1. Bell Ringer
How do plant roots prevent soil erosion?

2. Soil

3. Soil Development
Soil – the loose covering of broken rock particles and decaying organic matter (humus) that covers Earth’s bedrock
The result of long periods of both mechanical and chemical weathering
Found all over Earth and supports many life forms

4. Soil Development
In fact, there are more organisms in a handful of soil than there are humans on Earth!

5. Soil Development Weathering breaks solid bedrock into smaller pieces
As weathering continues, the pieces continue to get smaller, further increasing weathering (remember, the more surface area, the greater the weathering)

6. Soil Development
Organisms like bacteria begin to live in these weathered materials
Over time, the organisms die, decay, and add nutrients to the weathered materials to form soil

7. Soil Development
In general, this occurs over a long period of time. It can take hundreds of years for only a centimeter (cm) of soil to form
Because soil takes so long to create, we must protect and conserve it
Example: Plant vegetation off-season to keep the soil from eroding

8. Soil Composition
All soil forms on top of bedrock, a solid layer of rock
Because all soil originates from bedrock, bedrock is called the parent material

9. Soil Composition
The parent bedrock determines the type of minerals in the soil and how long it takes for the soil to form

10. Soil Composition
Residual soil – soil located directly above its parent material
Transported soil – soil that has been moved away from its parent bedrock
Which is the result of erosion?

11. Soil Composition Soil profile – vertical sequence of soil layers
Soil horizon – each layer in the soil profile
horizon
profile
horizon
horizon

12. Soil Composition
There are four main soil horizons, but not all soils have all four layers
Bedrock (not considered soil), abbreviated with an “R”

13. Soil Composition Horizon O – “organic” layer
Leaves and organic debris at the top of a soil profile
Not truly soil (doesn’t contain weathered rocks)

14. Soil Composition Horizon A – “topsoil”
Lots of organic matter makes soil dark and nutrient-rich
2nd soil horizon to form

15. Soil Composition Horizon B – “subsoil”
Lots of clay minerals, so red/brown color and slow water flow
3rd horizon to form (created as larger particles and minerals from Horizon A settle)

16. Soil Composition Horizon C – weathered bedrock
Lies just above the bedrock
1st horizon to form

17. Soil Characteristics
Fertility – measure of how well a soil can support plant growth
Macronutrients (needed in large quantities): Nitrogen, Phosphorus, Potassium
Secondary nutrients (needed in smaller quantities): Calcium, Magnesium, Sulfur

18. Soil Characteristics
Soil color – determined by the soil’s climate and composition
DOES NOT indicate soil fertility
Dark soils are often more fertile than light-colored soils, but not always!

19. Soil pH affects the color of hydrangea blossoms
Soil Characteristics
pH – different plant species grow better in specific pH ranges
Porosity – the amount of space between soil particles
Soil pH affects the color of hydrangea blossoms

20. Soil Characteristics
Soil texture – the relative percentages by size of clastic sediments in the soil
From largest to smallest particles: gravel, sand, silt, clay

21. Soil Texture Pyramid
Goal: determine the texture of a soil sample based on the % clay, silt, and sand present

22. Practice
20% clay
40% silt
40% sand
Loam

23. Practice
60% clay
20% silt
20% sand
Clay

24. Practice
10% clay
30% silt
60% sand
Sandy loam

25. Soil Triangle WS Complete the WS independently
Put in basket when you are finished

26. Soil Lab
Make sure to follow clean up (last step on procedure). Turn in when done.
EACH PERSON needs a Soil Pyramid WS, but you may work in PAIRS. Turn in when done or finish for HW.