Soil Types of India — Set 16

Correct Answer: B. Waterlogging and soil salinisation due to over-irrigation

Waterlogging and soil salinization are the most severe soil degradation problems in Punjab and Haryana states. Decades of intensive canal irrigation without adequate drainage have raised the water table, causing waterlogging. Capillary rise of saline groundwater deposits salts on the soil surface, forming Reh (white salt crust). This degrades fertile alluvial soil and reduces crop yields. Subsurface drainage installation and improved water management are needed to address this problem.

Correct Answer: B. A measure of the acidity or alkalinity of soil on a scale of 0-14

Soil pH is a measure of the concentration of hydrogen ions (H+) in the soil solution, expressed on a logarithmic scale from 0 to 14. A pH of 7 is neutral, values below 7 indicate acidity, and values above 7 indicate alkalinity. Soil pH is one of the most important soil chemical properties because it controls the availability of virtually all plant nutrients. Regular soil pH testing and appropriate amendment (liming for acid soils, gypsum for alkaline soils) are essential for productive agriculture.

Correct Answer: B. It is regularly renewed by floods carrying fresh silt from the Himalayas

The alluvial soil of the Ganga delta and flood plains is regularly renewed and enriched by annual floods that deposit fresh silt carried from the Himalayas and the upper catchment areas. This fresh silt replenishes nutrients that are removed by crops, maintaining high fertility. The fine-grained, mineral-rich nature of the fresh alluvium makes it highly productive. This is why Bengal has historically been one of India's most productive agricultural regions for rice and jute.

Correct Answer: B. Sheet erosion

Sheet erosion is often called the 'silent killer of productivity' because it removes a thin, uniform layer of topsoil that is barely visible to the farmer. Unlike gully erosion, which creates obvious channels, sheet erosion is gradual and goes unnoticed until significant fertility loss has occurred. Over years, it depletes the most fertile and biologically active topsoil layer. The Soil Conservation Society of America estimated that sheet erosion globally removes over 36 billion tonnes of topsoil annually.

Correct Answer: B. A triangular diagram that shows how proportions of sand, silt, and clay define different soil texture classes

The soil texture triangle (or textural triangle) is a triangular diagram used to classify soil texture based on the proportions of sand, silt, and clay. Each corner of the triangle represents 100% of one particle size. By plotting the percentage of any two components, the texture class (sandy, loamy, clayey, silty loam, etc.) can be determined. The USDA texture triangle is the standard reference used in soil science globally and helps farmers and agronomists understand soil physical properties.

Correct Answer: B. Soils store large amounts of carbon; increasing SOC sequesters CO2 from the atmosphere, mitigating climate change

Soil organic carbon (SOC) is significant in the context of climate change because soils collectively store more carbon than the atmosphere and all plant biomass combined. Improving agricultural practices to increase SOC (through cover crops, compost, reduced tillage) sequesters atmospheric CO2 in the soil, helping mitigate climate change. India's '4 per 1000' initiative commitment is aimed at increasing global soil carbon stocks by 0.4% per year. Degraded Indian soils with low SOC represent a potential sink for atmospheric carbon if properly managed.

Correct Answer: B. Command Area Development and Water Management Programme

The Command Area Development and Water Management Programme (CADWM) focuses on improving irrigation efficiency and managing waterlogging and soil salinity in canal command areas. It includes construction of field drainage channels, subsurface drains, and land levelling to prevent waterlogging. The programme also promotes improved on-farm water management to prevent over-irrigation that leads to secondary salinity. It is particularly important in Punjab, Haryana, and western UP where waterlogging and salinity are major problems.

Correct Answer: B. J.N. Mukherjee

J.N. Mukherjee is recognized as the 'Father of Soil Science' in India for his pioneering contributions to understanding Indian soils. He laid the foundation for systematic soil study in India in the early 20th century. His work on soil chemistry, colloids, and classification significantly advanced Indian soil science. The institutionalization of soil science in India owes much to his legacy, with modern institutes like NBSS&LUP carrying forward his work.

Correct Answer: C. In acidic soil, phosphorus is fixed (precipitated) with iron and aluminium, making it unavailable

In acidic soil conditions (pH below 5.5), phosphorus forms insoluble compounds with iron and aluminium, which are abundant in acidic soils like Laterite and Forest soils. This process is called phosphorus fixation or immobilization, and it makes phosphorus unavailable for plant uptake even when phosphate fertilizers are applied. Liming the soil to raise pH to 6-6.5 reduces iron and aluminium solubility, freeing up phosphorus. This is why liming acid soils in India increases crop response to phosphate fertilizers.

Correct Answer: C. 8

The ICAR classification recognizes 8 major soil types in India: (1) Alluvial soil, (2) Black soil (Regur), (3) Red soil, (4) Laterite soil, (5) Arid/Desert soil, (6) Forest/Mountain soil, (7) Saline/Alkaline soil, and (8) Peaty/Marshy soil. This 8-fold classification is the standard used in Indian textbooks, competitive exams, and government agricultural documents. Each soil type has a distinct origin, distribution, properties, and suitability for different crops.