The unknown ecosystem

What is soil? What is it made of? Where do we get if from? What is your “definition” of soil

The number of organisms in one shovelful of soil

The number of humans on earth

More in one shovelful than all the humans that have ever lived on earth

Many don’t even have names yet

Start with minerals

Add organic materials (humus)

WaterAir

A Recipe for Soil

It takes 100 to 100,000 years to form one meter of soil

Soil forms by weathering and decomposition.

Faster in warmer climatesWhy?

Mineral (weathered rock) = 45%

Air = 25%Water = 25%Organic matter (humus) = 5%

Dark organic matter from decomposed plants and animals

Provides nutrients for crops

Soil organisms feed on it

Absorbs and holds water

1000 fit on the head of a pin.

Divide to reproduce every 20 minutes.

ArachnidsNo eyes (it’s dark in the soil)

Eat only fungus

Also called round worms

Only 1 mm long

Some eat bacteria, some eat detritus, some eat fungus

Live 3 to 6 years

Eat detritus, also swallow soil

Add bacteria back to soil

Tardigrade

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

https://www.youtube.com/watch?v=YF8OJt_pujc

https://www.youtube.com/watch?v=cjV2WP0wkvo

The texture is caused by the size of the soil particles

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.

Silt – Between .002-.05mm in size.

Silt allows for air to circulate but still retains some water.

Silty soils do not usually hold enough water for most plants.

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.

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