Geography Quiz: Soils and its distribution in India |4 Feb, 2021

The northern plains are formed by the alluvial deposits brought by the rivers – the Indus, the Ganga and the Brahmaputra.
•These plains extend approximately 3,200 km from the east to the west. The average width of these plains varies between 150 – 300 km.
•The maximum depth of alluvium deposits varies between 1,000-2,000 m. From the north to the south, these can be divided into three major zones: the Bhabar, the Tarai and the alluvial plains.
•The alluvial plains can be further divided into the Khadar and the Bhangar. Bhabar is a narrow belt ranging between 8-10 km parallel to the Shiwalik foothills at the break-up of the slope.
•As a result of this, the streams and rivers coming from the mountains deposit heavy materials of rocks and boulders, and at times, disappear in this zone.
•South of the Bhabar is the Tarai belt, with an approximate width of 10-20 km where most of the streams and rivers re-emerge without having any properly demarcated channel, thereby, creating marshy and swampy conditions known as the Tarai.
Source: NCERT XI – India Physical Environment

Factors of soil formation:
Parent material: Few soils weather directly from the underlying rocks. These “residual” soils have the same general chemistry as the original rocks. More commonly, soils form in materials that have moved in from elsewhere.
•Materials may have moved many miles or only a few feet. Windblown “loess” is common in the Midwest. It buries “glacial till” in many areas. Glacial till is material ground up and moved by a glacier. The material in which soils form is called “parent material.”
•In the lower part of the soils, these materials may be relatively unchanged from when they were deposited by moving water, ice, or wind.
Climate: Soils vary, depending on the climate. Temperature and moisture amounts cause different patterns of weathering and leaching.
•Wind redistributes sand and other particles especially in arid regions. The amount, intensity, timing, and kind of precipitation influence soil formation.
•Seasonal and daily changes in temperature affect moisture effectiveness, biological activity, rates of chemical reactions, and kinds of vegetation.
Topography: Slope and aspect affect the moisture and temperature of soil. Steep slopes facing the sun are warmer, just like the south-facing side of a house. Steep soils may be eroded and lose their topsoil as they form.
Thus, they may be thinner than the more nearly level soils that receive deposits from areas upslope. Deeper, darker colored soils may be expected on the bottom land.
Biological factors: Plants, animals, micro-organisms, and humans affect soil formation. Animals and micro-organisms mix soils and form burrows and pores.
•Plant roots open channels in the soils. Different types of roots have different effects on soils. Grass roots are “fibrous” near the soil surface and easily decompose, adding organic matter.
•Taproots open pathways through dense layers. Micro-organisms affect chemical exchanges between roots and soil.
•Humans can mix the soil so extensively that the soil material is again considered parent material.
•The native vegetation depends on climate, topography, and biological factors plus many soil factors such as soil density, depth, chemistry, temperature, and moisture. Leaves from plants fall to the surface and decompose on the soil.
•Organisms decompose these leaves and mix them with the upper part of the soil. Trees and shrubs have large roots that may grow to considerable depths.
Time: Time for all these factors to interact with the soil is also a factor. Over time, soils exhibit features that reflect the other forming factors.
•Soil formation processes are continuous. Recently deposited material, such as the deposition from a flood, exhibits no features from soil development activities.
•The previous soil surface and underlying horizons become buried. The time clock resets for these soils.
•Terraces above the active floodplain, while genetically similar to the floodplain, are older land surfaces and exhibit more development features.
Source: NCERT XI – India Physical Environment and https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils

Red soil is formed as a result of weathering of metamorphic and igneous rocks. The red color of the soil comes from the high percentage of iron content.
•The soil’s texture varies from being sandy to clayey, but it is mainly loamy. Red soil is rich in potash content but lacks phosphate, humus and nitrogen content.
•The red soil is found in regions such as Tamil Nadu, Madhya Pradesh, Jharkhand, Odisha, some parts of Karnataka and southeast Maharashtra.
Source: NCERT XI – India Physical Environment

The Soils can be classified on the basis of dominating factors:
Zonal Soil – These soils occur in broad geographical areas or zones.
•They are influenced more by the climate and vegetation of the area rather than the rock-type.
•They are mature, as a result of stable conditions over a long period of time.
•For example – red soils, black soils, laterite soils, desert soils etc.
Azonal Soil – It is that soil which has been developed by the process of deposition by the agents of erosion.
•It means that it has been made by the fine rocky particles transported from the far-off regions.
•These are immature soils and lack well-developed soil profiles.
•This may be due to the non-availability of sufficient time for them to develop fully or due to the location on very steep slopes which prohibits profile development.
•For Example – alluvial and loess soils.
Intrazonal Soil – These soils occur within other zonal soils.
•It is a well-developed soil reflecting the influence of some local factor of relief, parent material, or age rather than of climate and vegetation.
•For example, calcareous soil (soils which develop from limestone), peat soil.
Source: G C Leong

Latosols are soils found under tropical rainforests which have a relatively high content of iron and aluminum oxides. They are typically classified as oxisols or ferralsols.
Source: G C Leong

India has varied relief features, landforms, climatic realms and vegetation types. These have contributed in the development of various types of soils in India.
•In ancient times, soils used to be classified into two main groups – Urvara and Usara, which were fertile and sterile, respectively.
•Saline Soils are also known as Usara soils. Saline soils contain a larger proportion of sodium, potassium and magnesium, and thus, they are infertile, and do not support any vegetative growth.
•They have more salts, largely because of dry climate and poor drainage. They occur in arid and semi-arid regions, and in waterlogged and swampy areas.
•Their structure ranges from sandy to loamy. They lack in nitrogen and calcium. Saline soils are more widespread in western Gujarat, deltas of
•The eastern coast and in Sunderban areas of West Bengal. In the Rann of Kuchchh, the Southwest Monsoon brings salt particles and deposits there as a crust. Seawater intrusions in the deltas promote the occurrence of saline soils.
Source: NCERT XI – India Physical Environment

The Ministry of Agriculture and Farmers’ Welfare introduced the soil health card scheme on December 5, 2015.
•Soil Health Card (SHC) is a printed report which contains nutrient status of soil with respect to 12 nutrients: pH, Electrical Conductivity (EC), Organic Carbon (OC), Nitrogen (N), Phosphorus (P), Potassium (K), Sulphur (S), Zinc (Zn), Boron (B), Iron (Fe), Manganese (Mn) and Copper (Cu) of farm holdings.
•SHC is provided to all farmers in the country at an interval of 3 years to enable the farmers to apply recommended doses of nutrients based on soil test values to realize improved and sustainable soil health and fertility, low costs and higher profits. Farmers can track their soil samples and also obtain their Soil Health Card report.
•It is a field-specific detailed report of soil fertility status and other important soil parameters that affect crop productivity.
Source: Press Information Bureau

Black cotton soil which is also called as Regur soil is derivative of trapped lava.
•These soils are rich in calcium carbonate, magnesium carbonate, potash and lime.
•Regur soil has high water retention capacity.
•It cracks in summer and hence oxygen reaches to the deeper layers of soil.
•Cotton is well grown in this soil and hence is also called as black cotton soil.
Source: NCERT XI – India Physical Environment

Alluvial is the mostly available soil in India (about 43%) which covers an area of 143 sq.km.
•Alluvial soil [43%]
•Red soil [18.5%]
•Black / regur soil [15%]
•Arid / desert soil
•Laterite soil
Source: NCERT XI – India Physical Environment

Karewa soils are the lacustrine deposits in the Kashmir valleys and Bhadarwah valley. The fine silt, clay, and boulder gravels are the composition of Karewa soil.
They are characterized with the fossils. These soils are mainly devoted to the cultivation of saffron, almonds, apple, walnut, etc.
Source: NCERT XI – India Physical Environment