Soils of India and Types - 2 | Agriculture Optional Notes for UPSC PDF Download

Laterite Soil

• Composition: Laterite soil is characterized by its richness in iron and aluminum oxides, clay, and silica. It contains smaller quantities of potash, lime, and magnesia. The iron oxide content contributes to its reddish or yellowish appearance.
• Acidity: Typically, laterite soil is acidic due to leaching caused by heavy rainfall, resulting in a pH level ranging from 4 to 6. This acidity makes it less suitable for crops that thrive in neutral or alkaline soils.
• Drainage: Due to its high clay content, laterite soil experiences poor drainage. It retains water for extended periods, leading to potential waterlogging in certain areas.
• Distribution: Laterite soil is widespread in India, with notable occurrences in the Western Ghats, Eastern Ghats, parts of Odisha, Karnataka, Kerala, Tamil Nadu, and the northeastern states. It is also present in select coastal regions.
• Crops: Given its acidic nature and drainage limitations, traditional agriculture is less favorable in laterite soil. However, specific crops like cashew nuts, tea, coffee, rubber, and spices (such as pepper and cardamom) have adapted to the unique characteristics and nutrient composition of this soil type.
• Soil Fertility: Generally, laterite soil is less fertile compared to alluvial soil. It is deficient in essential nutrients like nitrogen, phosphorus, and potassium. Nonetheless, with proper soil management and nutrient supplementation, agricultural productivity can be enhanced.
• Erosion: The sandy and loamy texture of laterite soil makes it susceptible to erosion, particularly during heavy rainfall. This erosion can lead to soil degradation and reduced fertility.
• Terracing: In hilly regions where laterite soil prevails, farmers often employ terracing techniques to combat soil erosion. Terracing involves creating leveled areas on sloping land to reduce water runoff and soil loss.

Arid Soil 

• Composition: Arid soils are primarily sandy and feature a notable sand particle content. They have limited organic matter and are deficient in nutrients like nitrogen. The absence of clay and silt particles results in a loose and friable texture.
• pH Level: Arid soils are generally alkaline or saline, with pH values ranging from slightly alkaline (pH 7.5-8.5) to strongly alkaline (pH above 8.5). The high alkalinity can impact plant growth and restrict crop choices.
• Nutrient Content: Arid soils lack essential plant nutrients, including nitrogen and phosphorus. This nutrient deficiency poses challenges for agriculture and necessitates proper soil management practices, such as nutrient supplementation.
• Water Holding Capacity: Due to their coarse texture and low organic matter, arid soils exhibit low water-holding capacity. They cannot retain water effectively, resulting in rapid drainage and quick drying.
• Salinity: Many arid soils in India suffer from salinity problems due to salt accumulation in the soil profile. This salt accumulation inhibits plant growth and limits crop production. Effective soil reclamation and management techniques are essential to address salinity issues.
• Vegetation: Arid soils support xerophytic vegetation, which comprises plants adapted to arid conditions with limited water availability. Common vegetation includes thorny shrubs, cacti, and drought-resistant grasses.
• Distribution: Arid soils are found in regions with low rainfall, including parts of Rajasthan, Gujarat, Haryana, Punjab, and regions of the Deccan Plateau. These areas feature a semi-arid to arid climate with hot and dry conditions.
• Agricultural Challenges: Cultivating crops in arid soil regions presents challenges due to water scarcity, nutrient deficiencies, alkalinity, and salinity issues. Nevertheless, with appropriate irrigation methods, the use of drought-resistant crop varieties, and soil management practices, limited agriculture is feasible in these areas.

Forest Soil

• Composition: Forest soil is characterized by its richness in organic matter, which results from the continuous accumulation and decomposition of plant materials like leaves, twigs, and fallen trees. The substantial humus content contributes to its dark brown to black color.
• Texture: The texture of forest soil varies based on factors such as parent material, climate, and vegetation. It encompasses a range from sandy loam to clayey loam, often with a significant presence of silt and clay particles. The organic matter enhances soil structure and water-holding capacity.
• Acidity: Forest soils in India typically exhibit a slight acidity to neutrality in their pH levels. Variations in pH can be attributed to factors like the tree species, climate conditions, and the rates of organic matter decomposition.
• Nutrient Content: Forest soil is abundant in nutrients, particularly organic carbon, nitrogen, phosphorus, and potassium. The continuous recycling of organic matter within the forest ecosystem contributes to the soil's nutrient richness.
• Moisture Retention: Forest soil displays excellent moisture retention capabilities due to its high organic matter content. This quality aids in regulating water availability for plant growth and supports the thriving of diverse forest vegetation.
• Biodiversity Support: Forest soils provide an ideal habitat for a wide range of flora and fauna. The rich nutrient content and moisture retention capacity support the growth of various plant species, including trees, shrubs, and understory vegetation. It also facilitates the presence of numerous soil organisms and microorganisms.
• Erosion Control: Forest soils play a pivotal role in the prevention of soil erosion. The dense vegetation cover within forests stabilizes the soil, reduces surface runoff, and promotes water infiltration.
• Distribution: Forest soil is present in various forested regions throughout India, encompassing the Western Ghats, Eastern Ghats, Himalayan foothills, northeastern states, and central Indian forests.

Saline Soil or Usara Soil

• Distribution: Saline soil is located in various parts of India, primarily in the northwestern and western regions. It includes states like Gujarat, Rajasthan, segments of Punjab, Haryana, and Uttar Pradesh. Coastal areas, such as portions of Gujarat, Maharashtra, and Andhra Pradesh, may also exhibit saline soil due to the influence of seawater.
• Salinity levels: Saline soils contain a high concentration of salts, notably sodium chloride (common salt), which can render the soil unsuitable for most crop cultivation. The electrical conductivity (EC) of saline soil generally exceeds 4 dS/m (decisiemens per meter) and may even surpass 40 dS/m.
• Causes of salinity: The principal factors contributing to soil salinity in India include inadequate drainage, excessive irrigation with low-quality water, high evaporation rates, and the presence of natural salt deposits. In specific cases, the intrusion of seawater in coastal regions can also enhance salinity.
• Effects on agriculture: Saline soil poses significant challenges to agricultural productivity. Excessive salt content can hinder water uptake by plant roots, resulting in stunted growth, reduced yields, and even plant mortality. It also affects soil structure, making it less permeable and more susceptible to waterlogging.
• Crop tolerance: Certain salt-tolerant crops and plants can be cultivated in saline soil. These include halophytic plants like saltbush, mangroves, and specific varieties of barley, wheat, and millets. However, the range of crop options is limited compared to non-saline soils.
• Remedial measures: Multiple measures can be employed to alleviate the impact of saline soil. These measures involve leaching out salts through effective drainage, implementing efficient irrigation practices, utilizing suitable amendments like gypsum to improve soil structure, adopting salt-tolerant crop varieties, and planting trees or windbreaks to reduce evaporation.
• Reclamation: Reclaiming saline soil is a long-term process involving a combination of measures such as land leveling, soil flushing, the application of soil amendments, and the adoption of appropriate cropping patterns. Reclamation efforts aim to restore soil fertility and reduce salt content to levels suitable for crop cultivation.

Peaty Soil

• Characteristics: Peaty soil primarily consists of partially decomposed organic matter, including plant materials and vegetation debris. It displays a dark brown to black coloration and contains a significant organic content.
• Texture: Peaty soil is characterized by its spongy and fibrous texture, primarily attributable to the abundance of organic matter. It is typically soft and easily compressible.
• Distribution: Peaty soil is prevalent in areas with substantial rainfall and waterlogging conditions. In India, it is mainly located in the coastal regions of Kerala, Tamil Nadu, West Bengal, and portions of the northeastern states.
• Crops: Peaty soil is not well-suited for agriculture due to its high organic content, inadequate drainage, and acidic nature. However, in specific areas with proper management, some crops like rice, water chestnut, and particular vegetables can be cultivated.

Marshy Soil

• Characteristics: Marshy soil is characterized by its elevated water content and inadequate drainage. It usually exhibits a dark hue, has a heavy texture, and contains a significant clay content.
• Texture: Marshy soil possesses a heavy and adhesive texture because of the presence of fine clay particles. It is prone to waterlogging and can retain water for extended periods.
• Distribution: Marshy soil is typically found in low-lying regions, deltas, and coastal areas where water tends to accumulate and drain slowly. In India, it can be observed in the Sundarbans region of West Bengal, portions of Assam, and other coastal areas.
• Crops: Marshy soil is generally unsuitable for most agricultural crops due to its inadequate drainage and high water content. Nevertheless, it can support the growth of specific crops like paddy, lotus, and certain aquatic plants.