Soils A look at this valuable resource & why we shouldn’t treat it like dirt. Scott Poague,...
-
Upload
bryan-allison -
Category
Documents
-
view
215 -
download
0
Transcript of Soils A look at this valuable resource & why we shouldn’t treat it like dirt. Scott Poague,...
Soils
A look at this valuable resource & why we shouldn’t treat it like dirt.
Scott Poague, Holtville High School
Lesson Objectives
• We will determine what exactly soil is.
• We will determine what makes up the soil’s composition.
• Identify effective procedures for soil management.
What exactly is soil?
That’s a good question, I’m glad that you asked!
Soil is a general term that is used to describe the thin, variable layer of mineral and organic matter that covers the Earth’s
land surface. This layer is usually biologically active.
Soil Defined
• There are many definitions of soils, all depend on the user’s viewpoint.
– Some consider it a living & breathing substance at the Earth’s surface which
fosters life all scales.
Soil Defined
Others consider it to be an aggravating layer that must be moved out of the way for progress.
Soils Defined
• The study of soil is not the study of “dirt.”– Dirt does not have life sustaining properties.
– Greenhouse media is not considered soil either.
• In order to be considered a soil, it must have evolved as a function of place, time, & the environment.
Soils Defined
“Dirt” is simply defined as soil out of place.
Soils DefinedDon’t confuse greenhouse
potting mixes with soil. Potting mixes are usually
blends of organic materials and non-organic materials.
Soil Facts
• It can take up to 1,000 years to form 1inch of productive topsoil.
This pile of topsoil took more than 1,000 years
to form, but only 20 minutes to dig from the
ground.
•Soil formation is a never ending process.
How Do Soils Form?
• Soils form from parent material.
(a.k.a. rock)
How Do Soils Form?
Over a period of thousands of years rock has become disintegrated by a
process called weathering.
Example of ice breaking rock apart.
How Do Soils Form?
• Warming & cooling, freezing & thawing, wetting & drying, wind & water erosion, root penetration are examples of mechanical forces that aide in disintegration.
• Chemical forces such as oxidation aide the disintegration process as well.
Soil FormationWeathering has shaped these
rocks into interesting shapes.
Where’s Waldo?
Soil Formation
Soil Formation
• Productive soils develop on the Earth’s surface as the atmosphere, sunlight, water, & living things meet & interact with the mineral world.
• Soil is suitable for plant growth to a depth of 36” or more, that soil is regarded as “deep.”
• Most soils are shallower than this.
Soil Make Up
• Soil is made up of 4 key elements;– Air, water, organic matter, & minerals
• Air & water is found in pore spaces between solid particles.
• Organic matter is mainly composed of plant debris, & microorganisms such as bacteria & fungi.(typically most abundant at the surface of the soil)
Soil Make Up
• Soils form from 3 types of rock:– Igneous– Metamorphic– Sedimentary
Igneous Rock Types
Basalt
Pumice
Scoria
Granite
Metamorphic Rock Types
Slate
Schist
Marble
Quartzite
Sedimentary Rock TypesBreccia
Sandstone
Shale
Chert
Rock Salt
Rock Gypsum
Soil Texture
• Once soils are broken down into smaller particles they are considered to be either 1 of 3 particles or a mix of the 3.– Sand (largest)– Silt– Clay (smallest)
Soil Texture
Sand
Sand can vary in coarseness from very fine to very coarse like the sand pictured above. Notice the rock particles
present.
Rock particles
Soil Texture
Silt
Soil Texture
Clay
Soil Texture
• Information about soil types in a
particular area can be found in a Soil Survey Report.
• Every county in each state has one.
Soil Texture
Information about soil texture for soil survey reports is
often collected using drilling probes like
this one.
Soil Horizons
• Horizon O- layer dominated primarily by organic matter(leaves, grass, etc.)
• Horizon A- (topsoil) Layer formed below the organic matter. It is primarily soil, but contains organic matter.
• Horizon B- (subsoil) Layer dominated by pieces of the original parent material. Usually contains clay, silicate, gypsum
• Horizon C- (parent material) Contains parent material, but excludes hard bedrock.
Soil Horizons
Horizon O- Organic Material Layer
Horizon A- Topsoil Layer
Horizon B- Subsoil Layer
Horizon C- Parent Material/Bedrock
Soil Horizons
Soil Profile
Limrock Series Decatur Series
Examples of soil series profiles from soils in North Alabama
Soil Profile
Bama soil series profile. This is the Alabama state soil.
Soil series- a grouping of soils with similar characteristics.
Alabama has 370 soil series across the state that fall into 7 soil regions.
Limestone Valleys & Uplands
Appalachian Plateau
Piedmont Plateau
Blackland Praire
Coastal Plains
Major Flood Plains & Terraces
Coastal Marshes
Soil Water
Important terms associated with water movement in soils.
Soil Water
• Percolation- the downward movement of water in soil.
• Perc test- a test to evaluate the suitability of soils for on-site waste disposal by measuring the rate at which water enters the soil layers.
• Saturated- soil pores contain all of the water they can possibly hold. There is no air movement.
Soil Water
• Waterlogged- soil is saturated with water.
• Impermeable- soils are unable to transmit water. (horizontal water movement)
• Evaporation- vapor loss from soil directly into the atmosphere.
Soil Water
• Clogging- water pores are stopped up preventing water movement through the soil.
Corn field in Iowa that flooded, resulting in waterlogged & saturated soils.
Soil Water
• On level areas water soaks in and moves through the soil in a process called percolation.
• Soils that develop on level land at low elevations tends to be poorly drained, while soils on slight elevations tend to be better drained & more productive.
• Drainage (or lack of it) affects the water table in a particular field.
• The water table has a direct bearing on soil formation.
• When soil is saturated with water, little or no air can penetrate it.
• The lack of air reduces the action of fungi, bacteria, and other soil forming activities in the soil.
Soil Water
Soil Water
• A wet soil, is a slow-forming soil and usually is low in productivity.
• Due to the lack of air, organic matter turns black, thus causing the soil to be a blackish/gray color.
Land Classes
Look At This
The soil on the side of this hill has moved downward. This is called soil creeping. Notice the trees trying to correct their
posture.