Q21. The characteristic red color of the red loam soils found in southern Rajasthan is most appropriately attributed to:
Soils of Rajasthan: RAS Prelims MCQs
37 RAS Prelims MCQs on the soils of Rajasthan cover the soil types, their districts and properties. Desert sandy soils, alluvial soils of the eastern plains, black soils of Kota and Bundi, the Bhangar and Khadar deposits, the Entisols of USDA taxonomy and the problem of salinity are asked as facts and causes.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
Showing 21–30 of 37 questions
Q22. Match the soil colours (List I) with their primary causative chemical compounds or conditions (List II):
| Soil Colours | Causative Factor |
|---|---|
| A. Deep Black | i. Hydration of iron oxides |
| B. Red | ii. Accumulation of surface salts |
| C. Yellow | iii. Unhydrated ferric oxides |
| D. White/Grey patches | iv. Titaniferous magnetite and clay-humus complex |
Explanation
Soil colors are determined by specific chemical compounds and environmental conditions. Deep black color arises from titaniferous magnetite and clay-humus complexes. Red is caused by unhydrated ferric oxides, whereas yellow results from the hydration of those oxides. White or grey patches on the surface indicate the accumulation of soluble salts, often seen in saline soils due to upward capillary action.
Q23. A farmer in Banswara district is planning his Kharif sowing on well-drained red loam soil. Based on the soil properties, which of the following crops is most conceptually suited and traditionally cultivated in this region?
Explanation
Red loam soils, predominantly found in the Banswara district of southern Rajasthan, are well-drained and suitable for specific crops. Maize is conceptually and traditionally the most suited crop for this region due to the soil’s moisture characteristics and the local climate. While other crops are grown elsewhere, maize remains a staple and a primary Kharif crop in these red-loamed areas.
Q24. Black (Regur) soils in Rajasthan are predominantly found in the:
Explanation
Black soils, also known as Regur soils, are predominantly found in the south-eastern part of Rajasthan, specifically within the Hadoti region. This area includes districts like Kota, Bundi, Baran, and Jhalawar.
Q25. Which of the following statements about the Black soils of the Hadoti region is incorrect?
Explanation
The black soils of the Hadoti region are formed from volcanic basaltic rocks and are rich in calcium carbonate and potash. One of their most significant characteristics is their exceptionally high water-holding capacity, which reduces the frequency of irrigation needed compared to sandy soils. They also exhibit self-ploughing behavior as they shrink and swell, creating deep and characteristic vertical cracks.
Q26. Consider the following soil textural classes found in Rajasthan:
I. Clayey soil
II. Sandy soil
III. Silty soil
IV. Loamy soil
Arrange the above classes in the increasing order of their inherent water retention capacity:
I. Clayey soil
II. Sandy soil
III. Silty soil
IV. Loamy soil
Arrange the above classes in the increasing order of their inherent water retention capacity:
Explanation
The water retention capacity of soil is primarily determined by its texture and pore space. Sandy soils have the lowest retention due to large pores. Loamy soils have intermediate retention, followed by silty soils. Clayey soils, characterized by very fine particles and small pores, possess the highest inherent capacity to hold water, making them the most moisture-retentive among all classes.
Q27. The characteristic shrink-swell behavior of the black soils in the Kota and Bundi districts is primarily due to the dominance of which clay mineral?
Explanation
The shrink-swell behavior characteristic of black soils in Kota and Bundi is caused by the dominance of the montmorillonite clay mineral. This specific type of silicate clay has a lattice structure that expands when water enters the layers and contracts upon drying. This mineralogical property is responsible for the deep cracks and the high plasticity observed in these heavy soils.
Q28. Which of the following pairs of soil type and its highly suitable commercial crop in Rajasthan is incorrectly matched?
Explanation
While black soils are excellent for cotton and soybean, and desert sandy soils support hardy crops like moth bean, the pairing of red loam soil with sugarcane is traditionally incorrect for Rajasthan. Red loams in the south are better suited for maize. Sugarcane typically requires deeper, more fertile alluvial or heavy soils with very high water availability and nutrient levels.
Q29. Saline and alkaline soils in Rajasthan are defined pedologically by the presence of:
Explanation
In Rajasthan, saline and alkaline soils are pedologically defined by the excessive accumulation of soluble salts, including sodium chlorides and sulfates. These salts often form a white crust on the surface. These conditions typically arise in areas with poor drainage and high evaporation rates, leading to chemical imbalances that hinder plant growth and degrade the overall productive capacity of the land.
Q30. Consider the following conditions:
I. Faulty agricultural practices and over-irrigation
II. High rate of evaporation in arid climates
III. Inadequate surface and subsurface drainage
IV. Capillary upward movement of water
V. Heavy application of organic farmyard manure
Which combination of the above contributes significantly to the development of soil salinity in Rajasthan?
I. Faulty agricultural practices and over-irrigation
II. High rate of evaporation in arid climates
III. Inadequate surface and subsurface drainage
IV. Capillary upward movement of water
V. Heavy application of organic farmyard manure
Which combination of the above contributes significantly to the development of soil salinity in Rajasthan?
Explanation
The development of soil salinity in Rajasthan is driven by several presidential factors, including faulty agricultural practices and over-irrigation. High evaporation rates in arid climates cause dissolved salts to rise through capillary action. When coupled with inadequate surface and subsurface drainage, these salts accumulate in the topsoil. While organic manure is beneficial, these other physical and climatic factors are the primary drivers.Answer key for these questions
| Q | Correct answer |
|---|---|
| 21 | (a) The diffusion of iron in crystalline and metamorphic rocks |
| 22 | (a) A-iv, B-iii, C-i, D-ii |
| 23 | (a) Maize |
| 24 | (d) Hadoti region |
| 25 | (c) Highly frequent irrigation needed due to low water retention |
| 26 | (a) II, IV, III, I |
| 27 | (a) Montmorillonite |
| 28 | (b) Red Loam Soil - Sugarcane |
| 29 | (b) Accumulation of soluble salts like sodium chlorides and sulfates |
| 30 | (b) I, II, III, and IV |
Key facts from Soils of Rajasthan
- In the arid west, extreme climate is the dominant factor in soil formation.
- Alluvial soils are most extensive in Bharatpur, Dholpur and Tonk; older alluvium is called Bhangar.
- Desert sandy soils have sandy and loamy sand textures with weak profile development.
- Black soils of Kota and Bundi shrink and swell because of the mineral montmorillonite; deep black soil is found in Jhalawar.
- Entisols occupy the largest area under the USDA soil taxonomy.
- Salts rise to the surface by capillary action and cause salinity.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Soils of Rajasthan?
This page has 37 practice MCQs on Soils of Rajasthan (Rajasthan Geography). Each has the correct answer, and most have an explanation.
Which soil occupies the largest area in Rajasthan?
The Entisols, according to the USDA soil taxonomy. They are young soils with little profile development, typical of sandy desert areas, and they cover the arid west of the State from Jaisalmer and Barmer to Bikaner.
Why do black soils crack and swell?
Because they contain the clay mineral montmorillonite, which expands when wet and shrinks when dry. This gives the black soils of Kota and Bundi their deep cracks in summer.
What is Bhangar?
The older alluvial deposits of the eastern plains, found on higher terraces above the flood level. The newer flood-plain deposits are called Khadar, and the two are used to describe the alluvial plains of north India.