1. Soil Chapter 12 Section 1

2. Soil Chapter 12 Section 1

3. What is Soil?
Renewable resource that can be replaced over LONG periods of time. 100’s or 1,000’s of years for just 1 inch of topsoil to form.
Mix of biotic and abiotic components
Topsoil is made up of living organisms, rock particles, water, air, and dead or decomposing organisms.
Quality depends upon composition

4. Soil as an ecosystem
Soil consists of mineral and organic matter, air, and water
Dead and living microorganisms
Decaying material
Bacteria, algae
Habitat for earthworms, insects, mammals, reptiles, and amphibians
Since soil is composed of interacting living and nonliving matter, it is considered an ecosystem

5. Soil Formation Factors
Effects
Climate
Soil forms faster in warm, wet climates.
Organisms
Earthworms and other burrowing animals mix and aerate soil, add organic matter, and affect the composition of the soil.
Land-forms
Hills and valleys affect exposure to sun, wind, and water.
Parent Material
Chemical and physical characteristics of parent material influence what type of soil will be formed.
Time
Soil formation takes decades, centuries, or millennia

6. Soil Formation

7. Soil Formation
Weathering: can be physical or chemical method of breaking down rocks and minerals.
Deposition: dropping off of eroded material in a new location
Decomposition: breaking down of organic material

8. Soil Components
Soil is made up of 45% mineral matter, 5% organic matter, and 50% water and air.
Parent material can be lava or volcanic ash, rock or sediment deposited by glaciers, sand dunes, sediment deposited by rivers, or bedrock.

9. Soil Horizons make Soil Profiles
Soil is sorted into 6 distinct
layers called soil horizons.
O = Top of the ground.
A = Topsoil: where most plant nutrients are found.
E = minerals leach from here down into the B layer.
B = subsoil
C= weathered parent material.
R= Parent material

10. Soil Characteristics
The soil horizons that we just looked at are what makes up a “typical” sample of soil.
U.S. soil scientists classify soils into 12 major groups based on how the soil is formed.

11. Soil Characteristics
Color: dark soil = nutrient richness, light soil does not.
Texture: texture is based upon particle size.
-Clay particles are tiny
-Silt particles are medium
-Sand particles are large
Structure: Arrangement of soil particles. Too clumpy, soft, or hard can be bad!
pH: Needs to be in the neutral range –too acidic or too alkaline (basic) can create poor growing conditions.

12. Soil Texture Test by Feel
Video

13. Deep Thinking
1. How does soil structure relate to flooding?