Soil Vocabulary

Sand

It has the biggest particles. It is rough in texture. Water passes through very easily

Clay

It has very small particles. It is smooth in texture. Water tends to puddle on top.

Organic Matter

Made up of living organisms such as plants and animals, dead plants and animals, and nutrients that have come from decomposed plants and animals.

Soil Horizon

Soil is made up of distinct horizontal layers; these layers are called horizons. They range from rich, organic upper layers (humus and topsoil) to underlying rocky layers ( subsoil, regolith and bedrock). Not all soil profiles will have each horizon.

Bedrock

The bottom layer. It is a thick layer of unweathered, solid rock that lies just below the subsoil.

Erosion

The carrying away of small pieces of sediment by wind, water or ice.

Humus

The decayed remains of once-living things.

Subsoil

The layer of soil right below topsoil. The particles are larger and it is lighter in color. There is less humus.

Soil

The loose material that covers much of the Earth's surface.

Loam

This is a mixture of clay, sand silt, and humus. It has several particles sizes and holds water well.

Horizon C

This is the layer that we call "regolith" and it is located just below the B Horizon. This layer is made up of slightly unbroken rock and only a little but of organic material is found here. Plant roots are not found in this layer.

Horizon A

This is the layer that we call "topsoil" and it is located just below the surface. This layer is made up of minerals and decomposed organic matter and it is also very dark in color. This is the layer that many plant roots grow in.

Horizon B

This is the layer we call "subsoil" and it is located just below the A Horizon. This layer has clay and mineral deposits and less organic materials that the layers above it. This layer is also lighter in color than the layers above it.

Horizon R

This is unweathered rock (bedrock) layer that is beneath all the other layers.

Topsoil

Very top layer of soil it has small dark particles and a lot of humus. This is the best layer for growing plants.