Soil

Soil may look like plain dirt, but it is actually a living, complex mixture. Soil is made of tiny rock particles, minerals, water, air, and billions of living things. It covers much of Earth's land surface. Without soil, plants could not grow and there would be no food. It can take hundreds of years to make just one inch of soil.

What Is in Soil

Soil has layers. The top layer is dark and full of nutrients from dead plants and animals. This is called humus. Below that is subsoil with minerals and clay. Deeper still is broken rock. The very bottom is solid bedrock. Soil also contains water, air, and more living things in a teaspoon than there are people on Earth.

Why Soil Is Important

Soil is essential for life. Plants grow in soil and get nutrients from it. Soil filters water and stores carbon. It is home to worms, insects, fungi, and billions of bacteria. Farmers depend on healthy soil to grow food. Protecting soil from erosion and pollution is very important for the future.

Fun Facts

• One teaspoon of soil contains more microorganisms than there are people on Earth.
• It can take 500 years for nature to make just one inch of topsoil.
• Earthworms are great for soil. They mix and aerate it as they tunnel through.

Did You Know?

Mars has soil too, but it is very different from Earth's. Mars soil has no organic material because there are no plants or animals. It also contains chemicals called perchlorates that would be harmful to most Earth plants. Scientists are studying how to treat Mars soil so future astronauts could grow food in it!