SOIL ASSIGNMENT ANSWER KEY
3.3 The Good Earth
1. Technology, the products & processes that improve life, allow
farmers in the U.S. to produce more food than we need. This
technology includes better seeds, human-made chemicals,
and equipment that reduces the amount of effort needed to
produce the food.
2. While most plants get nutrients from the soil, some plants can
be grown in a solution containing fertilizers. This method is
called hydroponics.
The Formation of Soil
3. Soil, a thin layer of matter that covers the earth’s surface, is
created by the interaction of rocks, sunlight, water, air, and
living organisms.
4. Soil formation is a slow process. The depth of the soil
covering the earth’s surface varies. Soil is carried away by
wind and water.
5. Soil formation is faster in a warmer climate. The speed of
chemical reactions increases as the temperature increases.
The rate of soil formation is faster if the climate is wet. Water
is needed for chemical reactions.
6. The type of soil formed depends upon the climate and the type
of materials available. New York has more rain than Montana.
Therefore, soil in New York has lower concentrations of some
minerals than soil made from the same type of rock in
Montana. This is due to the process of leaching.
The Parent Material
7. Match the words with the statements that best describe them:
(1) Minerals
(2) Rocks
__2___A.
__2___B.
__1___C.
__1___D.
__1___E.
are the parents of the soil.
Are broken apart by physical& chemical forces.
Are a part of the soil.
Are chemicals that determine the color of the soil.
Compounds that are found in rocks
Weathering
8. Weathering is the process in which rocks are broken apart or
minerals are removed from them.
9. Chemical and physical forces that break rocks apart or
remove minerals from them are called weathering agents.
10. Identify the weathering agent described in each statement.
freezing water (ice) a. breaks rocks when it expands in the
cracks in the rocks
tree roots b. grow into cracks splitting rocks apart
sand & rocks c. carried by moving water and glaciers;
acts as scouring pad
wind-blown sand d. acts as a sandblaster
temperature change e. causes rocks to expand and
contract
plant roots f. produce chemicals which dissolve minerals
from the rocks
11 Using the pie chart, identify the approximate percentage of
the soil that is made of each of the following:
25 air
25 water
45 mineral particles
5 organic matter
12. Most of the soil consists of mineral particles which are
produced by the actions of the weathering agents on rocks.
The smallest portion of the soil consists of organic matter
which was once living tissue or animal waste.
Chemical Changes in Rocks
13. Rocks containing FEO are bluish-gray in color. When
exposed to the air, oxygen combines with the FeO to form
FE2O3 (ferric oxide) which is red (rust) in color.
14. Match the following soils with the correct color.
(1) bluish-gray
(2) red
a.
b.
c.
d.
soil
soil
soil
soil
in a swamp 1
that contains pores filled with air 2
that is well drained 2
in a bog 1
15. Complete the passage
The type of chemical that causes chemical weathering is an
acid. Carbonic acid is formed when carbon dioxide (produced by
the roots of plants) combines with water. Carbonic acid
dissolves the mineral calcite from limestone or marble rocks. If
carbonic acid or acid rain dissolves too much aluminum from
rocks, it is poisonous to the plant roots. Caves are found in
regions that have limestone rocks. Evaporation of water leaves
behind deposits of the mineral calcite. Deposits of minerals form
stalactites that hang from the ceiling and stalagmites that
project from the floor of the cave.
Texture of the Soil
16. Mineral particles in the soil are classified by their size.
17. The property of soil that is determined by the size of the
mineral particles it contains is called the texture.
18. Which of the following is not usually considered to be a part
of the soil?
[ ] clay
[ ]sand
[ ] silt
[x] gravel
19. Soil texture is determined by the percentage of sand, silt,
and clay particles present in the soil sample.
20. Arrange the particles in question 19 in order from largest to
smallest (1) sand (2) silt (3) clay.
21. Which of the particles in question 19 cannot be seen without
being magnified by an electron microscope? clay.
22. Which of the particles in question 19 is the smallest particle
that can be seen with the unaided eye? sand
23. The term used to describe soils that contain a mixture of
sand, silt, and clay is loam .
24. The soil is difficult to work if it has too many clay particles.
25. It is important to have clay particles in the soil because they
increase the soil’s ability to hold water and nutrients.
26. Nutrients enter the soil as a result of the processes of
weathering and decay.
27. Nutrients are removed from the soil by plants and by the
process of leaching.
28. Clay particles have a negative charge. Because of this they
attract and hold nutrients such as calcium, magnesium, and
potassium.
29. Soils with large amounts of clay are more likely to contain
high levels of minerals than other soils.
Humus
30. There is no soil on the moon because there is no life on the
moon. Mood dust contains mineral particles, bur it does not
contain humus.
31. Humus is partly decomposed organic matter that was once
living or was produced by a living thing (waste).
32. Give two examples of materials that become humus.
1. Plant parts 2. Waste products or dead animals
33. How do earthworms, slugs, fungi and bacteria help create
soil? They change dead material into humus and mix the
humus with the mineral particles.
34. Adding humus to the soil increases the soil’s ability to hold
both (nutrients & water). The type of mineral particle that
holds water and nutrients is clay.
35. In order for humus to release its nutrients into the soil, the
humus must decay.
Can There Be Too Much Humus?
36.
Rank the soils according to humus holding ability:
1. Bog soil ~100%
2. Muck 20% or more
3. Loam 1 – 5%
4. Desert <1%
37. The color of muck soils is due to the high level of humus
(organic matter). Muck soils contain high levels of nitrogen
and phosphorus. The productivity of muck soils is greater
than that of most other soils.
38. Muck soils are formed in areas that are swampy and are
usually too wet to farm unless they are drained. When dry,
muck soils may be lost due to the force of the wind.
39. Since bog soils are nearly 100% humus, they often lack
certain minerals that normally come from rocks.
Structure of the Soil
40. Some organisms in the soil produce chemicals that glue
mineral particles together. Other organisms produce
chemicals, called enzymes, that digest the organic matter or
humus.
41. Soil in which the organic matter and mineral particles are
glued together to form clumps can be described as loose and
crumbly.
42. While the size of the mineral particles gives the soils its
texture, gluing these particles together to form clumps give
the soil it structure.
43. Give the name of the soil structures described below:
A. granular : rounded clumps, less than 1.5 cm in diameter.
B. crumb : irregular clumps, less than 1.5 cm in diameter.
C. platy : thin horizontal plates
44. Two types of soils that lack structure are sand and clay.
Structure can be developed in these soils by adding humus.
Spaces in the Soil
45. It is important that the soil contain pore spaces because the
soil must provide plant roots with water and air. Normally 40
to 60 percent of the volume of the soil is air space.
46. Describe how the plants will be affected in each of the
following situations.
A. Soil contains no pore spaces: lack of air & water
B. Soil contains many large pore spaces: lack of water
47. Pore space determines whether rainfall will run off .
Percolation refers to the ability of water to infiltrate .
Identify the term that is used to describe the percolation
rate of each of the following soils.
A. 1 inch per hour moderate
B. 10 inches per hour rapid
C. 0.10 inch per hour slow
D. 00.05 inches per hour very slow
48. The size of the pore spaces in the soil depends upon the
soil’s texture. Soil with smaller particles contains smaller
spaces than soil with larger particles.
49. Using the chart, identify the soil texture that has the best:
infiltration rate: sand
water –holding capacity: clay
aeration: sand
50. Soils that have good infiltration and aeration have poor
water-holding capacity. Soils that have poor infiltration and
aeration have good water-holding capacity.
51. Identify the type of soil that dries out rapidly after a rain:
sand. Identify the type of soil found in areas where water
either runs off or stands on the surface but does not readily
enter the soil: clay.
52. When heavy rains cause a river to overflow its banks and
flood a cornfield, the plants die. Why?
Roots can’t get enough oxygen
53. Explain how adding humus will affect each of the following
soils.
Clay soils: Improves aeration & infiltration
Sandy soils: improves ability to attract & hold water
Adding humus improves the soil’s structure.
A Soil Profile
54. Math the terms with the descriptions given below.
(1) parent material (2) subsoil (3) topsoil
A.
B.
C.
D.
E.
Layer that contains humus 3
Layer that has the highest clay content 2
Color is determined by minerals present 2
Broken pieces of rock 1
Uppermost layer 3
Vocabulary Review (Crossword)
1. Texture
2. Weathering Agents
3. Clay
4. Humus
5. Mineral Particles
6. Soil
7. Infiltration
8. Loam
9. Leaching
10. Hydroponics
DIAGONAL CLUE: Technology
-----------------------------------------------------------------------------------------------------------3.7 Fertilizers: Organic vs. Inorganic
1. Soils in which plants grow well are said to be fertile.
2. Identify two types of natural materials that early farmers
added to the soil to make plants grow better. (1) manure
(2) fish heads
3. To prove that plants need certain chemicals to grow,
scientists grew the plants in water or clean sand.
4. Soils that are “worn out” are lacking chemicals called
nutrients.
5. Nutrients are recycled by the process of decay, but some
nutrients are removed from the ecosystem by the processes
of harvesting, erosion, and leaching.
6. List two ways in which farming “robs” the soil of its nutrients.
(1) harvest (removal) of plants (organic matter)
(2) farming increases the rate of erosion
7. When the nutrients have been robbed from the soil, and it can
no longer grow healthy plants, the soil is said to be infertile.
Essential Nutrients
8. Scientists have determined that plants need to obtain at least
13 chemicals from the soil.
9. Identify the three primary nutrients that plants must absorb
from the soil.
(1) nitrogen (2) phosphorous (3) potassium
10. Identify the three secondary nutrients that plants get from
the soil.
(1) calcium (2) magnesium (3) sulfur
11. Humans need only very tiny amounts of some vitamins and
minerals. Plants need only very tiny amounts of some
elements. These elements are called micronutrients.
12. Place P beside those nutrients that are primary nutrients
Place S beside those nutrients that are secondary nutrients
Place M beside those nutrients that are micronutrients
S calcium
M iron
M zinc
M boron
S magnesium
P potassium
P phosphorous P nitrogen
M manganese M copper
S sulfur
M chlorine
The Primary Nutrients
13. The primary nutrient that is most often the limiting factor for
plant growth is nitrogen.
14. Plants that are lacking nitrogen will grow slower and have
yellow green leaves.
15. Place a checkmark beside the two forms of nitrogen that
most plants can use
x NH4 (ammonium ion)
____N2
x NO3 (nitrate ion)
16. Some plants remove large amounts of nitrogen from the soil.
Identify two other processes that are responsible for the loss
of nitrogen from the soil.
(1) leaching (2) vaporization
17. Farmers must be aware that cattle can be poisoned if the
weather is dry and too much nitrogen is present.
18. Phosphorous and potassium are needed by plants for proper
growth and resistance to disease.
19. Identify the primary nutrient that is the cause of each of the
following conditions: Use the proper symbol:
Nitrogen (N)
Phosphorous (P)
Potassium (K)
N If too much of this nutrient is present, plants will have tall
stems that break easily.
P If this nutrient is lacking, plants produce fewere flowers.
N If too much of this nutrient is present, plants are more easily
damaged by frost.
K Fruit does not ripen properly without this nutrient.
P This nutrient is needed for good root growth.
N Too much of this nutient results in large plants, but they do
not have a good flavor.
P Purple edges on the leaves of a corn plant tell a farmer the
plant did not get enough of this nutrient.
K Rows of kernels on corn cobs are crooked and sometimes
incomplete if this nutrient is lacking.
P Kernels do not fill out resulting in a small ear of corn that is
sometimes called a “nubbin.”
20. Purple-tinged leaves are not always a sign of a nutrient
deficiency. Some plants are normally purple while others
develop a purple-tinged leaf when the weather is cool.
21. Firing or browning of the edges of plant leaves may result
from a lack of the nutrient potassium or, in some plants, it
indicates the lack of humidity.
22. the leaves are a deep green color, but the plants are shorter
than normal. This may indicate a lack of phosphorous or
potassium.
23. Unless the soil has the proper pH, nutrients may not be in a
from that the plants can use.
Soil Testing
24. Give two reasons why farmers, gardeners, and orchard
owners are concerned about the the level of nutrients in the
soil.
(1) nutritional quality of vegetables, fruits, & grains
(2) yield is greater if proper nutrients are present
25. Give the advantage(s) of each of the following soil tests:
State University laboratory: accurate, detailed, cheaper
than private
Private laboratory: accurate, detailed
Soil Test Kit: quick & inexpensive
A Choice of Fertilizers
26. A substance added to the soil to supply one or more plant
nutrients is a fertilizer. If it is changed chemically, it is
called a synthetic fertilizer.
27. Fertilizers made from dead organisms or their waste
products are called organic.
28. Bone meal and rock phosphate are both organic fertilizers.
Superphosphate is a synthetic fertilizer because it has been
changed chemically.
29. Since the 1930’s synthetic fertilizers have been made from
natural gas.
30. Straw, used for animal bedding, absorbs urea, which is a
good source of nitrogen. It is a natural fertilizer.
31. Urea, when it is made using atmospheric nitrogen and
natural gas, is a synthetic fertilizer.
32. Identify three technological advances that increased the
yield and quality of crops.
(1) synthetic fertilizer (2) better seeds (3) pest control
An Unlimited Supply
33. The supply of synthetic nitrogen fertilizer is limited because
these fertilizers are made from a nonrenewable resource.
34. Synthetic nitrogen fertilizer is dependent upon the supply of
fossil fuels, natural gas, and crude oil.
35. Explain how war might affect the availability and cost of
synthetic fertilizers.
War may interrupt shipments of oil or the supply of natural
gas.
36. Rocks are the sources of all primary and secondary nutrients
except nitrogen.
37. Crops grown for food require more phosphorous than the
grass or trees that naturally grew in soil where we now grow
food crops.
38. Few rocks contain the primary nutrient phosphorus. Most of
the rocks that contain this nutrient are located in two
countries. Circle the two countries where these deposits are
found.
Africa Canada Russia South America United States
39. Describe 2 pathways that phosphorus might travel on its way
from the rock to the ocean.
(1) rocks soil plantanimalanimal waste sewage
treatment plant stream  ocean
(2) rock  soil  erosion  stream  ocean
Phosphorous that is a part of solid waste may be recycled
in a compost pile or buried in a landfill.
40. Does potassium follow the same pathway as phosphorus?
Yes. If so, why aren’t scientists as concerned about the loss
of potassium as they are about the loss of phosphorus?
Many rocks contain potassium.
The Organic Way
41. In what way is the organic farm or garden like a forest
ecosystem? Organic materials and wastes are recycled
42. Bacteria and fungi need the nutrient nitrogen during the
process of decay. After harvest when plant material is tilled
into the soil the amount of nitrogen in the soil will decrease.
43. To speed the process of decay, gardeners make compost. It
is made by alternating layers of soil that contains bacteria,
manure that contains nitrogen, and the plant material that
will be digested. The gardener must add water and turn the
mixture to increase the supply of air needed by the bacteria.
44. Fungi help break down organic matter in the soil. They also
help plants absorb nutrients. When farmers use only
synthetic fertilizer, the amount of organic matter in the soil
decreases and the fungi disappear. As a result, larger
amounts of fertilizer are needed.
45. Organic matter helps maintain good soil structure. Humus
increases the ability of the soil to hold water and nutrients.
As a result there is less erosion and leaching.
46. Give two examples of organic fertilizers produced from
slaughterhouse waste.
(1) dried blood
(2) bone meal
47. The solid material that remains after sewage is treated is
called biosolids or sludge. The sludge is mostly organic
matter that conditions the soil or improves the soil structure.
It is also a source of nutrients.
48. Biosolids applied to farmland must be treated to kill harmful
pathogens. Biosolids should not be applied to land that is
highly permeable or has a steep slope.
49. If a farmer or gardener wants to increase the amount of
organic matter in the soil, they might plant clover or rye.
These crops are called green manure crops. In addition to
adding organic matter, these crops decrease erosion.
Which is Better ---------Organic or Synthetic?
50. Place an (O) in the blank if the statement applies to organic
fertilizers, and (S) in the blank if the statement applies to
synthetic fertilizers, and an (SO) in the blank if the statement
applies to both:
SO A. Provide nutrients for plant growth.
S B. Contain more concentrated chemical.
O C. Makes nutrients available to plants for a longer period
of time.
S D. Nutrient levels are standard and can easily be
determined.
O E. Is more expensive if purchased.
O F. Contains low levels of nutrients.
O G. Nutrients are not immediately available to the plant.
S H. People often apply too much.
O I. Adds nutrients and increases the humus content of
the soil.
S J. Nutrients are more easily leached from the soil.
Vocabulary Review
1. Fertile
2. Green Manure Crops
3. Primary Nutrients
4. Potassium
5. Organic
6. Biosolids
7. Synthetic
8. Zinc
9. Nitrogen
10.Micronutrients
Diagonal Clue: Fertilzer