The Scoop on Dirt. Soil Soil is made up of weathered rock, including gravel, sand, and silt. Topsoil...

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