37

CHAPTER 3

GEOLOGY AND SOILS

3.1 INTRODUCTION

The Karnataka craton forming a part of the Indian shield is one of the oldest

Precambrian terrains (2.5 to 3.4 m.y.) of the world preserving within its limits, the

geological history of the earliest formed continental crust (Map 3.1). The narrow

coastal strip of about 5000 Km2 of Tertiary and Quaternary sediment and another

31,250 Km2 of Deccan basalts, the remaining area is dominated by Achaean

Proterozoic rocks, which are collectively known as the Precambrian rocks. The

Dharwar craton comprises Greenstone granites, Gneisses and Metavolcano

sedimentary sequences, surrounded and dissected by Peninsular Gneiss. At the

southern end of the craton these give way to granulite suite. The northern part of

Karnataka is covered by younger Kaladgi and Badami group of sedimentary rocks and

Deccan traps and the later represents a phenomenal outburst of volcanic activity at the

dawn of the Cenozoic era. The bulk of the lithology of Karnataka is Archaean to

Proterozoic in age.

3.2 REGIONAL GEOLOGY

The Dharwar craton that forms a part of the peninsular shield records more than a

billion years of history of the earliest period of the Earth, involving several periods of

episodic crustal growth. The Dharwar craton consists of several tectonomorphic units

(Mukhopadhyay, 1986) namely Supracrustal rocks, Peninsular Gneissic Complex,

Younger Granites, Granulites, etc. In addition to this, Proterozoic sediments (Bhima and

Kaladgi groups) and Deccan traps of Cretaceous occur in the region.

The oldest rocks dated so far in Karnataka are the peninsular gneisses and

associated ancient supracrustal rocks giving an age ranging from 3400 to 3000 m.y. (Map

3.1). The ancient supracrustal rocks are highly folded and occur as metamorphosed

remnants within the grey gneisses as enclaves and belong to the Sargur group (Janardhan

et al., 1978; Swaminath and Ramakrishnan, 1990). They predominantly occur along the

southern margin of the Dharwar craton. The next in order of age is a series of basic

igneous rocks of original basaltic composition together with associated intrusives. These

characteristically auriferous rocks are well developed in the eastern part of the state. The

38

type areas are the Kolar schist belt and Hutti schist belt. The name auriferous schist belts

have been given to these rocks (Radhakrishna and Vaidyanadhan, 1994).

Granites and gneisses of different types and ages cover a large part of Karnataka.

The basement for an extensive belt of schistose rocks are the grey gneisses designated as

the Older Gneiss Complex which are believed to have formed during three events, 3.47

3.4, 3.3 3.2 and 3.0 2.9 Ga (Jayananda and Peucat, 1996) under several tectono-thermal

events. A younger group of gneissic rocks, mostly of granodioritic and granitic

composition is found in the eastern parts of the state, representing remobilised parts of an

older crust for which the name Younger Gneissic Complex has been given (Radhakrishna

and Naqvi, 1986). However, more recent studies suggest that these granites are juvenile

additions and emplaced during 2.6 2.53 Ga (Jayananda et al., 1995; Krogstad et al.,

1995).

The schistose rocks of younger schist belts (Dharwar Supergroup) are Archaean

in age and formed during 2.9 to 2.6 Ga. Of the two main divisions of Dharwar

Supergroup, the older that is mainly of igneous in character is named the Bababudan

Group (Swaminath and Ramakrishnan, 1981). The overlying Chitradurga Group which is

more extensive group of schistose rocks, largely sedimentary in character, composed of

conglomerate, quartzite, lime stone, greywacke associated with manganiferous and

ferrugenous cherts. Ranibenur Group, which is youngest in the series, is classified as the

topmost formation within the Chitradurga Group.

The end of Dharwar cycle is marked by fresh outburst of granitic activity around

2600 m.y. ago. These granites extend in a north south direction as a narrow belt of 50

Km wide. The name Closepet Granite has been given to this granite, which is

characteristically porphyritic with large phenocrysts of pink and grey k-feldspar. The

Closepet batholith in South India is generally considered as typical crustal granite

emplaced 2.5 Ga ago and derived from partial melting of the surrounding Peininsular

Gneisses. In the field, it appears as a composite batholith made up of at least two groups

of intrusions: (a) an early SiO2-poor group (clinopyroxene quartz-monzonite and

porphyritic monzogranite) is located in the central part of the batholth, (b) a later SiO2-

rich group (equigranular grey and pink granites) is located along the interface between

SiO2-poor group and the Peninsular gneisses, thus indicating their anatectic derivation

(Jayananda et al., 1995). The linearity of Closepet granite parallel to the overall trend of

39

the supracrustal belts suggests that a major shear zone controlled its emplacement

(Jayananda and Mahabaleswar, 1991). Age data show that the granites are the youngest

intrusives in the Archaean complex of Karnataka, giving an age of emplacement around

2.5 to 2.6 Ga (Taylor et al., 1988; Jayananda et al., 1995).

In the southern part of the state, south of latitude 13° are a group of

orthopyroxene-bearing granulites, which have been named charnockites. They are

regarded to be the result of high-grade metamorphism of the older gneisses at great depths

in a dry crustal environment. Charnockites generally occur as massifs of large areal extent

and also as patches within the gneisses indicating that charnockitisation has taken place in

irregular blocks or shear zones cutting across the gneissic foliation. This patchy mode of

occurrence was first described by Pichamuthu (1960). Charnockites of different ages

ranging from 3.1 to 0.6 Ga have been reported from the granulite terrain of the South

India, which point to metamorphic events giving rise to granulitic rocks of different ages

and probably under different modes of origin (Jayananda and Peucat, 1996).

The close of the Archaean is marked by a period of dyke formation with both N

S and E W trending dykes traversing the rocks of earlier ages. Besides the dykes of the

doleritic composition, a number of alkaline dyke intrusives have been described from

Bangalore and Mysore districts. These dykes are younger, giving an age of 800 m.y. and

probably unrelated to the dolerite dykes.

The Proterozoic sediments of Karnataka are separated from the underlying

schistose and granitic rocks of Archaean age by a distinct unconformity known as the

Great Eparchean Unconformity. During this long period of crustal stability and no

sedimentation, the earlier rocks were exposed to sub-aerial weathering and denudation.

The northern part of the present day Karnataka was depressed below sea level

during Proterozoic era. In this basin large amount of sediments were deposited, which are

recognised as the Kaladgi and Bhima of Proterozoic age. Rocks of this age are well

developed at Kaladgi town in Bijapur district and the Bhima river valley. The elevation of

the Kaladgi and Bhima Group of sediments marked the end of Proterozoic era. After the

Proterozoic era, the Dharwar craton which forms a part of Indian Peninsula, remain

quiescence for a long period. Thus, the sediments of the subsequent periods are not seen

covering any part of the state.

40

The tremendous outburst of igneous activity at the end of Cretaceous (0.065 Ga)

is recorded as horizontal sheets of lava piled one above the other over a thickness of 1 Km

and covering an area of 500,000 Km2. The intertrappean beds between the flows of traps

show evidences of having been deposited in inland lakes. These volcanic rocks known as

Deccan traps cover most of northern Karnataka.

3.2.1 Geology of the Study Area

The study area of Dakshina Pinakini composed of peninsular gneisses, clospet

granites, lateritic hills and some basic dykes with undulating terrain (Map 3.1). The

granites occur as intrusive in the gneissic rocks and are varying in colour, texture and

structures. The area is traversed by numerous sets of basic and acidic intrusions. The

intrusions are dolerite dykes, pegmatites and some quartz gravels. The dolerite dykes

create problems in groundwater tapping since they obstruct the movement of water,

whereas pegmatitic veins are favourable for groundwater tapping.

3.2.2 Peninsular Gneiss

Peninsular gneiss covers a major portion of the study area and is highly

migmatitic in nature (Map 3.2). Their composition varies from tonalite and

trondhjemite to granodiorite and has fine to medium-grained texture. Peninsular

gneiss show a general trend of NNW SSE and NW SE with dips 60 to 80 towards

east. They are fine to medium-grained and generally grey in colour. In some places

they are regularly banded with alternate bands of felsic and mafic minerals and at

places the banding is irregular. They are jointed, sheet joints are almost parallel to the

ground surface. These are noticed in and around Bangalore. The gneisses are grouped

into four types viz, (i) Banded Gneisses, (ii) Granitic Gneisses, (iii) Gneissic Granites

and (iv) Granites and Granodiorites. The first three groups constitute a part of gneissic

complex and show intrusive relationship with older schists, whereas granites and

granodiorites constitute a part of younger clospet granites. These are intruded by a

number of basic dykes and pegmatitic veins.

3.2.2.1 Banded Gneisses

These are composed of several varieties which differ in colour, structure,

texture and mineral composition. They show well-defined banding at many places in

the study area. The mode of banding differs from place to place, varying from few

41

centimeters to several meters. They show crumbled appearances, because of intense

folding. Outcrops of granitic gneisses and banded gneisses are noticed in Rampura,

Yarapanahalli, Medahalli, Karakalaghatta, Hompalaghatta, Haralur, Singasandra,

Kudlu, Beguru villages of Bangalore North and South district.

3.2.2.2 Granitic Gneiss

The main rock formation in the study area is granitic gneiss. The granitic

gneisses are mainly of migmatitic type, highly banded varying in composition from

granite to diorite. Out crops of these are very infrequent and are confined to northern

(NW1, NW2 and NW3), eastern (EW), southern and western side of the basin (SW1,

SW2, SW3 and SEW). The rocks in the remaining part of the area lie under a mantle

of soil and river alluvia of varying thickness.

The prominent granitic gneiss rocks are noticed near Betta Halasuru,

Sadarahalli, Chikkasane, Huttanahalli, Koyra, north-west of Devanahalli in Bangalore

north. Hennur, Doddagubbi Chikkagubbi, Rampura in Bangalore east. These rocks are

extensively quarried for building materials. The rocks show fine to coarse-grained

texture and usually grey in colour. These gneisses and granites are intruded by basic

dykes, quartz and pegmatite veins. The average thickness of the weathered zone is 3

to 20 m, whereas the thickness in low lying areas ranges from 10 to 70 m. The

granitic gneisses are intruded by numerous east west running dolerite dykes of

varying dimension.

3.2.2.3 Gneissic Granite

These are mainly biotitic and hornblende granites, occasionally showing the

presence of phenocrysts. They show many time well-defined bands, whereas different

coloured minerals showing separate and distinct parallel disposition. These are

noticed near Hennur, Doddagubbi, Rampura in Bangalore east.

3.2.2.4 Granites

The granite occurs only in small portions of the study basin. These rocks are

noticed North-West region of Chikkaballapura (Plate 3.1) and small patches in and

around Bangalore district. They have a definite physiographic identity from the

surrounding gneissic plains. They have three sets of joints, medium to coarse-grained

and shows grey colour. They are closely jointed giving rise to numerous boulders

42

which are seen around the Nandi hills. Weathering also gives rise fine-to-coarse sandy

soil. The rocks are highly weathered and thickness ranges from 4 to 12 m. As the

depth of the weathered zone is deep and the texture of the soil is loose, there is ample

scope for ground water recharge through voids and joints present in the altered rocks.

The prominent granites exposures are noticed in Chennakeshava hills, Nandi hills,

Honnenahalli, Chokkanahalli, Devashettahalli, Koyra, Mudugurki, Muddenahalli,

Kalavara, Majjige Hosahalli villages in and around Chikkaballapura district (NW1,

NW2 and NW3), granitic gneisses are noticed in Lalbagh, Dodda Ganapathi temple

hill in Hanumanhtanagara, Iskon Temple hill in Mahalakshmi layout, Ragigudda in

Jayanagar, Hebbal hill and other parts of Bangalore district.

3.2.3 Pegmatite Veins/Quartz Gravels

Pegmatite veins and few patches of quartz gravels are found to occur in the

gneisses and granitic gneisses. These pegmatite veins or quartz gravels are noticed in

the study area. These are favourable sites for groundwater percolation and

development in hard rock regions.

3.3 SOILS OF THE STUDY AREA

Soil is a mixture of four main ingredients viz, weathered rock, organic matter,

air and water. The weathered rock can be in the form of sand, silt, clay, pebbles,

cobbles, boulders, etc. Organic matter can be anything from old leaves, dead animals

and plants, or tiny living things. Presence of organic matter enhances the water-

holding capacity of soil and infiltration. Soil is a reservoir of 14 mineral nutrients

which are essential and fundamental important for normal plant development and crop

production. Soils are primarily derived from parent rocks. Soil is the residual product

of physical disintegration and chemical decomposition of the underlying rocks. In due

course of time they are transformed into different colours and textures. The main

factors influencing the formation of the soil are rock material, climatic conditions and

slope of land, which reflects the geomorphic history of the area. Soils have

characteristic drainage conditions that depend on surface runoff, soil permeability and

internal soil drainage.

The porosity and permeability of soil influences the groundwater potential and

quality of water in any area. Soils are an important media promoting infiltration of

43

rain or surface water to the underground. The infiltration of water through soils is

dependent on texture, structure, surface conditions, storage capacity and

transmissibility of soils. A portion of rainfall infilters through the pores in the soil due

to the gravity. The water is absorbed by the soil due to surface tension, hydroscope,

etc.

The major soil types found in sub-basin of (Watersheds) Dakshina Pinakini River Basin

are clayey, clayey mixed, loamy skeletal, fine loamy and rocky land (NBSS and LUP,

2001) (Map 3.3).

3.3.1 Clayey Soil

The clayey soil found in southern watersheds (SW1, SW2 and SW3). It occurs

on gently sloping upper pediments with slope ranging from 2% to 5%. This series

represents very deep, gravely texture (Plate 3.2), moderate available moisture

retaining capacity and brown to dark brown and red in colour. Clayey soils have good

potential for cultivated crops and respond to fertiliser management, but require soil

conservation measures (Map 3.3).

3.3.2 Loamy Skeletal

The loamy skeletal soil found in northern, eastern and southeastern (NW1,

NW2, NW3, SEW and EW) watersheds of the study area. Soils of this association

occur on undulating to rolling upper pediments with slopes of 5% to 10%. These soil

series are very deep, red coloured and gravely in nature. The available moisture

retaining capacity is 10.5 for 90 cm depth (Map 3.3).

3.3.3 Red Loamy Soil

Red loamy soils exhibit fine texture, found in the gently upper pediplains, which is

found in northern, eastern and southeastern (NW1, NW2, NW3, SEW and EW)

watersheds of the study area. These soils have good water-holding capacity but poor

retention. This type of soils is noticed in parts of Chikabalapura, Bagaluru, White

field, Devanahalli, Hosakote taluks of Bangalore rural district.

3.3.4 Rocky Land

This type of soil occurs on undulating summits with outcrops of granite in

large proportion and found in undulating uplands with 5% to 10% slope. These

44

gravely textured soils are resting on hard substrata, which have very low available

moisture retaining capacity, very low nutrient status and are susceptible to erosion.

This type of soil found in all watersheds of sub-basin.

3.3.5 Red Soils

Red soil in the study area is derived from the residual products of granites and

gneisses. They are light textured, varying from sand or gravel to loams and are highly

leached. The red colour is due to the presence of iron, poor inorganic content and

plant nutrients. Red soils have good water-holding capacity. These are relatively more

permeable than black soil and have good infiltration capacity. On the basis of texture,

red soils further classified as follows:

3.3.5.1 Red Sandy Soils

These are poor in clay content and hence have a fairly good moisture-holding

capacity. They exhibit coarse to medium texture, found in the upper slopes of

pediments and upper pediplains, and thickness shows shallow to moderate depth. This

type of soil found in most of the study area.

3.3.5.2 Red Gravelly Soils

These are derived from weathering of grey granites and gneisses. These soils

occur on residual hills within pediments and in the severely eroded area of upper

pediplains. The soil thickness varies from place to place. It is found to be very

shallow on steeps having no vegetation. It is moderately thick on gentle slopes. These

soils supporting vegetation of different types and density. Water and nutrients get

drained quickly in this type of soils. This type of soil found in southern watersheds of

the study area (SW1, SW2 and SW3).

Red soils with different shades of red colour (Plate 3.3) are found in parts of

Keshavara, Giddanahalli, Karahalli, Koyra, Avathi, Devanahalli, Chikkajala,

Doddagubbi, Jadigenahalli, Kattigenahalli, Beguru, Hulimavu and other parts of the

study area.

45

3.4 SOIL ANALYSIS

Sixty-eight soil samples have been collected from different parts of the study

area in the month of May 2010 (Map 3.4). Samples location have been noted with the

help 12 channel global positioning system (Garmin GPS map 76CSX). The soil

samples have been collected at a depth of one and half feet by using wooden stick and

plastic covers to avoid contamination. All essential parameters such as pH, salinity,

organic carbon (OC), available macronutrients such as nitrogen (N), potassium (K),

phosphorus (P) and available micronutrients such as zinc (Zn), copper (Cu),

manganese (Mn), iron (Fe) and boron (B) have been analysed by using procedure of

Jackson (1973). The analysis has been carried out in the Agricultural Department,

Govt. of Karnataka, Bangalore by using instruments such as AAS, Flame photometer.

3.4.1 pH

The pH of soil gives various clues about the soil properties. The pH of soil is

very important because soil solution carries nutrients in it such as N, P, K that plants

need in specific amounts to grow and fight off diseases. Most of the agricultural crops

do best in slightly acidic soils (pH 6.5) and organic soils (pH 5.5). If the pH of the soil

solution is increased above 5.5, nitrogen (in the form of nitrate) is made available to

plants. In contrast, phosphorus is available to plants when pH is between 6.0 and 7.0.

The pH of soils in the study area is ranges from 4.7 to 8.0 with an average of

6.59. Out of 68 samples 13 samples are slightly acidic and remaining samples falls in

normal category (<6.3 acidity and 6.3 to 8.3 normal category, ICAR, 1997; Tables 3.1

and 3.2). The Iso-pH shows that anomalous zones in northeastern, central and

southeastern watersheds of the study area (Map 3.5). The lithologies of these

anomalous zones are peninsular gneisses, laterites, granitic rocks and doleritic dykes.

3.4.2 Salinity

Salinity of the soil is usually most damaging to germination of seeds and plant

growth. The most of salty soils occur in arid regions and in poorly drained soils of

subhumid regions. Salt-affected soils are caused by excess accumulation of salts,

typically most pronounced at the soil surface. Salts can be transported to the soil

surface by capillary transport from a salt laden water table and then accumulate due to

evaporation; they can also be concentrated in soils due to human activity. As soil

46

salinity increases, salt effects can result in degradation of soils and vegetation. All

samples fall in low salinity category (<1, ICAR, 1997; Tables 3.1 and 3.2). The Iso-

salinity shows within permissible limit (Map 3.6).

3.4.3 Organic Carbon

Organic Carbon in soil is one of the major sources of nutrient element present

in plants. It improves soil physical condition and also plays an important role in

balancing the carbon dioxide in the atmosphere. The organic carbon varies from soil

to soil and also it depends on climate, vegetation and biological activity of the area.

Quantifying the organic matter is based on determining the organic carbon content in

the soil. The organic carbon in the study area is ranges from 0.04 to 0.33 with an

average of 0.15. All samples fall in low organic carbon category (<0.5, ICAR, 1997;

Tables 3.1 and 3.2). The Iso-organic carbon shows within permissible limit (Map 3.7).

3.4.4 Soil Nutrients

Farmers are using fertilisers without applicable information on soil fertility

status and nutrient requirement by crops that they are growing may cause adverse

effects on soil and crops by way of nutrient toxicity of deficiency either by over use or

inadequate use. The nutrients are classified into two types depending on its quantity,

namely macronutrients and micronutrients.

3.4.4.1 Macronutrients

The nutrients required in large quantities are known as macronutrients and

they are N, P and K they are also called primary nutrients.

3.4.4.1.1 Nitrogen

Nitrogen is most often considered as the limiting nutrient in plant growth and,

it is the constituent of chlorophyll, plant proteins and nucleic acids. The main source

of nitrogen in nonfertilised soils is from organic materials. Deficiency in available

nitrogen retards growth, root development and chlorosis. The nitrogen concentration

in the study area ranges from 4.42 to 135 kg/ha with an average of 54 kg/ha (Table

3.2). The Iso-nitrogen map shows within permissible limit (<280, ICAR, 1997; Table

3.1 and Map 3.8).

47

3.4.4.1.2 Phosphorus

Phosphorus is the second important key plant nutrient, which controls the cell

division and plant growth. The natural source of phosphorus is the apatite. The toxicity of

phosphorus causes deficiency of iron and zinc, in turn causes the small leaves, erect

unusually dark green with a greenish red and greenish brown or purplish tinge. The

deficiency is due to the insoluble nature of soil phosphate. The phosphorus concentration

in the study area range from 3.2 to 56 kg/ha with an average of 18.8 kg/ha. Nine samples

fall in low and remaining fall in medium to high phosphorous category (<9 Low, 9 22

Medium, High>22, ICAR, 1997; Tables 3.1 and 3.2). The Iso-soil of phosphorus shows

the anomalous zones in central and southern parts of the study area (Map 3.9). The

lithologies present in these anomalous zones are younger granites, peninsular gneisses

and dolerite dykes.

3.4.4.1.3 Potassium

Potassium is an essential nutrient for plant growth. As large amounts of

potassium are absorbed from the root zone in the production of most agronomic crops,

it is classified as a macronutrient. The source of potassium is mica and potash

feldspars and these minerals are very low solubility in nature. Potassium helps the

plants to resist diseases, insect attack and other adverse effects. Deficiency of

potassium causes the chlorosis in the leaf tip. The range of potassium in the study area

is 41 to 243 kg/ha with an average of 122 kg/ha. All samples fall in low to medium

category (<41 Low, 141 336 Medium and >336 High; ICAR, 1997), which is

depicted in Map 3.10.

3.4.4.2 Micronutrients

The nutrients which are required in small quantities are known as

micronutrients or trace elements. These are Zn, Cu, Mn, Fe and boron. These

elements are very efficient and minute quantities produce optimum effects. In

contrast, even slight deficiency of it or excess is harmful to the plants.

3.4.4.2.1 Zinc

Zinc is an activator of certain enzymes and deficiency of zinc causes reduced

stem growth in crops and causes little leaf disease. Excess zinc may intract with other

nutrients. Normal concentration of Zn in soil is 0.96 ppm (Table 3.2). The available zinc

48

in the study area ranges from 0.16 to 0.93 ppm with an average of 0.53 ppm (<1, ICAR,

1997). The Iso-soil of zinc shows within permissible limit (Map 3.11).

3.4.4.2.2 Copper

The element of copper is required in very small quantity. It is very toxic and

when present in large quantity, it acts as a catalyst in oxidation reduction reactions.

Deficiency of Cu causes young leaf tips become yellow and it is often followed

periling of leaves. The average concentration of Cu in the study area is 0.127 ppm.

The Iso-Cu shows within permissible limit in the study area (Map 3.12).

3.4.4.2.3 Manganese

The manganese is an enzyme activator in several reactions of respiration and

nitrogen metabolism in plants. Deficiency of Mn causes chlorosis and leaf becomes

mottled appearance. The chloroplast loses chlorophyll and starch grains and become

yellowish green colour. The range of Mn concentration in soils in the study area is

0.36 ppm to 2.32 ppm. The toxicity of Mn causes the brown spot development on the

veins of the leaf blade and leaf sheath, especially on bottom leafs. The Iso-Mn

indicates anomalous zone in central and southern parts of the study area (Map 3.13).

The lithologies of the anomalous zones are granites and gneisses.

3.4.4.2.4 Iron

Iron is one of the important micronutrient in neutral or alkaline soil. It is

insoluble in nature, therefore Fe deficiency symptoms are noticed even though the soil

is rich in iron. Iron is always present in the soluble form in the acidic soil and is

therefore readily absorbed by the plants. The deficiency of iron causes interlineal

choloris and excess of iron causes tint brown spots appearing on the bottom leaves. In

some extreme cases, the entire leaf turns purplish brown colour. The concentration of

iron in soils in the study area ranges 2.71 to 6.52 ppm, with an average of 4.51 ppm.

The Iso-Fe indicates anomalous zone in eastern and southeastern parts of the study

area (Map 3.14). The lithologies of the anomalous zones are granites, gneisses and

laterites.

49

3.4.4.2.5 Boron

The most common micronutrient deficiency in the soil worldwide is boron.

Boron is associated with the soil organic matter and with many years of tilling our

lands the organic matter in the soil has decreased, and therefore, the principal source

of boron has also substantially decreased. As the soil pH increases above 6.5 it is

noted that boron decreases. In high rainfall regions boron is leached from the soil.

Boron deficiency results in death of shoot tip. Excess of boron causes the chlorosis.

The average value of the boron concentration in the study area is 0.12 ppm. The Iso-B

indicates anomalous zone in southern part of the study area (Map 3.15). The

lithologies of the anomalous zones are gneisses and laterites.

50

Table 3.1 Soil Fertility Rating Prescribed by ICAR (1997)

Sl. No

Soil Parameters Rating

Low Medium High

1 pH (1:2.5) <6.3 (Acidity)

6.3 8.3 (Normal)

>8.3 (Alkaline)

2 EC (E-mhos/cm) >1.00

3 Organic Carbon (%) <0.5 0.5 0.75 >0.75

4 Salinity <1

5 Available Nitrogen (Kg/ha)

<280 280 560 >560

6 Available Phosphorous (Kg/ha)

<9 9 22 >22

7 Available Potassium (Kg/ha)

<141 141 336 >336

8 Zinc (Mg/L) <1

9 Copper <0.40

10 Iron <4.50

11 Manganese <2.00

12 Boron <0.50

56

Map 3.1 Geology of Karnataka

57

Map 3.2 Lithology of the Study Area

58

59

Map 3.3 Soil Maps of the Study Area

60

67

Plate 3.1 Granitic Hill in the Study Area

Plate 3.2 Clayey Soil, Near Nandi Hills

68

Plate 3.3 Red Soil, Chikkaballapura