Soil

1. Soil Part 1

2. What is Soil? • Soil is the loose, weathered material on Earth’s surface in which plants can grow

3. What is it made of? • Soil is a mixture of rock particles, minerals, decayed organic material (humus), water, and air. • One of the main ingredients is bedrock

4. How is it formed? • Bedrock is broken down by weathering and breaks into soil particles (C Horizon) • Plants add organic material to the soil and plant roots weather pieces of rock (A Horizon) • In between the bedrock and the layer of organic material is a layer of clay and minerals that have been washed from horizon A by rainwater (B Horizon)

5. What is a soil profile? • A vertical section of soil at a particular place. • The profile shows layers of soil called horizons from the surface down to several feet.

6. What are the different soil horizons? O-horizon: this horizon is at the very top of the profile. It is composed of organic material such as humus or decayed crops. Most cultivated land will not have an O-horizon because it has been turned under. The O-horizon is usually no more than 2" thick. A-horizon: this horizon is usually called the topsoil. The topsoil is usually darker in color than the B-horizon because it contains more organic matter. Topsoil is usually gray to brown or black in color. B-horizon: this horizon is commonly known as subsoil. It is below the topsoil and contains more clay and less organic matter. Colors of the B-horizon may be red, yellow, brown or varying combinations. The B-horizon sometimes affects percolation (water movement through the soil) because it can become hard and compacted. C-horizon: the C-horizon is the parent material from which the soil is formed. It is the bedrock.It will eventually be broken down into soil.

7. Soil Conservation Part 2

8. Why is soil so important? • Soil is one of Earth’s most valuable natural resources because everything that lives on land • Plants need soil to live and grow • Humans and animals need plants for food

9. How can we damage or lose soil? • Loss of Fertility-farmers keep planting the same crops in an area without giving the soil time to regain nutrients • Loss of Topsoil-the exposure of soil to water and wind can erode the topsoil

10. Example of Soil Loss Dust Bowl of 1930’s People began to settle the Great Plains and in 1930 most of the land had ranches or farms. Periodic droughts and the farming of the land dried out the topsoil. The topsoil turned to dust and blew away, black clouds reached as far as New York City

11. How can we conserve soil? • Contour plowing • Conservation plowing • Crop rotation

12. Contour Plowing • Farmers plow their fields along the curves of a slope. • This helps to slow the runoff of excess rainfall and prevents soil from washing away.

13. Conservation Plowing • In this type of conservation farmers leave dead weeds and stalks from the previous year’s crops in the ground to return nutrients to the soil • This is also called no-till or low-till plowing

14. Crop Rotation Farmers plant different types of crops in a field each year This helps the soil because different types of plants absorb different amounts of nutrients from the soil. For example cotton and corn need large amounts while oat or barley only needs a small amount