1. Soil

2. What is soil?
Made up of weathered rock, air, water and organic matter and supports vegetation.

3. Why is it important? Plants grow from soil
Provides habitat for animals
Serves as a filter for water and pollutants

4. Forming soil Factors in soil type Climate Organisms Topography time
Parent material- the rock material from which soil is formed

6. Soil Horizons
As soils form they develop characteristic layers

7. Soil Horizons Vertical cross section
O – few cm thick; organic matter
A – AKA topsoil; organic matter and biological activity (roots, bacteria, fungus, animals); zone of leaching (water takes minerals to lower layers)
B – AKA subsoil; fewer organisms and less organic layer; zone of accumulation (where minerals deposit)
C – lowest soil layer; little organic matter; rock fragments
Boundaries are transitional; not sharp

9. Organisms- bacteria, fungi, insects, animals
Decompose leaf litter forming humus
Burrowing animals and earthworms churn and mix soils providing space for O2 and water
Change atmospheric nitrogen to useable form

10. Rove beetle
Pseudoscorpion
Flatworm
Centipede
Ant
Ground
beetle
Mite
Adult
fly
Roundworms
Fly
larvae
Beetle
Mite
Springtail
Protozoa
Millipede
Roundworms
Bacteria
Sowbug
Slug
Fungi
Actinomycetes
Snail
Mite
Earthworm
Organic debris

11. Soil Types Clay – very fine particles (sticky feel)
Silt – fine particles (smooth feel)
Sand – medium size particles (gritty feel)
Gravel – coarse particles
Loam – mixture of clay, sand, silt, and humus (spongy feel)
Humus – carbon-rich; gives nutrients and a dark color

12. Increasing percentage sand
100%clay
Increasing
percentage silt
percentage clay 20 40 60 80
100%sand
100%silt
Increasing percentage sand
sandy
clay
silty
silty clay
loam
silt
sandy clay
loamy
sand E D A C B

13. Soil Texture Determines porosity Volume and distance between pores
Need fine particles to hold water and coarse particles for air
Soil permeability (rate at which water and air move from top to bottom)

14. Water
Water
High permeability
Low permeability

15. Infiltration and Leaching
Infiltration: downward movement of water
Leaching: when nutrients are carried down with the water

16. Erosion Movement of soil components- mostly surface litter and topsoil
Main agents – flowing water (most) and wind
Natural and result of humans (farming, logging, construction, overgrazing, off-road vehicles, burning)
Effects – loss of fertility, pollutants, sedimentation of waterways

17. Economic and Ecological Effects – from erosion
Loss of plant nutrients
Can’t store water
Need more fertilizer
Increased water runoff
Buildup of soil in waterways
Desertification