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
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.
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
http://www.physicalgeography.net/fundamentals/10t.html What is the composition of most soil?
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
http://www.lee-county.com/utilities/Mobile%20Irrigation%20Lab/Soil%20Profile.htm 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 .
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.”
Why is soil important? <ul><li>Without soil, life on earth would be very different. </li></ul><ul><li>Imagine no plants that grew in soil. </li></ul><ul><li>No animals that grazed on plants. </li></ul><ul><li>Where would we get our food? </li></ul><ul><li>What would we eat? </li></ul><ul><li>What do you think? </li></ul>
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 ?