1. Notes on Soil

2. Soil is important to humans:
Where food is grown (no farms, no food)
Wood for shelter
Clothing (cotton)
Clay for dishes
Wood for paper
Habitat for many animals and plants
Oxygen
Medicine

3. Soil is formed by Rocks are broken down by weathering
Erosion, freezing and thawing, lightning, rain dissolving rocks and minerals, plant roots, animals burrowing, chemical decomposition, etc..
Dead organisms are decomposed into their simpler components

4. Two types of weathering
Chemical – a chemical reaction causes the rock to break down into smaller components
Mechanical – rock is broken down by mechanical forces such as wind, water, temperature changes, gravity, tree roots ,etc

5. Topsoil Made of five things Rocks and minerals 45% Water 25%
Air pockets 25%
Decomposed organic matter (Humus)5%
Living things

6. How to classify soil
pH – The amount of acid or base in the soil determines which vegetation grows best and which nutrients are available
Macronutrients – The nutrients that plants need the most of to be healthy:
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Fertility: Healthy soils have the right amount of all three macronutrients. The plants can grow and reproduce best in fertile soil.

7. Loam is a mixture of all three textures with humus
How to classify soil
Soil Texture
Sand – largest particle size, feels grainy or gritty
Silt - medium sized, feels smooth and silky
Clay – smallest sized, feels sticky
Loam is a mixture of all three textures with humus

8. Humus
Is made of decomposed organisms (plants, animals, bacteria, etc…) in the top soil
Best soil is dark brown. Also known as detritus

9. Nature’s recyclers
Decomposers like worms, insects, animals, bacteria, fungi take dead organisms and change the chemicals N, P, and K to substances that can be reused by plants

10. What is the best soil for growing plants?
The best soil has equal amounts of all 3 types of particles.
This is called loam
The soil is fertile with the right amounts of nutrients available

11. Permeability and Porosity
What is the difference between them?

12. Permeability vs. Porosity
This is how fast the water moves or percolates through the sample
Soil size determines permeability
Clay tends to hold soil/water better; sand increases permeability
Porosity – how much water the soil can hold
Increasing the humus/detritus increases the porosity

13. Why does the world have different types of soil?
Different parent rock
Different climate
Warm & moist climates increase chemical and biological weathering
Moist & large temperature ranges increase physical weathering
Different organisms