Soil Science

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

The Northern Plains of India are formed by alluvial deposits from the Himalayan river systems over millennia. These plains contain extensive alluvial soil brought down by rivers like the Ganga, Brahmaputra, and their tributaries. Red soil (A) is found in peninsular India, black soil (B) in Deccan, and 'regular soil' (C) is not a standard soil classification.

Terracing creates stepped levels on slopes, reducing water flow speed and preventing soil washout. This is highly effective in hilly areas (B) where steep gradients make soil vulnerable to erosion. Deserts (A) lack rainfall for significant erosion, plains (C) have minimal slope, and riverine areas (D) require different conservation methods like embankments.

India's eastern coast, particularly regions like Odisha, Andhra Pradesh, and Tamil Nadu, has significant laterite soil deposits. Laterite forms in areas with high rainfall and alternating wet-dry conditions. Black soil (A) is found in Deccan, alluvial (B) in plains, and 'red rocky' (C) is not standard terminology - the correct term is laterite for these regions.

Western Rajasthan's arid soils have high calcium carbonate content due to low rainfall which prevents leaching. The desert conditions lead to calcium accumulation. Phosphorus (A) is typically deficient in these soils, nitrogen (B) is low in desert soils, and aluminum (D) is more associated with acidic laterite soils, not arid regions.

Correct Answer: Tamil Nadu and Andhra Pradesh

Red-yellow soils are typically found in areas with moderate rainfall and are associated with the Deccan Plateau region covering parts of Rajasthan and Madhya Pradesh, among other states. These soils form from weathering of granite rocks under distinct climatic conditions. UP-Bihar (A) has alluvial soils, and West Bengal-Bihar (C) also has alluvial and deltaic soils.

Yes, it is correct. Earthworms are known as ‘friends of farmers’ because they make burrows in the soil and make it porous which helps in respiration and penetration of the developing plant roots.

Soil is the uppermost layer of the Earth's crust that supports plant life. It forms from the weathering of rocks and contains organic matter, minerals, air, and water. The deepest layer is bedrock, and there's no distinct 'mid layer' terminology in basic soil science.

Loamy soil is a balanced mixture of sand, silt, and clay with abundant organic matter (humus). Sandy soil has large particles with low humus retention. Clayey soil has fine particles but can become compacted. Loam's balanced composition makes it ideal for humus accumulation and plant growth.

Sandy soil has large particles with large pore spaces, which allows water to drain quickly rather than being retained. This low water-holding capacity is the main disadvantage. The other options describe advantages or neutral characteristics of sandy soil.

Sandy soil, particularly in the form of loess, is commonly transported and deposited by wind. This creates wind-borne deposits found in many parts of the world. Alluvial soil is water-deposited, colonial soil is not a standard classification, and glacial soil is deposited by glaciers.

Soil horizons are designated O (organic), A (topsoil), E (eluviated), B (subsoil), C (parent material), and R (bedrock). The R-horizon consists of unweathered bedrock that underlies all other soil layers. It is not soil but consolidated rock.

Topsoil (A-horizon) is the most fertile layer because it contains the highest concentration of organic matter, humus, nutrients, and biological activity. Subsoil (B-horizon) has less organic material. Bedrock and parent rock are unweathered or partially weathered rock with minimal fertility.

Topsoil is characterized by high organic content, including humus - the dark, organic material formed from decomposed plant and animal matter. It is softer, less compact, contains more living organisms, and is more fertile than subsoil. Option C correctly identifies this key feature.