WHAT IS THE DIRT ON SOIL?

SOIL

• Soil, is made from rocks that break apart or wear away over many years.  • This is referred to as

weathering.  • It may take 100 to 1,000 years

for 1 cm of soil to form through weathering.  • Soil also contains air, water,

and humus, the decayed remains of dead animals and plants. 

DIFFERENT TYPES OF SOIL

Soil can actually be separated into 5 main parts.

They are:• Humus• Gravel• Sand• Silt• Clay

HUMUS

Humus: A dark, moist soil composed of bits of dead, rotting insects, animals, leaves, roots, sticks, and food.  Humus adds nutrients to the soil which plants need to grow and live.

GRAVEL

Gravel: Visible rock particles, sometimes referred to as pebbles.

SAND

Sand: Soil that is coarse and drains quickly.  Sand particles measure from about 0.006 millimeters to 2.00 millimeters.

SILT

Silt: Soil that looks like fine grains or tiny pieces of rock.  Particles classified as silt measure from 0.004 millimeters to 0.006 millimeters.

CLAY

Clay: A soil that holds water.  When wet, clay feels slippery and slimy.  It is made of particles that are smaller than 0.004 millimeters.

THE GOOD GUYS!• Earthworms eat just about

every other organism in the soil. • They're miniature topsoil

factories—all the soil you have ever seen has passed through the stomachs of lots of earthworms. • When they eat, they leave

behind "castings," which are high in organic matter and plant nutrients and are a valuable fertilizer.

EARTHWORMS

• Earthworms move through the soil creating tunnels—areas that can be filled by air and water. • Fields that are "tilled" by

earthworm tunneling can absorb water at a rate 4 to 10 times that of fields without worm tunnels. • This reduces water runoff, restores

groundwater, and helps store more water for dry spells.

• The earthworm’s burrowing also helps nutrients enter the subsoil at a faster rate and opens up pathways for roots to grow into. •During droughts the tunnels

allow plant roots to penetrate deeper, to reach the water they need to thrive.

• Earthworms help keep soil healthy by moving organic matter from the surface into the soil. • Normally a tree leaf may take three to

five years to decompose and be incorporated into the soil. • In forests infested with night crawlers,

this process can take as little as four weeks! • By speeding up the breakdown of plant

material, earthworms also speed up the rate at which nutrients are recycled back to the plants.

FUN FACTS ABOUT EARTHWORMS

• An acre of land can contain more than a million earthworms! • Earthworms are amazingly strong.

They can easily shift stones 60 times their own weight! • The largest earthworm ever was

22 feet long and was found in South Africa. • Worms do not have eyes, but they

can sense light. If they're in light too long they'll become paralyzed. • Baby worms aren't born; they

hatch from a cocoon no bigger than a grain of rice.

THE RECIPE FOR SOIL

• Without life, there is no soil. Living things haven't just made a home in the soil on our planet. Life actually made the soil as we know it. Here's the recipe: • First, select a large quantity of

bedrock. You can start with a fresh lava flow, a solid granite dome, or some limestone. When weathered, or broken down, it will become the parent material that will make the next batch of soil.

PHYSICAL WEATHERING

• Physical weathering: Next, break some of the parent material into pieces. • Use a glacier to grind off big

boulders and fine sediment. • Wind or running water work

great to make small mineral particles. Be patient. • This can take several thousand

years.

CHEMICAL CHANGE

• Chemical change: Now change some of the parent material and the mineral particles into other kinds of minerals. • Run water over limestone to dissolve

the limestone and make the water more acidic. • Expose fresh rock with iron in it to

the air to oxidize the rock. This can also take a while. But you can go on to the next step while this cooks.

BIOLOGICAL ACTIONS• Biological actions: Finally, start with

some early colonizers like lichens. Then throw in some earthworms and other decomposers. They make humus out of dead organic matter. They also turn minerals from the parent material into nutrients that plants can use. • Pretty soon you'll have enough humus

for plants to begin growing. Your soil will now start to have a distinct structure. Instead of being just dust or sand, it will clump together. Water will stay longer instead of draining away.

• Simmer slowly in the sunshine for at least a few hundred years. • Add rain regularly as needed.

Now you've got living, breathing soil. • Yummy!