soil texture presented by: mr. brian oram, pg, paseo wilkes university geoenvironmental sciences and...

Soil Texture Soil Texture

Presented by:Presented by:Mr. Brian Oram, PG, PASEOMr. Brian Oram, PG, PASEO

Wilkes UniversityWilkes UniversityGeoEnvironmental Sciences and GeoEnvironmental Sciences and

Environmental Engineering DepartmentEnvironmental Engineering DepartmentWilkes - Barre, PA 18766Wilkes - Barre, PA 18766

570-408-4619570-408-4619

http://www.water-research.nethttp://www.water-research.net

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Your Hands will Get “Dirty”

Quick ReviewQuick Review

Major Components of SoilMajor Components of Soil

Pore Space (50%)Pore Space (50%) This may contain air and/or This may contain air and/or

waterwater

Soil Space (50%)• Organic Matter • Mineral Matter

Master Soil HorizonsMaster Soil Horizons O Horizon- leaf litter / humusO Horizon- leaf litter / humus A Horizon- organic accumulation A Horizon- organic accumulation

in mineral soilin mineral soil E Horizon- leached horizon E Horizon- leached horizon

(elluviation)(elluviation)

B Horizon- zone of illuviation B Horizon- zone of illuviation

C Horizon – unconsolidated parent C Horizon – unconsolidated parent materialmaterial

R Horizon – Lithic material (Rock)R Horizon – Lithic material (Rock)R

Not All the Master Horizons Will Be Present in All Profiles

Mineral SoilMineral Soil Is never saturated with water for more than a few Is never saturated with water for more than a few

days and contains less than 20 % (by weight) organic days and contains less than 20 % (by weight) organic carboncarbon

Is saturated with water for longer periods or Is saturated with water for longer periods or artifically drained and excluding live roots, has an artifically drained and excluding live roots, has an organic-carbon content of:organic-carbon content of: Less than 18 % if the mineral fraction contains 60% or Less than 18 % if the mineral fraction contains 60% or

more clay;more clay; Less than 12 %, if the mineral fraction contains no clays; orLess than 12 %, if the mineral fraction contains no clays; or Less than 12 + (clay percentage multiplied by 0.1) %, if the Less than 12 + (clay percentage multiplied by 0.1) %, if the

mineral fraction contains less than 60%.mineral fraction contains less than 60%.

Soil material containing more than the above organic carbon is an organic soil.

Describing Soil MorphologyDescribing Soil Morphologyfor Mineral Soilfor Mineral Soil

Soil Texture and Coarse Fragment ContentSoil Texture and Coarse Fragment Content Soil StructureSoil Structure Soil ColorSoil Color ConsistencyConsistency Redoximorphic FeaturesRedoximorphic Features BoundariesBoundaries

Soil Texture Soil Texture Describes the mineral content of the soil - Which is Describes the mineral content of the soil - Which is

typically less than 50% of the soil volume.typically less than 50% of the soil volume. Soil texture is based on a weight ratio of the 3 soil Soil texture is based on a weight ratio of the 3 soil

separates (sand, silt, and clay).separates (sand, silt, and clay). Material > 2mm are coarse fragments or “rock Material > 2mm are coarse fragments or “rock

fragments” and used as a modifier to the soil texture fragments” and used as a modifier to the soil texture term. Modifier used only when the fragments term. Modifier used only when the fragments represent more than 15 % of the soil volume.represent more than 15 % of the soil volume.

Material < 2mm represent the three (3) soil separates.Material < 2mm represent the three (3) soil separates. Sand - 2.0 - 0.05 mm - Sand - 2.0 - 0.05 mm - GRITTY Feel !GRITTY Feel ! Silt - 0.05 - 0.002 mm – Silt - 0.05 - 0.002 mm – Talc – Floury Feel !Talc – Floury Feel ! Clay - < 0.002 mm – Clay - < 0.002 mm – Tends to be Sticky when Wet !Tends to be Sticky when Wet !

Particle Size Classification SystemsParticle Size Classification Systems

USDA SystemUSDA System – Soil description for agricultural, land-based wastewater – Soil description for agricultural, land-based wastewater disposal, and most environmental applications. disposal, and most environmental applications. (i.e., loam)(i.e., loam)

AASHTO:AASHTO: American Association of State Highways and Transportation American Association of State Highways and Transportation Projects – potential use as road base (i.e., A-1)Projects – potential use as road base (i.e., A-1)

Unified Soil Classification System (ASTM D2487-92) EngineeringUnified Soil Classification System (ASTM D2487-92) Engineering Applications (i.e., SM)Applications (i.e., SM)

WentworthWentworth (phi #)- Geological and Geotechnical Studies Using screen (phi #)- Geological and Geotechnical Studies Using screen or sieve size using the phi number. (phi #, sieve no., or mm)or sieve size using the phi number. (phi #, sieve no., or mm)

Each system has unique (“jargon” or terminology)Each system has unique (“jargon” or terminology)

The Systems Do Not Group the The Systems Do Not Group the Soil Separates the SameSoil Separates the Same

USDA Particle-Size DistributionUSDA Particle-Size Distribution

This is the Particle System we will use in the course.This is the Particle System we will use in the course.

System is divided into: fine-earth fraction and rock fragments.System is divided into: fine-earth fraction and rock fragments.

Fine-earth fraction: Finer than 2 mm: This is the information used to Fine-earth fraction: Finer than 2 mm: This is the information used to describe the soil and is the Soil Textural Class, such as sandy loam. describe the soil and is the Soil Textural Class, such as sandy loam. Classification based on weight of 3 soil separates.Classification based on weight of 3 soil separates.

Rock fragments: 2 mm in diameter or larger. These are commonly described Rock fragments: 2 mm in diameter or larger. These are commonly described as part of the coarse fragment content.as part of the coarse fragment content.

The rock fragment modifier is based on a volumetric fraction of the soil and is The rock fragment modifier is based on a volumetric fraction of the soil and is used as a soil modifier. Therefore – Gravels made up 30 % of the volume for used as a soil modifier. Therefore – Gravels made up 30 % of the volume for a sandy loam the full description would be a sandy loam the full description would be gravelly sandy loam.gravelly sandy loam.

Fine-earth fractionFine-earth fractionThe Three Soil SeparatesThe Three Soil Separates

Sand - 2.0 - 0.05 mmSand - 2.0 - 0.05 mm Silt – 50 – 2 umSilt – 50 – 2 um Clay - < 2 umClay - < 2 um

USDA and NRCSUSDA and NRCS Textural Classes (12) Textural Classes (12)

Sand (S)Sand (S) Loamy Sand (LS)Loamy Sand (LS) Sandy Loam (SL)Sandy Loam (SL) Loam (L)Loam (L) Silt Loam (SIL)Silt Loam (SIL) Silt (SI)Silt (SI)

Sandy Clay Loam Sandy Clay Loam (SCL)(SCL)

Silty Clay LoamSilty Clay Loam(SICL)(SICL)

Clay Loam Clay Loam (CL)(CL)

Sandy ClaySandy Clay(SCL) (SCL)

Silty ClaySilty Clay(SIC)(SIC)

Clay ( C)Clay ( C)

Sand + Silt + Clay = 100%

Texture = LOAM

40 % Sand40 % Silt20 % Clay

The 21 Subclasses The 21 Subclasses in Soil Texturein Soil Texture

There are 12 soil texture classes.There are 12 soil texture classes. When a sand modifier is added there can be 21 When a sand modifier is added there can be 21

total subclasses, but 22 subclasses if very total subclasses, but 22 subclasses if very coarse sandy loam is included.coarse sandy loam is included.

FractionFraction SizeSize (mm) (mm)Very coarse sand.....................................2.0 to 1.0Very coarse sand.....................................2.0 to 1.0Coarse sand.............................................1.0 to 0.5Coarse sand.............................................1.0 to 0.5Medium sand.........................................0.5 to 0.25Medium sand.........................................0.5 to 0.25Fine sand..............................................0.25 to 0.10Fine sand..............................................0.25 to 0.10Very fine sand......................................0.10 to 0.05Very fine sand......................................0.10 to 0.05

Soil Texture SubclassesSoil Texture Subclasses

SANDS (5)SANDS (5)

Very Coarse SandVery Coarse Sand(VCOS)(VCOS)

Coarse Sand (COS)Coarse Sand (COS) Sand (S)Sand (S) Fine Sand (FS)Fine Sand (FS) Very Fine Sand (VFS)Very Fine Sand (VFS)

LOAMY SANDS (4)LOAMY SANDS (4)

Loamy Coarse Sand Loamy Coarse Sand (LCOS)(LCOS)

Loamy Sand (LS)Loamy Sand (LS) Loamy Fine Sand (LFS)Loamy Fine Sand (LFS) Loamy Very Fine Sand Loamy Very Fine Sand

(LVFS)(LVFS)


SANDY LOAMS (4)SANDY LOAMS (4)

Coarse Sandy Loam Coarse Sandy Loam (COSL)(COSL)

Sandy Loam (SL)Sandy Loam (SL) Fine Sandy Loam (FSL)Fine Sandy Loam (FSL) Very Fine Sandy Loam|Very Fine Sandy Loam|

(VFSL)(VFSL)

LOAMS (3)LOAMS (3)

Loam (L)Loam (L) Silt Loam (SIL)Silt Loam (SIL) Silt (SI)Silt (SI)


CLAY LOAMS (3)CLAY LOAMS (3)

Sandy Clay LoamSandy Clay Loam(SCL)(SCL)

Clay Loam (CL)Clay Loam (CL) Silty Clay Loam (SICL)Silty Clay Loam (SICL)

CLAYS (3)CLAYS (3)

Sandy Clay (SC)Sandy Clay (SC) Silty Clay (SIC)Silty Clay (SIC) Clay ( C )Clay ( C )

Using Rock Fragment ModifiersUsing Rock Fragment Modifiers Divided into Divided into Spherical (cubelike)Spherical (cubelike) and and Flat UnitsFlat Units

Less than 15 percent: No adjective or modifier terms are used. Less than 15 percent: No adjective or modifier terms are used.

15 to 35 percent: The dominant kind of rock fragment is used as an adjective 15 to 35 percent: The dominant kind of rock fragment is used as an adjective ie. "ie. "gravellygravelly loam”. loam”.

35 to 60 percent: An adjective term with the word "very" is used ie. "35 to 60 percent: An adjective term with the word "very" is used ie. "veryvery gravelly loam“. gravelly loam“.

More than 60 percent: An adjective term with the word “extremely" is used More than 60 percent: An adjective term with the word “extremely" is used i.e., "i.e., "extremelyextremely gravelly loam." gravelly loam."

NOTE:NOTE: > 90 %, less than 10 % soil separates it may be advisable to use the rock fragment > 90 %, less than 10 % soil separates it may be advisable to use the rock fragment

modifier – such as gravel.modifier – such as gravel.

Estimating Rock Fabric ContentEstimating Rock Fabric Content

How Do We How Do We Determine Texture ?Determine Texture ?

Determination of TextureDetermination of Texture

Field ProcedureField Procedure The “Feel” MethodThe “Feel” Method Estimating Sand and Clay ContentEstimating Sand and Clay Content Field Test Kit – “Volume Method”Field Test Kit – “Volume Method”

Laboratory ProcedureLaboratory Procedure HydrometerHydrometer SieveSieve PipettePipette

What Texture is This Material ?What Texture is This Material ?

Field Determination of Field Determination of Texture- The Feel MethodTexture- The Feel Method

Method 1: The Feel MethodMethod 1: The Feel Method

Key Features or Characteristic that We UseKey Features or Characteristic that We Use Cast Formation and StabilityCast Formation and Stability Feel – Grittiness, Floury, and StickyFeel – Grittiness, Floury, and Sticky Ribbon LengthRibbon Length Evaluate Samples that are Moist, but note Evaluate Samples that are Moist, but note

characteristics when the material is dry and wet.characteristics when the material is dry and wet. See “Feel of Textural Classes” in Appendix C See “Feel of Textural Classes” in Appendix C

of the Course Documentation.of the Course Documentation.

Go to this Handoutin Appendix C of the Course Manual.

Feel Method of Feel Method of Determination of TextureDetermination of Texture

Soil must be moist, not saturated; moist Soil must be moist, not saturated; moist enough to mold like putty when you try to enough to mold like putty when you try to form a ball in your hand.form a ball in your hand.

Question 1: Question 1: Does soil form a ball or cast?Does soil form a ball or cast? No - the texture is No - the texture is SANDSAND

Question 2: Does the soil form a stable cast, but does not form a ribbon No – the texture is loamy sand

Soil does not form a cast:

Textural class is SAND

Thank You – Dr. David Lindo (NCSU)

Feel Method of Feel Method of Determination of Texture (continued)Determination of Texture (continued)

Question 3: Question 3: Does soil form a weak ribbon less Does soil form a weak ribbon less than 2.5 cm?than 2.5 cm? Yes - the possible textures are sandy loam, silt Yes - the possible textures are sandy loam, silt

loam, or loamloam, or loam Does the soil feel gritty? ------- Does the soil feel gritty? ------- Sandy LoamSandy Loam Does the soil feels very smooth with some grittiness? ------ Does the soil feels very smooth with some grittiness? ------

Silt loamSilt loam Does not feel gritty or smooth? ----- Does not feel gritty or smooth? ----- LoamLoam

Making a ribbonMaking a ribbon

The length of the ribbon will depend on clay content and mineralogy.



Question 4: Question 4: Does soil form a ribbon from 2.5 Does soil form a ribbon from 2.5 to 5 cm?to 5 cm? Yes - the possible textures are sandy clay loam, Yes - the possible textures are sandy clay loam,

silty clay loam, or clay loamsilty clay loam, or clay loam Does the soil feel gritty? ------- Does the soil feel gritty? ------- Sandy Clay LoamSandy Clay Loam Does the soil feels very smooth with some grittiness? ------ Does the soil feels very smooth with some grittiness? ------

Silty Clay LoamSilty Clay Loam Does not feel gritty or smooth? ----- Does not feel gritty or smooth? ----- Clay LoamClay Loam


Question 4: Question 4: Does soil form a ribbon > 5 cm?Does soil form a ribbon > 5 cm? Yes - the possible textures are sandy clay, Yes - the possible textures are sandy clay,

silty clay, or claysilty clay, or clay Does the soil feel gritty? ------- Does the soil feel gritty? ------- Sandy ClaySandy Clay Does the soil feels very smooth with some grittiness? ------ Does the soil feels very smooth with some grittiness? ------

Silty ClaySilty Clay Does not feel gritty or smooth? ----- Does not feel gritty or smooth? ----- ClayClay

Forms a cast of moist soil material.

Textural class is LOAMY SAND


Method 2: Estimating Sand and Method 2: Estimating Sand and Clay ContentClay Content

Collect a soil sample and remove the Collect a soil sample and remove the observable the coarse fragments, organic observable the coarse fragments, organic material (roots, etc), and other materialsmaterial (roots, etc), and other materials

If sample is dry, moisten the sample. Do not If sample is dry, moisten the sample. Do not over wet or completely saturate the sample.over wet or completely saturate the sample.

Knead sample between your thumb and finger Knead sample between your thumb and finger and remove any other coarse fragments or and remove any other coarse fragments or non-soil aggregates.non-soil aggregates.

Crush all the soil aggregates.Crush all the soil aggregates.


Question 1: Does the soil have more than Question 1: Does the soil have more than 50 % sand?50 % sand? Yes- Therefore, the sand texture is dominant and Yes- Therefore, the sand texture is dominant and

the likely soil textures are sandy clay loam, sandy the likely soil textures are sandy clay loam, sandy clay, sandy loam, loamy sand, and sand. material clay, sandy loam, loamy sand, and sand. material (roots, etc), and other materials.(roots, etc), and other materials.

No – Therefore, the sand does not dominate and No – Therefore, the sand does not dominate and the likely soil textures are loam, silt loam, silt, clay the likely soil textures are loam, silt loam, silt, clay loam, silty clay loam, silty clay, and clay.loam, silty clay loam, silty clay, and clay.

> 50 %

< 50 %


Question 2: What is the range in clay content and is Question 2: What is the range in clay content and is the sand content > 20 %?the sand content > 20 %? The key is ribbon length and sand percentage.The key is ribbon length and sand percentage. Ribbon < 1 inch long – texture does not include the word Ribbon < 1 inch long – texture does not include the word

clay. (sand, loamy sand, sandy loam, loam, silt loam, and clay. (sand, loamy sand, sandy loam, loam, silt loam, and silt)silt)

Ribbon 1 to 2.5 inch (clay is 27 to 40 %), the soil texture Ribbon 1 to 2.5 inch (clay is 27 to 40 %), the soil texture includes the word clay. (sandy clay loam, clay loam, and includes the word clay. (sandy clay loam, clay loam, and silty clay loam)silty clay loam)

Ribbon > 2.5 inch (clay > 40%), clay is the dominant name Ribbon > 2.5 inch (clay > 40%), clay is the dominant name in the soil texture. (sandy clay, silty clay, and clay)in the soil texture. (sandy clay, silty clay, and clay)

Ribbon > 2.5 inches

Ribbon 1 to 2.5 inches

Ribbon < 1 inch


Combine Your ObservationsCombine Your Observations Sand content < 50 %Sand content < 50 % Ribbons 1.5 inchRibbons 1.5 inch Material has more of a floury feel and no real Material has more of a floury feel and no real

gritty feel. Sand content is likely under 20 %gritty feel. Sand content is likely under 20 % When near saturated the material is sl. sticky.When near saturated the material is sl. sticky.

Therefore, the field evaluation would suggest that the soil has a clay modifier. It is likely that the soil is a silty clay loam.

Method 3 – Volume MethodMethod 3 – Volume Method

Used to Estimate Soil TextureBased on a Non-Volume andNot on a Weight Bases

This does not account for differencesin material density, but settlingrates on particle size.

Method 4 – Hydrometer MethodMethod 4 – Hydrometer Method

The Bouyoucos hydrometer method of mechanical analysis used in routine work, where quick measurements are necessary and extreme accuracy is not required.

The method is based on the fact that water containing material in suspension has greater density than pure water. The more material in suspension, the greater the density.

The Bouyoucos hydrometer measures the density of the suspension. The higher the hydrometer floats, the greater the density of the suspension.

Requirements:1) Hydrometer- reading in grams2) Electronic Balance3) Dry Soil – 40 to 60 grams4) Dispersing Agent 5) Use of an Oxidizing Agent (H202)6) 1000 ml volumetric cylinder7) Readings at 40 seconds and 3 hours8) Temperature Correction

Method 5 -Sieve AnalysisMethod 5 -Sieve AnalysisParticle-Size DistributionParticle-Size Distribution

Particle size distribution describes the abundance (by Particle size distribution describes the abundance (by weight) of the various size particles that constitute the weight) of the various size particles that constitute the mineral portion of soil materials. mineral portion of soil materials.

The distribution of the size based on mm, pH #, or The distribution of the size based on mm, pH #, or sieze size is used for more detailed geological, sieze size is used for more detailed geological, engineering, and geotechnical applications.engineering, and geotechnical applications.

Distribution of Particles for (Sand) can be used to Distribution of Particles for (Sand) can be used to estimate the permeability using the Hazen equations.estimate the permeability using the Hazen equations.

Laboratory MethodLaboratory Method

Method 6 – Pipette MethodMethod 6 – Pipette Method•The pipet method utilizes Stoke's Law by the extraction of subsamples of the soil suspension at a given depth after a predetermined settling time for each size fraction of interest.

•As time passes, larger particles pass by the sampling depth, and smaller and smaller size fractions can be sampled.

•After extracting the sample, it is dried weighed, and a calculation can be done to determine the percentage of the total soil in suspension present in each sample.

• The pipet method is very accurate, but also time consuming. Pretreatment of the sample may include the use of dispersing chemicals or oxidizing agents.V = (2gr²)(d1-d2)/9µ (Stokes Law)Where,V = velocity of fall (cm sec-¹), g = acceleration of gravity (cm sec-²), r = "equivalent" radius of particle (cm), dl = density of particle (g cm -³), d2 = density of medium (g cm-³), and µ = viscosity of medium (dyne sec cm-²).

Time for Review ?Time for Review ?

ReviewReview

The three soil separates are ?The three soil separates are ?

Mineral Particles Greater than 2 mm are?Mineral Particles Greater than 2 mm are?

Are all soil and textural classifications the Are all soil and textural classifications the same?same?

sand, silt, and clay

Coarse Fragments or Rock Fragments

NO the classification systems are not the same !

Soil Texture Soil Texture

Presented by:Presented by:Mr. Brian Oram, PG, PASEOMr. Brian Oram, PG, PASEO

Wilkes UniversityWilkes UniversityGeoEnvironmental Sciences and GeoEnvironmental Sciences and

Environmental Engineering DepartmentEnvironmental Engineering DepartmentWilkes - Barre, PA 18766Wilkes - Barre, PA 18766

570-408-4619570-408-4619

http://www.water-research.nethttp://www.water-research.net

soil texture presented by: mr. brian oram, pg, paseo wilkes university geoenvironmental sciences and...

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