Soils of India: Types, Distribution, Erosion and PYQs

The correct answer is D, alluvial. A delta is built out of silt that a river carries down and drops where it meets the sea, so deltaic land is alluvial by definition, and the eastern coastal deltas of the Mahanadi, Godavari, Krishna and Kaveri are among the most fertile rice tracts of the country. Option A is wrong because black soil is a residual soil formed in place by the weathering of the Deccan lava and is found on the plateau, not in the deltas, although the same rivers flow across it upstream. Option B is wrong because arid soil belongs to the dry west, chiefly western Rajasthan, where rainfall is low and the soil is sandy and saline. Option C is wrong because forest soil forms on hill slopes and in valleys under a cover of trees, not on a coastal plain.

The correct answer is B, because black soil is poor in phosphoric acid, nitrogen and organic matter, not rich in them. What it is rich in is calcium carbonate, magnesium, potash and lime, and remembering that short list is the safest way to answer any statement question on this soil. Option A is a correct statement, since black soil formed from the weathering of the lava of the Deccan trap and its main belt lies over Maharashtra, Madhya Pradesh, Gujarat and Chhattisgarh. Option C is a correct statement, because the fine clayey texture of the soil lets it hold moisture through the dry months, which is exactly why cotton grows on it without irrigation. Option D is a correct statement, because the soil shrinks in the heat and opens deep cracks that let air into the lower layers, giving it the name self-ploughing soil.

The correct answer is C, sheet erosion. In sheet erosion water spreads over a wide slope and carries away a thin, even film of topsoil, so nothing obvious is left behind to see, and the loss is noticed only years later as falling yields. That invisibility is what makes it the most dangerous form for farmers. Option A is wrong because gully erosion cuts visible channels down a slope, deep enough to stop a plough. Option B is wrong because a landslide is a sudden and highly visible mass movement of rock and soil down a hillside. Option D is wrong because ravines are gullies that have widened and deepened over a large area, producing the badland of the Chambal valley, which is visible even from the air. The order of visibility runs from sheet erosion at the least to landslides at the most.

The correct answer is D, weathering. Weathering is the natural breaking down of rock by temperature, water, wind and living things, and it is the process that makes soil in the first place; it is not a technique that a farmer applies to save soil, so it cannot be a conservation method. Option A is wrong as an answer because intercropping, growing two crops together in alternate rows, keeps the ground covered through the season and reduces the impact of rain on bare soil. Option B is wrong as an answer because mulching covers the bare ground between plants with straw or crop residue, which cuts evaporation and stops the topsoil from being washed or blown away. Option C is wrong as an answer because contour ploughing runs furrows across the slope instead of down it, so each furrow acts as a small barrier to running water.

The correct answer is C, the right mix of minerals and organic matter. Fertility needs mineral nutrients such as nitrogen, phosphorus and potassium from the weathered rock, and organic matter, that is humus from decayed plants and animals, which holds water, feeds soil organisms and releases nutrients slowly. Option A is wrong because an excess of acid lowers the availability of nutrients and harms root growth, which is why lime is added to strongly acidic fields. Option B is wrong because it leaves out organic matter and mentions only inorganic material; a soil of pure mineral grains, such as desert sand, is not fertile however rich its minerals. Option D is wrong because high salt content is the mark of saline or usar land, which is among the least productive soil in the country and has to be reclaimed with gypsum and drainage before it can be cropped.

The correct answer is B, black soil. Black soil, called regur, formed from the lava of the Deccan trap and is so closely tied to this one crop that it is popularly called black cotton soil. Its fine clayey texture holds moisture deep in the profile, so the crop survives the long dry spell between showers without irrigation. Option A is wrong because laterite soil is leached of lime and silica and is poor in organic matter and nitrogen; it carries plantation crops such as tea, coffee and cashew on hill slopes rather than cotton. Option C is wrong because arid soil is sandy, saline and low in humus and needs irrigation even for bajra and barley. Option D is wrong because peaty soil is waterlogged and highly organic, found in Kuttanad in Kerala and coastal Odisha, and is used mainly for rice.

The correct answer is C, bhangar. Bhangar is the older alluvium of the northern plains, lying above the flood level on slightly raised terraces, coarser in texture and marked by nodules of calcium carbonate known as kankar, which lower its fertility and hinder the movement of water. Option A is wrong because khadar is exactly the opposite, the newer alluvium of the active floodplain, finer in texture, renewed by fresh silt at every flood and therefore more fertile. Option B is wrong because regur is another name for black soil of the Deccan lava region and is not an alluvial deposit at all. Option D is wrong because usar is the popular name for saline and alkaline land, which carries an excess of sodium and other salts and has to be treated with gypsum before it can be cultivated.

The correct answer is B, tea, coffee and cashew. Laterite soil forms on hill slopes of Karnataka, Kerala, Tamil Nadu, Odisha and Assam under heavy rain and high temperature, and after manuring it carries these plantation crops well; cashew in particular does well on the laterite of the Kerala and Karnataka coast. Option A is wrong because wheat and sugarcane belong to the deep alluvial soil of the northern plains, which holds more nitrogen-fixing humus once manured and has assured irrigation. Option C is wrong because cotton and jowar belong to the black soil of the Deccan trap. Option D is wrong because rice and jute need soil that holds standing water and a large supply of silt, which is the alluvial and deltaic land of the Ganga and Brahmaputra plains rather than the leached slopes where laterite forms.

The correct answer is A, gypsum. Gypsum, that is calcium sulphate, supplies calcium that replaces the sodium held on the soil particles, and once the sodium is set free it can be washed out of the field by irrigation and drainage, restoring structure to land that had become hard and impermeable. Option B is wrong because urea is a nitrogen fertiliser that feeds the crop but does nothing about the excess sodium, and heavy use of it can even worsen the reaction of the soil. Option C is wrong because common salt is itself the problem in such land, since saline soil already carries too much sodium chloride and other salts. Option D is wrong because lime is used the other way round, to correct soil that is too acidic, for example the leached laterite and hill soils of the high-rainfall belt.

The correct answer is C, badland topography. Running water cuts gullies in the soft alluvium of the Chambal basin, and where those gullies deepen and spread over a wide tract the land becomes a maze of steep channels and ridges unfit for cultivation, which geographers call badland and local people call the ravines or beehad. Option A is wrong because wind erosion, which works by lifting and rolling loose sand, dominates in the dry west of Rajasthan rather than in this river valley. Option B is wrong because sheet erosion removes a thin even film of soil and leaves no visible channels, the opposite of what the Chambal shows. Option D is wrong because waterlogging is the rise of the water table in canal-irrigated flat land, which brings salts to the surface and is a problem of Punjab, Haryana and western Uttar Pradesh.

The correct answer is A, Nagpur. The National Bureau of Soil Survey and Land Use Planning, an institute of the Indian Council of Agricultural Research, works from Nagpur and prepares the soil maps and land capability surveys on which district planning rests. Option B is wrong because Dehradun is the home of the Forest Research Institute and of the Survey of India, both important but concerned with forests and with topographical mapping rather than with soil. Option C is wrong because Hyderabad houses the National Institute of Rural Development and the Indian Institute of Millets Research, and is not the soil survey bureau. Option D is wrong because Karnal is known for the Central Soil Salinity Research Institute and the National Dairy Research Institute; salinity research there is a narrower field than the national soil survey.