4 . Study Area

The study area, Karnataka State, is situated between 11° 40' and 18° 27' north latitude and 74° 5' and 78° 33' east longitude in the centre of western peninsular India, covering an area of 19.1 Mha and accounts for 5.8% of the country's total geographic area. It has a 350 km long coastline, which forms the western boundary. According to the 2001 provisional census the population of the State is 52,733,958 (26,856,343 males and 25,877,615 females), with a rural population of 66.02% and an urban population of 33.98%. The quality and quantity of bioresource in a region depends on various parameters such as physiography, climate, geology, soil, etc. which are discussed for Karnataka State next.

4.1 Physiography

The State is divided into three major ph ysiographic divisions-the Deccan Plateau, hill ranges and the coastal plain. The plateau is divided into Malnad and Maidan. The Ghats with evergreen and semi-evergreen forests constitute the core of the Malnad. Malnad is an undulating upland covering 6.2 Mha in the districts of Belgaum, Uttara Kannada, Dharwad, Chikmagalur, Kodagu and Hassan. The Maidan lies east of the Malnad and has a rolling surface with gentle slopes. It is further subdivided into the northern and the southern Maidan. The landscape characteristics of the southern Maidan are a series of rolling granite hills between Tumkur and Kolar districts. The northern Maidan has a mountainous, treeless expansive plateau.

The Deccan Plateau is a continuation of the Malwa Plateau and extends southwards. It has a triangular slope and is flanked on both sides by the Western Ghats and the Eastern Ghats. The height of the Deccan Plateau varies from 300-900 m. The Western Ghats runs parallel to the Western Coast of Karnataka covering an area of 2.4 Mha. The Eastern Ghats is formed by a group of low and discontinuous mountains on the eastern side of the Deccan Plateau. They occur along the southeastern border of Karnataka, covering an area of about 0.38 ha. The Eastern and the Western Ghats converge at the Nilgiri Hills. The Plains cover an area of about 0 .74 ha and lie between the Western Ghats and the Arabian Sea, from Karwar in the North to Mangalore in the south.

4.2 Geology

Geological formations in Karnataka are placed under four main types. (Radhakrishnan and Vaidyanadhan, 1997)

4.3 Soil types

Eleven groups of soil orders are recognized, based on differences in soil formation processes, as reflected in the nature and sequence of soil horizons. The soil orders are given in Table 8.

Table 8: Soil Orders in Karnataka

As per the classification based on agricultural capability, the soils are grouped as red soils, laterite soils, black soils, alluvio-collovial soils, brown forest soils and coastal laterite and alluvial soils. These have been further divided into 11 sub groups. Red soils have 4 subgroups, Laterite soils have 2 subgroups, Black soils have 3 subgroups and alluvial soils have 2 subgroups (ICAR, 1980). Coastal laterite soils, alluvial soils and forest soils have no subgroups. The alluvial soils possess great natural fertility. These soils are suitable for the cultivation of a wide range of crops such as wheat, rice, sugarcane etc; nevertheless, at some places, gram, barley, maize etc are found to be the most common crops cultivated. The sandy soil consists of Aeolian sand (90-95%) and clay (5-10%). These soils are very light and comprise about 8.46% of the country's soil cover. These are suitable for high salt tolerant crops, such as barley, rape and cotton, and also medium salt tolerant crops, such as wheat, millets, maize and pulses. The black soils vary in depth from shallow to deep. The typical soil derived from the Deccan Trap is the regur or black soil. Many black soil areas have a high degree of fertility, but some, especially in the uplands are poor. Black soils are highly argillaceous, very fine grained and dark and contain a high proportion of calcium and magnesium carbonates. They are exceedingly sticky, when wet. On drying, they contract forming large and deep cracks. These soils contain abundant iron, and fairly high quantities of lime, magnesia and alumina. They are deficient in potash, nitrogen and organic matter. The black soils of Karnataka are fine-textured with varying salt concentration. The soils are generally rich in lime and magnesia. The intensively cultivated tracts where adequate rainfall occurs are most suitable for cotton, wheat and jowar. But where irrigation facilities have been made available rice and sugarcane crops are also cultivated.

The predominant soil in the eastern tract of Karnataka is the red soil overlying the granite from which it is derived. In the districts of Bangalore, Kolar, Mysore, Tumkur and Mandya, this soil is found in varying depths. They occur as shades of red and pass on to yellow. Loamy red soils are predominant in the plantation districts of Shimoga and Hassan. They are rich in P 2 O 5 (0.05-0.3%) and their lime content varies from 0.1-0.8%. Nitrogen is below 0.1%. Iron and alumina is high, being 30-40%. A broad strip of area running between the eastern and western parts of Coorg is covered by red loam. A large variety of crops, such as paddy, jowar, ragi, and cotton, are grown under irrigation but crops such as millets, pulses and even gram are raised under rain-fed conditions.

Laterite soils occur in the western parts in the districts of Uttara Kannada, Dakshina Kannada, Shimoga, Hassan and Mysore. They support tea, coffee, rubber and coconut plantations. The traditional soil groups of Karnataka and the soils of the major landforms of Karnataka are given below.

The soils of south Deccan Plateau are classified into two moisture regimes - ustic (deficient in water, but most of the water available comes from the cropping season) and aridic (highly water deficient). Ustic moisture regime covers major areas in the State except in parts of Bellary, Raichur, Chitradurga and Bijapur districts, which has an aridic moisture regime. The granite/gneiss landform covering an area of 8.1 Mha in Bangalore, Kolar, Tumkur, Mandya, Mysore, Hassan, Chikmagalur, Shimoga, Chitradurga, Raichur, Bellary and Gulbarga district is mostly covered with soils that are shallow to moderately shallow, excessively drained, gravely sandy clay in nature. The rolling lands have shallow to deep, somewhat excessively to well drained, red gravely loamy to clay soils. The soils of the valley are dominantly very deep, moderately well to poorly drained, fine textured and at places stratified. The major crops cultivated in these soils are rice and sugarcane. The soils of the basalt landform cover an area of about 2.7 Mha in the districts of Bidar, Gulbarga, Bijapur and Belgaum. These soils are moderately to very strongly alkaline, slightly to moderately calcareous and have organic carbon of 0.33 to 0.63%. Soils of laterite landform cover an area of 1.5 Mha in the districts of Bangalore, Kolar, Bidar, Gulbarga, Belgaum, Dharwad, Shimoga, Chikmagalur, Kodagu, Hassan and Uttara Kannada. Soils of metamorphic landform cover an area of 2.7Mha running Northwest to Southeast within the granite and gneiss landforms in Tumkur, Chikmagalur, Chitradurga, Kolar, Mysore, Belgaum, Bellary and Raichur districts. The landform includes ridges, rolling lands and valleys. The ridges and the rolling lands have gravely loam to clay soils. Valleys have deep, poorly drained, calcareous, cracking clay soils. Soils of sedimentary landform cover an area of 0.8Mha in the districts of Gulbarga, Bijapur and Bidar (Soils of Karnataka, 1998-NBSS).

Soils of the Western Ghats covers an area of 2Mha in the districts of Belgaum, Uttara Kannada, Dharwad, Dakshina Kannada, Shimoga, Chikmagalur, Hassan, Kodagu and Mysore. These soils are generally dark brown to dark reddish brown and black in colour due to the accumulation of high organic matter under the forest cover. The Eastern Ghats covers an area of 0.4 ha in the districts of Mysore and Bangalore bordering Tamil Nadu. The soils are very shallow, somewhat excessively drained, gravely loam to clay soils. Soils of the West Coast cover an area of 0.7 Mha in the districts of Uttara Kannada and Dakshina Kannada.

As per the taxonomic classification, the soils of Karnataka are grouped into 7 orders, 12 suborders, 27 great groups, 47 subgroups and 96 soil families. Of the total area of Karnataka, 27% is covered by Alfisols, 25% by Inceptisols, 16% by Entisols, 15% by Vertisols, 8% by Ultisols, 5% by Aridisols and 1% by Mollisols. An area of about 4% is miscellaneous land type and that includes rocky lands, water bodies and urban area.

The soil type in each of the agro climatic zones is listed in Table 9.

Table 9: Soil Types in Agroclimatic Zones of Karnataka

(Soils of Karnataka, 1998)