This document is a lecture on soil texture and structure given by Salman Saeed of the Botany department at the University college of management & Sciences in Pakistan. It discusses the components of soil texture, including sand, silt and clay particle sizes. It also explains how soil texture influences properties like water and nutrient holding capacity. The lecture describes the process of soil structure formation through processes like freezing and thawing or microbial activity. Well-structured soil is important for tilth, permeability and resisting crust formation.

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

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3. 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)

4. 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 – less than 0.002 mm
 Slits – 0.002mm to 0.02mm
 Sand – 0.02mm to 2.0mm
• very fine sand – 0.02mm to 0.10mm
• Fine sand – 0.10mm to 0.25mm
• Medium sand – 0.25mm to o.50mm
• Coarse sand – 0.50mm to 1.0mm
• Very coarse sand – 1.0mm to 2.0mm
 Gravel - larger than 2.0 mm
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Salman Saeed Lecturer (Botany)

5. FIGURE SHOWING DIFFERENT SOIL PARTICLES
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Salman Saeed Lecturer (Botany)

6. 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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Salman Saeed Lecturer (Botany)

7. • 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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Salman Saeed Lecturer (Botany)

8. 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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Salman Saeed Lecturer (Botany)

9. 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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Salman Saeed Lecturer (Botany)

10. SOIL TEXTURAL PYRAMID : describing the relative proportion of sand ,slit ,clay in
various type of soils.
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Salman Saeed Lecturer (Botany)

11. 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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Salman Saeed Lecturer (Botany)

12. 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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Salman Saeed Lecturer (Botany)

13. 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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Salman Saeed Lecturer (Botany)

14. • 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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Salman Saeed Lecturer (Botany)

15. 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.
Salman Saeed Lecturer (Botany)

16. What is soil structure, how does it
– 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:
– Plant roots surrounding the soil and separating
clumps
– Freezing and thawing of soil
– Soil becomes wet and then dries
– The soil is tilled
Salman Saeed Lecturer (Botany)

17. What is soil structure, how does it
form, and why is it important
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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.
–When soil microorganisms break
down plant residues, they produce
gums that also glue peds together.
Salman Saeed Lecturer (Botany)

18. What is soil structure, how does it
crusts that reduce crop stands.
form, and why is it important
• Soil structure is important for
several reasons:
–It improves soil tilth.
–It improves permeability.
–It resists the beating action of
raindrops, minimizing the formation of
Salman Saeed Lecturer (Botany)

19. What are the various soil structures
2. Massive
and what do they look like?
• There are eight primary types of structure.
They are:
– Granular
– Crumb
– Platy
– Prismatic or Columnar
– Blocky
– Structureless
• 1. Single grain
Salman Saeed Lecturer (Botany)

20. Salman Saeed Lecturer (Botany)

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

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Email: Salmanbotanist@gmail.com