Clay alone
- (C) Silt alone
- (D) Loam
Answer: (D) Loam
Explanation: Loam combines sand, silt and clay in proportions offering a useful balance between drainage and water storage. Sand contributes coarse pores, silt adds intermediate particles and clay increases moisture and nutrient retention. Exact proportions vary among loam subclasses.
Q18. Among clay, silt, sand and loam, which material was chosen as storing the most water?
[53rd–55th BPSC Preliminary (2011)]
- (A) Clay
- (B) Silt
- (C) Sand
- (D) Loam
Answer: (A) Clay
Explanation: Clay has minute particles and a large surface area, allowing substantial water adsorption. It commonly holds more total water than coarse sand. The distinction between total retained water and plant-available water remains important in practical soil science.
Q17. Which substance is mainly responsible for the red colour of soil seen in parts of India?
[UPSC CSE Preliminary (2010)]
- (A) Magnesium
- (B) Humus
- (C) Ferric oxides
- (D) Phosphates
Answer: (C) Ferric oxides
Explanation: Ferric iron compounds form when iron-bearing minerals oxidize during weathering. They produce reddish hues in soils derived from crystalline rocks across portions of peninsular India. Humus generally darkens soil, whereas magnesium and phosphate do not explain the characteristic red shade.
Q16. Which combination was accepted for soil conservation? 1. Crop rotation. 2. Sand fences. 3. Terracing. 4. Windbreaks.
[UPSC CSE Preliminary (2010)]
- (A) 1, 2 and 3
- (B) 2 and 4 only
- (C) 1, 3 and 4
- (D) 1, 2, 3 and 4
Answer: (C) 1, 3 and 4
Explanation: The published examination key accepts crop rotation, terracing and windbreaks for soil conservation. These practices maintain cover, slow surface runoff or reduce wind erosion. Sand fences may have specialised uses, but were not included in the accepted combination.
Q15. Crop rotation is primarily important for which agricultural purpose?
[Uttarakhand PSC Preliminary (2010)]
- (A) Increasing plant protein automatically
- (B) Obtaining unrelated crops only
- (C) Maintaining soil fertility
- (D) Eliminating all irrigation needs
Answer: (C) Maintaining soil fertility
Explanation: Rotating crops changes nutrient demand and can include legumes that contribute biologically fixed nitrogen. The practice also helps manage pests and soil structure. Continuous cultivation of a single crop tends to create imbalanced nutrient withdrawal over time.
Q14. Which Indian soil is popularly described as self-ploughing?
[UP Lower Subordinate Preliminary (2009)]
- (A) Alluvial
- (B) Lateritic
- (C) Black cotton soil
- (D) Desert
Answer: (C) Black cotton soil
Explanation: Expansive clays in black regur soil swell when moist and shrink during drying. This creates deep cracks that naturally loosen and aerate the ground. The distinctive self-ploughing behavior is associated with the basaltic Deccan black-soil region.
Q13. Which district of Madhya Pradesh is especially known for severe soil erosion?
[MPPSC Preliminary (2008)]
- (A) Jabalpur
- (B) Bhopal
- (C) Morena
- (D) Khandwa
Answer: (C) Morena
Explanation: Morena lies within the Chambal ravine region, where concentrated runoff cuts deep gullies into susceptible material. The development of ravines removes productive topsoil and fragments farmland. Vegetation protection and watershed management are important conservation responses.
Q12. Which state was identified as having the largest alkali-soil area?
[UPPCS Mains (2007)]
- (A) Gujarat
- (B) Haryana
- (C) Punjab
- (D) Uttar Pradesh
Answer: (D) Uttar Pradesh
Explanation: Uttar Pradesh has extensive alkali or sodic soil affected by exchangeable sodium and high pH. This condition is different from simple soluble-salt salinity. Gypsum, drainage and water management are commonly used to reclaim suitable sodic fields.
Q11. Assertion: Andhra Pradesh had a smaller net-sown-area share than West Bengal. Reason: Most of Andhra Pradesh has laterite soil. Which choice is correct?
[UPSC CSE Preliminary (2006)]
- (A) Both true and reason explains
- (B) Both true but unrelated
- (C) Assertion true, reason false
- (D) Assertion false, reason true
Answer: (C) Assertion true, reason false
Explanation: The exam’s assertion about relative net-sown-area shares was considered true, but Andhra Pradesh is not predominantly lateritic. It has extensive red and other soils. Hence soil-type generalisation cannot explain the agricultural land-share difference asserted.
