Soil Layers

If you could dig straight down into the ground, you would see that soil comes in layers. Each layer is called a horizon. The layers have different colors, textures, and materials. Together, these layers make up a soil profile. Understanding soil layers helps scientists and farmers.

The Main Layers

The top layer is called topsoil. It is dark and full of nutrients from decayed plants and animals. Below that is the subsoil, which is lighter in color and has more clay and minerals. Under the subsoil is a layer of broken rock. At the very bottom is solid bedrock.

Why Soil Layers Matter

Different layers serve different purposes. Topsoil is where most plant roots grow because it has the most nutrients. The subsoil holds water that deep roots can reach. The layers below filter water as it moves down toward aquifers. It takes hundreds of years for nature to build just one inch of topsoil.

Fun Facts

• Topsoil can take 500 to 1,000 years to form just one inch.
• About 25 percent of all known species on Earth live in the soil.
• The color of soil can tell you a lot about it. Dark soil is rich in nutrients. Red soil has a lot of iron.

Did You Know?

There are more living organisms in one tablespoon of healthy soil than there are people on Earth. Bacteria, fungi, insects, and worms all call the soil home!