1. Soil

2. What is soil?
The loose, weathered material on Earth’s surface in which plants can grow.

3. What is the main ingredient?
The main ingredient for soil is the solid layer of rock beneath the soil called bedrock.

4. Soil Composition
A mixture of rock particles, minerals, decayed organic materials, water and air.
Known as sand, silt, clay and gravel

5. What is humus?
Decayed organic material in soil from plant and animal remains
Provides spaces in soil for water and air
Also contains many nutrients that plants need to grow
Often dark in color

6. Soil Fertility The measure of how well soil supports plant growth
Soil rich in humus has a high fertility content
Sandy soil has low humus and a low fertility content

7. Soil Texture Depends on the size of soil particles
Sand feels coarse and grainy
Clay feels smooth and silky
Silt is dry or moist and sticky
Classified by size (smallest to largest)
Clay
Silt
Sand
Gravel

8. What is loam?
Soil that is made of equal parts clay, silt and sand and holds air and water

9. Process of Soil Formation
Soil forms as rock is broken down by weathering and mixes with other materials on the surface
Soil is constantly being formed whenever bedrock is being exposed
Soil forms into horizons or layers

10. What is a soil horizon?
A layer of soil that differs in color and texture from the layers above and below it

11. What are the different soil horizons and what are their characteristics?
Horizon A- topsoil- a crumbly, dark brown soil with a mixture of humus, clay, and other materials
Horizon B – subsoil- clay and other particles washed down from A, little humus
Horizon C – weathered rock

12. Soil Horizons Horizon A - Topsoil Horizon B - Subsoil Horizon C
Bedrock

13. What are soil organisms?
These living things make humus and other materials that makes soil fertile
These creatures mix the soil and make spaces for water and air

14. What is litter?
The loose layer of dead plant leaves and stems on the soil surface

15. What are decomposers?
Organisms that live in soil and turn dead organic material into humus
Includes fungi, bacteria, worms and other small animals or bugs
Worms do most of the work, they eat their way through the soil and carry soil between layers, the waste is enriched with nutrients