Soil physical properties sixth Presentation by Allah Dad Khan

1. Natural
Resources
Conservation
Service
Helping People Help the Land

2. Natural
Resources
Conservation
Service
Helping People Help the Land
Soil PhysicalSoil Physical
PropertiesProperties
Presentation 5Presentation 5
By Allah Dad khanBy Allah Dad khan

3. Natural
Resources
Conservation
Service
Helping People Help the Land
Mass or Weight of SoilMass or Weight of Soil
weight of soil. Soil mass is derived from: (a) minerals, (b)weight of soil. Soil mass is derived from: (a) minerals, (b)
organic matter, (c) water, and (d) gases. Minerals andorganic matter, (c) water, and (d) gases. Minerals and
organic matter are often lumped together and called “soilorganic matter are often lumped together and called “soil
solids.” The mass of an air-dried soil sample comessolids.” The mass of an air-dried soil sample comes
almost entirely from minerals.almost entirely from minerals.

4. Volume of SoilVolume of Soil
 : amount of “space” it takes up. Volume of soil is derived from its: amount of “space” it takes up. Volume of soil is derived from its
solid components (minerals and organic matter) and its pores. Bothsolid components (minerals and organic matter) and its pores. Both
solids and pores are important. The solids determine soil strengthsolids and pores are important. The solids determine soil strength
and many chemical properties. The pores are where water, gases,and many chemical properties. The pores are where water, gases,
roots, and other organisms reside.roots, and other organisms reside.
 Volumetotal = Volumesolids + VolumeporesVolumetotal = Volumesolids + Volumepores

5. PoresPores
 Pores: the volume not filled by solids in soils. Important porePores: the volume not filled by solids in soils. Important pore
characteristics include: (a) total volume (i.e., % pore volume); (b)characteristics include: (a) total volume (i.e., % pore volume); (b)
shape; (c) orientation; (d) continuity; and (e) tortuosity.shape; (c) orientation; (d) continuity; and (e) tortuosity.

6. Surface Area:Surface Area:
 SA = the area of the surfaces on minerals and organic matter perSA = the area of the surfaces on minerals and organic matter per
unit weight or volume of soil. It is on the surfaces of soil solids thatunit weight or volume of soil. It is on the surfaces of soil solids that
many of the important chemical reactions occur. Consequently,many of the important chemical reactions occur. Consequently,
increased surface area results in more potential for chemicalincreased surface area results in more potential for chemical
reactions and water adsorption.reactions and water adsorption.

7. Physical PropertiesPhysical Properties
of Soilof Soil
 Soil textureSoil texture
 Soil structureSoil structure
 Soil colorSoil color
 Bulk densityBulk density

8. Definition of Soil TextureDefinition of Soil Texture
 Soil textureSoil texture is defined as the relative proportion of sand, silt andis defined as the relative proportion of sand, silt and
clay. The ranges of diameters of the three separates are: sand (2.0-clay. The ranges of diameters of the three separates are: sand (2.0-
0.05 mm), silt (0.05-.002 mm), and clay (<0.002 mm).0.05 mm), silt (0.05-.002 mm), and clay (<0.002 mm).

9. Importance of soil textureImportance of soil texture
 Increases infiltration of water, thus reducing runoff and erosion andIncreases infiltration of water, thus reducing runoff and erosion and
increases the amount of plant available water.increases the amount of plant available water.
 Improves seedling emergence, root growth and rooting depth.Improves seedling emergence, root growth and rooting depth.
Large continuous pores increase permeability.Large continuous pores increase permeability.

10. Class of structure - Describes size of theClass of structure - Describes size of the
aggregatesaggregates..

very finevery fine
 finefine
 mediummedium
 coarsecoarse
 very coarsevery coarse

The size of each category varies with the type of structure.The size of each category varies with the type of structure.

11. Formation of soil structureFormation of soil structure
1.1.
freeze / thawfreeze / thaw
wetting / dryingwetting / drying
root pressureroot pressure
microorganismsmicroorganisms
cementing by clay, organic matter, iron and aluminum compoundscementing by clay, organic matter, iron and aluminum compounds


12. What affects soil texture?What affects soil texture?
 The parent material, as modified by weatheringThe parent material, as modified by weathering
and soil- forming processes, determines a soiland soil- forming processes, determines a soil
horizon’s texture.horizon’s texture.
http://soils.ag.uidaho.ed
u/soilorders/aridisols_07.
http://soils.ag.uidaho.ed
u/soilorders/ultisols_01.h
Residuum
(or
bedrock)
Marine
Sediments

13. Can soil texture be altered?Can soil texture be altered?
 Texture is a relativelyTexture is a relatively
permanent physical propertypermanent physical property
under natural conditions,under natural conditions,
and, for most agricultural orand, for most agricultural or
forestry uses, it is notforestry uses, it is not
practical to change soilpractical to change soil
texture.texture.
 In intensely managedIn intensely managed
systems texture can besystems texture can be
changed by adding coarserchanged by adding coarser
or finer material.or finer material.
http://www.gov.mb.ca/iedm
/profiles/images/alfalfa_lg.jp
g

14. Soil Textural ClassSoil Textural Class
 Soil textural classes are based on theSoil textural classes are based on the
relative proportions of the various soilrelative proportions of the various soil
separates (sand, silt, and clay).separates (sand, silt, and clay).
 There are 12 different soil textural classes.There are 12 different soil textural classes.
 We use the texture triangle to determineWe use the texture triangle to determine
the textural class.the textural class.

15. Texture TriangleTexture Triangle
 The percentage unitsThe percentage units
(0-100%) of sand, silt,(0-100%) of sand, silt,
and clay are listedand clay are listed
along the sides of thealong the sides of the
triangle.triangle.
 Also notice that theAlso notice that the
relative proportion ofrelative proportion of
sand, silt, and claysand, silt, and clay
always adds up toalways adds up to
100%.100%. http://www.public.iastate.edu/~
arossi/texture%20triangle.jpg

16. Soil Particle SizeSoil Particle Size
 The terms sand, silt, and clay refer to particle size; sand is theThe terms sand, silt, and clay refer to particle size; sand is the
largest and clay is the smallest. Gravel particles are larger than 2largest and clay is the smallest. Gravel particles are larger than 2
millimeters (mm), sand particles are 0.05–2 mm, silt particles aremillimeters (mm), sand particles are 0.05–2 mm, silt particles are
0.002–0.05 mm, and clay is smaller than 0.002 mm. To put this in0.002–0.05 mm, and clay is smaller than 0.002 mm. To put this in
perspective, if a particle of clay were the size of a BB, then a particleperspective, if a particle of clay were the size of a BB, then a particle
of silt would be the size of a golf ball and a grain of sand would beof silt would be the size of a golf ball and a grain of sand would be
the size of a chair (FAO 2007).the size of a chair (FAO 2007).

17. Soil separate particle diameter (mm)
____________________________
Sand . . . . . . . . . 2.0 - 0.05
Silt . . . . . . . . . . 0.05 - 0.002
Clay . . . . . . . . . . <0.002
SAND
SILT CLAY

18. Soil properties are influenced by textureSoil properties are influenced by texture
including:including:
1.1. DrainageDrainage
2.2. Water holding capacityWater holding capacity
3.3. AerationAeration
4.4. Susceptibility to erosionSusceptibility to erosion
5.5. Organic matter contentOrganic matter content
6.6. Cation exchange capacity (CEC)Cation exchange capacity (CEC)
7.7. pH buffering capacitypH buffering capacity
8.8. Soil tilthSoil tilth

19. Soil Texture TestSoil Texture Test
 Purpose:Purpose: Soil texture refers to the relative proportion of mineralSoil texture refers to the relative proportion of mineral
particles of various sizes (soil fractions): sand, slit, and clayparticles of various sizes (soil fractions): sand, slit, and clay
expressed as a percentage. The basis of the test is the particle sizeexpressed as a percentage. The basis of the test is the particle size
and its mass, as related to settling time when dispersed in solution.and its mass, as related to settling time when dispersed in solution.
Size classes according to their particle diameter are listed in theSize classes according to their particle diameter are listed in the
table below:table below:
Size Class Particle Diameter (mm)
Very coarse sand 2.0-1.0
Coarse sand 1.0-0.5
Medium sand 0.5-0.25
Fine sand 0.25-0.10
Very fine sand 0.10-0.05
Silt 0.05-0.002
Clay Less than 0.002

20. Definition of Soil StructureDefinition of Soil Structure
The arrangement and organization of primary and secondary particlesThe arrangement and organization of primary and secondary particles
in a soil mass is known as soil structure.in a soil mass is known as soil structure.
Soil structure controls the amount of water and air present in soil.Soil structure controls the amount of water and air present in soil.
Plant roots and germinating seeds require sufficient air and oxygenPlant roots and germinating seeds require sufficient air and oxygen
for respiration.for respiration.
Bacterial activities also depend upon the supply of water and air inBacterial activities also depend upon the supply of water and air in
the soilthe soil..

21. Mechanism of Aggregate Formation:Mechanism of Aggregate Formation:
 The bonding of the soil particles into structural unit is the genesis ofThe bonding of the soil particles into structural unit is the genesis of
soil structure. The bonding between individual particles in thesoil structure. The bonding between individual particles in the
structural units is generally considered to be stronger than thestructural units is generally considered to be stronger than the
structural units themselves.structural units themselves.
In aggregate formation, a number of primary particles such as sand,In aggregate formation, a number of primary particles such as sand,
silt and clay are brought together by the cementing or binding effectsilt and clay are brought together by the cementing or binding effect
of soil colloids. The cementing materials taking part in aggregateof soil colloids. The cementing materials taking part in aggregate
formation are colloidal clay, iron and aluminium hydroxides andformation are colloidal clay, iron and aluminium hydroxides and
decomposing organic matter. Whatever may be the cementingdecomposing organic matter. Whatever may be the cementing
material, it is ultimately the dehydration of colloidal mattermaterial, it is ultimately the dehydration of colloidal matter
accompanied with pressure that completes the process ofaccompanied with pressure that completes the process of
aggregationaggregation

22. Colloidal clay:Colloidal clay:
 By virtue of high surface area and surface charge, clay particlesBy virtue of high surface area and surface charge, clay particles
play a key role in the formation of soil aggregates. Sand and siltplay a key role in the formation of soil aggregates. Sand and silt
particles can not form aggregates as they do not possess the powerparticles can not form aggregates as they do not possess the power
of adhesion and cohesion. These particles usually carry a coating ofof adhesion and cohesion. These particles usually carry a coating of
clay particles; they are enmeshed in the aggregates formed by theclay particles; they are enmeshed in the aggregates formed by the
adhering clay particles. Colloidal particles form aggregates onlyadhering clay particles. Colloidal particles form aggregates only
when they are flocculated. There is vast difference betweenwhen they are flocculated. There is vast difference between
flocculation and aggregation.flocculation and aggregation.
Flocculation is brought about by coalescence of colloidal particlesFlocculation is brought about by coalescence of colloidal particles
and is the first step in aggregation.and is the first step in aggregation.

23. Classification of Soil Structure:Classification of Soil Structure:
 The primary particles sand, silt and clay usually occur groupedThe primary particles sand, silt and clay usually occur grouped
together in the form of aggregates.together in the form of aggregates.
 Natural aggregates are called peds where as clod is an artificiallyNatural aggregates are called peds where as clod is an artificially
formed soil mass. Structure is studied in the field under naturalformed soil mass. Structure is studied in the field under natural
conditions and it is described under three categoriesconditions and it is described under three categories
1. Type - Shape or form and arrangement pattern of peds1. Type - Shape or form and arrangement pattern of peds
2. Class - Size of Peds2. Class - Size of Peds
3. Grade - Degree of distinctness of peds3. Grade - Degree of distinctness of peds

24. Types of Soil StructureTypes of Soil Structure
 :: There are four principal forms of soil structureThere are four principal forms of soil structure
 Plate-like (Platy):Plate-like (Platy): In this type, the aggregates are arranged in relatively thinIn this type, the aggregates are arranged in relatively thin
horizontal plates or leaflets. The horizontal axis or dimensions are largerhorizontal plates or leaflets. The horizontal axis or dimensions are larger
than the vertical axis. When the units/ layers are thick they are called platy.than the vertical axis. When the units/ layers are thick they are called platy.
When they are thin then it is laminar.When they are thin then it is laminar.
Platy structure is most noticeable in the surface layers of virgin soils butPlaty structure is most noticeable in the surface layers of virgin soils but
may be present in the subsoil.may be present in the subsoil.
 This type is inherited from the parent material, especially by the action ofThis type is inherited from the parent material, especially by the action of
water or ice.water or ice.
 Prism-like:Prism-like: The vertical axis is more developed than horizontal, giving aThe vertical axis is more developed than horizontal, giving a
pillar like shape. Vary in length from 1- 10 cm. commonly occur in sub soilpillar like shape. Vary in length from 1- 10 cm. commonly occur in sub soil
horizons of Arid and Semi arid regions. When the tops are rounded, thehorizons of Arid and Semi arid regions. When the tops are rounded, the
structure is termed as columnar when the tops are flat / plane, level andstructure is termed as columnar when the tops are flat / plane, level and
clear cut prismaticclear cut prismatic..

25. Block likeBlock like
 :: All three dimensions are about the same size. The aggregatesAll three dimensions are about the same size. The aggregates
have been reduced to blocks. Irregularly six faced with their threehave been reduced to blocks. Irregularly six faced with their three
dimensions more or less equal.dimensions more or less equal.
When the faces are flat and distinct and the edges are sharpWhen the faces are flat and distinct and the edges are sharp
angular, the structure is named as angular blocky. When the facesangular, the structure is named as angular blocky. When the faces
and edges are mainly rounded it is called sub angular blocky. Theseand edges are mainly rounded it is called sub angular blocky. These
types usually are confined to the sub soil and characteristics havetypes usually are confined to the sub soil and characteristics have
much to do with soil drainage, aeration and root penetration.much to do with soil drainage, aeration and root penetration.

26. Spheroidal (Sphere like):Spheroidal (Sphere like):
 All rounded aggregates (peds) may be placed in this category. NotAll rounded aggregates (peds) may be placed in this category. Not
exceeding an inch in diameter. These rounded complexes usually looselyexceeding an inch in diameter. These rounded complexes usually loosely
arranged and readily separated. When wetted, the intervening spacesarranged and readily separated. When wetted, the intervening spaces
generally are not closed so readily by swelling as may be the case with agenerally are not closed so readily by swelling as may be the case with a
blocky structural condition.blocky structural condition.
 Therefore in sphere like structure, infiltration, percolation and aeration areTherefore in sphere like structure, infiltration, percolation and aeration are
not affected by wetting of soil.not affected by wetting of soil.
The aggregates of this group are usually termed as granular which areThe aggregates of this group are usually termed as granular which are
relatively less porous. When the granules are very porous, it is termed asrelatively less porous. When the granules are very porous, it is termed as
crumb. This is specific to surface soil particularly high in organic matter/crumb. This is specific to surface soil particularly high in organic matter/
grass land soilsgrass land soils..

28. Classes of Soil StructureClasses of Soil Structure::
 Each primary structural type of soil is differentiated into 5 size classes Each primary structural type of soil is differentiated into 5 size classes
depending upon the size of the individual peds.depending upon the size of the individual peds.
 The terms commonly used for the size classes are:The terms commonly used for the size classes are:
 1. Very fine or very thin1. Very fine or very thin
 2. Fine or thin2. Fine or thin
 3. Medium3. Medium
 4. Coarse or thick4. Coarse or thick
 5. Very Coarse or very thick5. Very Coarse or very thick
 The terms thin and thick are used for platy types, while the terms fine and The terms thin and thick are used for platy types, while the terms fine and
coarse are used for other structural types.coarse are used for other structural types.

29. Grades of Soil StructureGrades of Soil Structure
 Grades indicate the degree of distinctness of the individual peds. It Grades indicate the degree of distinctness of the individual peds. It
is determined by the stability of the aggregates. Grade of structure is determined by the stability of the aggregates. Grade of structure
is influenced by the moisture content of the soil. Grade also is influenced by the moisture content of the soil. Grade also
depends on organic matter, texture etc. Four terms commonly used depends on organic matter, texture etc. Four terms commonly used
to describe the grade of soil structure are:to describe the grade of soil structure are:
 Structure less: There is no noticeable aggregation, such as Structure less: There is no noticeable aggregation, such as
conditions exhibited by loose sand.conditions exhibited by loose sand.
 Weak Structure: Poorly formed, indistinct formation of peds, which Weak Structure: Poorly formed, indistinct formation of peds, which
are not durable and much unaggregated material.are not durable and much unaggregated material.
 Moderate structure: Moderately well developed peds, which are Moderate structure: Moderately well developed peds, which are
fairly durable and distinct.fairly durable and distinct.
 Strong structure: Very well formed peds, which are quite durable Strong structure: Very well formed peds, which are quite durable
and distinct.and distinct.

30. Granular
Platy
Blocky
(Angular)(Subangular)
Wedge
ColumnarPrismatic
Examples of Soil StructureExamples of Soil Structure

31. Aspects of Soil StructureAspects of Soil Structure
 The arrangement into aggregates of The arrangement into aggregates of
desirable shape and sizedesirable shape and size
 The stability of the aggregateThe stability of the aggregate
 The configuration of the poresThe configuration of the pores

32. Factors that Affect Aggregate StabilityFactors that Affect Aggregate Stability
 Kind of clayKind of clay
 Chemical elements associated with the clayChemical elements associated with the clay
 Nature of the products of decomposition or organic matterNature of the products of decomposition or organic matter
 Nature of the microbial populationNature of the microbial population

33. Factors that AffectFactors that Affect
Soil StructureSoil Structure
 Kind of clayKind of clay
 Amount of organic matterAmount of organic matter
 Freezing and thawingFreezing and thawing
 Wetting and dryingWetting and drying
 Action of burrowing organismsAction of burrowing organisms
 Growth of root systems of plantsGrowth of root systems of plants

34. Maintaining Soil StructureMaintaining Soil Structure
 Till soil only at the proper moisture contents. Never till when the soil is too wet. This Till soil only at the proper moisture contents. Never till when the soil is too wet. This
will cause the soil to become cloddy. Aggregates are easily destroyed. will cause the soil to become cloddy. Aggregates are easily destroyed.
Add the proper amounts of lime and fertilizer. Proper plant growth will lead to the Add the proper amounts of lime and fertilizer. Proper plant growth will lead to the
development of good soil structure. development of good soil structure.
Grow grasses and legumes. These plants may help form unstable aggregates and Grow grasses and legumes. These plants may help form unstable aggregates and
their organic matter will help stablize the aggregate. their organic matter will help stablize the aggregate.
Growth of legumes will also give the soil more microorganisms which give certain Growth of legumes will also give the soil more microorganisms which give certain
beneficial fungi which will stabilize peds. beneficial fungi which will stabilize peds.
Maintain or increase organic matter contents of Ap horizon. Maintain or increase organic matter contents of Ap horizon.
– plant cover crops in fall and winter plant cover crops in fall and winter
plant more grasses plant more grasses
– turn under crop residue turn under crop residue
– add manureadd manure

35. Bulk Density DefinitionBulk Density Definition
 Density, as applied to any kind of homogeneous monophasic Density, as applied to any kind of homogeneous monophasic
material of mass material of mass MM and volume and volume VV, is expressed as the ratio , is expressed as the ratio
of of MM to to VV. Under specified conditions, this definition leads to unique . Under specified conditions, this definition leads to unique
values that represent a well-defined property of the material. For values that represent a well-defined property of the material. For
heterogeneous and multiphasic materials, however, such as porous heterogeneous and multiphasic materials, however, such as porous
media, application of this definition can lead to different results, media, application of this definition can lead to different results,
depending on the exact way the mass and volume of the system are depending on the exact way the mass and volume of the system are
defined.defined.

36. Bulk Density:Bulk Density:
 The oven dry weight of a unit volume of soil inclusive of pore spaces is The oven dry weight of a unit volume of soil inclusive of pore spaces is
called bulk density. The bulk density of a soil is always smaller than its called bulk density. The bulk density of a soil is always smaller than its
particle density. The bulk density of sandy soil is about 1.6 g / cm3, whereas particle density. The bulk density of sandy soil is about 1.6 g / cm3, whereas
that of organic matter is about 0.5. Bulk density normally decreases, as that of organic matter is about 0.5. Bulk density normally decreases, as
mineral soils become finer in texture. The bulk density varies indirectly with mineral soils become finer in texture. The bulk density varies indirectly with
the total pore space present in the soil and gives a good estimate of the the total pore space present in the soil and gives a good estimate of the
porosity of the soil. Bulk density is of greater importance than particle porosity of the soil. Bulk density is of greater importance than particle
density in understanding the physical behavior of the soil. Generally soils density in understanding the physical behavior of the soil. Generally soils
with low bulk densities have favorable physical conditions.with low bulk densities have favorable physical conditions.

37. Soil Density PhasesSoil Density Phases
 1) the solid phase or the soil matrix (formed by mineral particles and 1) the solid phase or the soil matrix (formed by mineral particles and
solid organic materials);solid organic materials);
 (2) the liquid phase, which is often represented by water and which (2) the liquid phase, which is often represented by water and which
could more properly be called the soil solution; (3) the gaseous could more properly be called the soil solution; (3) the gaseous
phase, which contains air and other gasesphase, which contains air and other gases

38. Factors affecting bulk densityFactors affecting bulk density

1. Pore space:1. Pore space: Since bulk density relates to the combined volume of the solids and Since bulk density relates to the combined volume of the solids and
pore spaces, soils with high proportion of pore space to solids have lower bulk pore spaces, soils with high proportion of pore space to solids have lower bulk
densities than those that are more compact and have less pore space. Consequently, densities than those that are more compact and have less pore space. Consequently,
any factor that influences soil pore space will affect bulk density.any factor that influences soil pore space will affect bulk density.
 2. Texture:2. Texture: Fine textured surface soils such as silt loams, clays and clay loams Fine textured surface soils such as silt loams, clays and clay loams
generally have lower bulk densities than sandy soils. This is because the fine textured generally have lower bulk densities than sandy soils. This is because the fine textured
soils tend to organize in porous grains especially because of adequate organic matter soils tend to organize in porous grains especially because of adequate organic matter
content. This results in high pore space and low bulk density. However, in sandy content. This results in high pore space and low bulk density. However, in sandy
soils, organic matter content is generally low, the solid particles lie close together and soils, organic matter content is generally low, the solid particles lie close together and
the bulk density is commonly higher than in fine textured soils.the bulk density is commonly higher than in fine textured soils.
3. Organic matter content:3. Organic matter content: More the organic matter content in soil results in high More the organic matter content in soil results in high
pore space there by shows lower bulk density of soil and vice-versa.pore space there by shows lower bulk density of soil and vice-versa.


39. Density concept informs Density concept informs
(1) (1) Density of solids or soil particle densityDensity of solids or soil particle density
(2) Bulk or dry density, (2) Bulk or dry density,
(3) Total or wet density.(3) Total or wet density.

40. Measuring of DensityMeasuring of Density
 Density = Mass / VolumeDensity = Mass / Volume
 Soil density is expressed in two well accepted concepts as particleSoil density is expressed in two well accepted concepts as particle
density and bulk density. In the metric system, particle density candensity and bulk density. In the metric system, particle density can
be expressed in terms of mega grams per cubic meter (Mg/m3).be expressed in terms of mega grams per cubic meter (Mg/m3).
Thus if 1 m3 of soil solids weighs 2.6 Mg, the particle density is 2.6Thus if 1 m3 of soil solids weighs 2.6 Mg, the particle density is 2.6
Mg / m3 (since 1 Mg =1 million grams and 1 m3 =1 million cubicMg / m3 (since 1 Mg =1 million grams and 1 m3 =1 million cubic
centimeters) thus particle density can also be expressed as 2.6 g /centimeters) thus particle density can also be expressed as 2.6 g /
cm3.cm3.

41. Particle DensityParticle Density
 :: The weight per unit volume of the solid portion of soil is calledThe weight per unit volume of the solid portion of soil is called
particle density. Generally particle density of normal soils is 2.65particle density. Generally particle density of normal soils is 2.65
grams per cubic centimeter. The particle density is higher if largegrams per cubic centimeter. The particle density is higher if large
amount of heavy minerals such as magnetite; limonite and hematiteamount of heavy minerals such as magnetite; limonite and hematite
are present in the soil. With increase in organic matter of the soil theare present in the soil. With increase in organic matter of the soil the
particle density decreases. Particle density is also termed as trueparticle density decreases. Particle density is also termed as true
density.density.

Table Particle density of different soil textural classesTable Particle density of different soil textural classes
 Textural Classes Particle density ( g/ cm3)
Coarse sand 2.655
Fine sand 2.659
Silt 2.798
Clay 2.837

42. Bulk density of different textural classesBulk density of different textural classes
Textural class Bulk density
(g/cc)
Pore space %
Sandy soil 1.6 40
Loam 1.4 47
Silt Loam 1.13 50
Clay 1.1 58

43. Bulk DensityBulk Density
 Determined by dividing the weight of oven-dry soil in grams by itsDetermined by dividing the weight of oven-dry soil in grams by its
volume in cubic centimetersvolume in cubic centimeters
 The variation in bulk density is due largely to the difference in totalThe variation in bulk density is due largely to the difference in total
pore spacepore space

44. Effects of Bulk DensityEffects of Bulk Density
 Engineering propertiesEngineering properties
 Water movementWater movement
 Rooting depth of plantsRooting depth of plants

45. Soil ColorSoil Color
 Indicator of different soil typesIndicator of different soil types
 Indicator of certain physical and chemical characteristicsIndicator of certain physical and chemical characteristics
 Due to humus content and chemical nature of the ironDue to humus content and chemical nature of the iron
compounds present in the soilcompounds present in the soil

46. SOIL COLORSOIL COLOR
 Useful tool for providingUseful tool for providing
information about otherinformation about other
soil propertiessoil properties
– Organic matter contentOrganic matter content
– Soil mineralsSoil minerals
– Seasonal high waterSeasonal high water
tablestables
Appling Series, Granville Co, NC

47. SOIL COLORSOIL COLOR
 Useful tool for providingUseful tool for providing
information about otherinformation about other
soil propertiessoil properties
– Organic matter contentOrganic matter content
– Soil mineralsSoil minerals
– Seasonal high waterSeasonal high water
tablestables
Englehard Series, Hyde Co, NC
High
Low

48. SOIL COLORSOIL COLOR
 Useful tool for providingUseful tool for providing
information about otherinformation about other
soil propertiessoil properties
– Organic matter contentOrganic matter content
– Soil mineralsSoil minerals
– Seasonal high waterSeasonal high water
tablestables
Creedmoor Series, Chatham Co, NC

49. SOIL COLORSOIL COLOR
 RedoximorphicRedoximorphic
FeaturesFeatures
– Soil colors formed by theSoil colors formed by the
repeated chemicalrepeated chemical
oxidation and reductionoxidation and reduction
of iron and manganeseof iron and manganese
compounds resultingcompounds resulting
from saturation.from saturation.
– Useful for predicting theUseful for predicting the
presence and depth ofpresence and depth of
seasonal high waterseasonal high water
tables in the soil.tables in the soil.
Mattaponi Series, Chatham Co, NC