Soil

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 1/8th 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 1930s 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=MYOmjQO_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. 118-124

• Review figure on p. 120 and 122-123

• Answer questions on p. 124– 1a, 1b, 1c, 2a, 3a, and 3c