Soil Types of India — Set 12

Correct Answer: C. They decompose organic matter and recycle nutrients, making them available for plants

Soil microorganisms, including bacteria, fungi, actinomycetes, and algae, play a critical role in soil fertility by decomposing organic matter and recycling nutrients. Through the process of mineralization, they convert complex organic compounds into simple mineral nutrients that plants can absorb. Nitrogen-fixing bacteria (like Rhizobium) convert atmospheric nitrogen into plant-available forms. Mycorrhizal fungi enhance plant nutrient and water uptake from the soil.

Correct Answer: C. To check for deficiencies in nutrients like zinc, boron, iron, and manganese which affect crop yields

The Soil Health Card Scheme tests for micronutrient deficiencies such as zinc, boron, iron, manganese, copper, and molybdenum, which are often overlooked but critical for crop production and quality. Zinc deficiency in particular is widespread in Indian soils and affects crop yields significantly. Boron deficiency affects flowering and fruit setting in many crops. Identifying these deficiencies allows farmers to apply targeted micronutrient fertilizers to correct specific deficiencies.

Correct Answer: B. Because it inverts or churns itself due to swelling and shrinking

Black soil is classified as Vertisol (from Latin 'vertere' meaning 'to turn') in the USDA Soil Taxonomy because the soil turns or inverts itself. The high montmorillonite clay content causes the soil to swell when wet and shrink deeply when dry, forming wide cracks. Soil material from the surface falls into these cracks and is incorporated at depth, effectively inverting the soil. This self-churning property distinguishes Vertisols from all other soil orders.

Correct Answer: B. About 6 million hectares

Approximately 6 million hectares of India's cultivated area is affected by waterlogging, which is a form of land degradation that restricts plant root growth by reducing oxygen availability. Waterlogging occurs mainly in canal-irrigated areas of Punjab, Haryana, and Uttar Pradesh due to over-irrigation and inadequate drainage. It leads to secondary salinization as the capillary rise of groundwater deposits salts on the surface. Reclamation requires installation of subsurface drains and controlled irrigation.

Correct Answer: B. Decrease in the productivity potential of land due to natural or human-induced processes

Land degradation refers to the decrease in the productive potential of land due to natural processes like erosion, climate variability, or human-induced factors like deforestation, overgrazing, and unsustainable agriculture. In India, major forms of land degradation include water and wind erosion, waterlogging, soil salinity, and soil acidification. It is estimated that India loses billions of dollars annually due to land degradation. Addressing land degradation is essential for sustainable agriculture and food security.

Correct Answer: B. Acidic and rich in organic matter

Forest soils of the Himalayan region are generally acidic due to the accumulation of organic acids from decomposing coniferous leaves and high rainfall causing leaching of basic cations. They are rich in organic matter due to the continuous supply of forest litter. These soils support the growth of coniferous trees, apple orchards, and tea gardens in the sub-Himalayan belt. The high organic matter gives these soils dark colour and good moisture retention.

Correct Answer: B. Covering the soil surface to reduce evaporation, prevent erosion, and suppress weeds

Mulching involves covering the soil surface with organic material (straw, dry leaves, crop residue) or synthetic material. It reduces evaporation of soil moisture, keeps the soil cool, suppresses weed growth, and prevents splash and sheet erosion by protecting the soil from direct raindrop impact. As organic mulch decomposes, it adds organic matter to the soil, improving its structure. Mulching is an important conservation practice for both field crops and orchards.

Correct Answer: C. Maharashtra

Maharashtra is the largest producer of soybean in India, grown primarily on its extensive Black soil regions, particularly in the Vidarbha and Marathwada regions. Black soil's high calcium and magnesium content and neutral to slightly alkaline pH suit soybean cultivation. Soybean (also called soya) is an important kharif oilseed crop. Madhya Pradesh, also with large Black soil areas, is the second largest soybean producer in India.

Correct Answer: B. Removal of minerals and clay from the upper soil horizon by water

Eluviation refers to the removal of dissolved or suspended materials (clay, iron oxides, organic matter, and soluble salts) from the upper soil horizon (A horizon) by percolating rainwater. The removed material is transported downward and deposited in the lower B horizon, a complementary process called illuviation. Eluviation is particularly intense in high-rainfall tropical regions, leading to the formation of Laterite soils in India. The term comes from the Latin 'eluere' meaning 'to wash out'.

Correct Answer: D. Cashew nut

Cashew nut is among the most suitable crops for cultivation on Laterite soil and thrives on the well-drained, iron-rich, acidic Laterite soils of coastal Goa, Kerala, Karnataka, and Odisha. Cashew trees are tolerant of poor, acidic soils and do not require highly fertile conditions. India is one of the world's largest cashew producers, with most cashew grown on Laterite soils. Tea, rubber, and coffee are other suitable crops for Laterite soil.