1. Soil
Ch. 10
Sections 3 and 4

2. The Source of Soil Section 3
What Is Soil? Soil is a loose mixture of small mineral fragments, organic material, water, and air that can support the growth of vegetation.
Residual and Transported Soil: Soil that remains above its parent rock is called residual soil. Soil that is blown or washed away from its parent rock is called transported soil.

3. Loam
Loam, a type of very fertile soil is made up of air, water and organic materials as well as minerals from weathered rock.
Rich fertile soil that is made up of about equal parts of clay sand and silt.

4. Soil Properties
Soil Texture and Soil Structure Soil texture is the soil quality that is based on the proportions of soil particles. Soil structure is the arrangement of soil particles.
Transported soil may be moved long distances from its parent rock by rivers, such as this one.

5. Soil Texture
Gravel

6. Soil Properties 2
Soil Fertility A soil’s ability to hold nutrients and to supply nutrients to a plant is described as soil fertility.
Soil Horizons Because of the way soil forms, soil often ends up in a series of layers called horizons.
Soil pH Soils can be acidic or basic. The pH scale is used to measure how acidic or basic a soil is.

7. Soil Layers

8. Regolith
A term that describes the weathered material that is on top of the bed rock
Top soil is the top layer of regolith
Regolith protects the rock below from weathering because bedrock weathers easier than regular rock

9. Soil Triangle
A soil texture triangle is used to classify the texture of a soil.
The sides of the soil texture triangle are scaled for the percentages of sand, silt, and clay.
Clay percentages are read from left to right across the triangle
Silt is read from the upper right to lower left
Sand from lower right towards the upper left portion of the triangle
. The intersection of the three sizes on the triangle give the texture class. For instance, if you have a soil with 20% clay, 60% silt, and 20% sand it falls in the "silt loam" class.  

10. Soil and Climate
Lush tropical rain forests have surprisingly thin topsoil.
Tropical Rain Forest Climates The warm soil in tropical rain forest climates allows dead plants and animals to decay easily. This provides rich humus to the soil.
Desert Climates The lack of rain in desert climates leads to low rates of chemical and mechanical weathering.
The salty conditions of desert soils make it difficult for many plants to survive.

11. Soil and Climate 2
The rich soils in areas that have a temperate climate support a vast farming industry.
Temperate Forest and Grassland Climates Temperate forest and grassland climates get enough rain to cause a high level of chemical weathering, but not too much that nutrients are leached out.
Arctic Climates In arctic climates, as in desert climates, chemical weathering occurs very slowly. Low temperatures slow the formation of humus.
Arctic soils, such as the soil along Denali Highway, in Alaska, cannot support lush vegetation.

12. The Importance of Soil Section 4
Nutrients Soil provides minerals and other nutrients for plants. All animals get their energy from plants.
Housing Soil provides a place for animals to live.
Water Storage Without soil to hold water, plants would not get the moisture or the nutrients they need.

13. Soil Damage and Loss
Overuse Overused soil can lose its nutrients and become infertile.
Soil Erosion When soil is left unprotected, it can be exposed to erosion. Erosion is the process by which wind, water, or gravity transport soil and sediment from one location to another.
Providence Canyon, Georgia, shows the effects of cutting forests for farm land.

14. Providence Canyon
Providence Canyon is near Lumpkin, Georgia.  It has beautiful gullies formed by erosion 150 years ago. This park is part of Georgia's East Gulf Coastal Plain region. People call it Georgia's "Little Grand Canyon."  There are 16 canyons altogether.  Some canyons are 1 mile long and 300 feet across.  An ancient ocean formed all the canyons.

15. Georgia Red Clay Georgia is famous for its red clay.
This red color comes from the high iron content in the soil.
Think rust!

16. Dust Bowl
In the 1800’s settlers in the Great Plains turned the fertile, moisture laden sod into farmland.
In drought, this land dried up and blew away as dust.
In the 1930’s, severe drought over several years allowed this soil to be blown away in great, dark clouds.
Some of these dust storms reached New York City.
This lasted until Many farmers in the “Dust Bowl” had to abandon their homes and move away.
Read Steinbeck’s “The Grapes of Wrath”

17. Contour Plowing and Terracing
Contour Plowing In contour plowing, the rows of soil act as a series of dams to prevent water from eroding topsoil away.
Terracing If hills are steep, farmers can use terracing. Terracing changes one steep field into a series of smaller, flatter fields.

18. Cover Crop and Crop Rotation
Cover Crops Cover crops are crops that are planted between harvests to replace certain nutrients and prevent erosion. Cover crops prevent erosion by providing cover from wind and rain.
Crop Rotation Farmers can rotate crops that use different nutrients so that nutrients in the soil have time to become replenished.