CBSE Class 11 Geography Chapter 6: Soils NCERT Solutions

Solution: The most widespread and highly productive category of soil is Alluvial Soil. This is because alluvial soils are formed by the deposition of silt by rivers, making them rich in nutrients and suitable for a wide range of crops. They are found in vast plains and river valleys across India, contributing significantly to the country's agricultural output.

Solution: 'Regur Soil' is another name for Black Soil. This type of soil is predominantly found in the Deccan Plateau and is known for its high clay content, deep black colour, and excellent moisture-retention properties, making it ideal for growing cotton and other crops.

Solution: The main reason for the loss of topsoil in India is water erosion. Heavy rainfall, particularly in areas with steep slopes or inadequate vegetation cover, can wash away the fertile top layer of the soil, leading to significant land degradation and reduced agricultural productivity.

Solution: Arable land in irrigated zones of India is turning saline primarily due to over irrigation. When excessive water is applied, it raises the water table. As this water evaporates from the surface, it leaves behind dissolved salts, leading to the accumulation of salts in the topsoil and making it saline.

Solution: Soil is a complex and dynamic mixture that forms the uppermost layer of the Earth's crust. It is composed of disintegrated rock particles, organic matter (humus), water, air, and a vast array of living organisms. This intricate composition provides the medium for plant growth and supports terrestrial ecosystems.

Solution: The formation of soil is a complex process influenced by several key factors. These include:

1. Parent Material: The type of rock or deposit from which the soil develops.
2. Climate: Temperature and precipitation influence weathering and decomposition rates.
3. Topography (Relief): Slope and aspect affect drainage, erosion, and soil depth.
4. Vegetation and Other Life-forms: Organic matter addition and soil structure development.
5. Time: The longer the soil has been developing, the deeper and more mature it becomes.

Human activities can also significantly alter soil formation processes.

Solution: A soil profile is a vertical section through the soil, revealing its different layers or horizons. The three main horizons are:

1. Horizon A (Topsoil): This is the uppermost layer, rich in organic matter and minerals. It is the most fertile part of the soil and is crucial for plant growth as it contains essential nutrients and water.
2. Horizon B (Subsoil): Located below Horizon A, this layer contains accumulated minerals (like clay and iron oxides) that have leached down from the topsoil. It also receives some organic matter from above.
3. Horizon C (Parent Material): This layer consists of partially weathered parent rock material from which the soil has formed. It is less developed than the horizons above it.

Solution: Soil degradation refers to the decline in the quality and productivity of soil. This deterioration occurs due to various factors, primarily improper land use practices such as intensive agriculture, overgrazing, deforestation, and unsustainable industrial and infrastructural development. These activities can lead to loss of topsoil, reduced fertility, increased erosion, and salinization.

Solution: Khadar and Bhangar are two types of alluvial soils found in the riverine plains:

• Khadar: This is the newer, younger alluvium deposited by rivers during their annual floods. It is characterized by a fine silt texture and is highly fertile, making it ideal for intensive cultivation.
• Bhangar: This represents the older, older alluvium deposited by the rivers in the past, typically found on higher terraces away from the present floodplains. Bhangar soils are generally less fertile than Khadar and often contain 'Kankars' (calcareous concretions).

Solution: Black soils, also known as 'Regur Soil' or 'Black Cotton Soil', are a significant soil type found predominantly across the Deccan Plateau, covering areas in Maharashtra, Chhattisgarh, Gujarat, Madhya Pradesh, Telangana, and Andhra Pradesh.

Formation: These soils are believed to have formed from the weathering of volcanic rocks and lava flows. The parent material is typically basaltic rock.

Characteristics:

Composition: They are rich in minerals like lime, iron, magnesium, and potash, but are generally deficient in phosphorus, nitrogen, and organic matter.

Texture: Black soils are characteristically clayey, deep, and impermeable, meaning water does not easily pass through them.

Moisture Retention: They possess a remarkable ability to retain moisture for extended periods, even through dry seasons, which is beneficial for certain crops.

Colour: The colour ranges from deep black to grey, depending on the mineral content and degree of weathering.

Fertility: Despite some nutrient deficiencies, their moisture-retention capacity and mineral content make them highly suitable for growing cotton and other crops like groundnuts, tobacco, and millets.