SOIL: Make it Work for You!

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SOIL Make it Work for You!
We Study Soil Because Its A(n)
Great integrator all parts of ecosystem
Snapshot of geologic, climatic, biological, and
human history
Medium of crop production
Producer and absorber of gases
Waste decomposer
Medium for plant growth
Source material for construction, medicine, art,
etc.
Home to organisms (plants, animals and others)
Filter of water and wastes
Essential natural resource
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SOIL Make it Work for You!
Soil Forming Factors
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SOIL Make it Work for You!
What is Soil?

• Each discipline defines soil in a different way,
  depending on how soil affects it.
• In an engineering sense, soil is the relatively
  loose agglomerate of mineral and organic
  materials and sediments found above the
  bedrock.
• R.D. Holtz and W.D. Kovacs (1981)

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• Physical Characteristics
• Soil Texture, Consistency, Structure
• Soil Compaction (Bulk Density)
• Soil Moisture

• Nutrient Characteristics (Soil Chemistry)
• Chemical bonding
• pH
• Cation Exchange Capacity (CEC)
• Nutrient Availability

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SOIL Make it Work for You!
Physical Characteristics of Soil

• Texture the mineral components
• Consistency Structure How the mineral
  components are put together
• Bulk Density
• Soil Moisture

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• Soil Texture
• The way the soil feels is called the soil
  texture.
• Soil texture depends on the amount of each size
  of mineral particles in the soil.
• Sand, silt, and clay are names that describe the
  size of individual mineral particles in the soil.
• Sand are the largest particles and they fell
  gritty
• Silt are medium sized, and they feel soft, silky
  or floury
• Clay are the smallest sized particles, and they
  feel sticky

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Soil Texture Relative Size Comparison of Soil
Particles
frisbee
dime
Clay (feels sticky)
Silt (feels floury)
(lt 0.002 mm, USDA) (lt 0.002 mm, ISSS)
(0.05 - 0.002 mm, USDA) (0.02 - 0.002 mm, ISSS)
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SOIL Make it Work for You!
Soil Texture Triangle
Triangle Key S sand or sandy Si silt or
silty C clay L loam or loamy
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Effects of Soil Texture

• Soils are more cohesive when they have more fine
  particles (Clays).
• Soils are more loose when the have more coarse
  particles (Sand).
• Different combinations of coarse and fine
  contents produce different soil textures.
• A loam is a mixture of sand, silt and clay
  sandy clay loam is best in landscapes.
• Many other inclusions, such as cobbles, boulders.

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• Soil Consistency
• Describes the general organization of the soil.
• Hold a moist sample between the thumb and
  forefinger, and gently squeeze it until it falls
  apart.
• The soil is classified by the following
  categories
• Loose You have trouble picking out a single
  sample and the structure falls apart before you
  handle it.
• Friable The sample breaks with a small amount
  of pressure.
• Firm The sample breaks when you apply a good
  amount of pressure and dents your fingers before
  it breaks.
• Extremely Firm The sample can't be crushed with
  your fingers (you need a hammer!).

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SOIL Make it Work for You!
Soil Consistence
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Soil Structure the shape that the soil takes
based on its physical and chemical properties.
Possible choices of soil structure are

• With Structure
• Granular
• Blocky
• Platy
• Prismatic
• Columnar

• Without Structure
• Single Grained
• Massive

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Soil Structure

• With Structure

• Without Structure
• Single Grained
• beach sand
• Massive
• solid mass with no shape

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Soil Structure with Structure
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Soil Structure without Structure
Single Grained
Massive
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Bulk Density a measure of soil compaction
Sample is made of Solids and Pore Spaces
1 cm. (so, there is 1 cubic centimeter of soil)
1.33 gms.
To calculate Bulk Density
1.33
Volume 1 cm3
Bulk Density
1
Weight 1.33 gms
Bulk Density
1.33 gms / cm3
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SOIL Make it Work for You!
Bulk Density Compaction Zones
Depth
Bulk Density (grams / cm3
0 inches
1.43
Plow Layer
1.90
7 inches
1.87
Compacted Zone
8 inches
9 inches
1.84
10 inches
1.80
Uncompacted subsoil
1.60
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Basic Soil Components
Soil Particles Mineral and Organic
Pore Spaces location of air and water
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• Soil Moisture some terms and concepts
• Field Capacity water that remains in soil
  beyond the effects of gravity.
• Permanent Wilting Percentage amount of water
  after the permanent wilting point is reached.
• Available Water amount of water in the soil
  between the field capacity and the permanent
  wilting percentage.

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Relationship between soil texture and water
availability
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Inches of Water Per ft. of Soil
Field Capacity
3
Available Water
2
Permanent Wilting Percentage
1
Sand
Sandy Loam
Silt Loam
Clay Loam
Clay
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Soil at Different Moisture Levels
At Saturation
At Available Water
Water on soil particle surface
Pore Spaces are filled with water
Pore Space
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Soil at Different Moisture Levels
At Permanent Wilt
Compacted
No water remains attached to soil particles
Pore spaces are collapsed
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Compacted Zone
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Impermeable Layer
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Sand Over Clay
SOIL Make it Work for You!
Impermeable Layer
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Clay Over Sand
Perched Water Table
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Soil Sandwiches

• Wet Dry Layers

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Soil Salads

• Patchy Soil Moisture

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Summary of Water Movement
SOIL Make it Work for You!

• Rate depends on
• pore space (structure) and consitence
• particle sizes (texture) and particle size
  distribution.
• Changes in bulk density
• changes water movement (e.g. compaction).
• may result in perched water tables through
  creating an impermeable layer.

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Surface Drainage (Run-Off)
SOIL Make it Work for You!

• Severity of slopes
• Angle and length of slopes
• Soil or surface type
• Presence or absence of vegetation
• Total surface area of drainage basin
• Must include structural surface area
• Structures modify soil saturation, contact areas,
  and volume contact/unit area

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SOIL Make it Work for You!
Controlling Surface Drainage

• Contoured beds and or terracing
• Re-vegetation mats
• Organic vs. synthetics
• Run strips parallel to slope
• Soil modifications
• Replace high bulk density soils
• Incorporate OM or aggregates
• Break up soil surface crusts

• Divert run-off from adjacent sites
• Stabilize slopes with synthetic materials,
  mulches or vegetation
• Break up straight line flows, slows velocity
• Construct sediment fences
• Line drainage channels with coarse aggregates

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Altering Subsurface Drainage
SOIL Make it Work for You!

• Deep plowing (sub-soiling) can damage tree roots
  where landscape is established, utilities,
  impractical for small sites
• Avoid abrupt changes in soil type
• Incorporate OM or large quantities of
  aggregates
• Huge variety of drains

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SOIL Make it Work for You!

• Large Subsurface Drains
• Concrete pipes
• Usually for heavy traffic or very large drains
• High handling and transportation costs
• Large diameter - 12 to 24 diameter metal
  culverts
• Preferred under vehicular traffic
• Damaged ends hinder linking
• Expensive

• Smaller Subsurface Drains
• Ceramic tiles, out moded
• Corrugated plastic pipe
• Cheap, light, flexible
• Perforated - areas of collection of release
• Non-perforated - transport areas
• Avoid clods contacting during installation
• Cover on 3 to 4 sides with 3 to 4 of aggregates
• Cover with back-fill, preferably 12
• Topsoil in non-roads, road bed material in
  traffic areas

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French Drains
SOIL Make it Work for You!

• Old-fashioned, but very effective
• Numerous variations
• With or without pipes
• Covered or exposed
• Often connected to the surface with water
  permeable material
• Essentially a trench filled with aggregates
• Always slope to a lower elevation!
• Very useful for draining contained planting sites

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Soil Horizons

• Horizon A topsoil
• Specified by texture, OM content, available
  nutrients and drainage characteristics.
• Critical to landscape success.
• Should be removed prior to construction and stock
  piled on site
• Incorporate 1/3 into sub-soils after construction
  to create smoother transition zone
• Sharp transition between topsoil and subsoil
  creates perched water tables.

• Horizon B transition zone
• Constitutes much of the exposed soil in areas
  where construction has occurred and in some
  formerly cultivated portions of Ohio
• Horizon C true subsoil
• Little or no soil development.
• Often contains accumulated soluble salts, lime,
  etc. beneath cultivated areas.

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Characterization and Sampling Options
Soil Pit
Exposed Profile (road cut)
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Soil Chemistry

• Chemical bonding
• pH
• Nutrient Availability
• Cation Exchange Capacity (CEC)

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• What is chemistry?
• Elements the simplest kind of matter. They
  cannot be broken down into anything simpler.
• Elements can exist alone. Nitrogen (N),
  Phosphorus (P), Potassium (K), Oxygen (O), are
  elements and they can be made to exist alone, but
  in nature they seldom do.
• Elements tend to combine with each other. These
  are called compounds. When they combine, its
  called a chemical reaction.

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• What is chemistry?
• Chemistry is the study of the how and why
  elements combine, and break apart, through
  chemical reactions.
• Soil Chemistry is simply studying how and why
  compounds are formed and broken apart in the
  soil, and how these chemical reactions affect
  plants.

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Chemistry Made Simple The Atom
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The Electron negative charge
The Nucleus positive charge
Hydrogen
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Chemistry Made Simple The Atom
Hydrogen
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A Water Molecule
H2O
Hydrogen
Hydrogen
Oxygen
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• What happens when an atom has too many electrons?
• It has a negative charge ( - )
• These atoms are called anions
• What happens when an atom doesnt have enough
  electrons?
• It has a positive charge ()
• These atoms are called cations

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• What happens when an anion meets a cation?
• Anions have a negative charge (-)
• Cations have a positive charge ()
• When they meet, they combine to become a
  molecule, the simplest compound
• NaCl (sodium chloride salt).

Chlorine Cl-
Sodium Na
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Common soil cations and anions, their chemical
symbols and ionic forms
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The Chemistry of Clay
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Clay Particle
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Clay particles carry negative charges
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With Magnets
In Soil
Unlikes Attract
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Likes Repel
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The Strange Properties of Water

• Water ionizes it falls apart into ions.
• H2O H OH-
• Called the self ionization of water.
• Only a small amount.

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What is pH?

• Its simply a measure of the relative amount of
  H ions
• In the soil, it is driven by the ionization of
  water H2O H OH-
• We us pH to measure the acidity or the alkalinity
  (basicity) of a solution (a soil solution)

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Possible pH Ranges Under Natural Soil Conditions
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Clay and organic particles have a negative charge
Soil reactions in neutral to high (alkaline) pH
conditions
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K
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Clay Particle
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Al3
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Clay and organic particles have a negative charge
Soil reactions in low (acid) pH conditions
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Physical and Chemical Characteristics of Soil
what does it all mean to you?

• Soil Texture and physical nature of the soil
• Water availability
• soil texture
• bulk density
• Soil Chemistry
• Charged elements / molecules soil particles
• pH and nutrients