Soils

Alluvial soils vary in nature from sandy loam to clay. They are generally

[amp_mcq option1=”poor in potash and rich in phosphorus.” option2=”poor in both potash and phosphorus.” option3=”rich in both potash and phosphorus.” option4=”rich in potash and poor in phosphorus.” correct=”option4″]

Alluvial soils are formed by the deposition of silt, sand, and clay by rivers. They are generally fertile but tend to be rich in potash and lime, while being poor in phosphorus and nitrogen. The statement “rich in potash and poor in phosphorus” accurately describes a common characteristic of these soils.

– Alluvial soils are widespread in river valleys and deltaic regions.
– Their texture varies from sandy loam to clay.

The deficiency in nitrogen and phosphorus in alluvial soils often necessitates the use of fertilizers for optimal crop production, particularly for intensive agriculture practiced in these fertile plains. The presence of adequate potash and lime contributes to their overall fertility.

Identify the type of soil on the basis of the given characteristics :
1. They are rich in lime, iron, magnesia and alumina.
2. They are generally clayey, deep and impermeable.
3. They are mainly found in Maharashtra, Madhya Pradesh and Gujarat.

[amp_mcq option1=”Laterite soil” option2=”Red and yellow soil” option3=”Saline soil” option4=”Black soil” correct=”option4″]

The correct answer is D) Black soil. The characteristics provided – richness in lime, iron, magnesia, and alumina; generally clayey, deep, and impermeable nature; and prominent presence in regions like Maharashtra, Madhya Pradesh, and Gujarat – are definitive features of Black soils (also known as Regur soils), which are largely derived from Deccan Trap lava rocks.

Black soil is characterized by its high clay content, moisture-retentive capacity, and common occurrence in the Deccan Plateau region of India, particularly Maharashtra, MP, Gujarat, and parts of Karnataka and Andhra Pradesh.

Black soil is highly suitable for growing cotton, hence also called ‘black cotton soil’. It develops deep cracks during the dry season, aiding in aeration, a phenomenon called ‘self- ploughing’.

Which one of the following soils is characterized by very high content of organic matter?

[amp_mcq option1=”Vertisol” option2=”Histosol” option3=”Gelisol” option4=”Spodosol” correct=”option2″]

The correct answer is B) Histosol.

Soil taxonomy classifies soils based on their properties. Histosols are a soil order characterized by a very high content of organic matter, typically formed in saturated or anaerobic conditions like wetlands, bogs, and swamps where the decomposition of organic material is slow. Vertisols are clayey soils that shrink and swell significantly with changes in moisture content. Gelisols are soils of very cold climates that contain permafrost within 100 cm of the surface or exhibit evidence of cryoturbation. Spodosols are acidic soils common in coniferous or mixed forests, characterized by the accumulation of organic matter, aluminum, and/or iron in subsurface horizons, but they are not primarily composed of organic matter like Histosols.

Histosols are also known by common names such as peats and mucks. They are very fertile when drained, but drainage can lead to subsidence and oxidation of the organic matter, releasing carbon dioxide.

Consider the following statements regarding laterite soils of India :

• 1. Laterite soils are generally red in colour
• 2. Laterite soils are rich in nitrogen and potash
• 3. Laterite soils are well developed in Rajasthan and UP
• 4. Tapioca and cashew nuts grow well in this soil

Which of the statements given above is / are correct?

[amp_mcq option1=”1 only” option2=”2, 3 and 4″ option3=”1 and 4 only” option4=”1, 2 and 4″ correct=”option3″]

The correct option is C) 1 and 4 only.

Let’s evaluate each statement about laterite soils:
1. Laterite soils are generally red in colour: Correct. They are reddish-brown due to the presence of iron oxides.
2. Laterite soils are rich in nitrogen and potash: Incorrect. Laterite soils are typically poor in nitrogen, potash, phosphorus, lime, and organic matter due to intense leaching of bases in areas with high rainfall and high temperatures. They are rich in iron and aluminium oxides.
3. Laterite soils are well developed in Rajasthan and UP: Incorrect. Laterite soils are primarily found in areas with high rainfall and alternating wet and dry periods, which promote leaching. They are well developed in the Western Ghats, Eastern Ghats, parts of Odisha, West Bengal, Karnataka, Kerala, Assam, and Meghalaya. Rajasthan and UP are generally not areas where laterite soils are widespread.
4. Tapioca and cashew nuts grow well in this soil: Correct. Despite being infertile for most crops due to leaching, laterite soils, with proper management like irrigation and fertilization, are suitable for specific crops such as cashew nuts, tapioca, coffee, tea, and rubber.

Laterite soils are residual soils formed by intense leaching (laterization) under specific climatic conditions. They harden irreversibly when exposed to air, making them useful as building material (laterite bricks). Their low fertility is a major challenge for agriculture, requiring specific cultivation practices and crop selection.