soil taxonomy: orders suborders great groups subgroups families series geology and the evolution of...
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Soil Taxonomy:Orders
Suborders
Great groups
Subgroups
Families
Series
Geology and the Evolution of American Forests
Drummer – State soil of Illinois
Soil Orders
• All end in “sol” which is derived from “solum” meaning soil
• The twelve soil orders are: Alfisols, Aridisols, Entisols, Gelisols, Histosols, Inceptisols, Mollisols, Andisols, Spodosols, Ultisols, Vertisols and Oxisols
Geology and the Evolution of American Forests
Geology and the Evolution of American Forests
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Soil orders where natural forests occur
Maps and soil profiles NRCS
Geology and the Evolution of American Forests
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Soil orders where natural forests occur
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
High pHHigh OM accumulation in upper horizonsAreas of low rainfall
Grasslands with scattered trees
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Moderately high pHSome clay in B horizonsUsually rich in mineral nutrients
Areas of moderate rainfall with seasonal deficiencies
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Very recent deposits or exposures ofraw parent material
No soil development yetResult of a variety of events (volcanoes, landslides, etc)
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Organic soils on poorly aerated sites where water accumulates
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
AcidicResult of strongly leached soils with subsurface accumulations of aluminum and iron
Usually coarse-texturedRecently deposited by effects of
glaciation
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Moist, well-drained (adequate supply of water)
Effects of leaching have not yet led to subsurface accumulations of aluminum, iron, clay, or OM
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Geology and the Evolution of American Forests
Soil orders where natural forests occur
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
AcidicResult of strong leaching in temperate climates causing subsurface accumulation of clay
Moistaffected by brief seasonal dryness
Geology and the Evolution of American Forests
Mollisols
Alfisols
Entisols
Histosols
Spodosols
Inceptisols
Ultisols
Soil orders where natural forests occur
• Geologic definition: Loose surface of the earth as distinguished from solid bedrock (support of plant life not required).
• Traditional definition: Material which nourishes and supports growing plants (includes rocks, water, snow, air).
• Component definition: Mixture of mineral matter, organic matter, water, and air.
Soils
• Soil is the outer portion of the Earth’s crust that
supports plant growth ….• It is the natural medium on the Earth’s surface in which
plants grow ….• It is composed of organic and mineral materials ….
– 50% of soil volume is:
• decomposed rock
• plant and animal remains
– 50% of soil volume is:
• pore spaces (occupied by either air or water)
Soils
Major Components
• Minerals
• Organic matter
• Air
• Water
Air 25%
Mineral Matter 45%
Water 25%
Organic Matter 5%
Soils
GeologyChemistryPhysics
Soils
Engineering
Plant Sciences
Significance of soil science in natural resources:1) matching plant species to soil types2) evaluation of limitations to resource management
• Functions of soil– Offers mechanical support– Retains and transmits water and gases– Serves as a habitat for macro- and micro-organisms– Holds, exchanges, and fixes nutrients
Soils
Soil Formation
• Translocations
• Transformations
• Additions
• Losses
Soils
NRCS photo
• Soil formation is initiated by the process of weathering
• Weathering – the physical or chemical disintegration and/or decomposition of rocks and minerals under natural conditions
Soils
• Physical weathering – breaking down parent material by exposure to physical forces– Moving ice
– Moving water
– Wind
– Growing roots
• Chemical weathering – breaking down parent material by exposure to chemical forces– Rainwater
– Surface water
– Gases
– Secretions by organisms
Soils
• As a portion of the landscape: Collection of natural bodies occupying portions of the earth’s surface that support plants and that have properties due to the integrated effect of climate and living matter, acting upon parent material, as conditioned by relief, over periods of time.
Soils
• Factors influencing soil development– Parent material– Climate– Living organisms– Topography– Time
Soils
Parent Material
• The unconsolidated and more or less chemically weathered mineral or organic matter from which the solum of soils is developed
• Solum-The upper and most weathered part of the soil profile; the A and B horizons
Soils
Climate
• From an over-all standpoint, climate is perhaps the most influential factor affecting soil development
• Temperature and precipitation greatly influence the rates of chemical and physical weathering.
• Warm, wet, and flat areas have more rapid rates of soil formation than areas where the opposite conditions occur
Soils
Living Organisms
• Living organisms influence soil development by providing organic matter, profile mixing, nutrient cycling and structural stability
Soils
Topography
• Can speed up or slow down climatic forces
Soils
Time
• The actual length of time that materials have been subjected to weathering plays a significant role in soil formation
• Soils of the glaciated region are much younger and more fertile then soils that were not glaciated
Soils
• Residual soils – soils that are formed “in place”
• Transported soils – soils formed by the transfer of loose sediments from one area to another area by– Blowing wind
– Moving water
– Moving glacier
– landslides
Soils
• The detachment and movement of soil particles from one place to another
• Wind and water are the primary forces causing soil erosion
• Vegetative cover and roots help to keep the loss of soil in balance with topsoil replacement
Soils
Wind erosion
NRCS photo
Soil erosion by water is categorized into four types:
1. Splash
2. Sheet
3. Rill
4. Gully
Soils
Soil erosion by water is categorized into four types:
1. Splash
2. Sheet
3. Rill
4. Gully
Soils
The spattering of small soil particles caused by the impact of raindrops on very wet soils
The spattering of small soil particles caused by the impact of raindrops on very wet soils
Soil erosion by water is categorized into four types:
1. Splash
2. Sheet
3. Rill
4. Gully
Soils
Occurs when a wide flow of water moves across a sloping field
Recently tilled farmland with no vegetative cover
Occurs when a wide flow of water moves across a sloping field
Recently tilled farmland with no vegetative cover
Soil erosion by water is categorized into four types:
1. Splash
2. Sheet
3. Rill
4. Gully
Soils
Results from water moving through small channels in the soil surface
• Farmland that is partially tilled with some vegetative residue• Moderately overgrazed rangeland
Results from water moving through small channels in the soil surface
• Farmland that is partially tilled with some vegetative residue• Moderately overgrazed rangeland
Soil erosion by water is categorized into four types:
1. Splash
2. Sheet
3. Rill
4. Gully
Soils
Occurs where water is concentrated into a high velocity flow through a large channel that lacks vegetation
Occurs where water is concentrated into a high velocity flow through a large channel that lacks vegetation
NRCS photo
Controlling Erosion
• The key to controlling erosion is to maintain a good vegetative cover
• Farming practices used to control erosion include: conservation tillage, strip cropping, contour farming, terracing, gully reclamation, windbreak planting, and the retirement of highly erodible lands from cultivation
Soils
SoilsStrip Cropping
NRCS photo
Soils
Contour Farming
NRCS photo
Soils
Buffer Strip(gully reclamation)
NRCS photo
SoilsWindbreak Planting
NRCS photo
SoilsTree Planting
NRCS photo
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Most abundant elements in the soil:
O
Si
Al
Fe
Ca
Na
K
Mg
SiO2, Al2O3, Fe2O3, CaCO3
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Macronutrients:
C
H from water and atmosphere
O
N
P depleted
K from inorganic
Ca minerals in
Mg the soil
S
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Micronutrients:
Fe
Mn
Mo
Zn from inorganic
Cu minerals in the soil
Cl
B
Co
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Plant litter
Animal and insect remains
Feces
OM serves as:
reservoir for moisture
temperature moderator
barrier to water vapor diffusion
home and food for microorganisms
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Partially decomposed organic matter is called Humus
Humus improves:
soil water holding capacity
soil ion-exchange capacity
soil structure
water infiltration
aeration
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil ComponentsWater holding capacity is the ability to retain water ….
precipitation
infiltration
dissolved minerals
plant uptake
Infiltration rates depend on soil porosity
Many spaces Few spaces
poor water good water
holding capacity holding capacity
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Air is necessary for root respiration and gaseous exchange
Pore spaces are either occupied by water or air
Soils with high water holding capacity usually have poor aeration.
• Soil Components– Inorganic minerals– Organic matter– Water– Air– Living organisms
Soil Components
Living organisms mix, churn, aerate, and decompose soil and organic matter.
bacteria earthworms
fungi insects
molds moles
protozoa gophers
mites ground squirrels
nematodes badgers
Soil textureThe individual mineral particles in a soil are classified into three
texture size classes:
Sand (.05-2.0 mm)
Silt (.002-.05 mm)
Clay (<.002 mm)
The texture of a soil is then described as:
The proportion in which particles of different size classes are found in the soil
Physical Properties of Soils
NRCS photo
Physical Properties of Soils
Soil structureThe way soil particles clump together in larger lumps and
clods are called
––– “Peds” –––
Peds are characterized on the basis of their
- size
- shape
- degree of distinction
Physical Properties of Soils
Factors that Affect Soil Structure
• Kind of clay
• Amount of organic matter
• Freezing and thawing
• Wetting and drying
• Action of burrowing organisms
• Growth of root systems of plants
All of these have a loosening effect on the soil, but they have no effect on aggregate stability
Physical Properties of Soils
Aspects of Soil Structure
Physical Properties of Soils
• The arrangement into aggregates of desirable shape and size
• The stability of the aggregate
• The configuration of the pores
Aspects of Soil Structure
• The arrangement into aggregates of desirable shape and size
• The stability of the aggregate
• The configuration of the pores
Physical Properties of Soils
Granular
Platy
Blocky
(Angular)(Subangular)
Wedge
ColumnarPrismatic
Granular
Platy
Blocky
(Angular)(Subangular)
Wedge
ColumnarPrismatic
NRCS photo
Aspects of Soil Structure
Physical Properties of Soils
• The arrangement into aggregates of desirable shape and size
• The stability of the aggregate
• The configuration of the pores
Factors that affect aggregate stability
- Kind of clay- Chemical elements associated with the clay- Nature of the products of decomposition or organic matter- Nature of the microbial population
Factors that affect aggregate stability
- Kind of clay- Chemical elements associated with the clay- Nature of the products of decomposition or organic matter- Nature of the microbial population
Aspects of Soil Structure
Physical Properties of Soils
• The arrangement into aggregates of desirable shape and size
• The stability of the aggregate
• The configuration of the pores
Bulk Density
- Determined by dividing the weight of oven-dry soil in grams by its volume in cubic centimeters
- The variation in bulk density is due largely to the difference in total pore space
Effects of Bulk Density
- Engineering properties- Water movement- Rooting depth of plants
Effects of Bulk Density
- Engineering properties- Water movement- Rooting depth of plants
The chemical properties of soils are determined by:
oxygen ( O2 )
water ( H2O )mineral and nutrient contentorganic matter contentpH
degree of alkalinity or acidity depends on the concentration of H+ and OH- ions acidic neutral alkaline
0 7 14
Chemical Properties of Soils
Water Holding Capacity
• The readily available soil water is considered to be the amount of moisture retained in the soil between field capacity (upper limit) and permanent wilting point (lower limit)
Chemical Properties of Soils
H2O H2O holding ion-exch
texture infiltration capacity capacity aeration
Sand good poor poor good
Silt medium medium medium medium
Clay poor good good poor
Loam medium medium medium medium
Relationship of Physical and Chemical Properties
As soils develop, they form layers or horizons
• Each horizon has a distinctive – thickness– color– texture– composition
• Soil profiles are used to determine the properties of a soil– to match species to the site– to facilitate management
Soil Horizons
Soil Color
• Indicator of different soil types
• Indicator of certain physical and chemical characteristics
• Due to humus content and chemical nature of the iron compounds present in the soil
Soil Horizons
Major Forms of Iron and Effect on Soil Color
Form Chemical Formula Color
Ferrous oxide FeO Gray
Ferric oxide (Hematite) Fe2O3 Red
Hydrated ferric oxide (Limonite) 2Fe2O3 3H2O Yellow
Soil Horizons
Soil Horizons
NRCS photoNRCS photo
Ideal Soil Profile
Soil Profile under aDeciduous Forest
Soil Profile under aConiferous Forest
Land Capability ClassificationLand Class
Characteristics Primary Uses Secondary Uses Conservation
IExcellent land
flat, well-drainedAgriculture
Recreation
Wildlife
Pasture
None
II
Good land
minor limitations such as slight slope, sandy soil, or poor drainage
Agriculture
Pasture
Recreation
Wildlife
Strip cropping
Contour farming
IIIModerately good land
important limitations of soil, slope, or drainage
Agriculture
Pasture
Watershed
Recreation
Wildlife
Urban Industry
Contour farming
Strip cropping
Waterways
Terraces
IVFair land
severe limitations of soil, slope, or drainage
Pasture
Orchards
Limited agriculture
Urban industry
Pasture
Wildlife
Limited contour
farming
Strip cropping
Waterways
Terraces
Land Capability ClassificationLand Class
Characteristics Primary Uses Secondary Uses Conservation
VFarming prevented by shallow soil, wetness, or slope.
Slightly limited by rockiness
Grazing
Forestry
Watershed
Recreation
Wildlife
No special pre-cautions if properly grazed or logged; must not be plowed
VIModerate limitations for grazing and forestry
Grazing
Forestry
Watershed
Urban industry
Recreation
WildlifeGrazing or logging limited at times
VIISevere limitations for grazing and forestry
Grazing
Forestry
Watershed
Recreation
Wildlife
Urban industry
Careful management required when used for grazing or forestry
VIII
Unsuitable for grazing or forestry due to steep slope, shallow soil, lack of water or too much water
Recreation
Watershed
Wildlife
Urban industry
Not to be used for grazing or forestry