6.8   Soils of Tamil Nadu

. Soils of Tamil Nadu The soils in Tamil Nadu are broadly classified into five types according to their characteristics. They are . alluvial soil, . black soil, . red soil, . laterite soil, . saline soil. Alluvial Soil Alluvial soils are formed by the deposition of silt by the rivers. It is found in the river valley regions and the coastal plains of Tamil Nadu. Generally this type of soil is found in the districts of Thanjavur, Tiruvarur, Mayiladuthurai, Nagapattinam, Kallakurichi, Villupuram, Cuddalore, Tenkasi, Tirunelveli and Kanniyakumari. It is also found to a small extent along the river valleys in a few interior districts. Black Soil Black soils are formed by the weathering of igneous rocks. It is also known as regur soil. As cotton grows well in this soil, it is also called as black cotton soil. Black soils are found extensively in the districts of Coimbatore, Madurai, Virudhunagar, Tenkasi, Tirunelveli and Thoothukudi. Red Soil Red soils cover over two-thirds of the total area of Tamil Nadu. They are found particularly in the central districts of the state. It is dominantly found in Sivagangai and Ramanathapuram districts. Blossom showers) and some parts experience convectional rainfall. Southwest Monsoon The intense heating of the landmass of the north by the vertical sun rays during March to May creates a well-developed low pressure in North India, which draws wind from the Indian Ocean. This results in the formation of southwest monsoon. During this season, Tamil Nadu is located in the rain shadow region for the wind, which blows from the Arabian Sea. As a result, Tamil Nadu receives only a meagre rainfall from this monsoon. Rainfall during this season decreases from west to east. Coimbatore plateau receives an average of cm rainfall. However, Kanniyakumari, Tenkasi, Tirunelveli and The Nilgiris record – cm rainfall during this period. The rainfall is scanty in the eastern part of the state. Northeast Monsoon The northeast monsoon season commences from the month of October and lasts till mid- December. The high pressure created over Central Asia and northern part of India becomes the source for