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Transcript of Understanding Soils
Arcola High School Look Out Below!
Understanding Soils What does soil do?
Why is it important?
What do you think it is made of? Think About It... What the purpose of soil is.
How soil is formed.
What soil is made of.
Differences in soil types.
How to identify and describe soil particles, textures, and structures. What You Will Learn... Soil is the foundation of all living things.
Plants need it to survive.
Animals need it for support and shelter.
The earth needs it to provide structure. Why Do We Need Soil? Soil provides a place for plants to form roots.
Soil provides a source of water for plants.
Almost all nutrients that plants use come from the soil. Plants Soil provides a place for plants to live.
All animals have some connection to the soil.
Some animals rely on the soil for shelter.
What are some of these animals? Animals Soil provides a covering for most of the Earth's surface.
Soil performs important functions as the first layer of the earth.
What would the Earth look like without soil? Earth The base of all soils is bedrock, the same rock that makes up the interior layers of the earth.
Over the course of millions of years this bedrock was ground in different ways, which created soils. How Was Soil Formed? Thousands of years ago glaciers (large chunks of ice) covered most of North America.
These glaciers would move 6-12 feet per day.
As the glaciers moved, they crushed the bedrock into various, unsorted sizes of gravel, or Glacial Till. Glacial Till Not all of continent was hit by glaciers.
In these areas, the bedrock was not ground, leaving a solid rock base. Un-Glaciated Soils Wind can carry and grind soil particles, and over time these particles break down and accumulate.
Soil deposited by wind is calle "Loess".
This soil is often sorted in a profile by article weight. Loess Soils Water can carry and grind large amounts of soil.
Soils that were deposited by water are called "Alluvial".
This soil is often sorted by particle weight in the soil profile.
This soil often accumulated at the bottom of hills. Alluvial Soils What happens to plants and animals when they die? Organic Matter Organic Matter is decomposed biological materials.
Organic Matter provides nutrients and texture to the soil. Organic Matter The vegetation that historically existed in an area has an effect on the amount of organic matter in the soil.
Which do you think provided more OM? Organic Matter VS Soil Color tells us the amount of organic matter.
The DARKER the soil color, the MORE organic matter content.
The LIGHTER the soil color, the LESS organic matter content.
Which do you think is better for plant growth? Soil Color Oxidized Soil: Caused by high iron content in the soil.
What happens when iron is exposed to water? Soil Color Variances Oxidized Soil Poorly Drained Soils: Usually found in low lying clay soils.
Soil is starved of oxygen due to being water logged, which leaves a dull grey color. Soil Color Variances A Soil Particle is one (1) grain of soil.
Sand, Silt, and Clay all have different sizes.
Which do you think are bigger or smaller? Soil Particles Sand has the largest soil particle size, for instance, a basketball.
Silt had the second largest particle size, for instance Soil Particles Soil Texture measures the amount of sand, silt, and clay in a soil. To measure this we use the Soil Texture Triangle. Soil Texture Soil Structure: The arrangement of soil particles within the soil profile.
There are 5 primary Soil Structures:
5. Single Grain Soil Structure Resembles cookie crumbs.
Often found in the upper layers of the soil.
Leaves a lot of room between particles. Granular Particles are grouped together in large clumps, or blocks.
Leaves large spaces between particles, where a lot of air and water can pass through rather than stay. Blocky Particles group together into vertical columns.
This shape allows a lot of air and water to pass through.
Mostly found in the lower layers of the soil profile. Prismatic/Colmnar Particles are grouped together into thin, horizontal plates.
The organization does not allow air and water to move through the soil very well.
Usually found in compacted soils. Platy Particles do not stick together in a pattern.
Allows air and water to pass through freely, but does not hold water.
Often found in sandy soils. Single Grain The Soil Profile is viewed in Layers
Topsoil (A Horizon): uppermost layer, contains the highest amount of organic matter.
Subsoil (B Horizon): Old soil that has been been compressed by the topsoil.
Parent Material (C Horizon): Usually contains high amounts of rocks or gravel. Soil Layers An area of hard topsoil that has been compacted by large amounts of weight on the topsoil
What would cause this compaction? Compaction A layer of accumulated clay within the topsoil or subsoil layers.
Why would this effect plant growth? Claypan Layers of soil are moved from their original location to another location.
This can happen by way of water or wind.
Areas lose valuable topsoil, and the soil settles in other areas where it can block strams and rivers. Erosion Landowners can care for their soil by using different techniques:
Grassy Waterways What Can Be Done? Breaks the terrain into multiple, level plains.
Used heavily in areas with large slopes. Terraces Uses strategically planted trees to slow wind velocity before it reaches a field.
What kind of tree would be good for a windbreak? Windbreaks Both techniques manage "residue" on the soil to hold it in place.
What do you think residue is?
How do you think residue management is different between Non-Planing and No-Till. Non-Planting/No-Till Farming Landowners plant grass in waterways to keep running water from eroding the edges of the waterway. Grassy Waterways What is the purpose of soil?
How is soil formed?
What are the three types of soil particles?
What are soil textures? Structures?
What is organic matter?
What is the main issue in soils today?
How can we prevent it? Review