1. SOIL
What is it?

2. O:
partially decomposed leaves or grasses A:
small particles of rock mixed with decaying plant and animal matter
rich supply of nutrients and minerals
air and water for dead material to decompose B:
Lighter in color because more stones and small amount of organic matter

3. Formation of Soil Soil begins as bedrock.
Over time, rock is attacked by rain, wind, frost, snow, and living things and is broken down into smaller particles. (This is called weathering. )
Small plants can grow. Plants speed up the weathering process and add material from themselves to enrich the top soil.
Larger plants can then grow.

4. Soil Characteristics
Color -dark are rich in nutrients and lighter are not.
Texture
Structure clumpy soil tends to have more nutrients.
PH -soil’s acidity shows its ability to support plant growth. -plants die in soils too acidic or too alkaline for them.

5. Soil Texture

6. Particle Size Distribution (Texture)
Important for determining suitability for various uses
Considered a basic property because it doesn’t change

7. Properties Related to Texture
Permeability
Shrink-swell
Water Holding Capacity
Erodibility

8. Soil Components Most soils have a combination of soil particles sizes.
Sand
Silt
Clay

9. Sand Gritty feel Can be seen with the naked eye Hand sampling:
No residue left on hand or in pores

10. Silt Dry: Powdery smooth feel Wet: Creamy slick, slippery feel
No sticky or plastic feel
Can be seen with a hand lens or microscope
Hand sampling:
Coats hand, able to brush off
Remains in pores

11. Clay Dry: Hard feel Wet: Sticky, plastic feel
Can be seen with an electron microscope
Hand Sampling:
Thick film residue

12. Particle Sizes Clay: less than 0.002 mm Silt: 0.002-0.005 mm
Sand: 0.05 – 2 mm
mm fine
mm medium
mm course
1- 2 mm very course
Gravels: 2-75 mm
Cobbles: mm
Stones: mm
Boulders: >600 mm

13. Fine Textured Soil
Large components of silt and clay, making it "muddy" when wet. 
Pore spaces are smaller and hold more water
As clay soils begin to dry, they may still hold large quantities of water.
The small particle size and adhesive & cohesive properties of water make most of it will be unavailable for root uptake. 

14. Course Textured Soil Mostly sand & gravel
has large pore spaces and allows water to easily run through it beyond the reach of roots
drought-prone
little surface area for the particle volume, reducing the potential for nutrient weathering

15. Loamy Soil
A mix of sand, silt, and clay that optimizes agricultural productivity 

16. General Influence of Soil Separates on Properties and Behaviors of Soils
Property/Behavior
Sand
Silt
Clay
Water holding
Low
Med-high
high
Aeration
Good
Med
Poor
OM decomposition
Fast
Slow
Water erosion pot.
High
Compactability
Sealing (ponds, ect)
Nutrient supplying*
Pollutant leaching

17. Soil Texture and Surface Area
As particle size decreases, surface area increases
Clay has about 10,000 times as much surface area as sand
Has a big effect on:
Water holding capacity
Chemical reactions
Soil cohesion
Ability to support microorganisms

18. Soil Degradation and Conservation
Erosion: Certain farming, ranching, and forestry practices can erode soil but other practices can protect it.
Desertification: loss of more than 10% of productivity due to erosion, soil compaction, forest removal, overgrazing, drought, salt buildup, climate change, depletion of water sources and other factors.

19. Soil Conservation Techniques to Reduce Erosion
Intercropping
Crop Rotation
Shelterbelts
Conservation Tilling
Terracing
Contour Farming

20. Agriculture and Food Production
Only about 11% of the Earth’s land is suitable for growing crops.
Genetically Modified Organisms -a promising way to increase food production but there needs to be more research into potential risks.

21. Genetically Modified

22. GMO Potential Risks -New foods dangerous to eat
-pests would be resistant and become “superpests.”
Potential Benefits
-GM crops have only had positive affecst on humans