Soils of India - Part 1 - Indian Geography скачать в хорошем качестве

Soils of India - Part 1 - Indian Geography

Welcome back to the next lesson in Indian Geography in this lesson we would be seeing about Soils of India Soil is an important layer of earth’s outermost layer known as crust. It is the mixture of organic matter, minerals, gases, water and air and other organisms. Let us see How is Soil Formed? Soil originally comes from rocks, also called the ‘parent material’. Soil formation starts when rock is exposed to the atmosphere. Properties of a soil will depend upon the type of parent material and how the soil is formed. Atmospheric conditions play a vital role in both the process and rate of physical and chemical decomposition of the parent material. Types of Soil • Alluvial soils • Black soils • Red soils • Laterite and Lateritic soils • Forest and Mountain soils • Arid and Desert soils • Saline and Alkaline soils and Alluvial Soils • Alluvial soils are formed mainly due to silt deposited by Indo-Gangetic-Brahmaputra rivers. • Rocks of the Himalayas form the parent material. Thus the parent material of these soils is of transported origin. Characteristics of Alluvial Soils • They are immature and have weak profiles due to their recent origin. • Most of the soil is Sandy and clayey soils are common. • The soil is porous because of its loamy (equal proportion of sand and clay) nature. Distribution of Alluvial Soils in India • They also occur in deltas of the Mahanadi, the Godavari, the Krishna and the Cauvery, where they are called deltaic alluvium (coastal alluvium) • Some alluvial soils are found in the Narmada, Tapi valleys and Northern parts of Gujarat. Crops in Alluvial Soils • They yield splendid crops of rice, wheat, sugarcane, tobacco, cotton, jute, maize, oilseeds, vegetables and fruits. Black Soils • The parent material for most of the black soil are the volcanic rocks that were formed in the Deccan Plateau (Deccan and the Rajmahal trap). • In Tamil Nadu, gneisses and schists form the parent material. The former are sufficiently deep while the later are generally shallow. Colour of Black Soils • Various tints of the black colour such as deep black, medium black, shallow black , a mixture of red and black may be found in this group of soils. Chemical Composition of Black Soils Distribution of Black Soils Crops in Black Soils Red Soils • The main parent rocks are crystalline and metamorphic rocks like acid granites, gneisses and quartzites. Characteristics of Red Soils • The texture of these soils can vary from sand to clay, the majority being loams. Chemical Composition of Red Soils • They are acidic mainly due to the nature of the parent rocks. The alkali content is fair. • They are poor in lime, magnesia, phosphates, nitrogen and humus. • They are fairly rich in potash and potassium. Color of Red Soils • The red colour is due to the presence of iron oxide. • When limestone, granites, gneisses and quartzites are eroded the clay enclosed within the rocks remains intact with other forms of non-soluble materials. • In oxidizing conditions, rust or iron oxide develops in the clay, Distribution of Red Soils • These soils mostly occur in the regions of low rainfall. • Other regions with red soil include parts of Karnataka, south-east of Maharashtra, Telangana, Andhra Pradesh, Madhya Pradesh, Chhattisgarh, Odisha, Chota Nagpur plateau; parts of south Bihar, West Bengal, Uttar Pradesh; Aravalis and the eastern half of Rajasthan (Mewar or Marwar Plateau), parts of North-Eastern states. Crops in Red Soils • The red soils, with the proper use of fertilizers and irrigation techniques, give good yield of cotton, wheat, rice, pulses, millets, tobacco, oil seeds, potatoes and fruits. Laterite – Lateritic Soils • Laterite soils are mostly the end products of weathering. • Heavy rainfall promotes leaching (nutrients gets washed away by water) of soil whereby lime and silica are leached away and a soil rich in oxides of iron and aluminium compounds is left behind. Chemical composition of Laterite – Lateritic Soils • Laterite soils are rich in bauxite or ferric oxides. • They are very poor in lime, magnesia, potash and nitrogen. • Sometimes, the phosphate content may be high in the form of iron phosphate. Distribution of Laterite – Lateritic Soils • Laterite soils cover an area of 2.48 lakh sq km. •Eastern Ghats, the Rajmahal Hills, Vindhyan, Satpuras and Malwa Plateau. They are well developed in south Maharashtra, parts of Karnataka etc. and are widely scattered in other regions. Crops in Laterite – Lateritic Soils • Laterite soils lack fertility due to intensive leaching. plantation crops like tea, coffee, rubber, cinchona, coconut, etc.