Soil components and their properties Lecture by Allah Dad Khan

This is called the Pre-Cambrian period and is the earliest
geological period. It is, of course, difficult to be sure what
was happening so long ago but scientific research suggests
soil formation began in this period. Compared to today,
soil forming factors were very different so long ago. For
example, there was no vegetation and few organisms to
help to create the soil. It is thought that these earliest
soils formed in an atmosphere with little or no oxygen and
consisted of greenish clays.

This is called the Devonian period. By this time land
plants were becoming established and these required soils
in which to grow. There was more oxygen in the
atmosphere in this period and the soils were redder and
browner, like some of our soils today. Various organisms
developed and for the first time soil organisms began to
play a part in soil development.

 Carboniferous times, which were 354 to 290 millions years
ago, were characterized by forests and swamps but there
were major changes in the vegetation as the sub-tropical
climate developed. The most striking soils from this era
were the peat soils which eventually became buried and
converted into coal. The Permian period dating from 295
to 250 million years ago also experienced a wide range of
climate. Towards the end, conditions became hot and dry
and desert soils developed widely.

This was the Jurassic period, now well known for its
dinosaurs, living in the subtropical conditions that were a
bit like parts of Africa are today. By this time there was
quite a wide range of animals, including soil organisms.
The soils of this era would have resembled the subtropical
soils of today, quite deep and reddish under the warm
conditions that prevailed and capable of sustaining
luxuriant pines and ferns.

Many parts of the world have been affected by at least
one major Ice Age, resulting in the landscape being
covered by ice. In some parts of the world there have been
as many as four periods in the last 2 million years when
the temperature has fallen and the land has become
covered by an ice sheet. In these conditions pretty well all
previous soils are scoured from the landscape and soil
formation has to begin again. When the ice melted it left
behind large deposits of mixed sediments. It is in this
material that many of today’s soils have been formed.

Although soil formation began 2000 million years ago,
virtually all world soils are less than 1 million years old.
The oldest soils are probably those found on some of the
old landscapes of Africa. Most world soils are quite young
and date back less than 10,000 years when the last ice
sheets melted. Soils continue to form every day and even
today somewhere there will be a new soil, perhaps on an
exposed rock, beginning to form.

 This element is no less important than water for the perpetuation
and preservation of life. Nearly all terrestrial creatures are
utterly dependent on the air they breathe. The air also has other
functions which may be less apparent to man but which God has
created for definite purposes, as we have been made aware of by
the Glorious Quran -such as the vitally important role of the
winds in pollination. God has said:
 “Verily in the creation of the heavens and the earth; in the
alternation of night and day in the change of the winds, and
the clouds compelled between heaven and earth surely there
are signs for a people who have sense.” (Quran 2:164)
 “And He it is Who sends the winds as tidings heralding His
grace: until when they have raised a heavy-laden cloud, We
drive it to a dead land and cause the rain to descend upon it,
and thereby bring forth fruits of every kind.” (Quran 7:57)

 Like air and water, the land and soil are essential for the
perpetuation of our lives and the lives of other creatures. God
has declared in the Quran:
1. “Have We not made the earth a vessel to hold the living and
the dead? And We have made in it lofty mountains and
provided you sweet water to drink.” (Quran 77:25-27)
2. “And the earth, after that He has spread it out; from it He has
brought forth its waters and its pastures, and He has made fast
the mountains, a provision for you and for your cattle.”
(Quran 79:30-33)
3. “And the earth, We have spread it out, and made in it
mountains standing firm, and grown in it every thing in
balance. And We have provided in it sustenance for you, and
for those whom you do not support.” (Quran 15:19-20)
4. “And a sign for them is the lifeless earth: We bring it to life
and bring forth from it grain of which they eat. And we have
made therein gardens of palms and vines.” (Quran 36:33-35)

1. The Quran says (what means): “We sent down water
from the sky, blessed water whereby We caused to grow
gardens, grains for harvest, tall palm-trees with their
spathes, piled one above the other – sustenance for
(Our) servants. Therewith We gave (new) life to a dead
land. So will be the emergence (from the
tombs).” [Quran 50:9-11]
2. And (what means): “We sent down water from the sky in
measure and lodged it in the ground. And We certainly
are able to withdraw it. Therewith for you We gave rise
to gardens of palm-trees and vineyards where for you
are abundant fruits and of them you eat.” [Quran 23: 18-
19]
3. And (what means): “We sent forth the winds that
fecundate. We cause the water to descend from the sky.
We provide you with the water – you (could) not be the
guardians of its reserves.” [Quran 15:22]

 O: The O horizon is a surface horizon that is comprised of
organic material at various stages of decomposition. It is most
prominent in forested areas where there is the accumulation
of debris fallen from trees.
 A: The A horizon is a surface horizon that largely consists of
minerals (sand, silt, and clay) and with appreciable amounts
of organic matter. This horizon is predominantly the surface
layer of many soils in grasslands and agricultural lands.
 E: The E horizon is a subsurface horizon that has been heavily
leached. Leaching is the process in which soluble nutrients
are lost from the soil due to precipitation or irrigation. The
horizon is typically light in color. It is generally found beneath
the O horizon.
 B: The B horizon is a subsurface horizon that has accumulated
from the layer(s) above. It is a site of deposition of certain
minerals that have leached from the layer(s) above.
 C: The C horizon is a subsurface horizon. It is the least
weathered horizon. Also known as the saprolite, it is
unconsolidated, loose parent material.

Soils are composed of four main components:
1. Soil Minerals of different sizes
2. Soil Organic materials from the remains of dead plants and animals
3. Soil Water that fills open pore spaces
4. Soil Air that fills open pore space ( Gases)
The use and function of a soil depends on the amount of each
component. For example, a good soil for growing agricultural
plants has about 45% minerals, 5% organic matter, 25% air,
and 25% water. Plants that live in wetlands require more
water and less air. Soils used as raw material for bricks need to
be completely free of organic matter.


The largest component of soil is the mineral portion, which makes up
approximately 45% to 49% of the volume. Soil minerals are derived from
two principal mineral types. Primary minerals, such as those found in
sand and silt, are those soil materials that are similar to the parent
material from which they formed. They are often round or irregular in
shape. Secondary minerals, on the other hand, result from the
weathering of the primary minerals, which releases important ions and
forms more stable mineral forms such as silicate clay. Clays have a large
surface area, which is important for soil chemistry and water-holding
capacity. Additionally, negative and neutral charges found around soil
minerals influences the soil's ability to retain important nutrients, such as
cations, contributing to a soils cation exchange capacity (CEC).


Organic matter is the next basic component that is found
in soils at levels of approximately 1% to 5%. Organic matter
is derived from dead plants and animals and as such has a
high capacity to hold onto and/or provide the essential
elements and water for plant growth. Soils that are high in
organic matter also have a high CEC and are, therefore,
generally some of the most productive for plant growth.
Organic matter also has a very high "plant available"
water-holding capacity, which can enhance the growth
potential of soils with poor water-holding capacity such as
sand. Thus, the percent of decomposed organic matter in
or on soils is often used as an indicator of a productive and
fertile soil. Over time, however, prolonged decomposition
of organic materials can lead it to become unavailable for
plant use, creating what are known as recalcitrant carbon
stores in soils.

Water is a vehicle…a carrier…for the mineral nutrients. Later
in the course we will learn much more about water, but for
now the critical features are that water is a great solvent for
minerals and it dissociates.
 The dissociation of water means, that in all situations water
is not inert. It is in an equilibrium with different forms of
itself. Water (H2O) can come apart (dissociate) to make a
hydrogen ion (H+) and a hydroxide ion (OH-):
 H2O ---- OH- + H+
 The thin film of water around soil particles is the microscopic
location of much of the important biology for the relationship
between soil and plants. The water in these soil spaces is
called capillary water. This water is tapped by the microscopic root
hairs of the root for both water and minerals. A tree can go through
hundreds of gallons of water in a short time and all of it comes from
this thin film coating the soil particles and the root hairs. This water
contains the dissolved soil minerals.

Gases or air is the next basic component of soil. Because
air can occupy the same spaces as water, it can make up
approximately 2% to 50% of the soil volume. Oxygen is
essential for root and microbe respiration, which helps
support plant growth. Carbon dioxide and nitrogen also are
important for belowground plant functions such as for
nitrogen-fixing bacteria. If soils remain waterlogged
(where gas is displaced by excess water), it can prevent
root gas exchange leading to plant death, which is a
common concern after floods.

1.Parent Material
2.Climate
3.Organism
4.Topography
5.Time

 This is the material from which the soil is formed. Soil
parent material can be bedrock, organic material, or loose
soil deposited by wind, water, glaciers, volcanoes, or
material moving down a slope.

Climate also affects soil formation. In hot climates, many of
the minerals will be oxidized, and the iron in the soil and clay
will be a reddish color, rather than gray or black. Organic matter
will also decompose more rapidly in a hot climate, and within the
great plains region, the native soils in Minnesota will be darker,
and much higher in organic matter than those in Texas. Rainfall
also affects soil formation. In areas of extremely high annual
rainfall, some minerals, and in some cases, organic matter will
have been leached from the topsoil to a lower layer. The pH may
be lower on these soils, due to the leaching of calcium from the
topsoil. Areas of low rainfall, especially where annual rainfall is
less than the annual evaporation, will accumulate minerals,
including calcium and other salts on the surface.


Biological processes that affect soil have historically been determined
by the native or natural vegetation. Soils that form under forests are
very different than those that have formed in grassland regions. Much of
the soil in the great plains was formed when the region was covered by
prairie grasses. This soil is very fertile, and rich in organic matter
compared to soils of other regions. The deep grass roots added organic
matter to a depth of several feet in some cases, leading to the formation
of the rich, dark soils that have made Kansas the "breadbasket" of the
world. Tillage, and planting of annual crops on these soils has halted this
addition of organic matter, but reduced tillage and adding perennial
crops into the rotation can help maintain the organic matter that is left.

Topography often affects how much erosion has taken
place. Soils on top of hills or on steep side slopes tend to be
thinner, or more eroded than those on the slopes, and at the
bottom or "toe" of a slope, one can find zones of soil
accumulation. Management, along with topography will also
affect how much erosion has, and is continuing to take
place. The thinner, or more eroded soils will often be lower in
organic matter, since they have lost their topsoil layer. The clays
in the subsoil layers are then on the top. A field that is "patchy"
in color will probably have had some erosion historically.

 The time that a soil has had to form will often affect the amount of
layering, or differentiation from the top of the profile to the bottom. An
older soil will have a "topsoil" layer, that will be darker, and higher in
organic matter (from centuries of contributed plant and animal matter),
and the lower layers will be progressively lighter in color, and generally
lower in organic matter and nutrient content. An example of a "young"
soil would be an area where a river has recently deposited soil, or
alluvium, to a particular area. In parts of the world with active
volcanoes, the volcanic ash layers will begin to form soil layers, and then
may be covered again by ash. In some of these areas, one can find
buried soil horizons. A soil that is nearly the same color throughout the
profile, especially when there is little change in the properties of the
profile horizons is probably a young soil..

1) the starting natural fertility of the parent material (Kansas soils,
for example, tend to be naturally high in potassium),
2) the subtraction of nutrients as a result of erosion and crop use
since the land has been tilled (generally for the past 100 years or
so), and
3) additions of fertilizer sources such as manures, composts,
legumes, and mineral fertilizers.
When designing a soil sampling program, one needs to consider all
of these factors. Knowing the soil type (from soil survey maps),
topography, and field histories (crops grown and fertility sources)
will help you design a plan to answer specific farm management
questions.

1. The soil is an ecosystem in which millions, even billions, of living
creatures live and interact. Rather little is known about this huge
population because for the most part they are underground and out of
sight.
2. The soil ecosystem has been declared by some scientists to be the last
great biotic frontier that we need to discover. One thing we do know is
that there can be more organisms in a teaspoonful of good soil than
there are people in the entire planet earth -that is more than 6 billion.
Wow !
3. There is a very wide range of organisms in the soil, ranging from
protozoa which require the strongest of microscopes to detect them,
up to large burrowing animals like badgers and rabbits which can
readily be seen with the naked eye.

It takes 500
years for a
centimetre of
soil to form

1. When you take some moist soil in your hand and rub it between
your fingers, you will feel the texture of the soil. In particular,
you will be able to detect whether the soil feels rough or
coarse, in which case it is probably a sandy soil, or whether it
feels smooth which is the feel of a clayey soil.
2. The amounts of sand, silt, clay and organic matter in a
particular soil play a large part in the way that it behaves, how
it can be managed and what it can be used to grow.
3. Sandy soils are easy to cultivate but tend to hold little water
and may be droughty, whereas clay soils are more difficult to
cultivate, hold a lot of water and can become waterlogged,
especially in winter

Just as houses and buildings have a structure or architecture, so also
does the soil.
1. The particles of sand and clay that make up the soil rarely occur as
separate particles but are more or less loosely combined into
aggregates.
2. The type of structure in soil depends to a large extent on the texture
and the amount of organic matter in the soil and the way the land is
managed.
3. The aggregates that make up the structure may be as small as a few
millimeters, such as granules and crumbs, or as large as several
centimetres, such columns and prisms.
4. The granular or crumb structure is the one favoured by farmers and
gardeners as it makes a better bed for the seeds they plant

Name Particle Diameter
Clay below 0.002 millimeters
Silt 0.002 to 0.05 millimeters
Very fine sand
Fine sand
Medium sand
Coarse sand
Very coarse sand
0.05 to 0.10 millimeters
Gravel 2.0 to 75.0 millimeters
Rock greater than 75.0 millimeters (~2")

1. Forms free draining soils
2. Largest mineral particle size - between 2mm and 0.06mm in
diameter
3. Feels gritty to touch
4. Makes a rasping sound when rubbed together
5. Particles do not stick together and cannot be made into a ball
6. Soils warm quickly in Spring, but cool quickly in Autumn
7. Forms soils which cannot hold onto nutrients
8. No swelling or shrinkage in the soil
9. Can not hold onto nutrients

1. Forms soils which can be hard to drain
2. Holds on to a moderate amount of water
3. Medium mineral particle size - between 0.06 and 0.002mm in
diameter Feels soapy or silky
4. Makes a squeaky sound when rubbed together
5. Particles don’t easily hold together - a ball of them breaks
easily
6. Soils warm and cool more quickly than clay, but less quickly
than sand
7. Forms soils which can only hold limited nutrients
8. Limited swelling or shrinkage in the soil
9. Makes very fertile soils

1. Forms soils which readily become waterlogged Becomes heavy
when wet
2. Smallest mineral particle size - diameter less that 0.002mm
3. Feels smooth when dry and sticky when wet
4. Makes very little sound when rubbed together
5. Particles stick together and are easy to make into a ball
6. Soil takes a long time to warm up in Spring and to cool down in
Autumn
7. Forms soils which can hold onto nutrients Soil swells when wet
and shrinks when dry
8. Can be used to make bricks or pots

Soil is nothing but a thin layer on the surface of the
Earth. It is the medium through which plants gather their
nutrients. Depending on the size of the particles present in
the soil, it is divided into various types.

1. Warms much more quickly in Spring because of less water retention
2. Are light and easy to work having less essential nutrients.
3. Are free-draining ,water drains rapidly
4. Can dry out in dry weather
5. Tend to be low in nutrients
6. Can be worked at almost any time
7. Need liming little and often.
8. When we roll the slightly wet sandy soil in our palms, no ball should be formed
and it crumbles through your fingers
9. Ideal for crops like:
Watermelons, Peanuts, and Peaches
10. Ideal for plants like:
Tulips, Cistus, and Hibiscus

1. Deposited by rivers and lakes , not grainy or rocky
2. Warm up quicker than clay but slower that silt soils in Spring
3. Silty soils retain water longer than sandy soils
4. Difficult to drain, but less likely to waterlog that clay
5. Tend to be fertile and good for agriculture purposes.
6. Silty soil can also easily compact, so avoid trampling on it when
working your garden. It can become poorly aerated, too
7. When we roll it between your fingers, dirt is left on our skin.
All vegetables and fruits
Yellow Iris, Milkweed, and Red Chokeberry

1. Clay soil is cold and in the spring, takes time to warm since the water within also
has to warm up
2. Heavy soils needing well-timed cultivation
3. Lie wet and prone to water logging ,retains water , sticky when wet.
4. Tend to be rich in plant nutrients for better growth.
5. Should not be worked when wet Need regular liming
6. Rolls up easily, and forms into a ball or sausage-like shape, then you’ve got
yourself clay. Ideal for crops like:
Leafy vegetables, Peas, Tomatoes, and Peppers
Roses, Heleniums, Asters, and Chaenomeles

1. Contain a mix of sand, silt, and clay particles
2. It contains a balance of all three soil materials—silt, sand and
clay—plus humus.
3. It has a higher pH and calcium levels because of its previous
organic matter content.
4. Warm up fairly early in Spring , soft and crumby
5. Are easy to work Usually need draining
6. Should not be worked when wet
7. Tend to be rich in nutrients
Tomatoes, Carrots, Parsnips, and Potatoes
Roses, Amaryllis, Marigolds, and Zinnias

1. Come from chalk and limestone rocks , light in colour , lime rich soil
2. Contain calcium carbonate and flints
3. Tend to be alkaline
4. Usually free-draining
5. May be low in some nutrients
6. Do not usually need liming
7. Poor in nutrients , warm quickly in summer
Honeysuckle, Jasminum, Rosa, and Geranium

1. Dark brown in colour, soft and spongy to the touch ,so warm
up quickly in Spring
2. Hold on to water well and can be easy to work , protect the
roots from damage during very wet months , rich in organic
matter
3. Come from the build up of dead rotted plants, so contain lots
of organic matter
4. Tend to be acid Usually high in Nitrogen
5. When wet peat soil is rolled, you won’t form a ball. It’s spongy
to the touch and when squeezed, water could be forced out.
Sphagnum Moss, Ericaceous Shrubs, and Sedges

1. The soil in extremely dry regions is usually
brackish because of its high salt content
2. The salinity is due to the buildup of soluble salts in the rhizosphere—high
salt contents prevent water uptake by plants, leading to drought
stress.
3. It’s easy enough to test if you have saline soil. You’ll probably see a white
layer coating the surface of the soil, your plants are growing poorly,
and they’re suffering from leaf tip burn, especially on young leaves.

A teaspoon of soil
contains more
creatures
than there are people
on the whole planet!

Soil components and their properties Lecture by Allah Dad Khan

More Related Content

What's hot (20)

Similar to Soil components and their properties Lecture by Allah Dad Khan (20)

More from Mr.Allah Dad Khan (20)

Recently uploaded (20)

Soil components and their properties Lecture by Allah Dad Khan