Learning Outcomes for Test #8
Unit 6, Lesson 2
Name: ______________________________
Test Date: ___________________________
Students need to learn and understand the meaning of the following vocabulary words AND be able to
apply them to a variety of situations.
1.
2.
3.
4.
5.
6.
organic- having to do with or coming from living things
soil- a mixture of bits of rock and once-living plants and animals
inorganic- means that it did not come from living things
soil horizon- any of the layers of soil from the surface to the bedrock
humus- decayed plant or animal material in soil
conservation- saving, protecting, or using natural resources wisely
Students will learn in class about the following topics. Be prepared to be assessed on them.
1. What would you expect to be present in the top layer of soil? Why would you expect that?
More humus would be present in the top layer because most living things are in or above
this layer.
2. Why do you think there are more large pieces of rock deeper in soil?
The source of the rocks is closer. Rocks near the surface weather more, creating smaller
fragments.
3. Which layer of soil do you think contains the most living organisms? Why? The A Horizon
has more living organisms because it contains the most oxygen.
4. What are two reasons why the A Horizon could be deeper in a location where the ground is covered
with plants?
More plants die in this area and add to the humus and growing plants prevent the erosion
of topsoil.
5. When animals and plants die, their bodies add organic nutrients back to the soil.
6. Rock is an inorganic part of soil. Inorganic means that it did not come from living things. Soil
covers most of Earth’s landmasses. Without it, plants and animals would not be able to live on land.
Soil looks different in rain forests, grasslands, and deserts, but they all started from rocks that weather
and form soil in layers.
7. What are the main steps in the formation of soil?
Weathering of rock, breakdown of rock by microorganisms, growth of plants, and
decay of plants and animals
8. Each layer of soil is called a soil horizon. The A Horizon, which holds the most nutrients, contains
humus. Humus contains nutrients that feed plants. Humus also soaks up and holds water more easily
than bits of rock. The soil in this horizon is called topsoil. The B Horizon is called subsoil. There is less
humus in subsoil and lots of fine particles of rock, such as the particles that make up clay. Next is
the C Horizon, which is made mostly of larger pieces of weathered bedrock. These soil horizons rest
on solid, unweathered bedrock.
9. Why might an area be missing a soil horizon?
Not all areas have the components that go into all the soil horizons. For example, a desert
may have little or no topsoil due to a lack of decaying animal and plant matter.
10. How are the A Horizon and the C Horizon different? The C Horizon contains small and
large rocks. The A Horizon has roots and humus.
11.What is the relationship between the amount of rain a location receives and the usefulness of that
location’s soil to grow plants? Plants need water to grow, but large amounts of rain may wash away
nutrients; moderate amounts of rain are needed.
12. What else can happen to soil to make it less useful to grow plants? It can become polluted from the
addition of harmful materials. It can be eroded by water and wind.
13. Pesticides are useful for plant growth, but they can pollute the soil.
14. What can be done to allow use of these products and at the same time reduce the amount of pollution
they cause? Use natural methods of controlling pests – like introducing the natural predators of the
insects to the location and use the smallest amount of the products possible.
15. Most of the soil in the United States is mostly covered by one of three types of soil: 1-forest soil, 2desert soil, and 3-grassland and prairie soil.
Forest soil – has thin layer of topsoil with little humus; most of forest soil is found in
the U.S. in the eastern third of the country. Louisiana is mostly forest soil.
Louisiana has a small section of wetlands soil.
Desert soil- receives little rain and does not hold much humus, but it is rich in
minerals because they are not washed away by rain.
Grasslands and prairies soil – found between the Rocky Mountains and the eastern
forests; the soil is rich in humus, which holds water and
minerals and is good for crops
16. Plant roots help to prevent soil erosion by holding soil in its place.
17. What characteristics of soil are best for farming? High humus and mineral content, and the ability
to hold water
18. What methods are used to conserve soil? Fertilizing, crop rotation, strip farming, contour
plowing, terracing, wind breaks, laws, personal efforts, and education
19. Crop rotation is when farmers plant different crops on the same land in different years. They can
choose crops that add the nutrients that have been removed by other crops. Strip farming is when
farmers plant grasses between rows of other crops to have the grass roots help prevent soil erosion.
Contour plowing is when farmers plow furrows across the slop of the hill instead of plowing up and
down the slope of the hill. Terraces are flat shelves that are cut into a hillside that have crops planted
along each terrace. Windbreaks are tall trees that are planted by farmers along the edges of their
farmland to slow the speed of wind erosion.
20. What might cause mountaintops to have little or no topsoil? Topsoil is on the surface of the
land. On a mountaintop, rain can easily wash rain down the slope.
21. BE ABLE TO EXPLAIN why soil conservation is important even to people who do not
live on a farm.
22. BE ABLE TO ANSWER QUESTIONS ABOUT THE DIFFERENT SOIL HORIZONS.