1. Soil .

2. What is soil? 
Soil is the loose, weathered material on Earth’s surface where plants can grow

3. Why should you care about soil?
One of Earth’s most valuable natural resources
Everything that lives on land, including humans, depends directly or indirectly on soil

4. What is soil? One of the main ingredients of soil comes from bedrock
Bedrock is the solid layer of rock beneath the soil
Once exposed to the surface, bedrock gradually weathers into smaller and smaller particles which make up soil

5. What is it made of (what is its composition?)
Soil is a mix of rock particles (weathered bedrock), minerals, decayed organic material, water and air
Weathered bedrock = sand, silt and clay
Humus = dark colored material that forms as plant and animal remains decay. It helps create spaces in soil for air and water.
- Also contains nutrients including nitrogen, sulfur, phosphorus and potassium. Plants need nutrients in order to grow. They absorb nutrients from the soil.

6. What is Soil Fertility?
A measure of how well the soil supports plant growth
A measure of how nutrient-rich the soil is
The more humus there is in the soil, the more fertile it is!

7. Value of Soil
Fertile soil is valuable because there is a limited supply and takes a long time to form
Soil value goes down when it loses its fertility and/or when topsoil is lost due to erosion
Fertility loss – from exhaustion - George Washington Carver developed new crops and farming methods to help restore soil fertility to South (peanuts =legumes-add nitrogen that plants need)

8. Crop Rotation
Farmer plants different crops in a field each year so same nutrients are used up every year
After planting crops that use a lot of a certain nutrient, plants crops that put back that nutrient the next year

9. What is Soil Texture & Why is it Important?
Describes the feel of the soil
Depends on the size of the individual soil particles
Classified by size
Smallest particles to largest =
Clay – Silt – Sand – Gravel (pg. 119)

10. What is Soil Texture & Why is it Important?
Important for plant growth
Soils that are mostly clay have a dense, heavy texture. The hold lots of water so plants could “drown”
Sandy soils have a coarse texture. Water passes through quickly so plants could die from lack of water
Loam (= parts clay, sand & silt) is best for most plants

11. How Does Soil Form?
Forms as rock is broken down by weathering & mixes with other materials on surface.
Constantly being formed where ever bedrock is exposed
Gradually soil develops layers called horizons
A Soil horizon is a layer of soil that differs in color and texture from the other layers

12. What is a soil profile?
A soil profile refers to the layers of the soil
These are known as Horizons O, A, B, C and R

13. What does the color of soil tell us?
Generally, the darker the soil, the more nutrients it has. Darker soil usually means it has more humus in it.

14. How is Humus Formed? Decomposition=humus formation
Plants contribute most of the organic remains that form humus.
As plants shed leaves, they form a loose layer called litter
- Organisms that live in soil (decomposers) break down dead plant remains, dead plant roots, other dead organisms and digest them with chemicals into humus

15. How is Humus Formed?
Decomposers = fungi, bacteria, worms & other organisms
Fungi are organisms like mold and mushrooms
Very small animals such as mites and worms also decompose dead organic material and mix it with the soil

16. The soil must be mixed & aerated
Earthworms do most of the work of mixing humus with the other parts of the soil
Burrowing mammals (mice, moles, prairie dogs, gophers, etc.) also dig and break up hard, packed soil and mix in humus
Earthworms and burrowing animals help to aerate, or mix air into the soil
(pgs )

17. Mixing the Soil
These animals also add nitrogen to the soil when they produce waste
They add organic material when they die and decay.
Earthworms and burrowing animals also help to aerate, or mix air into the soil.
Plant roots need the oxygen that this process adds

18. The O horizon is made of decaying plant and animal remains
The O horizon is made of decaying plant and animal remains. It stands for organic matter.
Bedrock is under the C Horizon. It is called the R Horizon.
Textbook pg. 120

19. Litter It’s on top of the first layer of soil—the O horizon
Contains grass, plants, and animals

20. Horizon A; Topsoil 1st layer of soil
Darkest layer of soil (dark brown or black)
Crumbly brown soil that contains humus, clay, other minerals, plant roots, small animals, water, and nutrients for plant growth
The darker the soil, the more nutrients it contains

21. Horizon B; Subsoil 2nd layer of soil Lighter in color (reddish brown)
Fewer nutrients and water
Usually contains clay and other particles washed down A Horizon
Little humus
Limited plant growth

22. Horizon C 3rd layer of soil Lightest in color (gray)
No nutrients, animals, or plant growth
Contains partly weathered rock and sediment

23. R Horizon=Bedrock=Parent Material

24. In the order they form 1st = Horizon C 2nd = Horizon A 3rd =Horizon B
It forms as bedrock weathers and rock breaks into small particles
2nd = Horizon A
Forms as plants add organic material to the soil and plant roots weather pieces of rock
3rd =Horizon B
Forms last as rainwater washes clay and minerals from the A horizon to the B horizon

25. Soil Types
Scientists classify the different types of soil into major groups based on
Climate
Plants, and
Soil composition

26. pH A measure of how acidic or alkaline (basic) a material is 7=neutral
0-7 = more acidic (lower number = more acidic)
7-14 = more basic (higher number = more basic)
Different plants need different pH levels
If too acidic then add lime
If too basic then add sulfur

27. Moisture
Loam is about 25% water, and is the best soil for growing most types of plants

28. So what is soil conservation and stewardship
Stewardship = to take good care of something.
Soil stewardship reminds us of our responsibility to care for our soil resources
Soil conservation = management of soil to prevent its destruction

29. Humans can affect the quality of the soil
Soil quality can affect human health
Humans are responsible for monitoring and maintaining soil quality
Avoiding pollution
Chemicals
Animal and human waste
Soil Conservation

30. Con’t Loss of topsoil – water and wind erode exposed topsoil
Plant cover helps protect it
Dust Bowl – end of 1800’s , years of droughts, almost all Great Plains turned into farms or ranches, wind storms blew topsoil creating giant dust storms

31. 3 Methods of Soil Conservation
Contour Plowing
Farmers plow fields along curves of slope to help slow runoff of extra rainfall
Prevents extra rainfall from washing soil away

32. Conservation Plowing (Low-Till or No-Till Plowing)
Farmers leave dead weeds and stalks in ground
Try to disturb soil and plant cover as little as possible

33. Terraces
Flat, step-like areas built on a hillside to prevent rainwater from running downhill

34. Wind Breaks
Rows of trees between fields to “break” or reduce the force of winds.

35. Cover Crops or Vegetative Cover
Planting crops all year long so fields are never left bare and the plants hold the soil in place.

36. Responsible Land Use Things that increase soil erosion:
Logging, mining and construction
Animal grazing
Growing crops
Recreation
Off road vehicles