Soil and its physical behavior,Soil texture and structure

2.  The ground(soil),Physical behavior of soil, Water
system, soil mechanics.
The ground(soil),Physical behavior
of soil, Water system, soil mechanics.

3.  PRESENTED BY
 UM E HABIBA

4. Physical Behavior
of Soil:

5.  The word soil derived from Latin word “Solium” Which
means upper layer of earth surface.
 Having different meanings for different professions
 For agriculture:
 It is loose surface material of earth in which plants grow.
 For geologist:
 It is the material which is produced as a result of disintegration
of rocks. Which has been transported from its original
positions.
 For engineers:
 Soil is uncemented accumulation of minerals or organic
particles occurring in zone overlying the rock crust.

6.  “The upper layer in which plants grow , a black or dark
brown material typically consisting of mixture of
organic remains , clay and rock particles.”
 What formed soil?
 Soil is thin layer of material covering the earth’s
surface.
 It is formed from weathering of rocks.
 It contain minerals , water and living organisms.

7.  It causes the disintegration of rock near the earth
surface.
 Its major causes are plants , animal life , atmosphere
and water.
 There are two types of it.
 Mechanical weathering
 Chemical weathering

8.  It transform original material into substances with
different composition and different physical
characteristics.
 Newly formed material is more softer and susceptible
to the agent of erosion than original material.
 3 phases of soil:
 The three phases of soil are as follow:
 SOLID
LIQUID
GAS

9.  Sandy soil
 Silt soil
 Clay soil
 Loamy soil
 Chalky soil
 Peaty soil

10.  Contain mineral particles.
 Having water ,air, and organic matter.
 The combination of these determined the
properties of soil.

11.  The arrangement and organization of primary
and secondary particles in a soil known as
soil structure.
 Structure is described under three categories:
 Type – shape or form and arrangement
pattern of peds.
 Class- size of peds.
 Grade – degree of distinctness of peds.

13.  Plate like
 Prism like
 Block like

14.  Climate.
 Organic matter.
 Plant roots and residues.
 Exchangable cations.

15.  Soil color is due to the reflection of EMR by different
soil constituents like minerals organic matter, water,
salts etc.
 The occurrence of two or more patches of color is
called mottling (due to the presence of iron, manganese
and copper in soil in patches).
 Soil colour is inherited from the parent material and
that is referred to as lithocromic . Eg: red soils
developed from red sand stone.

16.  Soil colour is measured using Munsell colour chart and
expressed in terms of Hue, value and chroma.
 Hue denotes the dominant spectral color.
 Value denotes the intensity of color.
 Chroma indicates the purity of color.
 10YR 5/4 means , the Hue value is 10YR, 5 is the value
and 4 is the chroma.

18.  Parent material.
 Soil moisture.
 Organic matter.
 Mixture of organic matter and iron oxides.
 Alternate wetting and drying condition

19.  Relative portion of sand silt and clay .
 Mechanical analysis hydrometric method.
 Textural Classes:
 The proportions of predominant size of fractions of
sand silt and clay is the
basis for classification of soil texture.

21.  Arrangement of soil particles.
 Individual aggregates are known as peds or
secondary units.
 Two forms of structure less conditions are
recognized ;
 Single grain
 Massive

22.  Platy: -In recently deposited clay soil.
 This structure is commonly found in soil layers that
have been compacted.
 Prism: Vertically oriented
 When the tops are flat, these vertical aggregates are
called prismatic.
 These elongated columns vary in length with
different soil.

23.  These structures is commonly seen in soils with high
clay content and
 in horizons dominated by high shrink-swell clays.
 When rounded they are known as columnar .
 Most commonly seen in soils that have sodium
content in a dry climate.

24.  The original aggregates have been reduced to blocks
and basically equal in height, width and depth.
 Blocky structure is the most common type of
structure seen in the subsoil (B horizon) in North
Carolina.
Rounded aggregates usually less than 1/4 inch in
diameter .
 These complexes lie loosely on the surface and are
readily shaken apart.
 These are called granules and the pattern is called
granular .

25.  Each individual soil particle is separate and there is
no structure.
 This is only found in very sandy soils and is the type
of structure commonly seen in sand dunes at the
beach.
 Wedge:- The aggregates resemble wedges thinner at
one end and thicker on the
 other end.

26.  The weight of an individual soil particle per unit
volume is called particle density.
Typical particle densities for soils range from 2.60
to 2.75 g/cm3.
 However they can be as high as 3.0 g/cm3 for very
dense particles and as low as 0.9 g/cm3 for organic
particles

27.  Bulk density is the mass of dry soil per unit volume
including the airspace.
 It has major effect on the movement of air and water
in soils.
 Solis with high bulk densities are often compacted.
 Soil compaction restricts rooting depth which
reduces the uptake of water and nutrients by plants.

28.  The pore space of soil contains the liquid and gas phases
of soil ,everything but the solid phase that contains
mainly minerals of varying sizes as well as organic
compounds.
 Soil porosity is important for many reasons.
 A primary reason is that soil pores contain the
groundwater that many of us drink.
 Another important aspect of soil porosity concerns the
oxygen found within these pore spaces. All plants need
oxygen for respiration so a well-aerated soil is important
for growing crops.
 Clay soil have the highest porosity and sand the lowest

29.  Resistance of soil material to deformation or rupture.
 Rupture resistance is a measure of the soil’s ability to
withstand applied stress. For this test moist soil is
normally used.
 Plasticity is the degree to which a reworked soil can
be permanently deformed without rupturing.

30.  Soil air is a continuation of the atmospheric air .
 Unlike the other components it is constant state of
motion from the soil
 pores into the atmosphere and from the atmosphere
into the pore space.
 Composition of air in soil and atmosphere:-Nitrogen:
Soil Air: 79.2% and Atmosphere: 79.0%
 Oxygen: Soil Air: 20.6% and Atmosphere: 20.9%
 Carbon Dioxide: Soil Air: 0.25% and Atmosphere:
0.04%

31.  Soil temperature is simply the measurement of the
warmth in the soil.
 Ideal soil temperature for planting most plants are 65
to 75 F ( 18 to 24C)
 Night time and day time soil temperatures are both
important.
 Soil functions as a major storage mechanism of heat,
collection energy throughout the day and releasing heat
to the surface during the night

32.  Physical classification of soil water:-
 1. Hygroscopic
 2. Capillary
 3. Gravitational
 Field capacity
 Permanent wilting point
 Hygroscopic Coefficient