Geography - World & Indian (Soils):
Black Cotton Soils
These soils are also known as regur soils covers Maharashtra , Parts of Karnataka , TN,AP,MP and Gujarat. The black colour of this soil is attributed to the presence of titaniferrous magnetite, a compund of iron and aluminium. These soils derived from two types of rocks – Basaltic Deccan and Rajmahal traps and ferrogeneous gneisses and schists in TN and AP. These soils are very clayey (upto 50%) and therefore highly retentive of water. These soils are good for cotton and sugarcane.
Alluvial soil
Alluvial soils cover about 24% of the countries land surface and the largest share from agriculture comes from these soils. These soils cover 15 lakh square kilometres from the sutlej plain to the lower Ganga-Brahmaputra valley and along the east and west coast in the coastal plains. Alluvial soils in the northern plains are derived from the debris brought by rivers, in the coast plains by tides and in the desert by winds. Alluvial soils are deficient in Nitrogen and humus. With the use of fertilisers, these are highly used for agriculture.
Red Soils
Red soils are derived from the weathering of old crystalline and metamorphic rocks under dry conditions. The red colour is due to the presence of iron oxide. These are extensively found covering TN,Southern Maharastra, AP, South Bihar and western orissa. These lowlands are deep and fertile in lowlands and poor and thin in uplands.
Laterite Soil
These soils are formed under conditions of high rainfall and temperature with alternate wet and dry conditions. The high rainfall leaches away calcium and silica leaving behind iron with silica. These soils cover parts of Western Ghats in Kerala, coastal Orissa, coastal areas of WB , eastern Ghats and areas of high rainfall in North east and Bihar.
Forest Soil
Humus predominates in all forest soil but low in pH . These soils cover areas between 3000 m and 3100 m height in the coniferous region.
Arid and Desert Soil
These soils are formed under arid and semi arid conditions. The entire area west of the Aravelli Range has desert soils. These soil a high soluble salt content and a low humus content.
Mountain Soils
These soils are found in altitudes between 2000 m and 3000 m. They are poorly endowed in organic matter and moderately acidic. These soils are used for growing potatoes and subtropical fruits.
Saline and Alkaline Soils
These Soils cover arid and semi arid region of the northern plains and almost the whole of Maharastra. The salts of the soil get mixed with underground water and during the dry period , come up to the surface through capillary action. These are the salts of calcium, magnesium and sodium. These soils are called reh, usar, kallar, rakar, chopan etc.
Soil Erosion
Soil erosion is a process of detachment and transportation of soil by natural agencies such as water and wind. Rainfall, Slope, Vegitation, Nature of Soil, Wind Velocity are some of the factors that control Soil Erosion. The erosion caused by water can be classified as follows.
1) Splash Erosion occurs when raindrops splash on the soil thus loosens the top soil
2) Sheet Erosion occurs when the soil is removed uniformly as thin layer
3) Rill Erosion occurs when water run off forms a finger like channel along slopes
4) Gully Erosion occurs when the volume of water increases in the slopes, Rill erosion enlarges into Gully which result in Ravines
5) Slip Erosion is caused by landslides thus damaging the fields in the foothills.
Deforestation, Shifting Cultivation, Overgrazing, lack of proper drainage are some of the main reasons for soil erosion. Some suggested remedies to check soil erosion are Strip cropping, Mulching, crop rotation , contour tillage, contour bunding, terracing etc.
Peaty Soil
These soils are developed under humid conditions as a result of accumulation of large amount of matter. These soils are found in the coastal areas of WB,Orissa and Kerala.
