Soil

Soil is an unfastened material or upper layer of mantle rock. It is made up primarily of extremely minute particles and the humus that can sustain plant growth. Rock or mineral particles, soil water and air, decomposed organic matter, and live organisms make up the majority of soil. Parent material, climate, relief, vegetation, time and living forms are all key influences on soil formation.

Soil is made up of four elements in general. They are water, air, fraction of minerals produced from the source material and the matter that is made up of organic compounds (decomposed and decayed animals and plants)

Classification of Soil

Soil in India has been classified since the ancient period. The classification system is based on only two factors in the ancient period: whether the soil was Sterile or fertile. As a result, the classification was Urvara i.e. fertile and Usara i.e. Sterile.

Soil Profile

• Horizon A (the topsoil) – This is the topmost layer, where organic components have combined with mineral matter, nutrients, and water – all of which are essential for plant growth.
• Horizon B (the subsoil) – In this zone, minerals are more abundant, and humus is found in smaller amounts. It is a transition zone between the Horizon C and Horizon A, including stuff from both below and above.
• Horizon C (the weathered and the decomposed rock) – The loose rock material makes up this zone.

Types of Soil

Soils in India are divided into eight categories by the ICAR (Indian Council of Agriculture Research). They are as followed:

Yellow & Red Soil-

• Also known as omnibus group and takes up around 18.5% of the country’s overall land area.
• Found in low-rainfall areas. Red loamy soil covers a large region of the Western Ghats’ piedmont zone and can also be found in areas of Chhattisgarh and Odisha, as well as in the Middle Ganga Plain’s southern reaches.
• The presence of iron in metamorphic and crystalline rocks causes the red colour. When the soil is moistened, it appears yellow.
• Cultivated crops- millets, oilseeds, tobacco, pulses, cotton and wheat.

Alluvial Soil

• Common in the north plains and takes up almost 40% of the country’s entire land area.
• Mainly found in the Peninsular region’s east coast deltas and river valleys and the nature of soil ranges from sandy loam to clay
• The alluvial soil is abundant in potash; however, the phosphorus is scarce.
• The Middle and Upper Ganga plains have created two distinct kinds of soils: the Khadar and the Bhangar. Moreover, both of the soils have impure calcium carbonate concentration (kankars).
• The middle and lower Ganga plains, as well as the Brahmaputra valley, have more loamy and clayey soils.
• Maize, sugarcane, oilseeds, pulses wheat and other crops are primarily grown.

Black Soil

• The soil accounts for around 15% of the country’s overall land area and the colour ranges from deep black to grey.
• The black soil is quite deep in the upper reaches of the Krishna and Godavari rivers, as well as the northwestern part of the Deccan Plateau.

• Clayey, deep, and impermeable soils characterise the black soils. When wet during the rainy season, they swell and become sticky. Moisture evaporates during the dry season, causing the soil to shrink and form large fractures.
• Lime, Iron, magnesium, aluminium and potassium are all abundant in black soils. Nevertheless, these soils are phosphorus and nitrogen deficient.
• Main cultivation of pulses, castor, tobacco, citrus fruits, cotton etc.

Mountain Soil/Forest Soil

• This type of soil can be found in dense forests with adequate rainfall and the texture varies depending on where they are found in the mountains.
• Upper slopes have coarse-grained soils, while valley sides have silty and loamy soils.
• The soil is depleted and acidic, with minimal humus content, in the Himalayan snowbound areas. The soils in the lower valleys are rich in nutrients.

Marshy Soil

• Found in the areas of strong rain and high humidity.
• Vegetation growth is relatively slow.
• A lot of dead organic humus in the soil, which makes it alkaline.
• The soil is dark and heavy.

Alkaline Soil

• The symmetry of potassium, magnesium and sodium is greater.
• They can be found in arid climates, as well as wet and swampy environments.
• They are deficient in calcium and nitrogen.
• Found in western Gujarat, the eastern coast’s deltas, and West Bengal’s Sundarban region.
• Farmers are advised to use gypsum to overcome the problem of salinity in the soil in such measures, particularly in Haryana and Punjab.

Arid Soil

• It makes up about 4.42% of the country’s total land area and is also known as desert soil.
• The hues vary from crimson to brown.
• Desert soils have a sandy to gravelly texture, a low moisture content, and a low capacity to retain water.
• The soil contains normal phosphate levels but is nitrogen-deficient.
• The creation of ‘kankar’ layers is caused by an increase in calcium concentration in the lower horizon of the soil. These kankar layers prevent water from penetrating the soil, so when water is applied by irrigation, the moisture content is easily available for plant growth.
• Found in the western region of Rajasthan and contains little amount of organic matter.

Laterite Soil

• It makes up around 3.7 percent of the country’s total area.
• These are typical monsoon soils, which are distinguished by seasonal rainfall. Lime and silica are washed away by rain, leaving soil rich in iron oxide and aluminium, resulting in laterite soil formation.
• Organic matter, nitrogen, phosphate, and calcium are all low in laterite soil, although iron oxide and potash are rich.
• They react well to fertilisers and manures despite their low fertility.
• Found in Madhya Pradesh, Tamil Nadu, Kerala, and the hilly parts of Odisha and Assam. 

Conclusion

Soil is the top layer of the earth’s crust that contains weathered rock fragments and in India, they are the result of both physical and human causes. The problems associated with it are deficient in fertility of the soil, soil erosion, waterlogging etc.