Soil Science

Correct Answer: (A) - (iii), (B) - (iv), (C) - (ii), (D) - (i)

Black soil (regur) has high moisture retention capacity due to its fine texture and clay content. Cotton requires consistent moisture, especially during its long growing season, making black soil ideal for its cultivation. Options B and C describe formation and location but don't explain why it's suitable for cotton.

Red soil is typically well-drained, porous, and less fertile than alluvial soil. It's ideal for drought-resistant coarse cereals like jowar (sorghum) and bajra (pearl millet) that require less water. Rice and wheat need fertile, water-retentive soil; pea and cotton need different conditions; cotton and tea are not commonly grown together on red soil.

Chemical weathering requires water to dissolve, react with, and transform minerals. Humid tropical regions have constant high temperatures and abundant rainfall year-round, creating ideal conditions for rapid chemical weathering. The combination of moisture and heat accelerates chemical reactions that break down rocks. Arid regions lack sufficient water, while semi-arid and Mediterranean regions have seasonal dry periods that limit continuous chemical weathering.

Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock.

Soil texture is given after the soil formation and it is not a factor of formation of soil.

Alluvial soil is formed by accumulated sediments transferred by the rivers and rapids, so it is amongst the most fertile soils. Alluvial soils are well suited to irrigation which helps in raising a number of crops like rice, jute, sugarcane, wheat, cotton, maize, oil seeds, fruits and vegeta­bles.

Red soil, black soil, and peaty soil are all associated with tropical or subtropical regions (red and black soils are typical of tropical India, peaty soils form in tropical wetlands). Brown soil, however, is typically associated with temperate regions (like brown forest soils in Europe and North America), not tropical climates.

Laterite soil is formed in hot, wet tropical areas through intensive leaching - heavy rainfall washes away soluble minerals like silica and lime, leaving behind insoluble iron and aluminum oxides. This gives laterite its characteristic red/orange color. Black soil (regur) is a volcanic soil rich in clay, not formed through leaching.

Loess is a wind-deposited soil - it's composed of fine silt and dust particles carried by wind and deposited over large areas. Unlike alluvial (water-deposited) or glacial soils, loess forms from aeolian (wind) processes. This creates its characteristic homogeneous, loosely packed structure.

Alluvial soil is primarily found in river valleys and coastal plains. Among the options, Gujarat has extensive alluvial soil in the Narmada and Tapi valleys, Kerala has coastal alluvium, and Orissa has alluvial deposits in the Mahanadi and other river deltas. Maharashtra, while having some alluvial soil along coastal areas and river valleys, is predominantly known for Deccan basalt (black cotton soil) and red soil, making it the correct answer as the exception.

According to soil surveys of India, alluvial soils cover approximately 43% of India's total area - the largest coverage. Red soils cover about 18%, black cotton soils around 17%, and laterite soils only 8%. The descending order of areal coverage is therefore: alluvial > black > red > laterite, which matches option A.

Correct answer is (4). 

This question asks for the INCORRECT statement about black soil. Options A, C, and D are correct facts about black soil. Option B is incorrect because black soil (regur) is ideal for cotton, not sugarcane - sugarcane grows better in alluvial or well-drained soils. Therefore, B is the statement that is 'not correct'.