Page 2628 - index

TAMIL NADU

Geographical position and climate

Tamil Nadu lies with a North Latitude between 8°5' and 13°34' East Longitude between 76°14'
2
and 80°21' with an area of 1,30,058 km . It lies in the southern most part of the country and is
bounded by Eastern Ghats, Andhra Pradesh and Karnataka on the north, The Nilgiris and
Anaimalai hills and Kerala on the west, Bay of Bengal in the east, Gulf of Mannar and Palk
Strait on the southeast, and Indian Ocean on the south. The state has 32 districts with 285
talukas, 385 blocks and 12,713 numbers of panchayat villages. It has an uninterrupted coastal
line of 922 kms includes coastline of Pondicherry and Karaikkal as a lengthy east boundary. The
lands can be divided into five major physical divisions such as Kurinji or mountainous region,
Mullai or forest region, Palai or arid region, Marudham or fertile plains and Neidhal or coastal
regions. The Eastern and Western Ghats meet in Tamil Nadu and run along its eastern and
western boundaries. The Cauvery River, originating in the Coorg district of the neighboring state
of Karnataka, is the lifeline of the state. The lush Coromandal plains are irrigated by the Cauvery
and its Thanjavur-Nagapattinam delta is called the granary of Tamil Nadu. Palar, Pennar, Vaigai,
and Tamiraparani are the other rivers of the state.

The State has an equatorial, tropical climate in the inland and an equatorial, maritime
climate in its coastal regions. The climate of the state ranges from dry sub-humid to semi-arid
and has two distinct periods of rainfall, viz. south-west monsoon (from June to September, with
strong southwest winds) and North East Monsoon (from October to December, with dominant
north east winds). The mean annual precipitation is 848 mm in the plains and 946 mm in the
coastal areas (plain) and 1666 mm in the hill ranges of the Nilgiris and of which 46% is through
the north east monsoon, and 35% through the south west monsoon, 14% in summer and 5%
during winter periods. The mean annual temperature is 28.2°C in the plains and 15.2°C in the
hills. The temperature is minimum in the month of December with 24.7°C and maximum in May
with 37.3°C. Soil temperature data available for a few places indicate a range from 30.7°C to
32.3°C in the plains and around 14.4°C in the hills. On the basis of temperature, the coastal plain
(Aduthurai) is classified as hyperthermic (very hot), northern part (Coimbatore) and southern
part (Kovilpatty) are isohyperthermic (steadily very hot) and hill area (Uthagamandalam) is
isomesic (steadily cold).

Soils

The soils of Tamil Nadu have been classified into six soil orders such as Entisols, Inceptisols,
Alfisols, Ultisols, Mollisols and Vertisols. About 50% of the total area of the state is occupied by
Inceptisols, 30% by Alfisols, 7% by Vertisols, 6% by Entisols, 1% by Ultisols and a very
negligible area by Mollisols. Entisols include young river alluvium, sandy and eroded red and
laterite soils. Moderately deep red, laterite and black soils are included under Inceptisols, while
the deep red laterite soils with high base status are grouped under Alfisols. Ultisols consist of
highly weathered laterite soils with low base status. Deep black cotton and old alluvial soils are
classified under Vertisols. There are 12 suborders, 20 great groups, 44 subgroups and 94 soil