1. The unknown ecosystem
THE DIRT ON SOIL

2. In your notes…meaning actually write it down!...answer the question below
What is soil? What is it made of? Where do we get if from? What is your “definition” of soil

3. WHICH IS LARGER? The number of organisms in one shovelful of soil
The number of humans on earth

4. SOIL CREATURES
More in one shovelful than all the humans that have ever lived on earth
Many don’t even have names yet

5. A Recipe for Soil Start with minerals Add organic materials (humus)
Water
Air

6. Soil Characteristics
It takes 100 to 100,000 years to form one meter of soil
Soil forms by weathering and decomposition.
Faster in warmer climates
Why?

7. Physical Composition of Ideal Soil for Crops
Mineral (weathered rock) = 45%
Air = 25%
Water = 25%
Organic matter (humus) = 5%

8. HUMUS Dark organic matter from decomposed plants and animals
Provides nutrients for crops
Soil organisms feed on it
Absorbs and holds water

9. SOIL DECOMPOSERS: BACTERIA
1000 fit on the head of a pin.
Divide to reproduce every 20 minutes.

10. BEETLE MITES
Arachnids
No eyes (it’s dark in the soil)
Eat only fungus

11. NEMATODES Also called round worms Only 1 mm long
Some eat bacteria, some eat detritus, some eat fungus

12. Centipedes, millipedes, snails, slugs

13. EARTHWORMS Live 3 to 6 years Eat detritus, also swallow soil
Add bacteria back to soil
Aerate soil

14. Tardigrade

15. Soil Organisms https://www.youtube.com/watch?v=VuHznslr8aI

16. The texture is caused by the size of the soil particles
SOIL TEXTURE
The texture is caused by the size of the soil particles

17. Soil Texture (Sand) Sand – Between 0.06-2.0 mm in size
Sandy soil drains quickly so roots can penetrate. Too much sand in a soil does not hold enough water and nutrients for most plants.
Does not shrink or swell so it makes a good foundation for buildings.

18. Soil Texture (Silt)
Silt – Between mm in size. Need microscope to see
Silt allows for air to circulate but still retains some water.
Silty soils do not usually hold enough water for most plants.

19. Soil Texture (Clay)
Clay - < .002 mm in size. Water clings to tiny particles holding larger soil particles together forming clumps called aggregates.
Aggregates like gravel provide drainage channels for water. Water will not drain in soils with a lot of clay.
Clay is easily compacted, crushing air and water pore space. Plants root cannot penetrate through dense clay soils.
Clay is a poor material to build on because it swells with water.

20. Loam
Loam is soil with a mixture of sand, silt and clay. It is the best type of soil for most crops