PHYTOGRAPHICAL REGIONS OF INDIA

A phytogeographical region is defined as an area of uniform climatic conditions and having a distinctly recognisable type of vegetation. According to D. Chattarjee (1962), India can be divided into nine phytogeographical regions.

1. Western Himalayas

This region comprises north and south Kashmir, part of Punjab and Kumaon region of Uttaranchal. Average annual rainfall in the region is 100-200 cm. The region is wet in outer southern ranges and slightly dry in the inner areas. At high altitudes, snowfall occurs during winters. The region is subdivided into three zones.

1. Submontane (lower, tropical and subtropical) zone: This zone includes outer Himalayas i.e. regions of Siwalik Hills and adjoining areas from 300 to 1500 m altitude. Average annual rainfall of the zone is around 100 cm. The vegetation consists of subtropical dry evergreen, subtropical pine and tropical moist deciduous forests.

2. Temperate (montane) zone: This zone extends in the western Himalayas between the altitudes 1500 and 3500 m. The climate is wet between the altitudes 1500 and 1800 m and is drier at higher altitude. The vegetation consists of wet forests, Himalayan moist and Himalayan dry temperate forests.

3. Alpine zone: This zone extends between 3500 m and 5000 m altitudes. The rainfall is very scanty and climate is very cool and dry. The vegetation consists of alpine forests.

2. Eastern Himalayas

This region extends in the Himalyas from east of Nepal up to Arunachal. The climate is warmer and wetter than in western Himalayas. Tree line and snow line are higher by about 300 m than in the western Himalayas. The tropical temperature and rainfall conditions result in vegetation of the region having greater general species diversity, greater variety of oaks but lesser variety of conifers than in the western Himalayas. This region is also divided into three zones.

1. Submontane (lower, tropical and subtropical) zone: This zone extends from the foothills up to the 1850 m altitude. The climate is nearly tropical and subtropical. The vegetation consists of subtropical broad-leaved forests, pine forests and wet temperate forests.

2. Temperate (montane) zone: The zone extends from 1850 m to 4000 m altitude, about 500 m higher than in the western Himalayas. The vegetation consists of typical temperate forests with oaks and Rhododendron at lower and conifers at higher altitudes.

3. Alpine zone: This zone extends from 4000-5000 m altitude. The climate is very cool and dry. The vegetation consists of alpine forests.

3. Indus plain

This region comprises a part of Punjab, Delhi, Rajasthan, a part of Gujrat and Cutch. The climate has very dry and hot summers alternating with dry and cold winters. The annual rainfall is generally less than 70 cm and may be 10-15 cm in some areas. Most of the region is desert today though it had dense forests about 2000 years ago that were destroyed due to biotic factors particularly extensive cattle grazing. The vegetation today consists of tropical thorn forests and grasslands in some areas.

4. Gangetic plain

This region covers part of Delhi, Uttar Pradesh, Bihar, West Bengal and part of Orissa. Average annual rainfall ranges from 50 cm to 150 cm from east to west. The vegetation consists of tropical moist deciduous forests, dry deciduous forests, thorn forests and mangrove forests.

5. Assam

The region covers most of the Assam. The climate is characterized by very high temperature and rainfall. The vegetation consists of tropical evergreen and wet temperate forests in the lower plains while hilly tracts up to 1700 m altitude have subtropical pine forests.

6. Central India

This region comprises part of Orissa, Madhya Pradesh, Vindhyan region and Gujrat. The areas are mostly hilly with some places at 500-700 m altitude. The average annual rainfall is 100-170 cm. Biotic disturbances are very common in this region resulting in degradation of forests into thorny forests in the open area. The vegetation consists of tropical moist deciduous forests, chiefly Sal forests in areas of annual rainfall above 150 cm and mixed deciduous forest in areas of 125-150 cm annual rainfall. Tropical thorn forests are found in the areas of annual rainfall below 125 cm.

7. Western coast of Malabar

This is a small region extending from Gujrat to Kanyakumari along Western Ghats. The climate is warm humid having annual rainfall over 400 cm. The climate is tropical on the coasts and temperate in the hills. The vegetation consists of tropical wet evergreen, moist evergreen and moist deciduous forests. Wet temperate forests (Sholas) are present in Nilgiri while mangrove forests are found in the saline swamps on the coasts.

8. Deccan

The region comprises southern Peninsular India from southern Madhya Pradesh up to Kanyakumari excluding the Western Ghats. The average annual rainfall in the region is about 100 cm. The vegetation consists of tropical dry evergreen, dry deciduous and swamp forests.

9. Andman and Nicobar

This region includes Andman and Nicobar Islands. The climate of the region is warm and humid with very high temperature and annual rainfall. The vegetation consists of littoral mangrove, evergreen, semi-evergreen and deciduous forests.

NATURAL VEGETATION OF INDIA

India is situated at tropical latitudes and has diverse temperature and rainfall regimes. The overall climate of India is suitable for the growth of forests. The climax formations of Indian subcontinent have been altered much due to human activities in the last few thousand years. However, the remaining vegetation shows that the natural vegetation of India primarily consists of forests. The grasslands found in the region are not natural plant formations but have originated secondarily due to destruction of natural forests in some places. Therefore, these represent various stages of seral (successional) development due to the influence of a variety of biotic influences.

FORESTS OF INDIA

The most important factors influencing the physiognomy, species composition, phenology etc. of Indian forests are temperature, rainfall, local edaphic and biotic factors. These factors have been used in the classification of Indian forests. Most detailed classification of Indian forests is by Champion and Seth (1967) in which 16 major types of forests have been recognized. These 16 major types can be grouped into 5 major categories viz. moist tropical, dry tropical, montane sub-tropical, temperate and alpine forests.

1. Moist tropical forests

These forests are found in the areas of quite high temperature and rainfall. The forests are dense, multi-layered and have many types of trees, shrubs and lians. These forests are further categorized into 4 types depending on the degree of wetness in the area and the dominant life form in the forest.

1. Tropical wet evergreen forests

These are climatic climax forests found commonly in areas having annual rainfall above 250 cm and temperature 25-30^oC. These forests are chiefly distributed on the western face of Western Ghats, Assam, Cachar, parts of West Bengal, northern Canara, Annamalai Hills and Coorg in Meysore and Andman Islands.

The characteristic feature of these forests is dense growth of very tall trees having height of more than 45 m. Climbers, lians, epiphytes and shrubs are abundant but herbs and grasses are rare in these forests. The carpet layer of herbs and grasses can not grow because very dense layer of leaf canopy of trees does not allow enough light to reach to the ground.

Dominant trees in forests of west coast are Dipterocarpus indica, Palaquim and Cellenia while in forests of Assam Diptercarpus macrocarpus, D. turbinatus, Shorea assamica, Mesua ferrea and Kayea are the dominant trees.

Common subdominants in these forests are Mangifera, Eugenia, Myristica, Pterospermum, Polyalthia, Elaeocarpus, Schlechera, Artocarpus, Memeocylon, Poeciloneuron, Cinnamomum, Diospyros, Sapindus, Vitex, Holigarna, Alstonia, Hardwickia, Spondias, Dendrocalamus, Calamus, Bombax, Veteria, Calophyllum, Pandanus, Cedrela, Tetrameles, Strobilanthes, Emblica, Michelia, Ixora, Hopea, Lagerstroemia, several species of ferns and orchids.

2. Tropical moist semi-evergreen forests

These are also climatic climax forests found commonly in areas of annual rainfall 200-250 cm and temperature 25-32^oC.These forests are chiefly distributed along the Western Ghats, in upper parts of Assam and Orissa and in Andman Islands. These forests are more developed in the northern India than in southern India.

Characteristic feature of these forests is dense growth of evergreen trees intermixed with deciduous trees that shed their leaves for very brief period of relative dryness. Average height of trees in these forests is 25-35 m and shrubs are common. Forests have rich carpet layer of herbs, grasses ferns and orchids.

Dominant trees in these forests are Dipterocarpus alatus, Hopea, Terminalia and Salmalia in Andman Island; Artocarpus, Micheliaand Mangifera in Orissa; Schima wallichii, Bauhinia, Phobe and Ammora in Assam.

Common subdominants in these forests are Mylia, Schleichera, Bambusa, Ixora, Calamus, Sterculia, Webera, Strobilanthus, Cedrela, Shorea, Actinodaphne, Garcinia, Lagerstroemia, Mallotus, Vernonia, Dendrocalamus, Pelvetta, Elattaria, Pothos, Vitis, Garuga, Albizzia and Dellenia. Common herbs and grasses in the ground (carpet) layer are Inula, Andropogon, Crotolaria, Imperata, Leca, Desmodium, Fambosa and Woodfordia.

3. Tropical moist deciduous forests

These forests are found in the area having temperature of 25-30^oC and quite high annual rainfall of 150-200 cm spread over most of the year but periods of rain alternating with very short periods of dryness. In several areas, the forests have been converted into open savannahs due to intensive biotic factors. These forests are chiefly distributed in a narrow belt along Himalayan foothills, on the eastern side of Western Ghats, Chota Nagpur, Khasi hills, in moist areas of Kerala, Karnataka, sothern Madhya Pradesh, parts of northern Uttar Pradesh, Bihar and West Bengal.

Chief characteristic of these forests is dominance of deciduous trees that remain leafless for one or two months only along with lower story of smaller trees and evergreen shrubs.

Dominant trees of these forests in north India are Tectona grandis, Shorea robusta, Salmella, and Dalbergia while in south India only Tectona grandis and Shorea sp. are dominant.

Common subdominants in the forests are Cedrela, Albizzia, Terminalia, Adina, Melia, Sterculia, Grewia, Gariya, Lagerstroemia, Cordia, Pongamia, Bambusa, Dendrocalamus, Chloris, Mallotus, Anogeissus, heteropogon, Cymbopogon and Andropogon.

4. Littoral and swamp forests

These forests are found in wet marshy areas, in river deltas, in saline or other swampy areas and along the sea coasts. They are chiefly distributed in deltas of large rivers on the eastern coast and in pockets on the western coast (Tidal forests), in saline swamps of Sundarban in West Bengal, coastal areas of Andhra and Orissa (Mangrove forests) and in less saline or non-saline swampy pockets throughout the India.

Chief characteristic of these forests is dominance of halophytic evergreen plants of varying height with varying density of plants in different area.

Dominant plants of tidal and mangrove forests are Rhizophora, Bruguiera, Ceriops, Horitora, Avicennia, Nipa, Sonneratia and Acanthus. In less saline swamps, dominant plants are Ipomea, Phoenix, Phragmitis, Casuarina, Manilkara and Calophyllum. In other swamps, the dominant plants are Barringtonia, Syzygium, Myristica, Bischofia, Trowia, Lagerstroemia, Sophora, Pandanus, Entada and Premna.

2. Dry tropical forests

These forests are found in the areas where wet season is followed by a relatively long period of dryness during which trees remain leafless. These forests are dominated by smaller trees and shrubs and have abundance of shrubs or sometimes grasses. This category includes three types of forests.

1. Tropical dry deciduous forests

These forests are found in areas having temperature of 25-32^oC and annual rainfall of 75-125 cm along with a dry season of about six months. Distribution of these forests in northern India is in areas of Punjab, Haryana, Uttar Pradesh, Bihar and Orissa. In the southern and central India, these forests are distributed in dry areas of Maharashtra, Tamilnadu, Karnataka and Madhya Pradesh.

Chief characteristic feature of the forests is open canopy of small (10-15 m high) trees and abundance of shrubs.

Dominant species of the forests in north India are Shorea robusta, anogeissus, Terminalia, Buchnnania, Somocarpus, Carissa, Emblica, Madhuca, Acacia, Aegle, Diospyros, Bauhinia, Eugenia, Zyzyphus, Lannea, Sterculia, Dendrocalamus, Salmelia, Adina, Grewia, Adathoda and Helicteres. In south India, dominant plants are Tectona grandis, Dalbergia, Kydia, Terminalia, Pterospermum, Dillenia, Acacia, Diospyros, Anogeissus, Boswellia, Bauhinia, Chloroxylon, Hardwickia, Soymida, Gymnosporia, Zyzyphus, Dendrocalamus and Holorrhena.

Subdominant species in these forests are Bambusa, Lantana and grasses like Panicum, Andropogon and Heteropogon.

2. Tropical thorn forests

These forests are found in the areas of high temperature of 27-30^oC and very low annual rainfall of 20-60 cm with long periods of dryness. These forests are distributed in western Rajasthan, parts of Maharashtra, Madhya Pradesh and Tamilnadu.

Chief charateristic of such forests is sparse distribution of small (8-10 m high) mostly thorny trees with shrubs being more common than trees. The plants in these forests remain leafless for most of the year. They develop leaves only during the brief rainy season when grasses and herbs also become abundant.

Dominant plants in these forests are Acacia nilotica, A. leucophloea, A. senegal, Prosopis spicigera, P. juliflora, Albizzia and Capparis.

Common subdominant plants are Zyzyphus, Anogeissus, Erythroxylon, Euphorbia, Cordia, Randia, Balanites, Salvadora, Gymnosporis, Leptadenia, Suaeda, Grewia, Gymnoma, Asparagus, Butea, Calotropis, Adathoda, Madhuca, Salmelia, Crotolaria, Tephrosia and Indigophera.

3. Tropical dry evergreen forests

These forests are found in the areas of relatively high temperature and small rainfall available only during summers. The forests are distributed in some parts of Tamilnadu and Karnataka.

Chief characteristic features of the forests are dense distribution of mixed small evergreen and deciduous trees of 10-15 m height, absence of bamboos and abundance of grasses.

Dominant plants in the forests are Memecylon, Maba, Pavetta, Foronia, Terminalia, Ixora, Sterculia, Mesua and Schleichora.

3. Montane sub-tropical forests

These forests occur in the areas where climate is cooler than tropical but warmer than temperate areas i.e. on the hills between the altitudes of 1000 m and 2000 m. The forests are dominated by semi-xerophytic evergreen plants. This category includes three types of forests.

1. Sub-tropical broad-leaved hill forests

These forests occur in relatively moist areas at lower altitudes on mountain ranges. Their chief distribution is in eastern Himalayas of West Bengal and Assam , hills of Khasi, Nilgiri and Mahabaleshwar.

Chief characteristic feature of the forests is dense growth of evergreen browd-leaved trees with abundant growth of climbers and epiphytic ferns and orchids.

Dominant trees in the forests of north are Quercus, Schima and Castanopsis with some temperate species. In the southern areas, dominants are Eugenia and members of family Lauraceae.

Common co-dominants and subdominants in the eastern Himalayas are Dalbergia sissoo, Acacia, catachu, Sterospermum, Cedrela toona, Bauhinia, Anthocephalus cadamba, Lagerstroemia parviflora, Albizzia procera, Salmella, Artocarpus chaplasha and Dendrocalamus. In the western Himalayas, codominants and subdominants are Shorea robusta, Dalbergia sissoo, Cedrela toona, Ficus glomerulata, Eugenia jambolina, Acacia catachu, Butea monosperma, Carissa and Zizyphus. Other common plants in these forests of both north and south India are Actinodaphne, Randia, Glochidion, Terminalia, Olea, Eleagnus, Murraya, Atylosia, Ficus, Pittosporum, Saccopetalum, Carreya, Alnus, Betula, Phobe, Cedrela, Garcinia and Polulus. In the south, Mangifera and Canthium and climers like Piper trichostachyon, Gnetum scandens and Smilax macrophylla are also common.

2. Sub-tropical dry evergreen forests

These forests occur in areas having quite low temperature and rainfall. The forests are distributed in the lower altitudes of eastern and western Himalayas.

Chief characteristic feature of the forests is presence of thorny xerophytes and small-leaved evergreen plants.

Dominant plants in the forests are Acacia modesta, Dodonea viscosa and Olea cuspidata.

3. Sub-tropical pine forests

These forests occur at middle altitudes between 1500-2000 m in Himalayas. They are distributed in western Himalayas from Kashmir to Uttar Pradesh. In eastern Himalayas, the forests occur in Khasi Jayantia Hills of Assam.

Chief characteristics of the forests in open formations of pine trees.

Dominant trees in the forests are P. roxburghii and Pinus khasiana.

4. Temperate forests

These forests are found in the areas having quite low temperature along with comparatively high humidity than the comparable areas of higher latitudes. The cause of high humidity is greater rainfall in Himalayas except in parts of Uttar Pradesh, Punjab, Himachal Pradesh and Kashmir where humidity is lower. The forests occur mainly in the Himalayas at altitudes 2000-4000 m. The forests are generally dominated by tall conifers or angiospermic evergreen trees with abundance of epiphytic mosses, lichens and ferns. The category includes three types of forests.

1. Wet temperate forests

These forests are found at altitudes of 1800-3000 m in the cooler and humid mountains. They are distributed in the eastern Himalayas from eastern Nepal to Assam, in the western Himalayas from Kashmir to western Nepal and in Nilgiri Hills of south Indian.

Chief characteristic feature of the forests in the Himalayas is dense formation of evergreen, semievergreen broad-leaved and coniferous trees of up to 25 m height. In south India, these forests are termed Shola forests and mostly have 15-20 m high broad-leaved trees with dense leaf canopy, abundant epiphytic flora and rich herbaceous undergrowth.

Dominant trees in the forests of western Himalayas are angiosperms like Quercus, Betula, Acer, Ulmus, Populus, Corylus, Caprinus etc. and conifers like Abies, Picea, Cedrus etc. In eastern Himalayas, dominants are Quercus, Acer, Prunus, Ulmus, Eurya, Machilus, Symplocos, Mahonia, Begonia, Michelia, Thunbergia, Rhododendron, Arundinaria, Bucklandia, Pittosporum, Loranthus, Tsug and, Abies. In the Nilgiri Hills, the dominants are Rhododendron nilagiricum, Hopea, Balanocarpus, Artocarpus, Artocarpus, Elaeocarpus, Pterocarpus, Hardwickia, Myristica, Cordonia, Salmalia, Mucuna and Dioscorea. In all the areas, the undergrowth is formed by members of Asteraceae, Rubiaceae, Acanthaceae and Fabaceae.

2. Himalayan moist temperate forests

These forests are found at 1700-3500 m altitude in eastern and western Himalayas. These occur in areas having annual rainfall above 100 cm but relatively less than that in areas of wet temperate forests.

Chief characteristic feature of the forests is presence of tall (up to 45 m high) conifers, oaks or their mixture along with thin partly deciduous undergrowth.

Dominant trees in the eastern Himalayas are Tsuga dumosa, Quercus lineata, Picea spinulosa, Abies densa and Quercus pachyphylla. In the western Himalayas, dominants in lower zones are Quercus incana, . dialata, Cedrus deodara, Pinus wallichiana, Picea smithiana, Abies pindrew, Cotoneaster, Berberis and Spire while in the higher zones the dominants are Quercus semicarpifolia and Abies pindrew.

3. Himalayan dry temperate forests

These forests occur in the regions of Himalayas having very low rainfall. They are distributed in both eastern and western Himalayas.

Chief characteristic feature of the forests is dominance of evergreen oaks and conifers. Undergrowth is formed by scrubs.

Dominant trees in the forests of comparatively drier western Himalayas are Pinus gerardiana and Quercus ilex. In the comparatively wetter western Himalayan region, the dominants are Abies, Picea, Larix griffithia and Juniperus wallichiana.

Subdominant plants in these forests are Daphne, Artemesia, Fraxinus, Alnus, Cannabis and Plectranthus.

5. Alpine forests

These forests are found in the regions of Himalayas having extremely low temperature and humidity. The forests are dominated by perennial and annual herbs and grasses though some trees may also be present in areas of relatively high humidity. Abundant lichen flora is characteristic feature of these forests. This category includes three types of forests.

1. Sub-alpine forests

These forests are found in open strands throughout the Himalayas between the altitude 3500 m and the tree tine.

Chief characteristic feature of the forests is presence of some evergreen conifers and broad-leaved trees along with prominent shrub layer.

Dominant trees in the forests are Abies spectabilis, Rhododendron and Betula. Prominent shrubs in the forests are Cotoneaster, Rosa, Smilax, Lonicera and Strobilanthus.

2. Moist alpine scrub forests

These forests are found in the Himalayas above the tree line up to 5500 m altitude in somewhat moist areas.

Chief characteristic feature of the forests is dominance of dwarf, evergreen shrubby conifers and broad-leaved trees along with prominent shrub layer under them.

Dominant trees in the forests are Juniperus and Rhododendron while prominent shrubs are Thalictrum, Lonicera, Saxifraga, Arenaria, Bergia, Sedum and Primula.

3. Dry alpine forests

These forests are found in comparatively more dry areas of Himalayas upto 5500 m altitude.

Chief characteristic feature of the forests is open formation of xerophytic scrubs with many herbs and grasses.

Dominant plants in the forests are Juniperus, Caragana, Eurctia, Salix and Myricaria.

GRASSLANDS OF INDIA

The grasslands of India are not of primary origin. These have originated secondarily in many areas due to destruction of natural forests by biotic interference, particularly due to excessive grazing and land clearing for agriculture. These grasslands are maintained in various seral (successional) stages by a variety of biotic factors.

According to the dryness of the area, the Indian grasslands may be categorized into three types.

1. Xerophilous grasslands: These are found in semi-desert areas of north and west India.

2. Mesophilous grasslands (Savannahas): These are found in areas of Uttar Pradesh having moist deciduous forests.

3. Hygrophilous grasslands (Wet savannahas): These are found in wet regions of India.

Whyte et al. (1954) classified Indian grasslands on the basis of dominant grass species into eight major grass associations.

1. Sehima-Dichanthium association

These grasslands develop on black soil. They are found in some areas of Maharashtra, Madhya Pradesh, Uttar Pradesh, south western Uttar Pradesh, Tamilnadu and Karnataka.

Dominant grass species in the grasslands are Sehima sulcatum, S. nervosum, Dichanthium annulatum, Chrysopogon montanus and Themeda quadrivalvia.

2. Dichanthium-Cenchrus association

These grasslands develop on sandy-loam soils. They are found in Plains of Punjab, Haryana, Delhi, Rajasthan, Saurashtra, eastern Uttar Pradesh, Bihar, West Bengal, eastern Madhya Pradesh, coastal Maharashtra and Tamilnadu.

Dominant species in these grasslands are Dichanthium annulatum and Cenchrus ciliaris.

3. Pragmitis-Saccharum association

These grasslands develop in marshy areas. They are found in terai regions of northern Uttar Pradesh, Bihar, West Bengal, Sundarban region of Bengal, Tamilnadu, and Kaveri delta.

Dominant species in these grasslands are Phragmitis karka,, Saccharum spontaneum, Imeerata cylindrica and Bothriochlo pertusa.

4. Cymbopogon type

These grasslands develop on low hills. They are found in Eastern Ghats, Vidhyas, Satpura, Aravali and Chota Nagpur.

Dominant species in the grasslands is Cymbopogon.

5. Arundinella type

These grasslands develop on high hills. They are found in Western Ghats, Nilgiris and lower Himalayas from Assam to Kashmir.

Dominant species in the grasslands are Arundinella nepalensis, A. setosa and Themeda anthera.

6. Bothriochloa type

These grasslands develop on paddy tracts in areas of heavey rainfall in Lonavala tract of Maharashtra.

Dominant species in the grasslands is Bothriochloa odorata.

7. Deyeuxia-Arundinella association

These grasslands develop in temperate areas of upper Himalayas between 2100-3500 m altitudes.

Dominant species in the grasslands are Deyeuxia, Arundinella, Brachypodium, Bromus and Festuca.

8. Deschampsia-Deyeuxia association

These grasslands develop in temperate to alpine regions having thin soil cover over rocky substratum. They are found in Kashmir and in Himalayas above 2600 m altitude.

Dominant species in the grasslands are Deyeuxia, Deschampsia, Poa, Stipa, Glycera and Festuca.

SOIL TYPES OF INDIA AND THEIR AGRICULTURAL POTENTIAL

Indian soils have been classified into eight major types according to their origin and physico-chemical properties.

ALLUVIAL SOILS

These soils cover an area of about 1,500,000 square kilometers. The soils develop from the weathering material transported by rivers from their catchment areas and deposited in their basins during floods. Chemical nature and fineness of inorganic material depends on the type of rock in the catchment area and the degree of weathering of the rocks. Geologically these soils are of two types.

• New alluvium (Khadar): These are soils that have been deposited more recently and are constantly replenished by deposition or more transported material during regular floods. The soils are found in low lands and deltas. The soils are generally sandy and light coloured having lesser proportion of soil aggregates (kankars).

• Old alluvium (Bangar or Bhangar): These soils were deposited at an earlier time and have not naturally been disturbed much. These soils are found in upland areas of river deltas.They are more differentiated, more clayey, generally dark coloured and full of soil aggregates (kankars) than the new alluvium soils. Occasional pebble-beds may be present and hard pans may be formed sometimes at certain depths due to binding of soil grains by infiltrating silica or calcareous matter.

Alluvial soils may be broadly divided into coastal/deltaic alluvium and inland alluvium according to their location.

1. Coastal/deltaic alluvium: These soils are distributed in the deltas of major rivers e.g. Ganda, Brahmputra, Krishna, Kaveri, Narmada, Tapti, Godavari, Mahanadi etc. and on the coasts of Orissa, Andhra, Tamilnadu, Kerala, Karnataka and Maharashtra. These are new alluvial soils and vegetation provides humus in them. New inorganic material is deposited regularly during floods. The soils have dark colour (in southern India), loamy texture (in Sundarban delta), high humus, high water holding capacity, high base exchange capacity, neutral to saline pH, humid or swampy nature and rich in potassium in most of the areas. The soils are suitable for crops that require humid soils e.g. rice, jute and coconut.

2. Inland alluvium: These soils are found in the river basins of northern and southern India. They include new as well as old alluvium. Characters of the soil vary in different regions due to the type of parent rock material, climate and type of plant cover.

1. Brahmputra alluvium: This is old alluvium distributed in the uplands of Brahmputra valley. The soil is acidic, sandy, rich in total potash and phosphorus. They have moderate amount of organic matter and nitrogen. New alluvium is found along the banks of the river. It is less acidic and neutral or even alkaline in pH.

2. Indogangetic alluvium: These soils are distributed in large plains of the rivers Indus and Ganges in Punjab, Uttar Pradesh, Bihar and West Bengal.

1. Punjab alluvium: This soil is sandy or loamy in texture with soil crust of varying depth. The soil is undifferentiated and has soil aggregates (kankars) in lower layers. The soil has high soluble salts and high base-exchange capacity. Phosphorus and potash content of the soil is adequate while nitrogen and organic matter contents are deficient. The soil has alkaline pH.

2. Allluvium of Uttar Pradesh: These soils are broadly categorized into:

1. Light coloured alluvium: This soil is found in the plains of west and north-western Uttar Pradesh.

2. Intermediate textured alluvium: It is distributed in the central basins of rivers Ganges and Jamuna.

3. Dark coloured alluvium: The soil is found in the eastern Uttar Pradesh.

4. Calcareous alluvium: This soil develops on calcareous parent rock material and is found in north eastern Uttar Pradesh. These soils have varying amounts of soluble salts and base-exchange capacity in different regions. The pH of the soil is neutral to alkaline.

3. Bihar alluvium: It is categorized into:

1. Northern Bihar alluvium: These soils are found in the area north of river Ganges up to Himalayas in Bihar. The area includes a calcareous belt as a triangle in the west and broken inundated areas that remain flooded for different periods of the year in the middle of the region. The soils are sandy loam to clayey loam in texture, neutral to alkaline in pH rich in lime and potash and poor in phosphorus.

2. Southern Bihar alluvium: These soils are found in the area between river Ganges and the southern hilly region in Bihar. The area includes a depressed area in the middle that remains flooded during monsoon. The soils have texture similar to northern Bihar alluvium and almost neutral pH. In these soils, potash and phosphate content is higher while lime content is lower than in northern Bihar alluvium.

4. West Bengal alluvium: These soils are categorized into:

1. Old alluvium of West Bengal: These soils are distributed in Rath region of Murshidabad and Bankura areas. The soils are clayey in texture.

2. New alluvium of West Bengal: This soil is distributed in rest of the plains of West Bengal. The soil is sandy loam to clayey in texture with clay pan at certain horizons. This soil is more fertile than the old alluvium.

3. Gujrat alluvium: These soils are locally known as goradu and distributed in north Gujrat tract, Ahmedabad and Kaira districts. The soils are categorized into:

1. Old alluvium (Gorat soils): These are found in Baroda region. They are clayey in texture, brown in colour and have soil aggregates (kankars).

2. New alluvium (Bhata soils): These are fairly deep soils and mainly of secondary deposition. The soils are fairly rich in phosphorus and potash but poor in nitrogen and organic matter.

4. Red and yellow alluvium: The soils are found in the basin of river Mahanadi in Madhya Pradesh distributed in Balaghat, Durg, Raipur and Bilaspur areas. These soils are grouped into:

1. Bhata soils: These are gravely sandy in texture, reddish brown in colour and found in uplands of barren wastelands.

2. Matasi soils: These are loamy to clayey in texture, yellow in colour and found in upland areas. These soils are suitable for paddy cultivation.

3. Dorsa soils: These soils have texture like Matasi soils but a darker colour than those. The soils are found on the slopes. These soils are good for paddy cultivation.

4. Kanhar soils: These are darker and heavier soils found in lowlands. These are good for paddy and suitable for wheat cultivation.

5. Orissa alluvium: These soils are sandy and of finer texture having sufficient potash but poor phosphate content. According to the location, these soils are grouped into:

1. At soils: These are found in dry upland areas.

2. Mal soils and Berna soils: These are found on intermediate slopes.

3. Behal soils: These are the heaviest soils found in lowland area.

Alluvium soils are generally suitable for a variety of crops like wheat, rice, millets, pulses, maize, sugarcane, rubber, jute, vegetables etc. depending on the climate, texture and other soil characteristics. The nitrogen deficiency in the soil is the main limiting factor in crop production in all the alluvial soils except the calcareous and saline alkali alluvial soils. In these later soils, high salinity and low phosphate limit the crop production. With suitable irrigation, fertilizers and proper agricultural practices, alluvial soils are generally very fertile.

BLACK SOILS (REGUR)

These soils cover about 5,46,000 square kilometers in India. They are distributed in Bundelkhand region of Uttar Pradesh, western Madhya Pradesh, Bundi and Tonk districts of northern Rajasthan. They are also present in parts of Gujrat, Karnataka, Andhra, Maharashtra and Tamilnadu. The soils are residual soils derived from the rocks of Deccan Trap, Rajmahal Trap, ferruginous gneisses and schists under semi-arid conditions. Soils have been formed by alternate deposition and assimilation of organic matter with weathering products of the rocks. The black colour of soils is due to superficial rock iron. The soils have high content of montmorillonite mineral. These soils are categorized into three types according to the depth, colour and rock matter.

1. Shallow black soils: These are 30-50 cm deep and derived from basalts of trap rocks.

2. Medium black soils: These are 50-120 cm deep soils derived from a variety of rocks including basaltic trap, Dharwar schists, basic granites, gneisses, hornblende and chlorite schists.

3. Deep black soils: These are 120-200 cm deeps soils derived from basaltic traps and contain irregular lime nodules (kankars).

Black soils are deep gray to black in colour, clayey or clay-loam in texture, fine grained with small surface grains, transparent or semi-transparent, cemented by coloured matrix of double hydrated ferrous and aluminum silicates. They are rich in oxides of iron and aluminum and carbonates of calcium and magnesium. The soils are poor in phosphate and nitrogen. The soils have high water holding capacity, high content of exchangeable bases and alkaline soil pH. The soils are sticky in wet condition and contract in dry condition resulting in heavy cracks and fissures in the soil. This phenomenon is termed self-ploughing. In Maharashtra, upland soils and soils of slopes are light-coloured, thin and poor while lowland and valley soils are deep, clayey and rich with much sub-soil lime. The soils along the Ghats are very coarse and gravely. In Madhya Pradesh, both shallow and deep black soils are found. Black soils in Karnataka are quite heavy with high amounts of salts, lime and magnesia.

Black soils are best suited for the cultivation of cotton. With proper irrigation and ploughing, the soils can also be used for cultivation of wheat, millet, sugarcane, linseed, gram and pulses. These soils require good preparation of land before irrigation. Conservation of the moisture in shallow and medium black soils by contour-bunding is useful in increasing the production of rabi crops like jowar. Owing to high amounts of salts, uncontrolled irrigation of black soils makes these soils alkaline or saline.

RED SOILS

These soils cover about 3,50,000 square kilometers in India. The soils are distributed in major portion of Tamilnadu, Karnataka, southeastern Maharashtra, eastern Andhra, Madhya Pradesh, Orissa, Chota Nagpur, southern Assam, western West Bengal, eastern hills of Aravali in Rajasthan and southern districts (Jhansi, Banda, Hamirpur, Varanasi and Mirzapur) of Uttar Pradesh. The soils have developed on crystalline rocks by prolonged weathering in hot climate. Ferrous oxide is precipitated after evapouration of soil moisture giving the red colour. The soils are generally dark red, red-black or grey-brown in clour, rich in mineral kaolinite and neutral to acidic in pH. The soils have low base-exchange capacity, low water-holding capacity, low organic matter content, low nitrogen, low phosphate, high potash and high lime. Soil aggregates (kankars) are absent in the soils. The soils have silica and aluminum with free quartz or sand and the soil aggregation is poor. The soils are grouped into:

1. Red loam soils: These are dark red in colour and loamy in texture.

2. Red gravelly soils: These are dark red and gravelly in texture.

3. Mixed red and black soils: These soils are found in areas that intergrade into black soil regions.

Cultivation of red soils depends on the irrigation. Most of soils in Tamilnadu, Karnataka and Andhra have been cultivated by tank irrigation and manuring. These soils can be used for the cultivation of wheat, rice, millet, gram and sugarcane. Groundnut, coconut and ragi are also cultivated on these soils.

LATERITE SOILS

These soils are found in about 2,48,000 square kilometers in India. They are distributed on the hills of peninsular India, in eastern Ghat region of Orissa, parts of Assam and central India. The soils are also found in Karnataka, Maharashtra, Malabar, parts of West Bengal, Bihar, Madhya Pradesh and Tamilnadu. The soils are residual soils developed on aluminum-rich rocks e.g. greisze, sandstone, granite and basaltic rocks in regions of high rainfall with alternating wet and dry seasons. The soils develop by the process of laterization in which silica and alkali are leached down and remaining compounds rich in oxides of iron and aluminum form the soil. The soil is compact to vesicular rock essentially composed of a mixture of hydrated oxides of aluminum and iron with small amounts of the oxides of manganese, titanium etc. The soil may be broken and transported by streams to lower levels and deposited there becoming cemented again into compact mass. Thus the higher elevation laterite is residual and lower elevation laterite is alluvial in nature.

The soils are compact, reddish or yellowish-red in colour and turn black on exposure to the sun. The texture of these soils is gravelly, loamy or clay-like loam. The soils are deficient in available exchangeable bases, essential plant nutrients, potash, nitrogen and organic matter. The nitrogen content of the soils varies from 0.03% to 0.06% and pH ranges from 4.8 to 5.5. The base-exchange capacity of these soils is generally low. The laterites of higher elevation are more acidic and comparatively richer in nutrients than the laterites of lower elevation. Occasionally the humus content of the soils may be high e.g. in Kanara region of Maharashtra where nutrients, nitrogen and potash are also high. Sometimes soils may contain iron phosphate.

The cultivation of these soils requires good management practices to check the soil erosion, application of proper fertilizers, liming and proper irrigation. Higher elevation soils grow good crops of tea, cinchona, rubber and coffee. Lower elevation soils with proper management can grow paddy, rice, sugarcane and pulses like green gram and gram. Soils generally show good response to liming and application of potash and nitrogenous fertilizers according to the type and pH of the soil. In some lowland areas, iron and manganese cause toxicity due to reduction of ferric and trivalent Mn to ferric and divalent Mn respectively. Liming can correct the situation and uptake of nitrogen and phosphorus is normalised.

FOREST, PEAT AND ORGANIC SOILS

1. Forest soils: These cover an area of about 2,85,000 square kilometers in India. Soils are found in forests of Malabar, hills of Coorg, hilly districts of Assam, Darzeeling in West Bengal, sub-Himalayan tracts of Uttar Pradesh and Himachal Pradesh. These soils develop in areas under heavy forest cover. In some areas, the soils are under acidic conditions with presence of acidic humus and low base-exchange capacity. In other areas, the soils are under slightly acidic to neutral conditions where brown earths with high base-exchange capacity are developed. The chief factor in the development of these soils is abundance of organic matter derived from forest growth. These soils are mostly under forest cover but are suitable for the cultivation of crops particularly sugarcane, rice, paddy and millet.

2. Peat and organic soils: These develop in waterlogged, swampy or marshy areas. The soils develop due to deposition of large amount of poorly decomposed organic matter on the weathered rock material. These soils are found in coastal tracts of Orissa, Sunderban in West Bengal, Almora in Uttar Pradesh, northern Bihar, southeastern Tamilnadu and Kerala. The soils are bluish, very loose due to excess of organic matter, acidic, very rich in free aluminum-iron componds of blue colour and poor in lime. The soils become waterlogged during monsoon. These soils are put under paddy cultivation after monsoon is over. These soils are generally very poor for agriculture.

MOUNTAINEOUS AND SKELETAL SOILS

These soils develop in the foothills and mountains up to the altitude of 12,000 feet. Thickness, texture and properties of the soils depend upon altitude. At higher altitudes, the soils are thin and gravelly while at lower levels, they are fine and rich. The soils generally have variable colours depending on the type of rock and the amount of organic matter. The texture of the soils is loose, gravelly, sandy, loamy or sometimes clayey. These are young and immature soils. The A-horizon of the profile is formed directly on the rock and soil particles are loosely aggregated on the soft sandy beds. Humus content of the soils is generally high. Soils are usually acidic but those developed on limestone are basic in reaction. Soils are deficient in lime but rich in minerals, iron salts and nitrogen. These soils are categorized as:

1. Terai soils: These are found near foothills of Himalaya in Uttar Pradesh and in Simla region of Himachal Pradesh. The soils are clayey in texture with high humus content and high water-holding capacity.

2. Tea soils: These are found in Assam, Dehradun district of Uttar Pradesh, Darzeeling district of West Bengal and slopes of Nilgiri hills. The soils are loamy in texture with low lime content.

3. Igneous soils: These are fine soils derived from granite rocks and rich in nutrients.

4. Soils of old rocks: These are found in Nanital district of Uttar Pradesh. The soils are rich in clay and iron.

5. Limestone soils: The soils are found near Mussouri in Uttar Pradesh. The soils are rich in lime, loamy in texture and basic in pH.

The Terai soils are very good for the cultivation of wheat, maize and sugarcane. Tea soils are very good for plantations of tea. Limestone soils are particularly good for rice. Igneous soils and soils of old rocks are fertile soils good for various crops, fruit trees and vegetables. All these soils are generally suitable for timber plantations of sal, pine, deodar etc.

DESERT SOILS

These soils cover about 1,42,000 square kilometers in India and develop in areas of very low rainfall, very high temperatures and absence of vegetation. The evapouration from the soil is very high owing to absence of plant cover and soils have almost no soil moisture for major part of the year. These soils are distributed in northwest Rajasthan, southern Punjab, Haryana, in the areas between the river Indus and Arawali hills. The soils are of geologically recent origin. The areas are covered under a mantle of brown sand that inhibits the growth of soil. Sands of Rajasthan are partly derived from the disintegration of subjacent tracks but are largely blown in from coastal regions and valley of Indus river.Some soils have high soluble salts, alkaline pH and deficiency of organic matter.

These soils are normally infertile but management of irrigation can make these soils cultivable. By gradually introducing plant cover, these soils can be stabilized along with the increase in their humus content and water-holding capacity. With availability of proper irrigation, these soils can support the cultivation of paddy, millet, oat and even wheat.

ALKALI AND SALINE SOILS

These soils develop in arid areas having low rainfall, poor drainage, high temperature and high evapouration. These soils are found scattered within all the major types of soils. They are present in the indogangetic alluvium of Punjab, Haryana, Delhi, Uttar Pradesh and Rajasthan; in deltaic coastal alluvium of West Bengal, Orissa, Andhra, Tamilnadu, Kerala and Gujrat; in deep and medium black soils of Gujrat, Madhya Pradesh, Mharashtra, Karnataka and Andhra and in desert gray brown soils of Gujarat and Rajasthan. The normal soil of the area becomes alkaline or saline owing to deposition of high amounts of the soluble salts of sodium, magnesium or calcium due to poor drainage. In summers, capillary action in the soil brings the salts to the surface where they are deposited in the form of a white or black effervescent crust.

These soils are normally infertile (Usar soils). However, the management of drainage, good irrigation and application of lime and/or gypsum combined with biological management can make these soils fit for the cultivation of a variety of crops. Alkali soils can grow wheat, barley, oat, sorghum, sugarbeat, cotton, grapes etc. Saline-alkali soils can grow paddy, oat and barley while saline soils can grow rice, sugarcane, barley and castor. These soils can be successfully managed with green manuring by Dhaincha or Barseem in rotation with cereal crop.

SOILS OF UTTAR PRADESH

The soils of Uttar Pradesh can be grouped into following categories:

ALLUVIAL SOILS

These include both new and old alluvium developed by transportation of weathered rock material from Himalayas by rivers Ganges, Jamuna, Sarda and Rapti and its deposition in their basins.

Alluvium of Uttaar Pradesh has sandy loam, loam or clay loam texture. It is generally poor in nitrogen and available phosphorus but rich in calcium carbonate. The colour of the soil depends on the amount of sand and organic matter in it. In the areas of poor drainage due to presence of hard pans in the sub-soil or in areas where water table has risen due to heavy irrigation, the soils have become impregnated with salts. In extreme cases, these have turned into saline-alkaline soils. Alluvial soils of Uttar Pradesh are categorized into:

1. Alluvium of northeast: It is light sandy loam in texture, calcareous in nature with neutral to slightly alkaline pH and deficient in nitrogen. These soils are quite fertile if nitrogen and phosphate fertilizers are added.

2. Alluvium of west: It is comparatively more sandy in texture, grayish-yellow in colour, low in nitrogen, phosphorus and organic matter, impregnated with salts, mostly neutral in pH and quite fertileif proper fertilizers and irrigation are given.

3. Alluvium of central region: These soils having medium loam texture may be grouped as:

   1. Northern calcareous alluvium: It is rich in calcium carbonate.

   2. Southern gray-brown alluvium: It is rich on impregnated salts and gray-brown in colour.

4. Alluvium of east: These are heavier and more clayey in texture with slightly higher available potash and phosphate than the southeastern alluvium. These soils are also gray-brown in colour and impregnated with salts. Soil pH is almost neutral.

5. Alluvium of northeast: Soils in the districts of Gorakhpur and Deoria are developed on calcareous parent material. These have variable amounts of calcium carbonate and soluble salts. Soil pH is neutral to alkaline. The soils are quite fertile and sugarcane is the major crop on these.

MIXED RED AND BLACK SOILS

These soils are found in the northern districs of Jhansi, Hamirpur, Banda, Mirzapur and some southern areas of Varanasi. The soils have patches of red soil over the black soil or vice versa. In some areas, red and black soils have become thoroughly mixed giving a brown colour. These soils may be grouped as:

1. Black clay soils: These are found in lower Gangetic basin and are locally known as karail. These soils are thought to have developed from the parent rock material similar to that of black (regur) soils of southern India. The basaltic alluvial material from Deccan trap rocks of Bundelkhand region has been by rivers coming from that region and added to the river Ganges. From there, it has been deposited in its southern basin in the areas where conditions were favourable. These soils have high montmorillonite mineral, high water-holding capacity and high exchangeable bases like potassium, calcium and Magnesium. Calcium carbonate kankars are common in the soils. The soils become saline alkaline on uncontrolled irrigation due to the presence of high amounts of soluble salts.

2. Red soils: These are formed by very old crystalline and metamorphic rock material. The soils are generally poor in nitrogen, phophorus, potash and humus. Compared to black soils, these soils are poor in lime, potash, phosphorus and iron oxide.In Jhansi district, these soils are of two types that are locally known as:

   1. Parwa soils: These are brownish-gray in colour owing to mixing of black and red soils. Texturre of the soil varies from good loam to clayey loam.

   2. Rakar soils: These are true red soils having low nutrients and are not fit for agriculture.

3. Red-yellow soils: These soils are found in Mirzapur district where black soil component is very low and yellow colour is due to hydration of the ferric oxide. Soil pH is neutral and texture is loam to silty loam. Soils are well drained, rich in aluminum and moderately rich in humus.

FOREST AND PEATY SOILS

These soils have eeveloped on lower altitudes of Himalayas in the areas that are under dense plant cover and have low temperatures with temperate climate.

1. Forest soils: These soils are found in Himalayan region of Uttar Pradesh between the altitudes of 1,000 and 3,500 meters. The soils show strong characteristic influence of vegetation on their development. These soils are categorized as:

   1. Sub-montane soils: These soils are found in the regions having rainfall of 170-225 cm and vegetation of coniferous forests. Soil has dark brown to black colour, acidic soil pH and a thick surface layer of organic matter. Soils are similar to podosol soils but show lesser leaching.

   2. Brown hill soils: These soils are found under temperate type vegetation. The soils have been derived from Shale and Sandstone rock materials. The are brown in colour, loamy to silty loam in texture and quite rich in organic matter. Soil pH is acidic but base exchange capacity of the soil is quite high. The soils are suitable for cultivation of cereals like rice, paddy, millets etc.

2. Peaty soils: These soils have developed in waterlogged, low-lying areas in under the plant cover in Almora district. Low oxygen content and low temperature results in poor and slow decomposition of the organic matter deposited by the forest cover resulting in accumulation of a thick layer of peat on the weathered parent rock material. The soils are bluish in colour, very loose in structure, acidic in pH, rich in blue coloured free compounds of Aluminum and Iron, poor in lime and have low base exchange capacity. The soils are not good for agricultural purposes.

MOUNTAINEOUS SOILS

These soils are found in the foothills of Himalayas. They are present from lower Kumaon-Garhwal region up to Gorakhpur district in the east extending along the Nepal border. These soils are grouped into five categories in Uttar Pradesh.

1. Bhabar soils: These soils are found immediately below the hills and haveen formed by deposition of parent material from erosion of hills. These soils are dry and generally have food good organic matter.

2. Terai soils: After the Bhabar soils, these soils form a zone of different width along the foothills and Nepal border. The soils are sandy or silty loam in texture with moderate clay and high humus content. Generally these soils are waterlogged and have very rich vegetation. In the areas of good drainage, these soils form very fertile lands for various cash crops particularly sugarcane.

3. Plain mountaineous soils: After the zone of Terai soils, these soils are found in comparatively more level areas. These soils have clayey texture and are rich in humus. The base-exchange capacity of the soils is quite high and soils are very fertile.

4. Tea soils: These soils are found on the slopes in the hills of Dehradun district. The soil pH is acidic and they are very good soils for plantations of tea.

5. Limestone soils and soils of old rocks: These soils have developed on the limestone rock material and show characteristic features.

   1. Limestone soils: These are found near Mussouri. These have developed on the limestone rock material. The soils have very high lime content, basic pH and loamy texture.

   2. Soils of old rocks: These are found in some areas of Nainital district. They have developed on very old rocks in very long geological time and are very rich in clay along with iron contents.

SKELETAL SOILS

These soils are found in higher altitudes of Himalayan regions i.e. Kumaon and Garhwal regions of Uttar Pradesh. The soils extend in regions beyond the tree line up to the region of snow covered rocks. The soils are very thin, undifferentiated and have very slow decomposition of organic matter due to cold temperatures. These soils are commonly grouped as:

1. Mountain meadow soils: These soils are found in the hills beyond tree line in the areas of comparatively more rainfall but quite low temperature. The soils have been derived from Shale and Sandstone parent materials and are gravely in texture with surface layer of undecomposed or partially decomposed organic matter. Soils are covered mostly with herbaceous vegetation or grass cover.

2. Skeletal soils: These soils are found at higher altitudes in the hills where both temperature and rainfall are very low. Due to very slow weathering, the soils are very thin, usually 7-15 cm in thickness and undifferentiated. The soils are pale brown to dark brown in colour and sandy loam to loam in texture. The soils are covered mostly by xerophytic and sclerophyllous vegetation.

SALINE AND ALKALINE SOILS

These soils are found in patches all over the state, particularly in the districts of Kanpur, Hardoi, Lucknow, Unnao, RaiBareilly, Azamgarh and Mirzapur. Such soils have also developed secondarily in area of heavy irrigation and high summer temperatures. In these areas, water table rises that brings the soluble salts of calcium, magnesium and sodium to the surface of soil. The saline and alkaline soils are infertile termed Usar. However, these soils can be reclaimed by proper soil management practices and can be cultivated.