Soils

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Soils By Alan Siewert Urban Forester Ohio
Division of Forestry
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Soil Formation
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Soil Formation
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Soil Formation
Parent material
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Soil Formation
O layer (organic)
Parent material
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Soil Formation
O layer
Parent material
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Soil Formation
O layer
A Layer
parent material highly modified organic material
Parent material
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Soil Formation
O layer
A Layer
B Layer
Parent material modified by leachates from O and
A layers
Parent material
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Soil Formation
O layer
A Layer
B Layer
C layer
Unmodified parent material
Parent material
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Soil Formation
O layer
A Layer
Top Soil
B Layer
C layer
Sub soil
Parent material
Only difference between top soil and sub soil is
organic material and time.
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Good Soil
25 Air
45 Soil particles
25 Water
5 Organic material
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Characteristics of Soils
Physical Texture Structure Bulk Density
Chemical pH Cation exchange capacity Nutrients
Biological Organic matter Soil life
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Soil Texture
Silt .05 mm-.002mm
Sand 2mm-.05 mm
.
Clay lt.002mm
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28
50
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7
21
52
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2mm
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2mm
2mm
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4mm
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Surface Area of a Sphere 4Pir2
.002mm .012566 mm2
2mm 12.566mm2
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Surface area in 2 mm3 of soil
Sand 2mm 12.566mm2
Clay .002mm 12.5 Billion mm2
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Soil Structure
How soil particles are glued together.
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Soil Structure
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Soil Structure
Structure forms when organic acids bind soil
particles together into large clumps
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Compaction
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Compaction
Pore Space
Wilt Point
Macro pores
Micro pores
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Compaction
Pore Space
Field Capacity
Macro pores
Micro pores
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Soil Compaction
Macro pores
Micro pores
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Soil Compaction
Bulk density is a measure soil compaction
Bulk Density is measured in gams per cubic
centimeter
Bulk density that will inhibit root
growth Sand 1.7g/cm3 Clay 1.4 /cm3
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Chemical Properties of Soils
pH
The amount or activity of Hydrogen in solution
Acid Neutral
Alkaline 1 2 3 4 5 6 7 8 9 10
11 12 13 14
0 10 100 1000 10,000 100,000 1,000,000
10,000,000
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Acid Neutral
Alkaline 1 2 3 4 5 6 7 8 9 10
11 12 13 14
Do not hold nutrients well Nutrients leach out
Hold nutrients too tightly Not available to plant
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Cation Exchange Capacity
Cations are positively charged ions
Cations H N P K Na All 14 essential nutrients
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Cation Exchange Capacity
Cations are positively charged ions Soil
particles are negatively charged
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H
K
P
N
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Cation Exchange Capacity (CEC)
Cation Exchange capacity is the ability of the
soil to hold nutrients It is directly related to
surface area There fore CEC can be used to
estimate soil texture
-
H
K
P
N
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Cation Exchange Capacity (CEC)
Based on surface area, there is a limited amount
of space on the soil particle to attach and hold
nutrients
P
N
K
P
N
K
-
H
N
K
P
H
H
K
P
K
K
N
K
P
H
H
K
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Cation Exchange Capacity (CEC) and soil pH
If the soil is acidic there are a lot of H ions
in solution
P
N
K
P
N
K
K
-
H
P
H
N
P
N
H
H
N
K
K
P
-
H
H
H
H
N
H
K
P
K
K
N
K
P
K
P
H
H
H
H
H
K
P
K
K
K
H
H
K
P
H
N
H
H
K
Acid
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Cation Exchange Capacity (CEC) and soil pH
If the soil is acidic there are a lot of H ions
in solution
Lime CaOH
K
H
P
P
N
H
H
N
K
CaOH
CaOH
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H
H
N
H
K
P
CaOH
H
H
H
K
P
K
K
H
H
K
P
H
N
CaOH H HOH Ca
H
H
K
Acid
HOH H2O
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Cation Exchange Capacity (CEC) and soil pH
If the soil is acidic there are a lot of H ions
in solution
P
N
K
P
N
K
-
P
Fe
H
N
P
N
Fe
N
K
K
P
-
H
H
Mn
N
K
P
Mn
K
K
N
K
K
P
H
Fe
K
H
K
P
K
K
Fe
Mn
K
P
K
Alkaline
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Cation Exchange Capacity (CEC) and soil pH
If the soil is acidic there are a lot of H ions
in solution
Hydrochloric acid HCl
P
Fe
P
N
Fe
N
K
HCl
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H
N
HCl H KCl or NaCl
H
K
Fe
K
K
P
H
K
H
Mn
Mn
K
P
K
Mn
Fe
Alkaline
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Buffering Capacity
The resistance of the soil to pH change
Small Leak Small Bilge Pump Equilibrium
Big Leak Big Bilge Pump Equilibrium
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Buffering Capacity
The resistance of the soil to pH change
Small Leak Small Bilge Pump Equilibrium Low
Buffering Capacity
Big Leak Big Bilge Pump Equilibrium High
Buffering Capacity
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Soil Biology
Worms Fungi Arthropods Nematodes Bacteria Virus
Worms Fungi Arthropods Nematodes Bacteria Virus
Organic material
Rhizosphere
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Nutrient Cycling
Tree
Worms Fungi Arthropods Nematodes Bacteria Virus
Organic material
Mineralized Nutrients
Worms Fungi Arthropods Nematodes Bacteria Virus
Worms Fungi Arthropods Nematodes Bacteria Virus
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Soils/Water Relations By Alan Siewert Urban
Forester Ohio Division of Forestry
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Adhesive Water
Drain No Evaporate No Available to plant No
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Cohesive Water
Drain No Evaporate Yes Available to plant Yes
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Cohesive Water
Wilt Point
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Cohesive Water
Field Capacity
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Free Water
Saturation
Drain Yes Evaporate Yes Available to plant No
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Pore Space
Field Capacity
Macro pores
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Pore Space
Macro pores
Micro pores
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Soil Compaction
Macro pores
Micro pores
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Soil Compaction
Macro pores
Micro pores
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Soil Compaction
Bulk density is a measure soil compaction
Bulk Density is measured in gams per cubic
centimeter
Bulk density that will inhibit root
growth Sand 1.7g/cm3 Clay 1.4 /cm3
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Water usage
Field Capacity
Wilt point
Evapotranspiration(ET)
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Water usage
Field Capacity
Wilt point
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Water usage
Field Capacity
Wilt point
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Water usage
Field Capacity
Wilt point
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Water usage
Field Capacity
Wilt point
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Water usage
Field Capacity
Wilt point
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Soil Air Exchange
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Oxygen Rich Air
Soil Air Exchange
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Oxygen Rich Air
Soil Air Exchange
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Oxygen Rich Air
Soil Air Exchange
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Carbon Dioxide Rich Air
Soil Air Exchange
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Carbon Dioxide Rich Air
Soil Air Exchange
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Water Movement in the Soil
Hydrologic Discontinuity
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Root ball
Back fill
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Sandy loam topsoil
Clay subsoil
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Water Movement in the Soil
Capillary Action
Clay
Silt
Sand
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Root ball
Back fill
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Sandy loam topsoil
Subsoil
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Water Movement in the Soil
Water infiltration and Percolation
Infiltration is the movement of water into the
soil Percolation is the movement of free water in
the soil
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Water Movement in the Soil
Wetting Patterns
Clay
Sand
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Water Movement in the Soil
Wetting Patterns
Clay
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Water Movement in the Soil
Wetting Patterns
Sand
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Water Movement in the Soil
Wetting Patterns
Clay
Perched Water Table
Gravel
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Questions?