Soil Types of India — Set 8

Correct Answer: C. Laterite soil

Laterite soil is the most acidic soil type in India, with pH values often below 5. The intense leaching of basic cations (calcium, magnesium, potassium) by heavy rainfall leaves behind iron and aluminium oxides, which make the soil acidic. Forest and Mountain soils can also be acidic due to the accumulation of organic acids from decomposing leaves. To grow crops on Laterite soil, lime must be added to reduce acidity.

Correct Answer: D. Saline/Alkaline (Usar) soil

Saline and Alkaline (Usar) soil is the most alkaline soil type in India, with pH values often exceeding 8.5. The accumulation of sodium carbonate (soda) and other salts makes these soils highly alkaline. High alkalinity makes many nutrients unavailable to plants and directly toxic to crop roots. Treatment with gypsum (calcium sulphate) and leaching with irrigation water is needed to reclaim these soils.

Correct Answer: C. Unweathered bedrock at the bottom of the profile

The R horizon represents the unweathered bedrock at the very bottom of the soil profile. It is the parent material from which the overlying soil layers have formed over thousands of years of weathering. The R horizon is impenetrable to roots and water. Drilling or blasting is required to break through the R horizon. The nature of the R horizon largely determines the mineral composition of the soil above it.

Correct Answer: B. Rich in phosphorus and potash, deficient in nitrogen

Alluvial soils are generally rich in phosphorus and potash (potassium) but deficient in nitrogen. This is because nitrogen is highly soluble and is easily lost through leaching and crop harvesting, while phosphorus and potassium are held more firmly by soil particles. The nitrogen deficiency of alluvial soil is compensated by the application of urea and other nitrogenous fertilizers. Legume crops grown in rotation also help add nitrogen through biological fixation.

Correct Answer: C. Assam

Assam is India's largest tea-producing state, with tea grown extensively on Forest/Mountain and Laterite soils of the Brahmaputra Valley and Barak Valley. The acidic, well-drained soil and high rainfall of Assam are ideal for tea cultivation. The Assam tea (Camellia sinensis var. assamica) thrives in these conditions. Darjeeling in West Bengal and the Nilgiris in Tamil Nadu are other major tea-growing areas with similar soil and climate conditions.

Correct Answer: C. Reclamation

The process of converting degraded Saline/Alkaline Usar soil into productive farmland is called reclamation. Reclamation involves physical, chemical, and biological measures such as levelling the land, applying gypsum to replace sodium, leaching with good quality water to remove excess salts, and growing salt-tolerant crops or plants. Bio-reclamation using plants like Karnal grass and Dhaincha is an economical method. Successful reclamation restores the soil's ability to support normal crop cultivation.

Correct Answer: C. It gives information on soil nutrient status and fertilizer recommendations for the farmer's field

The Soil Health Card gives farmers critical information about the nutrient status of their specific field, including levels of nitrogen, phosphorus, potassium, pH, organic carbon, and micronutrients. Based on this analysis, the card provides customized fertilizer recommendations to achieve optimal crop yields at minimum cost. The scheme was launched in 2015 with the target of covering every farmer in India. It helps reduce over-application of fertilizers and improves soil health over time.

Correct Answer: C. Growing trees and grasses to bind soil particles and prevent erosion

Growing trees, grasses, and other vegetation is a biological method of soil conservation. Plant roots bind soil particles together, preventing erosion by wind and water. Vegetative cover also intercepts rainfall, reducing the impact of raindrops on bare soil and slowing down surface runoff. Afforestation, social forestry, and cover cropping are important biological measures used in India's soil conservation programmes.

Correct Answer: C. About 30-35%

Approximately 30-35% of India's total geographical area of about 329 million hectares is estimated to be affected by soil erosion and land degradation in various forms. This includes water erosion, wind erosion, waterlogging, salinity, and alkalinity. Soil erosion leads to loss of agricultural productivity, silting of reservoirs, and increased flooding. Addressing soil degradation is a critical challenge for India's food security and rural livelihoods.

Correct Answer: B. Peaty/Marshy alluvial soil

The Sundarbans delta region in West Bengal is characterized by Peaty/Marshy alluvial soil, which is waterlogged, saline, and high in organic matter. The deltaic location with tidal influence and mangrove forests creates conditions for organic matter accumulation and soil salinization. The soil supports mangrove forests but is challenging for conventional agriculture. The Sundarbans is one of the world's largest mangrove ecosystems, dependent on this unique soil type.