About Soil Thematic Unit

28 Pages·2013·2.821 MB·English

by  Joy of Learning

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About Soil
About Soil
Name __________________________
Date __________________________
Copyright@2013 The Joy of Learning
About Soil
Soil is one of the elements that controls life on earth.
• Plants take their food and water needs from the soil.

• All animals get their food needs from these plants or
the animals that eat them, or both.

Many plants can survive with low light, but
they can not survive without the nutrients and water
they receive from the soil. Other plants can survive
with low levels of water, but still must have good
soil to keep them healthy. A very few plants, like
cactus, can thrive in bad soil and a little water.

The mineral nutrients in the soil are like food to the plants. The minerals help them to
grow into healthy plants.

Today people have learned to grow plants without soil. This is called hydroponics. The
plants are grown with their roots in water that has mineral nutrients.

The amount of land on the earth that is usable by people to grow food and build homes
and towns are only 4% of the surface area. Of this 4%, only about the top four feet is usable for
farming. This is referred to as the topsoil.

Land that is the right kind for food crops is called arable. This tiny bit must support all
people, animals, and plants that live on the Earth.
Copyright@ 2013 The Joy of Learning 1
About Soil

You might think that dirt and soil are the same thing, but they are not.
Scientists that study soil are called pedologists. Most pedologists consider dirt
to be made up of only crushed rocks. Soil contains so much more than just dirt.

Just below the topsoil, you will find the subsoil. This is where the roots for trees and
many other plants come to get food to help them grow. Good subsoil will have spaces available
for water to seep down. This area is full of animal life. Tiny wormlike
creatures called nematodes live here beside bacteria and fungi.

Sometimes when this soil level is dug up by farmers or building
companies the bacteria and fungi get into the air. Since humans have not
lived with them before they may cause new sicknesses. These life forms
are good for the soil, but maybe not for humans.
Write the words below into the correct spaces. You may need to use a pencil with an eraser.
bacteria pedologist topsoil subsoil fungi nematode
Copyright@ 2013 The Joy of Learning 2
About Soil
Soil is made up of dirt, dead plant and animal matter, and tiny animals and bacteria.
The dead material is called humus. Pockets of air and tiny puddles of water
are also in the soil.

Humus is also a material that needs a long time to
develop. Plants and animals that have died fall to the earth
and slowly break down into their chemical parts. Most of
this product is carbon and nitrogen. Water, sunlight, and bacteria play an
important part in the speed of this breakdown, or decomposition.

Dirt is rock that has been crushed by the actions of the earth over many thousands of
years. These rocks were made of many different minerals. Some might be high in iron or
bauxite. Others could be mostly quartz or cooled lava.
Read each sentence below. Fill in the missing words.
1. _________________ is made up of dirt, dead plant and animal matter,
and tiny animals and bacteria.
2. ______________ is also a material that needs a long time to develop.
3. Pockets of air and tiny puddles of ____________________ are also in
the soil.
4. Dirt is rock that has been crushed by the actions of the earth over
many ____________________________ of years.
5. Water, _____________________, and bacteria play an important part
in the speed of this breakdown, or decomposition.
Copyright@ 2013 The Joy of Learning 3
About Soil

Thousands, of kinds of small creatures live their lives under the soil. Worms and
nematodes help break down decaying plant and animal matter. Bacteria and fungi also play a
part in making the soil rich.

Moles, mice, shrews, and gophers are some of the animals that
live in the topsoil. Many species of insects spend part, or all, of their
lifecycle in the soil. The digging and tunnels of these animals and
insects create areas for water and air to settle. The
soil clumps are broken up and are able to provide
more room and nutrients for plant roots.

The use of too much chemical fertilizers and pesticides by farmers,
ranchers, and gardeners can cause big breaks in this beneficial cycle.

Nature friendly products and methods are available. The use of non chemical plant and
insect control methods is called organic land management.
Do some research on the Internet or in books. Look up a about organic gardening.
Write a little of what you learn on the lines below.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
Copyright@ 2013 The Joy of Learning 4
About Soil

Pedologists separate soils into 10 different groups based on the
amount of humus, water, and air in a sample area. Each different type
of soil is called a polypedon. The polypedons range from types that
have lots of humus, air and water to areas that have almost none.
• Swamps and bogs are a type of polypedon that have a high amount of water and humus.
• Desert polypedons are made mostly of dirt and air.
• In between are rainforests, prairies, farmlands, tundras, forests, and other types of land.
What does the soil look like where you live? Tell about the color. Is it hard or easy to dig in?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
Look up the definitions of the words below. Write them on the lines.
swamp ____________________________________________________________________
___________________________________________________________________________
desert ____________________________________________________________________
___________________________________________________________________________
tundra ____________________________________________________________________
___________________________________________________________________________
Copyright@ 2013 The Joy of Learning 5
About Soil
Soil is made by the joining of the minerals with the organic (humus) material.
They form tiny lumps called soil particles.

Water and air fill in the spaces between the particles. The areas around
the particles are where the roots of plants grow. The growth of the roots and
the actions of the underground animals help the soil stay loose. The deeper
the roots grow the deeper the water, air, and subsoil animal life can go. These
factors help make good, rich, arable land.
What does arable mean? __________________________________________________________
____________________________________________________________________________
The mineral content of the soil is classified into three main groups.

• sands • silt • clays

The difference between them is the size of their particles. Sands are the
largest particles and clays are the smallest.

Also in the soil mix are many tiny pieces of other nutrients called trace
minerals. Trace minerals are chemicals like calcium, potassium and phosphorus. These are
very important for proper plant growth. Most arable soil areas are made up of about 80%
mixed minerals.

Soil may be acid, alkaline, or neutral because of the kind of minerals in it. The minerals
release chemicals into the soil that affects the growth of plants. There are a few plants that will
grow in acid soil and a few that enjoy alkaline soil. Most plants need neutral soil.

A soil test can be done at home or in a laboratory to figure out the measure of acid. This is
called the soil pH. Material can be added to change a soil’s pH level.
Copyright@ 2013 The Joy of Learning 6