Science of Life Explorations
Let’s Learn About Soil:
What is Soil?
What is soil?
Is soil dirt?
How is soil formed?
What does organic mean?
What is in soil?
How can we collect soil?
Can soils be different?
Why?
What can we learn
by examining soil?
Why is soil important?
Is soil part of the food chain?
Compare the
two photographs
of soil. What
makes them
different?
What is soil?
Soil is a thin covering of land areas on
the earth’s surface. It has many sizes of
PARTICLES, and is made up of MINERALS,
ORGANIC MATERIAL, water and air. It is
important to all living creatures.
Soil covers much of the land on earth.
What covers most of the earth’s surface?
Is Soil Dirt?
You might think that dirt and soil
are the same things. But soil is the
substance plants grow in. Dirt or ‘dirty’
means something is not clean. When an
adult says your room is dirty, it doesn’t
mean it is full of soil. Your hands may
become dirty by playing in the soil.
Just remember to use the term soil to
describe the useful part of the earth’s
surface needed for plant growth.
Plants use soil for NUTRITION, water,
OXYGEN and stability. Now that you
are older, you can understand the
difference.
How is soil formed?
Soil is formed from large rocks that have broken down over time by forces of
nature. There are many types of soil, each with different colors and textures.
These are called soil properties. Can you see layers in the soil ‘profiles’ below?
One soil
profile is
from New
York State.
One is from
Florida.
Do you see a
difference?
Which one
is from New
York?
A soil profile is a way to
look at the layers in soil.
When someone digs a
hole in the ground, you
may see the difference in
these layers. In New York
State, the soil closest
to the surface is usually
darker. We will learn why.
Can you guess?
New York state is a great
agricultural state because
we have good soil for
plants.
What is in soil?
Sand
Silt
Clay
fungus
Soil is formed slowly as rocks break down into tiny pieces,
through EROSION. Organic material decays and mixes
with INORGANIC MATERIALS and water to form soil.
Soil even has air in it!
Soil is layered. The upper layer or SOIL HORIZON has
more organic matter and water, causing it to be darker.
Plant roots use this area to get nutrition, water and
oxygen.
Soil is described by its particle size. All soil is made up
of sand, silt and clay. The larger or ‘coarser’ particles are
sand. The smallest particles cling together to make clay.
bacteria
Does soil cover all of the earth?
yes____
no____
Is soil formed by wind and water breaking down rocks (erosion?)
yes____
Circle the things that are organic:
earthworms
leaves
no____
rocks
a dead insect
Are soils the same everywhere?
yes____
no____
Why is soil important to you?
___________________________________________________________
___________________________________________________________
___________________________________________________________
Soil is made up of three types of soil particles:
_ _ _ _, s i l t and c l a y
Bacteria: one celled micro-organisms that can be helpers to plant and human
health or can cause disease
Clay: the smallest of the soil particles; when wet it is sticky and when dry it is very hard
Components: an ingredient or one of many ‘parts’ that make up something
Erosion: the wearing down of soil by wind, water, heating and freezing
Fungus: a living organism which absorb nutrition by decomposing its food source
Horizon: in soil, horizons are another name for its layers
Inorganic Matter: things that are not alive and never were, such as rocks
Magnification: using glass lenses that magnify (make things seem larger) so that
small things are easier to see
Nutrition: the energy (food source) needed by living things to be able to
survive and thrive
Organic Matter: things that are living or were once living (leaves are ‘dead’ but
were once alive)
Oxygen: an essential element that animals and most plants need to survive; it is
found in the atmosphere, the soil and in water
Parent Materials: in soil, parent materials are the types of rocks and minerals
that eventually become soil over time
Particles: small parts of something, especially soil
Silt: a type of soil particle between the smallest (clay) and the largest (sand)
Surface: the top of something
Textures: the varying structure of something, such as rough or smooth
Background for teaching this lesson:
Soil covers much of the land on Earth. All soils are made up of sand, silt, or clay. This describes the particle sizes, not the type of parent material it is composed of. Parent materials are the types of rocks and minerals it is derived from. Soils have other components:
air, water and organic matter (decomposing plants and animals). There are many types of
soils, and each has different colors, textures, structure and mineral content. The depth
of the soil also varies.
Soil is formed slowly as rock breaks down into tiny pieces near the Earth’s surface. This
is called erosion and results from the affects of wind, water, geological movement and
freezing and thawing. Most soil has some amount of organic matter, which decays and
mixes with inorganic materials (rock particles, minerals) and water to form the makeup
of each particular soil. Soil is catalogued around the world, and in the United States, is
mapped by type in each county and state. A soils map is available at public libraries to
document the type of soils found right in your neighborhood.
Soil is layered (horizons); the upper A Horizon has more organic matter, water and air.
This is good for plants. The lower layers tend to be less ‘broken down’, with less organic
matter, air and water.
New York is a great agricultural state because we have good soils for plants.
Once students understand the nature of soil, they may see a difference between soil and
dirt. Remind them that plants grow in soil, and that it is an intricate environment of living
and non-living things.
An important property of soil is active, living soil microorganisms such as bacteria, fungi
(fungus) and mites. Some things can be seen with a hand lens or magnifying lens. We
can only see bacteria with a microscope.
Soil Fungus – good fungi help plants get nutrients from the soil.
Mites - soil mites eat good and bad fungus. They carry bacteria around on their backs! They are an important part of healthy soil.
Bacteria – Bacteria can be good or bad. 1000 bacteria can fit on the head of a pin. They decompose other elements of the soil into nutrients. When you smell “soil” in the springtime, you are smelling bacteria at work after a long winter!
Spiders, beetles, earthworms, ants and many other arthropods are some of the visible
members of the soil community.
Soil is important to every living creature on earth. All living things need an energy
source; a majority of it is based on plant life at the bottom of the food chain. Poor soils
do not contain minerals needed by plants and other living creatures. Healthy soils pass
on minerals to plants, which pass them on to us! Soil must be cared for!
For Teachers and Parents:
Pg. 1 Read the soil questions in a group setting, then have a discussion about the
photographs. Students may recognize that the top photo shows rich farm soil supporting
a new crop. The bottom photo is probably from the western U.S. The farm soil is dark
and rich and probably has a lot of moisture in it, as well as organic matter. The western
soil may well be very rich in minerals, such as iron or copper to cause its color, but due
to the arid climate and lack of organic matter such as leaves and earthworms, these soils
may be considered unusable for farming.
Pg 2 Sometimes soil gets no respect! Dirt is a pretty negative word. Throughout these
activities, students may start to understand the properties of and importance of soil. Soil
should be protected; it is an irreplaceable resource in our lifetime, when not taken care
of.
The oceans cover most of the earth’s surface, and when you consider the amount of land
that is covered with snow and ice, blacktop and bare mountaintops, soil becomes even
more
Pg 3 Soil profiles: Each state actually has its own ‘official’ state soil. Florida’s looks a
bit sandy, but we know they have a huge agricultural industry also. There are probably
hundreds of soil profiles found in each state, so a dark, rich silty farm soil can be found
there also.
Pg 4 Soil profiles: Each state actually has its own ‘official’ state soil. Florida’s looks a
bit sandy, but we know they have a huge agricultural industry also. There are probably
hundreds of soil profiles found in each state, so a dark, rich silty farm soil can be found
there also.
Pg 5 You may suggest students look for a copy of the “soil triangle” in the library or
online.
By placing a small amount of soil sample and water into a test tube and letting it settle
out, farmers, horticulturalists, geologists and engineers can estimate what percentage
of the soil is sand, silt, and clay. If it is mostly clay - it’s a ‘clay’ soil of course. The
prime soil for agriculture is called loam - it is a soft mix of all three, clumps when wet,
but breaks apart easily unlike clay. Sand is very porous and does not retain nutrients and
water long enough for most agricultural crops.
Pg 6 When discussing soil - organic refers to something that is alive or was alive. If it
was never alive - such as a rock - then it is inorganic. This is a good discussion point. Is
a wooden fence organic? a book? a leather glove? Trees were alive, but what about
leather? Remind students that leather is a by product of animals, and because leather is
part of something that was once living, it is organic.
Organic items will break down due to their nature, much faster than inorganic items. This
is why soil is created so slowly. A rock will sit and seem to stay the same for hundreds
of years.
name____________________________
Student Lesson: Let’s Learn about Soil: What did you learn?
Does soil cover all of the earth?
x
no____
yes____
Is soil formed by wind and water breaking down rocks (erosion?)
x
yes____
no____
Circle the things that are organic:
earthworms
leaves
rocks
a dead insect
Are soils the same everywhere?
x
yes____
no____
Why is soil important to you?
___________________________________________________________
Students
should begin to understand that soil should be taken
___________________________________________________________
care of because healthy soil is the basis of plant life. Plants are
___________________________________________________________
the
basic food source for all animals and humans, directly or
indirectly.
Soil is made up of three types of soil particles:
S_A_ N
D s i l t and
_ _,
clay
Are air and water in soil?
yes____
no____
13
An Apple and the Earth!
To show an example of how much soil there is on the earth, and how
much of it is available for farming our crops, use this apple example:
Explain to students that 3/4 of the earth is covered with water.
Remove 3/4 of the apple. Hey, look! Both the earth and the apple have
a core!
Only 1/4 or 25% of the earth is left.
But that doesn’t mean that all 25% is farmland soil waiting to be
planted! Ask students what types of things on the ‘land’ part of the
earth can’t be used for farming.
Remind them about mountains (may be too steep to plant on, or too cold, windy or may have no soil)
Snow or glaciers or ice - The globe will remind them just how
much of the earth is covered with snow or ice.
Deserts! Although some desert areas, like the Southwest,
do support plants like cactus it does not support agriculture without amendments and significant watering.
What about cities, towns and highways? Concrete, blacktop and buildings cover a lot of land!
A shocking amount of the land surface is unusable
for farming due to these conditions. Remove most of
what’s left and leave just a sliver to represent the
10% of the earth usable for agriculture.
(Adapted from the Natural Resources Conservation Service. Check out
their website!)