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 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:

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