Soil Types of India — Set 2

Correct Answer: B. Iron oxide (ferric oxide)

Red soil gets its characteristic red colour due to the presence of iron oxide (ferric oxide or Fe2O3) in the soil. When iron-bearing rocks weather under oxidizing conditions, iron oxidizes and gives the soil its red colour. The higher the iron oxide content, the deeper the red colour. In some areas, the topsoil appears yellowish because iron is in its hydrated form.

Correct Answer: C. Igneous and metamorphic rocks

Red soil is formed by the weathering of ancient igneous and metamorphic crystalline rocks. These rocks, which are rich in iron minerals, undergo chemical weathering to form the red-coloured soil. The process is slow and occurs under hot, dry conditions with alternating wet and dry periods. The red soil is found mainly in peninsular India where such old crystalline rocks are exposed.

Correct Answer: C. Tamil Nadu

Tamil Nadu has one of the largest areas under Red soil in India, particularly in the non-delta regions of the state. Red soil is also found extensively in Andhra Pradesh, Karnataka, Odisha, and Jharkhand. The soil is suitable for crops like millets, groundnut, and tobacco. Despite its wide distribution, Red soil is generally less fertile than alluvial and Black soils.

Correct Answer: B. Nitrogen, Phosphorus, and Humus

Red soil is generally deficient in nitrogen, phosphorus, and humus, which limits its natural fertility. The soil tends to be porous and lacks the ability to retain moisture and organic matter. Despite being deficient in these key nutrients, Red soil can be made productive with the addition of fertilizers and proper irrigation. It responds well to intensive farming practices.

Correct Answer: B. Millets, groundnut, and tobacco

Millets (jowar, bajra, ragi), groundnut, and tobacco are most suitable for Red soil because they are drought-tolerant crops. Red soil, despite low fertility, supports these crops under rainfed conditions. Groundnut in particular thrives in the light, well-drained Red soil of Andhra Pradesh and Karnataka. With irrigation and fertilizers, Red soil can also support cotton and pulses.

Correct Answer: B. A soil formed by leaching of silica and accumulation of iron and aluminium oxides

Laterite soil is formed by the process of laterization or intense leaching, where heavy rainfall dissolves and washes away silica and other soluble minerals from the soil. What remains is a soil rich in iron and aluminium oxides, giving it a brick-red colour. The name 'laterite' comes from the Latin word 'later' meaning brick, as this soil hardens on exposure to air. It is typical of humid tropical regions with alternating wet and dry seasons.

Correct Answer: B. Tea, coffee, cashew, and rubber

Tea, coffee, cashew, and rubber are best suited for Laterite soil because they are perennial plantation crops that can tolerate acidic and iron-rich conditions. Laterite soil is acidic and low in nitrogen, phosphorus, and potassium, making it unsuitable for food crops without heavy fertilization. Kerala, Karnataka, and Tamil Nadu grow tea and coffee on Laterite soil. Cashew nut cultivation thrives especially on the laterite soils of the coastal plains.

Correct Answer: B. Kerala, Karnataka, Tamil Nadu, Assam, and Odisha

Laterite soil is predominantly found in Kerala, Karnataka, Tamil Nadu, Assam, Odisha, and parts of Meghalaya and Mizoram. These regions experience high rainfall during the monsoon followed by a dry period, which is the ideal climate for laterization to occur. The Western Ghats and the northeastern hills are major Laterite soil zones. In some areas, the hard laterite rock is quarried and used as building material.

Correct Answer: C. Arid/Desert soil

Arid or Desert soil is found in the Thar Desert region of Rajasthan and extends into parts of Gujarat and Haryana. This soil is sandy, low in moisture, and has very little organic matter and humus. It is, however, relatively rich in soluble salts and phosphates. With proper irrigation, as seen in the Indira Gandhi Canal command area, Desert soil can be made productive for crops like wheat and cotton.

Correct Answer: C. Phosphate

Arid or Desert soil is naturally rich in phosphate, which is unusual given its low overall fertility. The lack of rainfall prevents the leaching of phosphates, so they accumulate in the soil. However, the soil lacks nitrogen, humus, and organic matter due to sparse vegetation. With irrigation and nitrogen fertilizers, this soil can support crops in arid regions.