Soil types-1, zonal soil , azonal soil ,interzonal soil ,laterite soil

1. EDITED BY :- ARVIND YADAV
ID :- 721 ,BATCH :-2017,
ARVINDY2510@BUAT721
BANDA UNIVERSITY OF AGRICULTURE AND
TECHNOLOGY BANDA

3.  Due to variations in soil texure, pH values,
colour, structure and consistence, a variety of
soils occur in the world.
 On the basis of maturity, soils can be classified
into three broad groups :
• Zonal soils
 Soils which are fully mature and have well developed profile.
• Azonal soils
 Soils are of recent age and not mature, do not have a
developed soil profile as they have not undergone climatic
and biological action for longer duration.
• Intrazonal soils
 Soils are half mature and have been formed under
inadequate drainage which produces alkalinity and salt
accumulation. Such soils are formed in between the main
belts of zonal soils.

4.  Classified into two groups, viz.
• Pedalfers
 Non lime accumulating soils have and abundance of
aluminium and iron compounds
• Pedocals
 Lime accumulating soils with abundance of calcium
compounds

5.  Tundra soils
• Found in tundras, always covered with snow and ice
round the year.
• Due to low temperatures, vegetal growth is poor and
so the soils lacks humus content.
• In summer when the snow melts large areas are
covered with water and so water logging occurs
which makes the soil illdrained and poorly aerated.
So the oxidation process is withheld.
• Under these conditions the top soil is covered with
an layer of humus beneath which is a blue-grey layer
of clay, silt and sand.
• The blue-grey colour is due to insufficient oxidation
of ferrous-iron compound.

6.  Podsols
• Russian word which means “ash beneath”.
• Soils have ash-grey colour in the A2 horizon.
• Characteristics soils of coniferous forest area, chiefly found in the
mid latitudes of Europe, Siberian Russia and North America.
• Temperature are cool and the rainfall and snowfall doesnot
exceeds 5 cm. per year.
• Top soil is covered with a layer of needle-like leaves, below which
lies the black humus.This imparts and acidic character to it.
• Podsols are leached soils.
• Leaching is not due to heavy rainfall but is an account of the
sudden melting of snow with the onset of the summer season.
• Strong leaching of bases is noticeable in the A2 horizon which has
high silica contents.
• Leaching also causes accumulation of collides and the oxides of
iron and aluminium in the B horizon.
• So B1 horizon is often reddish-brown, some times having an
accumulation of iron pan while B2 horizon is a buff-coloured layer.
• On account of heavy leaching these soils are unfertile and have
limited use in crop cultivation.
• Acidic in character, having low pH values.

7.  Grey brown forest soils
• Found in mid-latitudes where broad leaved deciduous trees
grow as in western Europe , north China, north-eastern United
States and parts of southern Russia.
• Suffer from leaching which imparts them grey colour in the A1
horizon.
• Deciduous trees shed their leaves before the commencement
of winter.
• In winters snow falls upon this thick mantle of dead leaves
which undergo a slow process of decomposition to yield mild
humus on the top soil, and also return many bases to the lower
layers of the soil abstracted by plants.
• A2 horizon is grey-brown in colour due to slight leaching.
• Soils are productive and so vast areas have been deforested for
cultivation.
• Due to deficiency of calcium salts, liming and manuring are
often needed.
• B horizon is darker due to accumulation of salts of iron and
aluminium oxides.

8.  Prairie soils
• Found in temperate grassland called prairie and
steppes in North America and central parts of
Asia.
• Climate is moist and cool with snowfall in
winters.
• have neither lime accumulation nor ferrous
accumulations and are neither acidic nor basic
the rainfall is high enough to percolate through
the soluble salts of calcium carbonate but
evaporation is not high enough to cause
capillary action and upward movement of salts .
• Tall grasses produces high humus .
• Soils are fertile .

9.  Chernozems
• Fertile of soils of central Asia ,Ukraine and Canadian
prairies where the are grasses are short and
precipitation is little, nor exceeding 53 cm per year.
• Rainfall is mostly in summers and winters the ground
is covered with snow which thaws at the onset of
spring.
• Black crumby soils.
• A1 horizon is of great thickness which is rich in organic
matter owing to thick sod layer at the top layer.
• Little leaching in winter due to melting snow and
rainfall.
• A2 horizon is rich in lime having nodules of calcium
carbonates which accumulate due to upward
movement of water through capillary action in the
winter period of drought.
• B horizon is not well differentiated and contains brown
coloured calcium carbonate concretions.
• Because of rich humus content and fertile soil and
mainly used to cultivate wheat.

10.  Chestnut-brown and brown soils
• Found in semi-arid lands, they are calcareous soils,
having nodules of calcium carbonate in B horizon,
and therefore, they belong to the pedocal group.
• Closely resemble the chernozem soils and usually
occur on the margins of chernozems.
• But in the areas of brown soils the rainfall is even
less and only short tussocky grasses grow.
• So lacks in humus and the colour remains brown.
• Unleached soils having rich parent material.
• On account of low rainfall, lack of humus and
generally infertility such soils can hardly be used
for agriculture and are best utilised as pasture.

11.  Grey desert soils
• Occurring in the mid-latitude deserts of Central Asia, North
America and Europe, these soils are typically grey in colour and
may show pale reddish tinge.
• Usually such deserts are surrounded by high mountains or exist in
the form of inter-montanne plateaus e.g. Colorado and Utah in the
USA.
• Due to lack of rainfall, the vegetation cover is thin and the soils
have low humus content – ‘Sierozems’.
• In arid areas, evaporation of water far exceeds precipitation. So the
water tends to rise up by capillary action bringing the
underground salts to the top soil layer.
• Soluble salts are mostly carbonates of calcium, sodium and
magnesium which often impart grey-white colour.
• Some times thick layers of lime deposits may be found deposited
on the surface called as ‘Caliche’
• Soils are fine textured, rich in plant nutrients and hence fertile.

12.  Red desert soils
• These soils range from pale-reddish grey, through
reddish brown to deep red.
• Found in hot tropical deserts where rainfall is less than
50 cm per year.
• Vegetation is sparse and spasmodic and so there is a
general lack of humus in the soil.
• The alluvial erosion is to a minimum while the aeolian
erosion is maximum. So the soil is coarse-grained,
highly permeable and well drained.
• A horizon is red due to the presence of parent material
but the B horizon has a ‘Kankar Pan’ of calcareous
matter.
• Calcium salts may sometimes rise up through capillary
action, forming saline surface encrustations.
• Alkaline soils having pH values of more than 8.
• Rich in nitrogen content and so productive.

13.  Red and yellow forest soils
• found in areas of high temperatures and rainfall, particularly in
sub tropical latitudes as in south-east China, south-east United
States and south-east Brazil.
• Climatic conditions promote the growth of forests and fairly dense
ground vegetation causing thick litter.
• Litter is easily decomposed by heavy bacterial growth and so the
humus formation is much less.
• On account of high rainfall the leaching action is more
pronounced.
• Most of the alkalies and colloides are washed down into the B
horizon, leaving the top mantle acidic.
• Top soil has a thick layer of leaf litter, below which lies a very thin
layer of black humus.
• The A1 horizon is reddish due to the abundance of parent
material and may sometimes more than a foot deep.
• The A2 horizon is light buff coloured because of the presence of
many colloids and bases leached out by the A1 horizon.
• The B horizon is dark coloured, as it is a zone of accumulation of
most of the salts.
• Due to low humus contents, these soils soon lose fertility when
cultivated.

14.  Red tropical Soils
• They are also called latosols. Their formation is characteristic in
those areas which have abundant moisture and warm
temperatures, as in the equatorial forests of Congo, Amazon and
Malaya.
• On account of typical climatic conditions these soils are deeply
weathered and highly leached. They do not show distinct
horizons.
• The red soils may be grouped into four sub classes viz. ferrillictic,
ferrisols, ferruginous soils and vertisols.
• The ferrallitic soils are those which have been intensively
weathered to great depths and that are highly leached. They are
characteristic of older land surfaces within the tropics.
• Perrisols. like the ferrallitic soils are highly weathered, but their
superficial material is continuously removed by surface erosion
and so there is little differentiation in their horizons.
• Ferruginous soils develop in savanna type climates and
monsoonal climates where there are alternating wet and dry
seasons. They display a better horizon development, the A
horizon having more humus contents.
• Vertisols, also called as ‘black clays' are found in depressions of
tropical, wet areas, having a clear dry season in some parts of the
year.They are poorly drained and fine-textured.
• In more dry areas, they display an accumulation of salt on the top
layer due to upward movement of water through capillary action.

15. • Laterites are red brick-like soils and the term was first applied to
the hard, red soils found in Madras. Now it is applied to all
extremely hard, red tropical soils. They occur in areas where the
moist and dry seasons alternate.
• 'Laterisation' is a process in which the soils are heavily leached of
silica and alkali salts, leaving behind a concentration of insoluble
salts of aluminium and iron, which are mostly their sesquioxides.
• This first stage of laterisation begins in the wet season. But in the
dry season the second stage of the process occurs in which the soil
solution is drawn back up towards the surface by capillary action.
Thus the hydrated oxides of iron and aluminium accumulate, bind
together to form a crust at or near the surface.
• Sometimes the iron compounds form nodule and concretions in the
soil also.
• Laterisation may make the soils sterile.
• Laterite soils are found in coastal parts of peninsular India, West
Indies, southern Brazil and tropical Africa.

16.  Soils develop under special circumstances in zonal soils e.g. when
there is imperfect drainage or the predominance of parent rock
material.They are categorized into three main groups.
• Hydromorphic
 have an excess of soil moisture on account of water-logging as in low-
lying areas.
 This may impede water drainage and cause lack of aeration which may
eventually diminish the bacteriological action in the soil causing
accumulation of under-composed organic matter to greater depths.
 In the lower horizons, ferrous iron may not get oxidized and these
horizons may look blue-grey colour. The entire process is called
'gleyzation‘which means a gley horizon of undecomposed organic
matter.
 Hydromorphic soils are commonly found in tundras where temperature
is too low to cause any bacterial activity and the summer melting of snow
and ice may cause accumulation of water in depressions.
 Bog soils, peat soils and meadow soils are other forms of hydromorphic
soils.

17.  Soils, which have a high soil content, are usually associated with
pedocals e.g. chernozems, brown soils and desert soils.
 These saline soils are found in dry continental interiors as in the Aral-
Caspian depression, American cordilleras etc.
 They have an abundance of salts like the chlorides, sulphates arid
carbonates of sodium, calcium and magnesium,
 It is estimated that 40 percent of the arid areas of the world are
covered with these intra zonal soils.
 These soils have been further sub-divided into three main groups :
• Solanchaks
 They are formed in most arid areas where evaporation far exceeds precipitation and so on
account of the upward movement of ground water soluble salts of potassium, sodium, calcium
and magnesium accumulate on the upper layer of the soil in the form of saline crusts.
• Solonetz
 They are also alkaline soils but here the deposition of soluble salts is in the B horizon instead
of the top layer of the soil. This happens when the solonchaks get subjected to a prolonged
period of moist climate in which the salt salts collected at matter at the top layer are again
washed down due to increased rainfall and the alkalis collected in the B horizon.
• Soloths
 Also called as solods, these are former saline soils which have undergone continued
improved drainage and leaching periods, leading to the removal of alkali salts even from the
B horizon, thus making them more fertile.

18.  Soils have rich lime contents consisting of calcium carbonate
and their their formation is affected by the parent material
instead of climatic factors.
 These soils which are also called ‘Calcisols’ occur in limestone
regions where most of the parent materials is calcareous.
 All regions of karst topography in the world have this type of
soil.They are of two types:
• Rendzinas:
 They develop on limestone rocks under moist conditions, as in southern Poland
coastal parts ofYugoslavia, Greece and Alabama (U.SA.).
 They are also called ‘Brown Earth’, because their A horizon is dark-coloured,
friable and rich in organic content.
• Terra Rosa:
 They are heavy clayey soils, rich in lime and sesquioxides of aluminium and
silicon.
 They are formed in drier climatic conditions, as in the Mediterranean climatic
zones.

19.  Poorly developed soils having no distinct horizon development.
 Three types are usually found :
• Lithosols
 Typical soils of young mountains which have high slope gradient.
 Very thin and usually get washed down due to run-off in periods of rainfall.
 course texture, little organic matter and poor vegetal growth.
• Regosols
 Deep, soft, unconsolidated deposits of organic matter in areas of wind-blown
sands, glacial drifts , glacial outwash plains and volcanic ash.
 Finest e.g. loess deposits of central Europe, southern Russia, north-western
China, north central United States, and Argentina.
 Glacial tills of Sweden, Norway, Finland and Denmark.
• Alluvium
 Also called as entisols, formed by the erosion and transportation of sand, silt and
clay by streams and rivers.
 ‘Khadar’ and ‘Bangar’ deposits of Ganga plains in India.
 Found in flood plains, valley bottoms or deltaic regions.