Soils

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.

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.

Mulching involves covering soil with organic material or plastic to conserve moisture, suppress weeds, and protect soil structure - it actually PREVENTS soil erosion rather than causing it. Excessive ploughing loosens topsoil making it vulnerable, overgrazing removes vegetation cover, and contour ploughing is a protective measure. Therefore, mulching is the action that does not cause soil erosion.

Reh or Kallar refers to saline and alkaline soils that contain excess salts, rendering the land infertile and resulting in sparse or absent vegetation. Bhangar and Khadar are fertile alluvial soils.

Correct Answer: animal husbandry

Contour trenching involves digging pits or trenches along the contour lines of a slope. These trenches accumulate runoff water, allowing it to infiltrate the soil rather than flowing down the slope and causing erosion. Bench terracing creates level platforms, contour terracing follows contours, and leveling creates flat surfaces - but specifically digging pits on slopes for runoff accumulation is contour trenching.

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.

Heavy grazing affects soil at multiple levels: it loosens and exposes upper soil layers to erosion (option A), compacts lower layers making them impermeable and hard for roots (option B), and these compacted layers prevent proper root penetration (option C). Since all three effects occur simultaneously due to heavy grazing, option D 'All of the above' is the correct answer.

pH measures the concentration of hydrogen ions (H+) in a solution, including soil. A lower pH indicates higher acidity (more H+ ions), while higher pH means more alkaline (fewer H+ ions). Options A, B, and C are incorrect because pH is not about phosphorus, percentage of hydrogen, or potash content.

Soil erosion in India is caused by multiple human activities and natural factors. Deforestation (2) removes vegetation that holds soil, while overgrazing (4) destroys protective grass cover and compacts soil. Excessive rainfall (1) can accelerate erosion, and excessive cultivation (3) depletes soil structure. The combination of factors 2 and 4 represents major anthropogenic causes.

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'.

Correct Answer: Both (A) and (R) are true, and (R) is the correct explanation of (A).
The tarai soils are rich in nitrogen and organic matter, but are deficient in phosphate. These soils are generally covered by tall grasses and forests, but are suitable for a number of crops, such as wheat, rice, sugarcane, jute and soyabean under reclaimed conditions.

The most effective crop in controlling soil erosion is pigeon pea.