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Soil basics!

The excited skin of the earth!

•Physical components•Chemical processes•Biological processes

Chuck Henry

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Ecological Restoration HandbookBy: Chuck Henry & Elena Olsen

Chapter 2 from:

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Proportions of the physical parts of soil

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Relative sizes of the three mineral soil particles

Gravels and rocks (mineral particles > 2 mm do not count as soil to a soil scientist! They just take up space!

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Sand

• Relatively big and not very reactive

• Water passes through sand quickly

• Doesn’t hold on to nutrients very well

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Silt

• In size, between clay and sand

• Can hold some water, can hold some nutrients

• Can erode!

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Clay

• Almost the opposite of sand

• Very small

• Holds water very tightly

• Very sticky!

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Mixtures of particles• If you have just the right amount of each

type or soil particle– the best characteristics of each one blend

to make a really good soil

• Best soils:– loams

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“the fuel that runs the soils engine!”

And then… organic matter!

• Holds and also releases water

• Holds and also releases nutrients

• Energy for healthy microbial populations

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The other half of soil: pore space!

air

water

• Where water and air is held

• Where roots grow

• Macropores– Water drains

• Micropores– Hold water

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Soil forms in layers called horizons

All the soil horizons make a soil profile

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Soil forming factors make soil the way it is

• Parent material– The original mineral particles

• Time– How long processes have been working

• Climate– Precipitation and rainfall

• Biota– Plants and animals living on the soil

• Topography– Slope, depressions, ridges, etc.

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Local soils around Western Washington

• Till

• Outwash

• Lacustrine

• Alluvial

• Organic/mucK

• Residual

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Till

• Ablation till– Loose, unsorted

over

• Basal till– Highly compacted

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Outwash

• Coarse material

• Left from water rushing off glaciers

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Lacustrine

• Clay deposited in lakes

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Alluvial

• Particles sorted by rivers

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Organic/muck

• Forms in bogs

• Dead plant parts

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Residual

• Decomposed rock– Volcanic– Sedimentary– Metamorphic