Soils Science 200 U of A

Hue
Range from yellow to red in a soil.
Value
Lightness or darkness of a soil
Chroma
Intensity or brightness. Example: a chroma of 0 would be a neutral gray.
Land Capability Classes
Used to manage soil usage. It can minimize soil erosion. The classes state what factors limit the usage of each area of land. There are 8 classes and 4 subclasses that show what that limiting factor is.
Land Capability Classes I-VIII
Class I is the least limited, So a class I land will be the most useful for agriculture (prime agricultural land). Class VIII is the most limited, So a class 8 land is very susceptible to damage and will be reserved for soley plant and animal use.
Land Capability Sub Classes
Sub-classes shows which each area of land is most susceptible to, and is added along with the class number. (e) erosion, (w) wetness, drainage, flooding, (s) root zone limitations, acidity, density, and shallowness, (c) climate limitations, short growing season. Example: 2e would be land that is slightly susceptible to erosion.
Stoke’s Law
V=kr^2 The velocity is proportional to the squared
k is a constant radius of each particle of soil. There is little
V=velocity variation in the density of soil particles.
r=radius of each particle
Master Horizons: O horizon
Organic layers formed from fallen leaves and other plant and animal remains. They undergo varying transformations for this formation to occur. Referred to as the forest floor.
A horizon:
Most eroded layer, lost some materials because of translocation. This horizon is dominated by mineral particles but have been darkened by water leaching organic materials from the surface layer down into the soil. AKA: topsoil, plow layer. Usually the layer that is plowed and brought up that helps plants grow the most.
E horizon
Zone of maximum leaching or EEEluviation. of clay, Al Fe oxides. lighter than the A horizon above it, and lighter than the B horizon below it. Common in forests, never grasslands
B horizon:
Subsoil horizon with much less organic matter. Composed of Iron, silicate clays, oxides, aluminum, gypsum, calcium carbonate. These materials accumulated from being washed down from the surface. Mostly formed by illuviation: Materials washing in from horizons above.
C horizons
Plant roots and microorganisms extend below horizon B usually in humid regions. Chemical change in soil water occurs. Least weathered horizon of soil.
Diagnostic Horizons: Epipedons
Diagnostic horizons that occur at the soil surface. The whole upper part of the soil that contains organic matter.
Mollic Epipedon
Noted for its dark color. Accumulated organic matter,
Umbric
Organic matter, dark color, but lower saturation than mollic
Ochric epipedon
mineral horizon not as deep as mollic or umbric. lighter in color.
Argillic Horizon
accumulation of silicate clays
Kandic
Accumulation of Fe and Al oxides. But low acidic silicate clays.
Oxic Horizon
highly weathered, high in Fe and Al oxides and low-activity silicate clays. Found in tropical areas.
Spodic Horizon
illuvial horizon with colloidal organic matter and Al oxide. Forest soils. Cool humid climates
Albic Horizon
light colored eluvial low in clay and oxides of Fe and Al.
Illuviation
The movement of materials or materials being washed from an upper horizon layer to a lower one.Result of Eluvation, illuviation is an accumulation of those materials leached by the process of eluviation.
Eluviation
Maximum leaching, or water seeping through the soil bringing down chemicals such as silicate clay, Al and Fe oxides.
Soil Structure
The nature of the system of pores and channels in the soil. Determines the ability for the soil to hold and conduct the water and air necessary for sustaining life growing in it. Drainage; erosion susceptibility; air flow (aeration) gas transport.
Peds
Dirt clods, used to determine structure. Such as… shape and size
Alluvial Deposition
Water deposition: Water moving soil elsewhere. Causes some additions to the soil horizons. Example: alluvial fan: a deposit of sediment built up by a stream causing a fan shape in the soil.
Colluvial Deposition
Down slope deposition. develops at the base of a hill slope from concentration surface runoff. Consisting of silt and bigger rock fragments. Avalanches, GRAVITY.
Loess
Wind blown deposition, soil moved by wind.
Particle Density
Does not change is an assumed value. Drainage aeration a microbial value.
Bulk Density
Mass of Dry soil/ volume of the soil cylinder

Volume of cylinder= V=(Pi*r^2)(Height)

Particle Density
fixed value used to find porosity
Porosity
Bulk density/ Particle density (fixed value) multiply by 100 then subtract from 100.
Jenny Equation: 5 soil forming factors
1. Climate: Very important in determining the environment that the soil will be forming in. Affects the types of organic materials, such as which plants will grow. It affects amount of moisture, and which soil horizons will end up forming either because of aeration or leaching.
2. Organic material: (biota) dead plants and animals, and living. Animals prevent erosion and recycle material from under the soil to the top of the soil creating organic material.
3. Relief or topography: The way the landscape is shaped or sloped affects soil formation greatly, because depending on how it is shaped can cause water to flow down a slope creating a different soil structure than if it stayed at the bottom of a slope.
4. Parent Material: The parent material is the building block of every soil formed. The type of parent material depends on the location and also depends on the other four soil forming factors.
5. Time: Very important because the longer the parent material has had to break down the more developed all the soil horizons will be.
Soil Taxonomy: Orders

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SOIL ORDER 1

Gelisols: Soils with a lot of permafrost, found in the tundra. (Cryoturbation)
(Root: EL)
ORDER 2: Histosol Root= ist
Histosols: Very high water capacity, more than 20 percent organic matter. Very rare. Many cations
ORDER 3: Spodosols Root= Od(s)
Spodosols: Acid, sandy forest soils, highly leached giving andic properties. Light upper horizons to darker yellowish lower horizons.
ORDER 4: ANDISOLS Root: Ands
Volcanic ash soils. Not as much development time. high water capacity. Easily tilled, low density. Organic matter accumulation.
ORDER 5: Oxisols Root: OX
Most weathered soil order. Hot moist climates. tropical rain forest. deep oxic subsurface horizon Moderatley acidic clay, and high concentrations of Al and Fe
Order 6: Vertisols: Root: ERT
Dark swelling and cracking clays. subhumid/semiarid environments. rainfall moistens cracks in clay and then it expands and hardens again. almost black in color most times.
Order 7: Mollisols Root: OLL
Dark solft soils of grasslands. Calcium rich organic matter. granular or crumb surface horizon.
Order 8: alfisols Root: ALF
Argillic (Clay bearing) or natric horizon, moderately leached. more weathered then most soils besides spodosols and ultisols and oxisols. Mediterranean climates. deciduous forests. Less acidic clay than Ultisols.
Order 9: Ultisols Root: ULT
More highly weathered than alfisols, also argillic horizons, the only difference is ultisols have acidic clay and alfisols have less acidic clay.
Order 10 :Ardisols Root: ID like arid
Dry soils. Arid environments. most abundant soil next to entisols. Water deficiency. Light colored top layer (epipedon). and little to no organic matter.
Order 11: Entisols: Root: ENT
Recent soils: little to no development. no B horizon. Forms in shifting sand or on steep rocky slopes. or in recent alluvium (Water deposition).
Order 12: inceptisols Root: ept
Has few diagnostic characteristics. ochric or umbric epipedon, cambic horizon.
Sub-orders
Based on the root of the order. Entisols= order suborder=aquents
Sub-orders
Based on the root of the order. Entisols= order suborder=aquents
Great- group
more than 400 Examples: umbric, argillic (more clay) (, and natric….)
Sub-group
more devisions of great group…. (Vermic Hapludolls …)
Families
Names are normally longer
example: Loamy sandy, mixed, active, cryic…
Silt
.05-.002 cm particles spherical smoother than sand
Sand
Larger particles 2mm-0.05mm in diameter spherical, more coarse than silt and clay.
Clay
less than .002mm plate shaped, sticky texture. attracts cations. reacts with water causing shrinking and swelling
Physical weathering:
Size and shape alterations intensity of weathering can help determine soil type
Chemical weathering
Soil composition changes adding or loss of chemicals in the soil.