- Slides: 16
Soil Formation • Over many years, weathering and erosion will cause the formation of soil. • Soil is the loose, weathered material on the Earth’s surface in which plants can grow. • Soil forms as rock is broken down by weathering and mixes with other materials on the surface.
Soil Composition • Soil is constantly being formed wherever bedrock is exposed. – Bedrock is the solid layer of rock beneath the soil. • Soil is a mixture of rock particles, minerals, decayed organic material, air, and water.
Soil Composition and Texture • The decayed organic material in the soil is humus. – Humus is a dark-colored substance that forms as plant and animal remains decay. • Soil texture depends on the size of individual soil particles. – Soil texture is important for plant growth.
Life in Soil • Some organisms mix the soil and make spaces in it for air and water. • Other soil organisms make humus, the material that makes soil fertile. – Humus forms through decomposition. – Fertile soil is rich in nutrients that plants need. • As plants shed leaves, they form a loose layer called litter.
With and Without Worms
North Carolina has Southern forest soil that is formed in warm, wet climates; may be low in humus. .
Soil Conservation • Soil is one of Earth’s most valuable resources because everything that lives on the land depends directly or indirectly on soil. • Fertile soil is valuable because there is a limited supply. – Less than 1/8 th of the land on Earth has soils well suited for farming.
Soil Damage and Loss • Soil can become exhausted, or lose its fertility. • Soil can also become lost to erosion by water and wind. – Water erosion can occur wherever soil is not protected by plant cover. – Wind erosion caused the Great Dust Bowl!!
The Dust Bowl • In the 1930 s plowing removed the grass form the Great Plains and exposed the soil. In times of drought, the topsoil quickly dried out, turned to dust, and blew away. • This event helped people appreciate the value of soil. https: //www. youtube. com/watch? v=MYOmj. QO_ UMw
Soil Lost To The Seas!!
Soil Conservation • Soil Conservation is the management of soil to prevent its destruction. • Two ways that soil can be conserved include contour plowing and conservation plowing.
Contour Plowing • Contour plowing is the practice of plowing fields along the contours of a slope. • This helps slow the runoff of excess rainfall and prevents it from washing the soil away.
Conservation Plowing • Conservation Plowing disturbs the soil and its plant cover as little as possible. • Dead weeds and stalks of the previous year’s crops are left in the ground to help return soil nutrients.
Living Organisms in Soil • Read p. 122 -124 • Review figure on p. 120 and 122 -123 • Answer questions on p. 124 – 1 a, 1 b, 1 c, 2 a, 3 a, and 3 c