Download Soil Under Your Feet

Soil Under Your Feet Soil is an important natural resource. Just like the air we
breathe and the water we drink, we need soil! Plants grow in soil,
and they provide food for people and animals. We use trees for
lumber to build our homes. But what is soil, and where does it come
from? How much do you know about soil?
Most, but not all, of Earth's land is covered with soil. Soil
may be just a thin layer over solid rock. It may be over one hundred
feet thick in other places. Soil is a mixture of things. Most soil is
about 45% rocks and minerals. Soil is about 25% water and 25%
air. The worms, trees, grass, and other living things make up only
5% of the soil we see. This is the living part of soil or the organic part.
Soil is formed when forces such as wind, water, or ice weather rocks. These forces break
apart rocks into smaller and smaller pieces. It takes hundreds or even thousands of years for one
inch of soil to form.
There are different types of soil. They have different colors, textures, and chemicals.
These traits come from the parent rock the soil came from, the minerals present, and the organic
matter in the soil.
Dark colored soils are rich in humus. Humus is found in the top soil layer, called topsoil. Humus
is the dark organic material that is in soil. It is made from decayed organic materials from onceliving plants and animals, such as dead vegetables or even worm poop ☺. Bacteria, earthworms,
ants, moles, and other animals live in topsoil and they help process the dead material into
nutrients for plants.
Microbes, living things that are too small to be seen without a microscope, live there, too.
Fungi (such as mushrooms) and algae live in soil. They, along with bacteria and other microbes,
help break down organic materials into substances plants can use.
Different minerals give soil different colors. Reddish soil has iron in it. Calcite particles
are white. Gypsum is a pale brown. In deciduous forests (deciduous is where trees lose their
leaves) the soil may be deep, rich, and dark brown in color. Ohio is deciduous since the trees in
this area lose their leaves. In sandy areas (Florida) the soil will be dry with a dusty grey color. In
tropical regions the soil is often very deep and bright red.
Clay is soil with a fine texture so soils that have a lot
of clay will feel very smooth. Clay soil is tightly packed soil
with tiny grains. It is made of particles that are less than
0.002 mm thick. The particles are so small that they can
only be seen by someone using a hand lens or magnifying
glass. Clay sticks together and feels slimy when wet. Clay
soil has many nutrients and holds water well. Many plants
cannot grow in clay soil. The grains are so close together the
plant roots cannot spread easily through it.
Silt is soil with particles a little bigger than clay - from 0.002 to 0.05 mm thick. The
particles are just big enough to be seen with the eye. When wet, silt clumps together but doesn't
feel sticky or slimy as clay does.
Sandy soil has larger particles, from 0.05mm to 2 mm thick. We will call sand a larger
grain. Sandy soil feels gritty, is very loose and easy to dig into. When it is wet, sandy soil breaks
apart. Most plants do not grow well in sandy soil. Sand does not hold water so plants dry out
quickly and it has few nutrients that plants need.
Loam is soil that has a mixture of clay, silt, sand, and humus. It is the best soil for
growing plants. Many plants grow well in this soil. Loam holds water and has many nutrients for
plants.
Pore spaces are spaces between the soil particles. They are important, because they
provide space for air and water in the soil. Soils like clay and silt that have small particles have
small pore spaces. They restrict the movement of water and air in the soil. Sandy soils have
much larger pore spaces. They allow water to drain too quickly.
Soil can be "rich" or "poor" depending on the amount of organic matter in it. Soil can be
well-drained or waterlogged depending on the size of its particles and pore spaces. Soil evolves,
or changes, over time. Particles are weathered into smaller and smaller pieces. More organic
matter is added as plants and animals die and decay. Some soil is lost to erosion.
Without soil, many of Earth's living things would die. Plants growing in soil make food
for people and animals. Soil is home to many animals and to bacteria, fungi, and algae. Soil is
important to life on Earth.
Questions:
1. Soil is made of:
A. pieces of rock
B. air and water
C. matter that was once alive
D. all of the above
2. What is humus?
A. decayed matter that was once alive
B. minerals
C. air and water
D. all of the above
3. What does humus do for soil?
A. adds water
B. adds nutrients to the soil and gives it a dark color
C. adds minerals
4. How do minerals become part of the soil?
A. Minerals come from rocks.
B. Minerals come from decayed matter that was once alive
C. Minerals must be added to the soil by man.
5. Which type of soil is tightly packed with tiny grains?
A. humus
B. loam
C. sand
D. clay
6. Which type of soil is the best for growing plants?
A. clay
B. loam
C. sand
7. What is erosion?
A. movement of soil or rocks by wind or water
B. a type of soil
C. matter that was once alive
8. Why do plants, animals, and soil need each other?
9. Explain how soil evolves from rock over time.
10. Name something that lives in soil.