Soil Types of India — Set 9
Indian Agriculture · भारत की मृदा प्रकार · Questions 81–90 of 160
Soil formed at the original site of rock weathering without transportation is called:
Correct Answer: B. Residual soil (in situ soil)
Residual soil, also called in situ soil, is formed directly from the weathering of underlying bedrock at the same location without any transportation. Black soil (Regur) in the Deccan Trap region is a good example of residual soil formed from basalt. In contrast, transported soils are formed from material carried and deposited by agents like water, wind, or glaciers. Red soils developed from weathered igneous rocks in peninsular India are also largely residual soils.
Which soils in India are formed by transported material deposited by rivers?
Correct Answer: C. Alluvial soil
Alluvial soils are classic examples of transported soils, formed from sediments carried and deposited by rivers. Rivers like the Ganga, Yamuna, Brahmaputra, Indus, and their tributaries transport eroded material from the Himalayas and the upper catchment areas. This material is deposited in the plains, delta regions, and river valleys. The thickness of alluvial deposits in the Indo-Gangetic plains can reach several thousand feet.
Which of the following soils is formed by wind-transported material (aeolian deposits)?
Correct Answer: C. Desert/Arid soil
Desert or Arid soil in Rajasthan is primarily formed from wind-transported (aeolian) material deposited over time. Strong winds carry sand and dust particles from one place to another, depositing them in the Thar Desert region. These aeolian deposits form the sandy, low-organic soils of Rajasthan and parts of Gujarat and Haryana. The Loess soils found in some parts of India are also of aeolian origin.
What is the primary cause of Saline/Alkaline soil formation in India's canal command areas?
Correct Answer: C. Over-irrigation leading to waterlogging and capillary rise of salts
In canal command areas, over-irrigation without adequate drainage leads to waterlogging. As the waterlogged soil dries, capillary action brings dissolved salts from the groundwater upward to the surface, where they concentrate and form a salt crust. This process is called secondary salinization and is a major problem in Punjab, Haryana, and Uttar Pradesh. Proper drainage infrastructure and controlled irrigation are needed to prevent waterlogging-induced salinity.
What does 'soil texture' refer to?
Correct Answer: B. The relative proportion of sand, silt, and clay particles in the soil
Soil texture refers to the relative proportion of different-sized mineral particles (sand, silt, and clay) in the soil. Sand particles are the largest (0.05-2 mm), silt particles are medium-sized (0.002-0.05 mm), and clay particles are the smallest (less than 0.002 mm). Soil texture determines water retention, drainage, aeration, and nutrient-holding capacity. Loam soil has roughly equal proportions of sand, silt, and clay, making it ideal for most crops.
Why is sandy soil not ideal for most crops despite being easy to till?
Correct Answer: B. It has low water and nutrient-holding capacity due to large particles and pores
Sandy soil is not ideal for most crops because its large particles create large pores that allow water and dissolved nutrients to drain away rapidly. This results in low water-holding capacity and frequent leaching of nutrients. Plants in sandy soil face drought stress even after rain. However, sandy soil is well-aerated and easy to work, and with drip irrigation and regular fertilization, it can support some crops like groundnut and watermelon.
The Deccan Trap region primarily has which type of geological formation?
Correct Answer: C. Volcanic basalt
The Deccan Trap region in peninsular India is dominated by volcanic basalt, which is the parent rock from which Black (Regur) soil has formed. The Deccan Traps were formed by massive volcanic eruptions about 65-68 million years ago at the end of the Cretaceous period. The lava flows solidified into layers of basalt that now underlie much of Maharashtra, Madhya Pradesh, Karnataka, and Andhra Pradesh. Weathering of this basalt over millions of years produced the fertile Black soil.
Which Indian state has the highest proportion of its area under Black soil?
Correct Answer: B. Maharashtra
Maharashtra has the highest proportion of its area under Black soil in India. The Deccan Plateau of Maharashtra, formed from ancient volcanic basalt, has extensive Black soil cover that is highly suitable for cotton, soybean, jowar, and other crops. Maharashtra is also the largest producer of cotton in India, which directly correlates with the dominance of Black soil. Vidarbha and Marathwada regions of Maharashtra are entirely on Black soil.
The Indira Gandhi Canal has transformed the desert soil of which state into productive agricultural land?
Correct Answer: C. Rajasthan
The Indira Gandhi Canal (formerly Rajasthan Canal) has transformed vast areas of Desert soil in Rajasthan into productive agricultural land. The canal brings water from the Harike Barrage in Punjab to the arid Thar Desert region of Rajasthan. With irrigation, the sandy Desert soil of Rajasthan now supports wheat, cotton, mustard, and even paddy cultivation. This transformation is one of the most significant examples of land reclamation in independent India.
What is the soil pH of Black (Regur) soil generally?
Correct Answer: C. Neutral to slightly alkaline (pH 7-8)
Black soil (Regur) is generally neutral to slightly alkaline in reaction, with pH typically ranging from 7 to 8. The presence of calcium carbonate (lime) and other basic minerals from the volcanic basalt parent rock maintains the alkaline to neutral character. This pH range is suitable for most kharif crops like cotton, soybean, and jowar. However, the alkaline pH can limit the availability of some micronutrients.