Laterite soils develop chiefly under which of the following conditions?

High temperature and heavy rainfall, which leach away lime and silica and leave iron and aluminium oxides behind

Low rainfall and high evaporation, which draw salts up to the surface

Cold, waterlogged ground where dead plant matter piles up

High temperature and heavy rainfall, which leach away lime and silica and leave iron and aluminium oxides behind

Annual floods that spread a fresh layer of river silt

Which one of the following groups consists only of rabi crops?

Watermelon, cucumber and muskmelon

In West Bengal, Odisha and Assam, the rice crops known as aus, aman and boro differ from one another mainly in:

The season in which each crop is sown and harvested

The soil group they are grown on

Which one of the following sources irrigates the largest share of the net irrigated area of India?

Lift irrigation from rivers and streams

Which one of the following statements about Operation Flood is correct?

It was launched in 1970 and implemented by the National Dairy Development Board

It was a programme to control floods in the Ganga basin

It aimed to raise fish output from flood-plain wetlands

It was a scheme to build foodgrain storage after floods

It was launched in 1970 and implemented by the National Dairy Development Board

Soils, Natural Vegetation & Agriculture of India

Soil, vegetation and farming are one story told three times. The rock underneath and the climate above decide what soil forms; the same rainfall and temperature decide which forest grows on it; and soil, water and season together decide which crop a farmer can raise and when. Questions on this area reward exactly that chain of reasoning: why black soil suits cotton, why laterite is poor for grain but good for cashew, why thorn forest and bajra share the same dry country, why rice needs standing water and wheat needs a cool, bright ripening spell. This chapter builds the chain link by link — soil formation and the eight soil groups, the five broad forest types, the three cropping seasons, the major crops and their conditions, irrigation, the coloured "revolutions" and the agro-climatic regions. Production rankings shift from year to year, so the chapter teaches the conditions and the regions, which do not.

How Soil Forms and How India's Soils Are Grouped

Soil is the thin, loose upper layer of the land in which plants grow: a mixture of weathered rock particles, humus (decomposed organic matter), air, water and living organisms. It forms slowly — a few centimetres can take centuries — which is why soil lost to erosion is, on a human timescale, lost for good. Soil scientists name five soil-forming factors, and every soil group below is simply a different combination of them.

Parent material — the rock the soil weathers from. It sets the minerals and the texture: basalt gives clayey black soil, granite and gneiss give sandy-to-loamy red soil, and river silt gives alluvium.
Climate — the most important active factor. Rainfall decides how much is washed downward (leaching) and temperature decides how fast rock weathers and humus decays. In the same parent rock, heavy rain plus heat produces laterite; scanty rain produces arid soil.
Relief — slope controls drainage and erosion. Steep slopes keep soil thin and immature; flat, low ground collects deep soil and, where drainage is poor, waterlogged or saline soil.
Organisms — plants supply organic matter, while bacteria, fungi, earthworms and termites break it into humus and mix the soil. Grasslands build humus-rich soils; in hot, wet forests bacteria destroy humus almost as fast as it forms.
Time — the longer these factors work, the more distinct the soil's layers become. Young soils (fresh alluvium, mountain soils) show weak layering; old soils show a well-developed profile.

Dig a pit and the soil profile shows horizons. Horizon A is the topsoil, dark with humus, where roots and organisms are most active. Horizon B is the subsoil, where minerals washed down from above accumulate and organic matter is scarce. Horizon C is weathered parent material, grading down into solid bedrock. Leaching strips Horizon A in rainy climates; capillary rise of salty water spoils it in dry, over-irrigated ones.

The grouping most textbooks follow — by genesis, colour, composition and location — goes back to the soil survey work of the Indian Council of Agricultural Research (ICAR), whose All India Soil Survey Committee divided India's soils into eight major groups: alluvial, black, red and yellow, laterite, arid, saline, peaty and forest soils. Forest soils are also called mountain soils, because in India the two largely coincide. For scientific mapping ICAR also uses the USDA Soil Taxonomy, in which soils are named by "order": the black cotton soils are Vertisols (from their swelling and cracking clay), the dry-region soils Aridisols, and much of the young alluvium falls under Entisols and Inceptisols.

🧠 Memory trick

The eight groups in one breath: "All Black Rocks Lie Around Some Peaceful Forests" — Alluvial, Black, Red-and-yellow, Laterite, Arid, Saline, Peaty, Forest (mountain).

The Eight Soil Groups: Properties and Regions

Alluvial soil is the most widespread group, covering roughly two-fifths of the country: the Northern Plains, the river valleys and the coastal deltas. It is transported soil, laid down by rivers, so its texture changes downstream from coarse and sandy near the hills to fine and clayey in the deltas. In the plains, the older alluvium of the Bhangar contains lime nodules (kankar) and is less fertile; the newer Khadar, renewed by floods, is the most fertile. Alluvium is generally rich in potash but poor in phosphorus, and with irrigation it carries rice, wheat, sugarcane, pulses and oilseeds.

The other seven groups at a glance
Soil	How it forms	Character	Main regions
Black (regur, black cotton)	Weathering of basaltic lava of the Deccan Traps; climate also matters	Clayey, very moisture-retentive; swells when wet and cracks deeply when dry ("self-ploughing"); rich in lime, iron, magnesia and potash; poor in nitrogen, phosphorus and organic matter	Deccan plateau: Maharashtra, Malwa (Madhya Pradesh), Saurashtra (Gujarat), parts of Telangana, Andhra Pradesh, Karnataka and Tamil Nadu; Godavari and Krishna valleys
Red and yellow	Crystalline igneous and metamorphic rocks (granite, gneiss) under low to moderate rainfall	Red from iron diffused through the rock; yellow where the iron is hydrated. Fine-grained types are fertile, coarse upland types poor; generally low in nitrogen, phosphorus and humus	Eastern and southern Deccan — Tamil Nadu, Karnataka, Odisha, Chhattisgarh, Jharkhand; the piedmont of the Western Ghats
Laterite (Latin later, brick)	High temperature and heavy rainfall with alternating wet and dry seasons: intense leaching removes lime and silica	Iron and aluminium oxides stay behind; humus is destroyed quickly by bacteria. Poor in organic matter, nitrogen, phosphate and calcium; hardens on exposure, so it is cut into building bricks	Summits of the Western and Eastern Ghats, Kerala, Karnataka, Tamil Nadu, the Odisha and Meghalaya hills; with manure it suits tree crops such as cashew, and on hill slopes tea and coffee
Arid (desert)	Low rainfall and high evaporation; mechanical weathering and wind deposit	Sandy, red to brown, low in humus and moisture, often saline; nitrogen is insufficient but phosphate is normal; calcium rising with depth forms a kankar layer that blocks infiltration	Western Rajasthan and adjoining dry tracts; productive where canal water reaches, as along the Indira Gandhi Canal
Saline and alkaline (usar; locally reh, kallar, thur)	Salts of sodium, potassium and magnesium accumulate where drainage is poor, by sea-water intrusion, or by capillary rise under over-irrigation	Infertile; often a white crust on the surface; lacks nitrogen and calcium. Reclaimed by drainage and leaching, and — for alkaline (sodic) soil — by adding gypsum	Western Gujarat and the Rann of Kachchh, deltas of the east coast, the Sundarbans, and canal-irrigated parts of Punjab and Haryana
Peaty and marshy	Heavy rainfall, high humidity and waterlogging let dead vegetation pile up faster than it decays	Very high organic matter — up to 40–50 per cent; heavy and black	Coastal West Bengal, Odisha and Tamil Nadu, and the backwater (kari) lands of Kerala
Forest (mountain)	Forest areas with enough rainfall; texture depends on the mountain setting	Loamy and silty on valley sides, coarse on upper slopes; acidic and low in humus in the snow-bound higher Himalaya, fertile in the lower valleys	Himalaya, the Western and Eastern Ghats, and other forested hills

⚠️ Exam trap

Three nutrient traps examiners love. (1) Black soil is rich in lime, iron, magnesia and potash but poor in nitrogen, phosphorus and humus — its fertility comes from moisture retention, not from nitrogen. (2) Laterite is poor in nitrogen, phosphate, calcium and humus; the iron and aluminium that remain make it red and brick-hard, not fertile. (3) Arid soil lacks nitrogen but has normal phosphate. If a statement makes any of these three soils "rich in nitrogen", it is false.

🎯 Why black soil and cotton go together

Cotton is a kharif crop of the drier Deccan, where the monsoon can pause for weeks. Black soil's fine clay soaks up the rains and releases the water slowly, carrying the crop through dry spells without irrigation. When the soil dries it shrinks and cracks, letting air reach the roots — the cracks do some of the farmer's ploughing. The same stickiness that holds water makes it hard to work when wet, which is why tillage is timed to the first showers or the end of the rains.

Soil Degradation and Conservation

Soil erosion is the removal of topsoil by running water and wind faster than it can form. Water works in stages: sheet erosion strips a thin, even layer over a slope and is hard to notice; rill erosion cuts small finger-like channels; gully erosion deepens them into ravines that make land unfit for farming. The Chambal ravines of Madhya Pradesh, Rajasthan and Uttar Pradesh are the classic Indian badlands. Wind erosion dominates the Thar and its margins, where loose sand drifts over farmland. Deforestation, overgrazing and ploughing up and down slopes all accelerate both.

Erosion is not the only loss. Canal irrigation without drainage raises the water table and brings salts to the surface — waterlogging and salinisation, seen in parts of Punjab, Haryana and the command areas of large canals. Heavy rainfall leaches bases and leaves soils acidic, corrected by adding lime. Continuous cropping with chemical fertilisers alone depletes micronutrients such as zinc and sulphur. The Soil Health Card scheme (2015) tests farm soil on 12 parameters — the major nutrients, secondary and micronutrients, pH, electrical conductivity and organic carbon — and gives the farmer a fertiliser recommendation for that field.

Matching the remedy to the problem
Problem	Remedy	How it works
Erosion on hill slopes	Terracing, contour ploughing, contour bunding	Breaks the slope into steps or ridges across it, so water cannot gather speed
Erosion on gentle slopes and open fields	Strip cropping, cover crops, mulching	Alternating strips of grass and crops, or a mulch layer, keep the ground covered and slow runoff
Wind erosion in dry areas	Shelter belts of trees, sand-dune stabilisation	Rows of trees cut wind speed; grasses and shrubs pin the sand
Gullies and ravines	Check dams, plugging gullies, afforestation	Slows the water, traps silt and lets vegetation re-establish
Acidic soil	Lime	Raises the pH
Alkaline (sodic) soil	Gypsum, drainage and leaching	Calcium in gypsum displaces sodium, which is then washed out

⚠️ Exam trap

Lime for acid, gypsum for alkali. The two are swapped in options more often than any other pair in this topic. Lime (calcium carbonate) neutralises acidity; gypsum (calcium sulphate) supplies calcium that pushes sodium off clay particles in sodic soil.

Natural Vegetation: The Five Broad Forest Types

Natural vegetation is the plant cover that grows without human help and has been left undisturbed long enough to adjust to its climate and soil. Across India it is controlled above all by rainfall, and in the mountains by altitude, which does to temperature what latitude does across the globe. The standard scheme is H. G. Champion's, revised by Champion and Seth (1968) into 16 major forest type groups. For understanding — and for most questions — they collapse into five broad types.

Five broad forest types of India
Type	Climate	Where	Character and typical trees
Tropical evergreen and semi-evergreen	Rainfall over 200 cm, mean annual temperature above 22 °C	Western slopes of the Western Ghats, hills of the North-East, Andaman and Nicobar Islands	Dense, multi-layered, trees up to 60 m; no common season of leaf fall, so the forest is always green. Rosewood, mahogany, aini, ebony; semi-evergreen: white cedar, hollock, kail
Tropical deciduous (monsoon) — moist	Rainfall 100–200 cm	Himalayan foothills of the North-East, eastern slopes of the Western Ghats, Odisha, Jharkhand, Chhattisgarh	Shed leaves for six to eight weeks in the dry season. Teak, sal, shisham, hurra, mahua, amla, semul, kusum, sandalwood
Tropical deciduous — dry	Rainfall 70–100 cm	Rainier parts of the Peninsular plateau and the middle Ganga plains	Open forest that grades into thorn scrub as rain falls off. Tendu, palas, amaltas, bel, khair, axlewood
Tropical thorn	Rainfall under 50 cm	Semi-arid Rajasthan, Gujarat, south-west Punjab and Haryana, and the rain-shadow interior of the Deccan	Scattered trees with thorns, small leaves and long roots; tussocky grass. Babool, ber, khejri, khair, neem, wild date palm
Montane	Temperature falls with height	Himalaya; Nilgiri, Anaimalai and Palani hills	Wet temperate broad-leaved oak and chestnut at 1,000–2,000 m; conifers — pine, deodar, silver fir, spruce, cedar — at 1,500–3,000 m; alpine vegetation (silver fir, juniper, birch, rhododendron) and pastures above about 3,600 m. In the southern hills the temperate forests are the sholas
Littoral and swamp (mangrove)	Tidal, saline, muddy coasts	Sundarbans (Ganga–Brahmaputra delta); Mahanadi, Godavari and Krishna deltas; Bhitarkanika; Andaman and Nicobar; Gulf of Kachchh	Pneumatophores (breathing roots that grow up out of the mud), stilt roots and vivipary (seeds germinate on the tree). The Sundarbans are generally said to take their name from the sundari tree

The tropical deciduous forests are the most widespread in India, which is why they are often simply called monsoon forests: most of the country receives 70–200 cm of rain concentrated in one season. They are also the most valuable commercially — teak and sal are their timbers — and the most cleared for farming. Mangroves, by contrast, are small in area but have an outsized role: they hold coastlines against storm surges, trap sediment and serve as nurseries for fish and prawns.

For administration, forest land is classed as reserved (the most strictly protected, and about half of all forest land), protected and unclassed forest. The National Forest Policy, 1988 set the goal of bringing one-third of the geographical area under forest or tree cover, and two-thirds in the hills. Actual cover is measured every two years by the Forest Survey of India in the India State of Forest Report; because those figures change with each edition, learn the policy target rather than the latest number.

⚠️ Exam trap

"Evergreen" does not mean the trees never shed leaves — every tree sheds leaves. It means there is no common season in which they all do, so the canopy is never bare. And "deciduous" forests are not a cold-climate type in India: they are tropical, and they lose leaves in the dry hot season, not in winter snow.

Cropping Seasons and Types of Farming

Indian farming keeps time with the monsoon. Over most of the north and centre, three cropping seasons follow one another. In the south, where temperatures stay high all year, the boundaries blur: given water, a crop can be raised in almost any season, and rice can be grown more than once a year.

The three cropping seasons
Season	Sown · harvested	What drives it	Typical crops
Kharif	June–July · September–October	Onset of the south-west monsoon; heat and rain	Rice, maize, jowar, bajra, ragi, tur (arhar), moong, urad, cotton, jute, groundnut, soybean
Rabi	October–December · April–June	Cool winter; residual soil moisture, irrigation, and winter rain from western disturbances in the north-west	Wheat, barley, gram, peas, masur, mustard and rapeseed, linseed
Zaid	March · June (short, between rabi and kharif)	Summer heat with irrigation	Watermelon, muskmelon, cucumber, vegetables, fodder crops

ℹ️ Aus, aman and boro

In West Bengal, Odisha and Assam, rice is named by its season rather than its variety. Aus is the autumn rice, sown with the pre-monsoon showers and harvested around August–September. Aman is the main winter rice, transplanted in the monsoon and harvested in November–December. Boro is the summer rice, sown in winter on irrigated or low-lying wet land and harvested in spring. The same names therefore tell you the season, not the seed.

Farming systems differ as much as seasons. Subsistence farming grows food mainly for the family on small plots with simple tools. Shifting cultivation (slash-and-burn) clears a patch of forest, farms it for a few years until fertility falls, and moves on; it is called jhum in the North-East, podu in Andhra Pradesh and Odisha, and bewar in Madhya Pradesh. Intensive farming squeezes high yields from small, densely farmed land with heavy inputs. Plantation agriculture grows a single cash crop — tea, coffee, rubber — on large estates with hired labour and processing on site. Dry farming relies on rainfall in areas receiving under about 75 cm and favours hardy crops such as millets, pulses and oilseeds; wet farming suits high-rainfall or irrigated land. Cropping intensity measures how many crops the land carries in a year: gross cropped area divided by net sown area, times 100.

Major Crops: Growing Conditions and Regions

Every crop question is really a climate question. Learn each crop by its temperature, water and soil, and the regions follow: a crop that needs over 100 cm of rain will be found in the wet east and the deltas, or wherever canals supply the difference.

Food crops
Crop	Conditions	Main regions (pattern)
Rice (mainly kharif)	Above 25 °C, high humidity, over 100 cm rain or irrigation; standing water; clayey alluvium	Eastern and northern plains, coastal plains and deltas; grown with canal water in Punjab and Haryana
Wheat (rabi)	Cool growing season and bright sunshine at ripening; 50–75 cm rain spread over the season, or irrigation	Two zones: the Ganga–Satluj plains of the north-west and the black soil region of the Deccan; Uttar Pradesh, Punjab, Haryana, Madhya Pradesh, Rajasthan
Millets — jowar, bajra, ragi	Hardy, short-duration, largely rain-fed; tolerate poor soils. Bajra suits sandy and shallow black soils; ragi is very rich in calcium and iron	Jowar: Maharashtra and Karnataka (grown in both kharif and rabi); bajra: Rajasthan, Gujarat, Uttar Pradesh, Haryana; ragi: Karnataka and Tamil Nadu
Maize	21–27 °C; old alluvial soil; a food and fodder crop, mainly kharif	Karnataka, Madhya Pradesh, Maharashtra, Rajasthan, Andhra Pradesh, Telangana
Pulses	Leguminous, so they fix atmospheric nitrogen and restore fertility in rotation; need little water. Tur, moong, urad in kharif; gram (the largest pulse), peas, masur in rabi	Madhya Pradesh, Rajasthan, Maharashtra, Uttar Pradesh, Karnataka. India is the world's largest producer and consumer of pulses

Cash, fibre and plantation crops
Crop	Conditions	Main regions (pattern)
Sugarcane	Tropical and subtropical; 21–27 °C, hot and humid, 75–100 cm rain or irrigation; occupies the field for about a year	Uttar Pradesh in the north; Maharashtra, Karnataka and Tamil Nadu in the peninsula, where the tropical climate gives higher sugar content and a longer crushing season. India is second only to Brazil in sugarcane
Cotton (kharif)	High temperature, light rain or irrigation, 210 frost-free days, bright sunshine; black soil	Gujarat, Maharashtra, Telangana and the black soil Deccan; also irrigated Punjab, Haryana and Rajasthan. Bt cotton, approved in 2002, was India's first genetically modified crop cleared for commercial cultivation
Jute — the "golden fibre"	High temperature and heavy rain; well-drained fertile flood-plain soils renewed by silt every year	The Ganga–Brahmaputra delta: West Bengal above all, with Assam and Odisha
Oilseeds	Groundnut (kharif, light sandy soils); mustard and rapeseed (rabi); soybean (kharif); sesamum, castor, linseed, sunflower	Groundnut: Gujarat and the south; mustard: Rajasthan and the north-west; soybean: Madhya Pradesh and Maharashtra
Tea	Warm, moist, frost-free; frequent showers through the year; deep, humus-rich, well-drained soil on slopes, because stagnant water damages the roots; labour-intensive	Assam (Brahmaputra valley), Darjeeling and Jalpaiguri in West Bengal, the Nilgiris
Coffee	Warm, humid hill slopes, usually under shade trees; the Arabica variety was brought from Yemen and first grown in the Baba Budan hills	The Western Ghats of Karnataka, Kerala and Tamil Nadu
Rubber	Equatorial crop: over 200 cm rain and above 25 °C	Kerala above all; Tamil Nadu, Karnataka, Andaman and Nicobar, the Garo hills of Meghalaya and Tripura

⚠️ Exam trap

Read crop questions for the limiting condition, not the region. Wheat fails without a cool growing spell; tea fails where water stands; cotton fails with frost before the bolls open; rubber needs equatorial heat and rain, which is why it is a Kerala crop and not a Himalayan one. A statement that pairs a crop with the opposite condition — "tea grows best on waterlogged flats", "cotton needs a frosty winter" — is the usual trap.

Millets have returned to policy attention as nutri-cereals: they need little water, withstand heat and are rich in fibre and minerals. At India's proposal the United Nations declared 2023 the International Year of Millets. Beyond field crops, India is the world's second-largest producer of fruits and vegetables, after China.

Irrigation: Sources, Methods and Side-Effects

Irrigation exists because Indian rain is seasonal, uneven and unreliable: most of it falls in four months, it varies sharply from place to place, and it can fail in any year. It also allows a second and third crop on the same land, and the water-hungry high-yielding varieties of the Green Revolution depended on it.

Sources of irrigation
Source	Where it suits	Note
Wells and tube wells (groundwater)	Alluvial plains with soft, porous strata and a high water table — the Ganga plain, Punjab, Haryana, Gujarat	The largest share of the net irrigated area. Over-extraction has caused steep falls in the water table in the north-west
Canals	Level plains fed by perennial rivers or reservoirs — the Indo-Gangetic plain, the deltas, the Indira Gandhi Canal in Rajasthan	Inundation canals draw water only in the flood season; perennial canals draw from a barrage or dam all year. Seepage without drainage causes waterlogging
Tanks	The Peninsula — Tamil Nadu, Karnataka, Telangana, Andhra Pradesh	Hard crystalline rock lets little rain soak in, and the undulating surface makes it easy to impound runoff behind small earthen bunds
Micro-irrigation — drip and sprinkler	Water-scarce areas; orchards, vegetables, sugarcane, cotton	Drip delivers water drop by drop to the root zone; sprinkler sprays it like rain. Both save water and fertiliser and reduce salinisation

The Pradhan Mantri Krishi Sinchayee Yojana (2015) brings irrigation schemes under one umbrella with two slogans that summarise its two aims: "Har Khet Ko Pani" (water to every field — expanding the irrigated area) and "Per Drop More Crop" (water-use efficiency through micro-irrigation). Watershed development, which conserves rain where it falls through check dams, bunds and farm ponds, is the dryland complement to canals.

⚠️ Exam trap

Two traps. (1) Canals are not the largest source of irrigation in India — wells and tube wells are, by a wide margin. Canals dominate only particular command areas. (2) Tanks are a peninsular feature because of hard rock and undulating relief, not because the Peninsula has more rain; the alluvial north, with abundant groundwater, has little need of them.

The Agricultural "Revolutions"

In the mid-1960s, after two droughts and dependence on food imports, India adopted a package of high-yielding varieties (HYV) of seed, chemical fertilisers, assured irrigation and pesticides — the Green Revolution. It began with wheat: dwarf varieties bred from Mexican stock at the centre where Norman Borlaug worked (he received the Nobel Peace Prize in 1970). Rice followed with IR-8 from the International Rice Research Institute in the Philippines. In India the programme is associated above all with M. S. Swaminathan, and the High Yielding Varieties Programme began in 1966–67.

The gains were real — foodgrain self-sufficiency and buffer stocks — but uneven. They were concentrated in Punjab, Haryana and western Uttar Pradesh, where irrigation already existed, and in wheat and rice rather than pulses, millets or oilseeds. Rain-fed regions were largely left out. The long-run costs are now familiar: falling water tables, soil degradation from fertiliser imbalance, pesticide residues, a narrowing of crop diversity, and wider gaps between regions and between large and small farmers.

The four revolutions most often asked
Revolution	Sector	Key facts
Green	Foodgrains, chiefly wheat and rice	From the mid-1960s; HYV seeds, fertiliser, irrigation; Borlaug, Swaminathan; Punjab, Haryana, western Uttar Pradesh
White	Milk	Operation Flood, launched in 1970 and run by the National Dairy Development Board (set up in 1965 at Anand); Verghese Kurien; the Anand (Amul) cooperative model of village societies linked to processing and markets. India is the world's largest milk producer
Blue	Fisheries and aquaculture	Growth of inland and marine fish output, especially pond aquaculture; later the Blue Revolution scheme and the Pradhan Mantri Matsya Sampada Yojana (2020). India is the world's second-largest fish producer
Yellow	Oilseeds	Technology Mission on Oilseeds (1986); often credited to Sam Pitroda; aimed to cut edible-oil imports

Milestones

1965
National Dairy Development Board set up at Anand
1966–67
High Yielding Varieties Programme — the Green Revolution begins with wheat
1970
Operation Flood launched (White Revolution)
1986
Technology Mission on Oilseeds (Yellow Revolution)
2015
Soil Health Card scheme; PM Krishi Sinchayee Yojana
2020
Pradhan Mantri Matsya Sampada Yojana

⚠️ Exam trap

Operation Flood has nothing to do with floods — the "flood" is a flood of milk. It is the single most reliable trap in this topic. The minor colours are a second trap: silver (eggs and poultry), round (potato), grey (fertilisers) and golden (horticulture, and honey) are the commonest attributions, but sources disagree on several others (pink, red, brown), so a question will rarely turn on them. Build your answers on Green, White, Blue and Yellow.

Agro-Climatic and Agro-Ecological Regions

State boundaries are poor units for farm planning: western and eastern Uttar Pradesh farm differently, while the Punjab and Haryana plains farm alike. So at the end of the 1980s the Planning Commission divided India into 15 agro-climatic regions, drawn on soil, climate, physiography and water resources, so that crops, irrigation and research could be planned region by region.

Western Himalayan Region
Eastern Himalayan Region
Lower Gangetic Plains Region
Middle Gangetic Plains Region
Upper Gangetic Plains Region
Trans-Gangetic Plains Region (Punjab, Haryana and adjoining areas)
Eastern Plateau and Hills Region
Central Plateau and Hills Region
Western Plateau and Hills Region
Southern Plateau and Hills Region
East Coast Plains and Hills Region
West Coast Plains and Ghats Region
Gujarat Plains and Hills Region
Western Dry Region
The Islands Region

A second scheme comes from ICAR's National Bureau of Soil Survey and Land Use Planning (NBSS&LUP), which mapped 20 agro-ecological regions on the basis of physiography, soils, bio-climate and the length of the growing period — the number of days in a year when soil moisture and temperature allow a crop to grow. The two schemes answer the same question with different tools, and options often mix their numbers.

🧠 Memory trick

Keep the numbers of this chapter apart: 8 soil groups, 15 agro-climatic regions (Planning Commission), 16 forest type groups (Champion and Seth), 20 agro-ecological regions (NBSS&LUP). Each is a favourite distractor for the others.

Key takeaways

Five soil-forming factors — parent material, climate (the main active factor), relief, organisms, time. The eight ICAR groups: alluvial (most widespread, rich in potash, poor in phosphorus), black, red and yellow, laterite, arid, saline, peaty, forest/mountain. In USDA terms black soils are Vertisols.
Black soil: Deccan basalt, moisture-retentive, self-ploughing, rich in lime, iron, magnesia, potash, poor in N, P and humus — the cotton soil. Laterite: heat plus heavy rain, leached of lime and silica, poor in N, P, Ca and humus, brick-hard, good for cashew. Arid: N low, phosphate normal, kankar layer.
Lime for acidic soil, gypsum for alkaline (sodic) soil. Erosion runs sheet → rill → gully (Chambal ravines); terracing and contour ploughing on slopes, shelter belts against wind. Soil Health Card (2015) tests 12 parameters.
Forests follow rainfall: evergreen >200 cm, moist deciduous 100–200, dry deciduous 70–100, thorn <50; montane by altitude (sholas in the southern hills); mangroves on tidal coasts. Tropical deciduous forests are the most widespread. Champion and Seth (1968): 16 type groups; National Forest Policy 1988: one-third under forest or tree cover.
Kharif (June–July to September–October: rice, cotton, jowar, bajra, tur, groundnut, soybean), rabi (October–December to April–June: wheat, gram, mustard, barley), zaid (summer: melons, cucumber, fodder). Aus, aman and boro are rice crops named by season.
Crops by limiting condition: rice >100 cm and standing water; wheat a cool season and bright ripening sun; cotton 210 frost-free days on black soil; jute silt-renewed flood plains; tea frost-free, well-drained slopes; coffee shaded Western Ghats (Baba Budan hills); rubber equatorial heat in Kerala. India is the largest producer and consumer of pulses.
Wells and tube wells irrigate the largest share of land; tanks are peninsular (hard rock, undulating relief); PMKSY 2015: "Har Khet Ko Pani", "Per Drop More Crop". Revolutions: Green (foodgrains, mid-1960s), White (milk, Operation Flood 1970, NDDB, Kurien), Blue (fish), Yellow (oilseeds, 1986). 15 agro-climatic regions (Planning Commission) vs 20 agro-ecological regions (NBSS&LUP).

Practice questions (16)

Attempt each one before opening the answer. Every explanation names the tempting wrong option as well as the right one, because that is where marks are lost.

Consider the following statements about the black soils of India:
1. They are derived largely from the weathering of the basaltic lava of the Deccan Traps.
2. They are rich in nitrogen and phosphorus.
3. They develop deep cracks in the dry season, which helps aerate them.
Which of the statements given above are correct?
1. 1 and 2 only
2. 1 and 3 only
3. 2 and 3 only
4. 1, 2 and 3
Show answer
Answer: B — 1 and 3 only
Statements 1 and 3 are correct: black soil weathers from Deccan basalt, and its swelling clay shrinks and cracks when dry — the "self-ploughing" property. Statement 2 is the trap: black soil is rich in lime, iron, magnesia and potash but poor in nitrogen, phosphorus and organic matter. Its value for cotton comes from holding moisture, not from nitrogen.
Laterite soils develop chiefly under which of the following conditions?
1. Low rainfall and high evaporation, which draw salts up to the surface
2. Cold, waterlogged ground where dead plant matter piles up
3. High temperature and heavy rainfall, which leach away lime and silica and leave iron and aluminium oxides behind
4. Annual floods that spread a fresh layer of river silt
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Answer: C — High temperature and heavy rainfall, which leach away lime and silica and leave iron and aluminium oxides behind
Laterite is a product of intense leaching under tropical heat and heavy, seasonal rain: soluble lime and silica are washed out, and the iron and aluminium oxides that remain make it red, poor and brick-hard. The first option describes saline or arid soils, the second peaty soils and the fourth the alluvium of the Khadar — each a different group of the same classification.
Consider the following pairs (soil : characteristic):
1. Alluvial soil : generally rich in potash but poor in phosphorus
2. Laterite soil : rich in nitrogen and humus
3. Peaty soil : very low content of organic matter
How many of the pairs given above are correctly matched?
1. Only one pair
2. Only two pairs
3. All three pairs
4. None of the pairs
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Answer: A — Only one pair
Only pair 1 is correct. Laterite is poor in nitrogen, phosphate, calcium and humus, because heavy rain leaches it and bacteria destroy humus quickly in the heat. Peaty soil is the opposite of pair 3: it forms where dead vegetation accumulates in waterlogged ground, so its organic matter can reach 40–50 per cent.
Fields in a canal-irrigated tract have turned alkaline, with a white crust of sodium salts on the surface. Which of the following is the standard amendment applied to reclaim such soil?
1. Gypsum
2. Lime
3. Urea
4. Rock phosphate
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Answer: A — Gypsum
Gypsum (calcium sulphate) supplies calcium that displaces sodium from the clay, after which drainage and leaching wash the sodium away. Lime is the tempting wrong answer: it raises pH and is used to correct acidic soils of high-rainfall areas — the opposite problem. Urea and rock phosphate add nutrients but do nothing about sodium.
Which one of the following forest types covers the largest area in India?
1. Tropical evergreen forests
2. Montane temperate forests
3. Tropical thorn forests
4. Tropical deciduous forests
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Answer: D — Tropical deciduous forests
Tropical deciduous (monsoon) forests are the most widespread, because most of India receives 70–200 cm of rain concentrated in one season — exactly their range. Evergreen forests are the most luxuriant and are often mistaken for the most extensive, but they need over 200 cm of rain and are confined to the Western Ghats, the North-East and the islands.
Consider the following statements about mangroves:
1. Many mangrove species have pneumatophores, roots that grow upward out of the mud to take in air.
2. Some mangroves show vivipary, in which seeds germinate while still attached to the parent tree.
3. Mangroves grow best on rocky coasts exposed to strong waves.
How many of the statements given above are correct?
1. Only one
2. Only two
3. All three
4. None
Show answer
Answer: B — Only two
Statements 1 and 2 are correct: breathing roots and vivipary are the two classic adaptations to waterlogged, oxygen-poor, saline mud. Statement 3 is wrong — mangroves need sheltered, muddy, tidal coasts such as deltas, estuaries and lagoons, where fine sediment settles; strong waves on rocky shores would uproot their seedlings.
Consider the following pairs (vegetation : setting):
1. Shola forests : Nilgiri, Anaimalai and Palani hills
2. Tropical thorn forests : areas receiving more than 200 cm of rainfall
3. Tropical evergreen forests : western slopes of the Western Ghats
Which of the pairs given above are correctly matched?
1. 1 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3
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Answer: C — 1 and 3 only
Pairs 1 and 3 are correct: sholas are the temperate montane forests of the southern hills, and the rain-drenched windward slopes of the Western Ghats carry tropical evergreen forest. Pair 2 inverts the rainfall: thorn forests grow where rain is under 50 cm; over 200 cm is the evergreen range.
Which one of the following groups consists only of rabi crops?
1. Rice, cotton and jowar
2. Maize, groundnut and soybean
3. Watermelon, cucumber and muskmelon
4. Wheat, gram and mustard
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Answer: D — Wheat, gram and mustard
Wheat, gram and mustard are sown in October–December and harvested in spring, helped in the north-west by winter rain from western disturbances. The first two groups are kharif crops sown with the monsoon, and the melons and cucumber are the classic zaid crops of the short summer season between rabi and kharif.
In West Bengal, Odisha and Assam, the rice crops known as aus, aman and boro differ from one another mainly in:
1. The season in which each crop is sown and harvested
2. The soil group they are grown on
3. Hybrid versus traditional seed
4. Canal versus well irrigation
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Answer: A — The season in which each crop is sown and harvested
The three names mark seasons: aus is the autumn rice sown with pre-monsoon showers, aman the main winter rice transplanted in the monsoon, and boro the summer rice sown in winter on irrigated or low-lying land. Many people assume the names are varieties, which is the trap; any variety can be grown as aman or boro.
Consider the following statements:
1. Tea is grown on slopes because water must not stagnate around its roots.
2. Coffee in India is grown mainly in the Western Ghats of Karnataka, Kerala and Tamil Nadu.
3. Coffee is generally grown under shade trees.
Which of the statements given above are correct?
1. 1 only
2. 1 and 2 only
3. 2 and 3 only
4. 1, 2 and 3
Show answer
Answer: D — 1, 2 and 3
All three are correct. Tea needs plentiful rain but well-drained soil, so it is planted on hill slopes in Assam, Darjeeling and the Nilgiris. Coffee belongs to the Western Ghats, with Karnataka the core, and is raised under a canopy of shade trees. The usual trap is to assume a plant that needs heavy rain must tolerate waterlogging; tea does not.
Which one of the following sources irrigates the largest share of the net irrigated area of India?
1. Canals
2. Tanks
3. Wells and tube wells
4. Lift irrigation from rivers and streams
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Answer: C — Wells and tube wells
Groundwater drawn through wells and tube wells irrigates by far the largest share of India's net irrigated area, spread across the alluvial plains. Canals are the tempting answer because the great canal systems are famous, but they dominate only their command areas; tanks matter mainly in the hard-rock Peninsula.
Consider the following statements:
1. Tank irrigation is important in peninsular India partly because hard rock limits the recharge of groundwater.
2. Drip irrigation delivers water directly to the root zone and suits orchards and widely spaced crops.
3. Canal irrigation without adequate drainage can cause waterlogging and salinisation.
How many of the statements given above are correct?
1. Only one
2. Only two
3. All three
4. None
Show answer
Answer: C — All three
All three are correct. Hard crystalline rock lets little rain soak in, and the undulating surface makes it easy to store runoff in tanks; drip irrigation saves water by wetting only the root zone; and seepage from canals without drainage raises the water table and brings salts to the surface. A candidate who distrusts "all correct" options loses this one.
Consider the following pairs (revolution : sector):
1. Yellow Revolution : oilseeds
2. Blue Revolution : fisheries
3. White Revolution : fertilisers
How many of the pairs given above are correctly matched?
1. Only one pair
2. Only two pairs
3. All three pairs
4. None of the pairs
Show answer
Answer: B — Only two pairs
Pairs 1 and 2 are correct. Pair 3 is wrong: the White Revolution is milk, built on Operation Flood from 1970. Fertilisers are usually attached to the "grey" revolution — one of the minor colours on which sources vary, which is why a question rarely tests it directly but may use it as a decoy.
Consider the following statements about the Green Revolution in India:
1. It first showed its results in wheat, using high-yielding dwarf varieties developed from Mexican stock.
2. Its early gains were concentrated in Punjab, Haryana and western Uttar Pradesh.
3. It was driven chiefly by rain-fed dryland farming on the Deccan plateau.
Which of the statements given above are correct?
1. 1 and 2 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3
Show answer
Answer: A — 1 and 2 only
Statements 1 and 2 are correct. Statement 3 reverses the story: high-yielding varieties needed assured water and fertiliser, so the revolution took hold where irrigation already existed — the north-western plains — while rain-fed regions such as much of the Deccan were largely left behind. That regional imbalance is one of its best-known criticisms.
Which one of the following statements about Operation Flood is correct?
1. It was a programme to control floods in the Ganga basin
2. It aimed to raise fish output from flood-plain wetlands
3. It was a scheme to build foodgrain storage after floods
4. It was launched in 1970 and implemented by the National Dairy Development Board
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Answer: D — It was launched in 1970 and implemented by the National Dairy Development Board
Operation Flood, launched in 1970 and run by the National Dairy Development Board under Verghese Kurien, created a "flood of milk" by linking village dairy cooperatives on the Anand pattern to processing plants and city markets — the White Revolution. The other three options all read the word "flood" literally, which is precisely the trap the name sets.
The agro-climatic regionalisation of India carried out by the Planning Commission, based on soil, climate, physiography and water resources, divided the country into how many regions?
1. 8
2. 15
3. 16
4. 20
Show answer
Answer: B — 15
The Planning Commission drew 15 agro-climatic regions, from the Western Himalayan region to the Islands region. Each distractor is a real number from the same topic: 20 is the count of agro-ecological regions mapped by NBSS&LUP using the length of the growing period, 16 is Champion and Seth's forest type groups, and 8 is the ICAR soil groups.