Soil Science

This is the correct answer as snow on mountain soils causes them to become acidic with a low humus content.

This is the correct answer. After adopting appropriate soil conservation techniques, particularly in the hilly areas of Karnataka, Kerala and Tamil Nadu, laterite soil is very useful for growing tea and coffee.

This is the correct answer. Black soil is made up of lava flows. Parent rock material and climatic conditions are responsible for this type of soil. It is found in the Deccan trap region of the Deccan plateau.

Red soils develop their characteristic reddish color due to wide diffusion of iron in ancient crystalline and metamorphic rocks, which oxidizes to form iron oxides. While tropical conditions contribute to the weathering process, the red color itself specifically comes from iron content, not from potash, magnesia, or deforestation.

The Indo-Gangetic plains have alluvial soil deposited by the Indus and Ganges river systems over millennia. Alluvial soils are fertile, deep, and ideal for agriculture. While some areas have loam or sandy loam textures, 'alluvial' is the definitive soil type of this region.

Playas are the most common desert landform - flat, dust-filled basins formed by evaporated lakes in arid regions. While sand dunes (barchans, seifs) are iconic, they cover smaller areas. Pediments are concave surfaces at mountain bases, pediplains are broader erosional surfaces. Playas dominate deserts like the Great Basin (USA) and Rajasthan (India), forming through repeated wet-dry cycles where water accumulates temporarily then evaporates completely.

Topography, climate, biological activity, time and parent material are the controlling factors for the formation of soil.

Sandy soil has large particles with large pore spaces, allowing water to drain quickly through gravity. This results in poor water-holding capacity. In contrast, clay and silt have smaller particles that retain water effectively.

There are five factors for soil formation – parent material, time, climate, biota and relief/topography. Among these factors, climate and biota are called the active agents because they act on the rest of the three factors, which are called ‘passive agents’ for the formation of soil.

‘Soil profile’ is a vertical section of the earth's crust showing the different horizons or layers. Soil profile consists of various layers of soil; horizons A, B, and C. ‘Horizon A’ refers to the upper layer of soil nearest to the surface. The layer below horizon A, of course, has to be horizon B. Litter is not present in horizon B and therefore, there is much less humus. Horizon C must be below horizon B. Horizon C consists mostly of weathered big rocks. It must be understood that ‘soil profile’ does not include the ‘bedrock’, which is non-weathered.

Grey desert soil is also called sierozem and it is the typical soil of the mid-latitude desert regions. Due to lack of the natural vegetation in these regions of dry climate, the grey desert soil is phenomenally poor in humus. Red desert soil is a characteristic of still more arid regions, and their colour ranges from pale reddish grey to deep red. The humus content reaches its lowest possible limits and the role of plants as soil formers is also reduced to the minimum. Chernozem soil is the most widespread among all zonal soils of the semi-arid climate. It is rich in humus. Chestnut soil lies on the arid side of the chernozem soils. It is lighter in colour and contains less amount of humus.

Loam is soil composed of sand, silt and clay in relatively even concentration (about 40-40-20% concentration respectively). It is considered ideal for gardening and agricultural uses. Loam soils generally contain more nutrients and humus than sandy soils, which have better infiltration and drainage than silty soils and are easier to till than clay soils.

The soils of the Indo-Gangetic plains are primarily alluvial in texture, deposited by the Indus and Ganges river systems over thousands of years. These soils are deep, fertile, and well-suited for agriculture. While they may contain loamy or sandy loam components, their fundamental classification is alluvial.

Clay soil has the smallest particle size among soil types (less than 0.002mm), resulting in very tiny pore spaces between particles. This compact structure makes it the least porous and poorly aerated. Loam is moderately porous, peaty soil has high porosity due to organic matter, and chalky soil has moderate porosity. Clay's low porosity also explains its poor drainage and high water-holding capacity.