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Course Title:
Plant Physiology and
Ecology
Course Instructor:
SALMAN SAEED
Botany department
UNIVERSITY college of management & Sciences, Khanewal,
PAKSITAN

SOIL TEXTURE
?The look and the feel of a soil is referred as
soil texture which is determined by the relative
proportion of mineral particles of different sizes
present in the soil.
? Soil are composed of sand ,slit and clay
particles.
? Stones and gravels are excluded from the
textural classes.
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Salman Saeed Lecturer (Botany)

SIZE OF THE PARTICLES
?Particle size is determined by the diameter of individual
soil fragments.
? According to the International system of soil
classification ,size of different particle are as follows:
? Clay �C less than 0.002 mm
? Slits �C 0.002mm to 0.02mm
? Sand �C 0.02mm to 2.0mm
? very fine sand �C 0.02mm to 0.10mm
? Fine sand �C 0.10mm to 0.25mm
? Medium sand �C 0.25mm to o.50mm
? Coarse sand �C 0.50mm to 1.0mm
? Very coarse sand �C 1.0mm to 2.0mm
? Gravel - larger than 2.0 mm
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FIGURE SHOWING DIFFERENT SOIL PARTICLES
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HOW THESE PARTICLES CAN BE
SEPARATED
? To separate the particle of different sizes ,the
organic matter of soil is oxidized and inorganic
cementation is removed to breakdown structural
aggregation.
? Fine fractions are removed from coarser material
by sedimentation technique.
? Coarse fraction is dried and graded by sieving.
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? Stones and gravels are retained by 2.0 mm
perforated plate sieve , the coarse sand retain
on a 70 mesh wire sieve ( 0.23 mm per
opening) while the fine sand passes through
the 70 mesh.
? Slit and clay fractions are graded according to
sedimentation velocity in a liquid column.
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TEXTURAL GROUPS
? On the basis of proportion of different size particle
,soils are classified into different textural groups;
TEXTURAL GROUPS RELATIVE PROPORTION OF DIFFERENT SIZED
MINERAL PARTICLE
Sandy soil 85% sand + 15%clay or slit or both
Loamy sand 70% sand + 30% clay or slit or both
Loam soil 50% sand +50% clay or slit or both
slit 90% slit + 10% sand
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TEXTURAL CLASSES OF SOILS
SERIAL
NUMBER
SOIL CLASSES
OR
TEXTURAL NAMES
RANGE IN RELATIVE PERCENTAGE OF SOIL
SEPARATES
SAND SLIT CLAY
1 Sandy soil 85-100 0-15 0-10
2 Loamy sand 70-90 0-30 0-15
3 Sandy loam 43-80 0-50 0-20
4 Loam 23-52 28-50 7-27
5 Slit loam 0-50 50-88 0-27
6 Slit 0-20 8-10 0-12
7 Sandy clay loam 45-80 0-28 20-35
8 Clay loam 20-45 15-53 27-40
9 Slity clay loam 0-20 40-73 27-40
10 Sandy clay 45-65 0-20 35-45
11 Slit clay 0-20 40-60 40-60
12 clay 0-45 0-40 40-100
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SOIL TEXTURAL PYRAMID : describing the relative proportion of sand ,slit ,clay in
various type of soils.
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PROPERTIES
? Loamy soil are a balance between sand , slit and clay
particles and considered as the most desirable soils for
agricultural.
? Sandy soil have coarse texture .They hold water and mineral
poorly . Water and air penetrate easily thats why ,they warm
readily in spring and cool quickly in autumn.
? Clayey soil hold large volume of water and retain minerals .
They are very slow to warm in spring and cool more slowly in
autumn.
? Slity soil are intermediate in characteristics and properties
between sandy and clayey soil.
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WHY DIFFERENT SOIL TEXTURES HAVE
THE PROPERTIES THEY DO ?
? Sand and slit are generally irregular in shape ,ranging
from rectangular or blocky to chunky ,spherical
shapes.
? Clay particles are made up of two to three flat
crystalline plates , layered or laminated together.
These particle can be hexagonal in shape with distinct
edges , or they may form irregularly shaped flakes or
even rods.
? Allophane (an amorphous material ) have same tiny
size as clay particle and is prevalent in soils developed
from volcanic ash.
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ROLE OF SOIL TEXTURE
? Soil texture is a qualitative classification tool
used in both the field and laboratory to
determine classes for agricultural soils based
on their physical texture.
? It directly influences soil-water relationship
,aeration and root penetration through its
relationship with interpartical pore space.
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? Soil texture is of ecological interest ,for the
dominant particle size present in any area
have a effect on the flora and fauna of an
area.
? It affects the nutritional status of soil
? The presence of fine textured soil in lower
part of soil body may partially compensate for
coarser soil in upper layers , through a mixture
of fine coarse soil particles can combine many
of the advantages provided by either type
texture.
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What is soil structure, how does it
form, and why is it important?
? Soil structure is the arrangement of
the soil particles into clusters or
aggregates of various sizes and shapes.
? Aggregates that occur naturally in the
soil are referred to as peds, while
clumps of soil caused by tillage
are called clods.

�C Fungal activity
form, and why is it important
? Structure is formed in two steps.
? 1. A clump of soil particles sticks loosely
together. These are created through:
�C Plant roots surrounding the soil and separating
clumps
�C Freezing and thawing of soil
�C Soil becomes wet and then dries
�C The soil is tilled

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? 2. Weak aggregates are cemented
to make them distinct and strong.
? Clay, iron oxides, and organic
matter may act as cements.
�CWhen soil microorganisms break
down plant residues, they produce
gums that also glue peds together.

crusts that reduce crop stands.
? Soil structure is important for
several reasons:
�CIt improves soil tilth.
�CIt improves permeability.
�CIt resists the beating action of
raindrops, minimizing the formation of

What are the various soil structures
2. Massive
and what do they look like?
? There are eight primary types of structure.
They are:
�C Granular
�C Crumb
�C Platy
�C Prismatic or Columnar
�C Blocky
�C Structureless
? 1. Single grain

THANK YOU
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Salman Saeed Lecturer (Botany) Email: Salmanbotanistgmail.com

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Email: Salmanbotanist@gmail.com

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Soil Texture and Structure by Salman Saeed

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Soil Texture and Structure by Salman Saeed