Soil is made up of weathered rock and decayed organic matter that provides nutrients for plants to grow. It forms over time as bedrock is broken down by weathering and inhabited by soil bacteria and fungi, whose remains along with dead plants are broken down into humus. Soil is important because it supports nearly all life on land by providing habitat and nutrients, and it must be conserved since it develops very slowly and our supply is limited.

1. What is soil and why is it important?

2. Much of the life on earth depends on soil. Soil is made of weathered rock and decayed parts of plants and animals. Soil provides the nutrients needed by most plants to grow. http://tiee.ecoed.net Photo: A. Criminger

3. How does soil form? The first step is for bedrock to be broken down by weathering . This weathering can happen by wind, water, or changes in temperature. Wind Water Temperature Copyright © Bruce Molnia, Terra Photographics Copyright © Marli Miller, University of Oregon Photo: A Criminger

4. Second step to soil formation: Organisms such as bacteria and fungi begin to grow in the broken down bedrock . http://waterandlife.org/MicroBiota.htm Soil bacteria (Image: USDA) Soil fungi These organisms live and die providing the soil with nutrients that other plants need to grow.

5. As plants live and die, more bacteria and fungi break down these organic materials. This provides additional organic nutrients for more plants to grow and use. The material that is produced is called humus . Photo: J. Criminger

6. http://www.physicalgeography.net/fundamentals/10t.html What is the composition of most soil?

7. When we dig into the earth, we can see that the soil changes with depth. This is called a soil profile. http://epod.usra.edu

8. O – organic material on the surface A – Topsoil high in organic material. Where insects and worms live among the shallow plant roots. B – Subsoil that is high in clay and minerals. Deep roots reach into the subsoil. C – This layer is made of broken bedrock and contains less nutrients Each layer of a soil profile is called a horizon . R – This layer is made of bedrock and contains large, unbroken rock.

9. Our North Georgia soil profile http://www.ga.nrcs.usda.gov/technical/soils/red.html Not all Georgia soils are red, but many of them are. The State is well known for its abundance of "Georgia Red Clay". People often ask why the soils are red. The red color that is so evident in Georgia soils is due primarily to iron oxides. Georgia soil is red because the iron in it has bonded with oxygen forming molecules of “rust.”

10. Why is soil important? Without soil, life on earth would be very different. Imagine no plants that grew in soil. No animals that grazed on plants. Where would we get our food? What would we eat? What do you think?

11. Soil is one of our most valuable resources. Everything that lives on land depends on soil . We have a limited supply of fertile soil. We must conserve and protect our soil. What are some ways you can think of to protect this resource ?

12. Copyright © Bruce Molnia, Terra Photographics This is a view of the US desert taken from an airplane. What caused these circles? What causes the different colors? Why are they circles?

13. Why was this hillside shaped like this for farming? http://www.acca21.org.cn/nrp3-12.html These are terraces – walls built to prevent erosion by making flat places for farming.

14. These trees are used as a wind break to stop erosion by wind.

15. Contour plowing – following the shape of the land to prevent water erosion.

16. Why is soil conservation important? In the 1930’s, farmers removed all the grasses holding the soil in place. After a drought, the wind blew all the topsoil away. Millions of people were affected. This event was called the “Dust Bowl.” http://earthobservatory.nasa.gov

17. Review What is soil? How does soil form? Why is soil important? What is the difference between a wind break, contour plowing, and terracing? What was the Dust Bowl?