the scoop on dirt. soil soil is made up of weathered rock, including gravel, sand, and silt. topsoil...
TRANSCRIPT
The Scoop on Dirt
Soil
• Soil is made up of weathered rock, including gravel, sand, and silt.
• Topsoil comes from subsoils and rocks beneath the surface.
• Topsoil takes thousands of years to form.
Photo courtesy of USDA NRCS
What is a Natural Resource?
• Something that people can use in order to live.• Something that is not man-made, but has formed
naturally over hundreds, thousands, or even millions of years.
• Something that cannot be easily replaced once it is used up.
Can we say that topsoil is a valuable natural resource?
• How is it used by people in order to live?
• Can we make it in a “topsoil factory”?
• If we use it up, can we easily get more?
How can we lose topsoil?
• Water can wash it away with rain and flooding.
• Wind can blow it away.
• This process is called erosion.
Photo courtesy of USDA NRCS
How can we conserve topsoil and prevent erosion?
• Roots of plants help to hold the topsoil in place.
• Where can we put plants so that their roots can hold the soil?– On hillsides.
– Along rivers and streams.
– Around the edges of fields.
– Can you think of a place?
Photo courtesy of USDA NRCS
• Soil is made up of organic and inorganic substances.
Soil Types
Soil Types
• Soil is made up of organic and inorganic substances.
Organic means substances that were once living such as leaves, twigs, remains of animals, and microorganisms.
• Soil is made up of organic and inorganic substances.
Inorganic means non-living substances such as rocks and gravel.
Soil Types
We can group soil into three types:
We can group soil into three types:
• Clay (or clayey soil)
We can group soil into three types:
• Sand (or sandy soil)
We can group soil into three types:
• Loam (or loamy soil)
We can group soil into three types:
• Clay (or clayey soil)
• Sand (or sandy soil)
• Loam (or loamy soil)
Clay
• Clayey soil is made up of tiny particles that are too small to separate.
• Clay feels powdery when dry and sticky and slimey when wet.
• Clay forms hard clods when dry and sticky clumps when wet.
• Because the particles are so small, water cannot drain well from clay.
Photo: Martha Rogers
Sand
• Sandy soil is made up small bits and pieces of rock and smaller particles called silt.
• Sand does not stick together when it is wet or dry.
• Sand particles are loosely packed and water drains through it quickly. Photo: Martha Rogers
Loam
• Loamy soil is a mixture of sand, clay, and organic materials called humus.
• Loam does not become sticky when wet, nor is it powdery when dry.
• Because it contains humus, loam is a rich soil that holds water and also drains well. Photo: Martha Rogers
Let’s do an experiment to see which soil would be best for
growing plants!
Photo: Martha Rogers