This document discusses the biological properties of soil and biodiversity. It begins by defining soil and describing the different types of soil horizons and profiles. It then covers various soil properties like texture, structure, consistency, drainage and pH. The importance of soil moisture, minerals and organic matter in soil composition is explained. Different types of soils like clay, sandy, silt and loamy soils are defined. The document emphasizes the significance of soil in supporting plant growth and various life forms.

1. Biological
properties of soil
and biodiversity
By HAFSA ARSHAD
BBOF17M006

2. SUBMITTEDTO:Dr.ABDULGHANI
DEPARTMENT OF BOTANY
UNIVERSITY OF SARGODHA
2

3. 3
 What is soil
 Soil profile
 Types
 Soil horizons
 Properties
 Soil moisture
 Soil drainage
 Stages of soil
 How is soil formed
 Composition
 Importance
OUTLINE

4. 4
 Technically, soil is a mixture that contains
minerals, organic matter, and living organisms.
 But broadly speaking, soil can refer to any loose
sediment.
 Soil is usually referred to as the naturally
occurring organic materials found on the earth’s
surface.
 It is mainly composed of mineral, nutrients, water,
other inorganic particles and some residues of
plants and animals.
WHATISSOIL

5. 5
 “Soil profile is defined as the vertical section of
the soil from the ground surface downwards to
where the soil meets the underlying rock.”
 The soil is the topmost layer of the earth’s crust
mainly composed of organic minerals and rock
particles that support life.
 A soil profile is a vertical cross-section of the soil,
made of layers running parallel to the surface.
These layers are known as soil horizons.
SOILPROFILE

6. 6
 There are many types of soil that are distributed
around the world and these are generally
classified into the following:
» Clay Soil
» Sandy soil
» Loamy Soil
» Silt Soil
TYPESOFSOIL

7.  Clay is the smallest particles amongst the
other two types of soil.
 The particles in this soil are tightly
packed together with each other with very
little or no airspace.
 This soil has very good water storage
qualities and making hard for moisture and
air to penetrate into it.
CLAYSOIL
7

8.  It is very sticky to the touch when wet,
but smooth when dried.
 Clay is the densest and heaviest type of
soil which do not drain well or provide
space for plant roots to flourish.
CLAYSOIL
8

9.  It consists of small particles of weathered
rock.
 Sandy soils are one of the poorest types
of soil for growing plants because it has
very low nutrients and poor in holding
water, which makes it hard for the plant’s
roots to absorb water.
SANDYSOIL
9

10.  This type of soil is very good for the
drainage system.
 Sandy soil is usually formed by the
breakdown or fragmentation of rocks like
granite, limestone, and quartz.
SANDYSOIL
10

11.  Silt is known to have much smaller
particles compared to the sandy soil.
 It is made up of rock and other mineral
particles which are smaller than sand and
larger than clay.
 It is the smooth and quite fine quality of
the soil that holds water better than sand.
SILT
11

12.  Silt is easily transported by moving
currents and it is mainly found near the
river, lake, and other water bodies.
 The silt soil is more fertile compared to
the other three types of soil. Therefore it is
also used in agricultural practices to
improve soil fertility.
SILT
12

13.  Loam is the fourth type of soil.
 It is a combination of sand, silt, and clay
such that the beneficial properties from
each is included.
 For instance, it has the ability to retain
moisture and nutrients, hence, it is more
suitable for farming
LOAM
13

14. » This soil is also referred to as
an agricultural soil as it includes an
equilibrium of all types of soil materials
being sandy, clay, and silt and it also
happens to have hummus.
» Apart from these, it also has higher
calcium and pH levels because of its
inorganic origins.
LOAM
14

15. 15
Various properties of soil include:
 Soil Texture
 Organic matter
 Soil Color
 Structure
 Consistence
 Cation exchange capacity
 pH
PROPERTIESOFSOIL

16. SOILTEXTURE
16
Soil Separate Diameter (mm)
Sand 2.0 - 0.05
Silt 0.05 - 0.002
Clay < 0.002
 Refers to the proportions of sand, silt and clay
sized particles that make up the mineral
fraction of the soil.

17.  Color is foremost property which can be
seen with naked eye and is useful in
interpretation of valuable insight into the
soil environment, thus it can be very
important in assessment and classification
of soil.
 Can be used to understand parent
material of the soil, the soil drainage,
amount of iron and organic matter in soil.
SOILCOLOR
17

18. The most influential colors in a well drained soil are
white, brown, red and black.
 White indicate the pre-dominance of silica
(quartz) or the presence of salts.
 Red indicates the presence of iron oxides.
 Brown and black indicates the level and type of
organic matter.
 A color triangle can be used to show the names
and relationships between the influential colors.
SOILCOLOR
18

19. Structure influences the movement of water and gas
through soils.
 Soil particles that are held together by chemical
and physical forces are called “peds”.
 The types of soil peds define soil structure.
 Structure is classified by describing:
 Distinctiveness – structure of peds.
 Size – size of peds.
 Shape – shape of peds.
SOILSTRUCTURE
19

20.  Relates to soil strength, the resistance of the soil to
breaking.
 Influences soil aeration and water movement through
the soil and how the soil will respond to surface traffic
and root penetration.
 By crushing a soil ped in your hand soil consistence can
be determined.
SOILCONSISTANCY
20

21. .
21
SOILCONSISTANCE
Loose - Non-coherent
Very Friable - Soil crushes under very gentle pressure, but keeps a form
when pressed together.
Friable - Soil crushes under very gentle to moderate pressure, but
keeps a form when pressed together.
Firm - Soil is hard to crush under moderate pressure
Very Firm - Soil crushes under strong pressure, barely crushable.
The classes of consistence for moist soil are:

22. A measure of the acidity or alkalinity of soil and is
measured in pH units.
 pH scale goes from 0 (acidic) to 14 (basic) with
pH 7 as the neutral point.
 Most soils have pH values between 4 and 8.
 The solubility of minerals and nutrients in soil is
highly dependent on the pH of that soil.
pH
22

23. Drainage is defined by the length of time it
takes water to be removed from the soil in
relation to the supply.
Drainage is affected by:
• Soil-External Factors
• Soil-Internal Factors
SOILDRAINAGE
23

24. External Factors:
 Position on the slope – soils in upper positions tend to
be better drained than those in the lower slopes.
 Aspect – Southern aspects are warmer than northern
aspects, therefore southern aspects will have less soil
water and better drainage.
 Climate – Areas that receive high amounts of rainfall
will have poorer drainage than those that receive low
amounts.
 Bedrock – The presence and type of bedrock can affect
the rate and the flow direction of soil water.
SOILDRAINAGE
24

25. Internal Factors:
 Soil texture – Coarse to medium textured soils will
tend to have better drainage.
 Stoniness – Soils with gravels and cobbles have a
improved drainage.
 Consistence – Soils with loose and friable
consistence will have better drainage than those
with firm and very firm consistence.
SOILDRAINAGE
25

26. 26
 The soil is arranged in layers or horizons during
its formation. These layers or horizons are known
as the soil profile.
 It is the vertical section of the soil that is exposed
by a soil pit. The layers of soil can easily be
identified by the soil colour and size of soil
particles
 Topsoil
 Subsoil
 Parent rock
LAYERSOFSOIL

27. 27
 The soil profile is composed of a series of
horizons or layers of soil stacked one on top of the
other.
 These layers or horizons are represented by
letters O, A, E, C, B and R.
• O horizon
• A horizon
• E horizon
• C horizon
• B horizon
• R horizon
SOILHORIZONS

28.  The O horizon is the upper layer of the topsoil.
 It is mainly composed of organic materials such
as dried leaves, grasses, dead leaves, small rocks,
twigs, surface organisms, fallen trees, and other
decomposed organic matter.
 It contains about 20 to 30% of organic matter.
 This horizon of soil is often black brown or dark
brown in colour and this is mainly because of the
presence of organic content.
O-HORIZON
28

29.  This layer is rich in organic material and is known
as the humus layer.
 This layer consists of both organic matter and
other decomposed materials.
 The topsoil is soft and porous to hold enough air
and water.
 In this layer, the seed germination takes place
and new roots are produced which grows into a
new plant.
 This layer consists of microorganisms such as
earthworms, fungi, bacteria, etc.
A-HORIZON
29

30.  It is the subsurface horizon, present just below
the topsoil and above the bedrock.
 It is comparatively harder and compact than
topsoil. It contains less humus, soluble minerals,
and organic matter.
 It is a site of deposition of certain minerals and
metal salts such as iron oxide.
 This layer holds enough water than the topsoil
and is lighter brown due to the presence of clay soil.
 The soil of horizon-A and horizon-B is often mixed
while ploughing the fields.
B-HORIZONORSUBSOIL
30

31.  This layer is devoid of any organic matter
and is made up of broken bedrock.
 This layer is also known as saprolite.
 The geological material present in this
zone is cemented.
C-HORIZONORSAPROLITE
31

32.  It is a compacted and cemented layer.
 Different types of rocks such as granite,
basalt and limestone are found here
R-HORIZONORSAPROLITE
32

33. 33
 Apart from the rocks, minerals, and layers, soil
profile also consists of a water content, which
is referred to as soil moisture.
 Water in the soil is referred to as soil moisture.
 Water absorption in soil is determined by
various factors. It plays a major role in soil
formation.
 Moisture content in the soil can be measured
using a device known as Tensiometer.
SOILMOISTURE

34. 34
The different types of water present in the soil
include:
Gravitational Water
The water that reaches the water table of the soil
due to the gravitational force is referred to as
gravitational water. This is not available to the
plants.
Hygroscopic Water
This water is also not available to the plants. It is a
thin film of water tightly held by the soil particles.
TYPESOFSOILMOISTURE

35. 35
Chemically Combined Water
The chemical compounds present in the soil
particles contain water. This is known as chemically
combined water. This is also not available to the
plants.
Capillary Water
This water is available to the plants for absorption.
This water exists between soil particles in small
capillaries.
Atmospheric Humidity
The hanging roots of the epiphytes absorb the
moisture in the air due to the presence of
hygroscopic hairs and spongy velamen tissues.
TYPESOFSOILMOISTURE

36. 36
There are three stages of soil:
 Solid soil,
 Soil with air in the pores,
 Soil with water in the pores.
STAGESOFSOIL

37. 37
Essentially, soil is formed when rocks
eventually weather away and break down
into small particles. Solid rock can weather
away one of the three ways into the soil,
namely:
» Mechanical Weathering
» Chemical Weathering
» Biological Weathering
HOWISSOILFORMED

38. » This is commonly observed near the
surface of the earth.
» Also called physical weathering, as this
process is influenced by physical forces such
as wind, water and temperature.
MECHANICALWEATHERING
38

39. » As the name suggests, chemical
weathering occurs when rocks are broken
down by chemical reactions.
» Often, such types of weathering can
change the chemical composition of soil.
CHEMICALWEATHERING
39

40. » Though not an actual weathering process, living
organisms weaken and subsequently disintegrate
rocks, often by initiating mechanical or chemical
weathering.
» For instance, tree roots can grow into cracks in the
rock, prying them apart and causing mechanical
fractures.
» Microorganisms can secrete chemicals that can
increase the rock’s susceptibility to weathering.
BIOLOGICALWEATHERING
40

41. 41
The soil is composed of:
 5% organic matter
 45% minerals
 20-30% different gases
 20-30% water.
Therefore, soil is known as a
heterogeneous body.
COMPOSITIONOFSOIL

42. Organic substance is found in very small
amounts in soil.
Plants and animals are the main sources
of organic matter.
Depending upon the decomposition stage,
the organic matter is of the following three
types:
 Completely decomposed organic matter
 Partially decomposed organic matter
 Undecomposed organic matter
ORGANICMATTER
42

43.  Mineral is an important element of the
soil.
 These are solid components composed
of atoms.
 These occur naturally and have a fixed
chemical composition.
 Olivine and feldspar are the main
minerals present in the soil.
MINERAL
43

44.  The air-filled pores of the soil contain the
gaseous components.
 Nitrogen and oxygen present in the pores
is generally the atmospheric air fixed by the
microorganisms.
 However, the composition of carbon
dioxide is higher due to the gas produced
by microorganisms present in the soil.
GASEOUSCOMPOUNDS
44

45.  The soil dissolves the minerals and
nutrients in water and transports it to
different parts of plants.
 Water is essential for the growth and
development of the plant.
WATER
45

46. 46
» Soil is an important element essential for
the survival of living organisms.
The importance of soil is mentioned below:
 The fertile soil helps in the growth and
development of the plants.
 The plants thus produced are healthy
and provide food, clothing, furniture, and
medicines.
 Provides habitat for organisms
IMPORTANCEOFSOIL

47. 47
» The topsoil supports certain life
activities such as reproduction, hatching,
nesting, breeding, etc. of a few
organisms.
» The organic matter present in the soil
increases the fertility of the soil which is
responsible for the growth of the plants.
» It also contains certain minerals and
elements that are necessary for the plants
to carry out their cellular activities.
IMPORTANCEOFSOIL

48. 48
 It supports many life forms including
bacteria, fungi, algae, etc.
 These microbes, in turn, maintain
environmental balance by retaining the
moisture and decaying the dead
organisms.
» Useful mineral medicines such as
calcium, iron, and other substances such
as petroleum jelly for cosmetics are
extracted from the soil.
IMPORTANCEOFSOIL

49. 49
 The soil absorbs the rainwater.
 This water is evaporated and released
into the air during sunny days, making
the atmosphere cooler
 Providing a growth medium for the
plants
 Acts a modifier of the earth’s
atmosphere
 One of the most crucial components of
the biosphere
IMPORTANCEOFSOIL

50. 50
 Which soil is called as the gardener’s best
friend?
Loam or Loamy soil is called as the gardener’s best
friend.
 Which crop can be grown in Loamy soil?
Loamy soil is suitable and best soil for growing crops
such as Cotton, oil seeds, sugarcane, wheat, pulses,
jute, and other Vegetables.
 Which soil is preferable to grow coconut and
melon?
Sandy soil is the preferable soil to grow coconut and
melon.
SOMEQUESTIONSABOUTSOIL

51. 51
 What are the basic components of Soil?
Air, water, minerals and other organic matter are
the basic components of soil.
 What are the horizons of soil?
The soil profiles are composed of a series of
horizons or layers of soil, which are stacked one
above the other. The 4 horizons of soil are:
• The O-Horizon.
• The A-Horizon.
• The B-Horizon.
• The C-Horizon.
SOMEQUESTIONSABOUTSOIL

52. SOIL BIODIVERSITY
My subtitle

53. 53
 Soil biodiversity is generally defined as the
variability of living organisms in soil and the
ecological complexes of which they are part
 This includes diversity within species, between
species and of ecosystems
 Soil biodiversity refers to the relationship of soil
to biodiversity and to aspects of the soil that can
be managed in relation to biodiversity.
 Soil biodiversity relates to some catchment
management considerations.
SOILBIODIVERSITY

54. 54
The diversity of organisms living within soils is
critical to all earth ecosystems because soil
organisms are
 essential for the cycling of ecosystem nutrients
 necessary for plant growth and plant nutrition.
 improve the entry of water into soil and its
storage in the soil
WHYISSOILBIODIVERSITYIMPORTANT

55. 55
 The highest amount of the soil ecological capital
is in the form of microbial biomass (bacteria and
fungi).
 The absolute and the relative amount of these
organisms give a good indication of the activity
and stability of the ecosystem.
 Both can be determined in one measurement,
e.g. by automised spectroscopy.
HOWISSOILBIODIVERSITYMEASURED

56. 56
 The activity of soil biodiversity can be stimulated
by improving soil living conditions, such as
aeration, temperature, moisture, and nutrient
quantity and quality.
 In this regard, reduced soil tillage and minimized
compaction - and refraining chemical use - are of
particular note
HOWISSOILBIODIVERSITYIMPROVED

57. Thank You
HAFSA ARSHAD
hafsaranjha.botanist@gmail.com