Stephen Herr
AP Environmental Science
Section 1
stephen_herr@verizon.net
Cookie Mining - Lab 3
Lab 4 Soil Analysis
January 30, 2005
Stephen Herr
page 1
Data Worskheet
Test site #1
Location
hillside in Sylmar, CA
sand vol.
(mL)
10
soil type
silt volume
(mL)
6
sandy clay loam
clay volume
(mL)
4
total vol.
(mL)
20
Sand
%
Silt
%
50
soil pH Test
6.5 Aalkaline, neutral or basic:
Soil nitrogen test
N-0 Depleted
soil potasium test
K-4 surplus
soil phosphorous test:
P-4 suprlus
soil pH:
soil nitorgen:
soil poteassium:
soil phosphorous
30
Clay
%
20
slightly acidic
Data Worskheet
Test site #2
Location
lawn in Sylmar, CA
sand vol.
(mL)
50
soil type
silt volume
(mL)
115
clay loam
soil pH:
soil nitorgen:
soil poteassium:
soil phosphorous
clay volume
(mL)
70
total vol.
(mL)
235
Sand
%
21%
soil pH Test
6.5 Aalkaline, neutral or basic:
Soil nitrogen test
N-0 depleted
soil potasium test
k-4 surplus
soil phosphorous test:
P-4 surplus
Silt
%
49%
slighly acidic
1. The proportions of what three particles are used to determine soil texture?
Which of these particles has the smallest surface area? Which has the largest?
The proportions of sand, silt, and clay are used to determine soil texture. Silt particles
have the smallest surface area, and sand particles have the largest surface area. However,
silt has the largest surface area to volume ratio which accounts for its retention of water.,
2. Using the soil texture triangle (Fig. 1), determine the soil type of this sample.
What is a soil with 20% clay, 40% silt, and 40% sand called?
Cookie Mining - Lab 3
Stephen Herr
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Clay
%
30%
According to the soil texture triangle in figure 1, this soil sample can be classified as
loam.
3. Looking at the Soil Texture Triangle (Fig. 1), which soil type has the greatest: a.
water retention ability? b. water percolation rate?
Clay has the greatest water retention ability, where as sand has the highest water
percolation rate.
4. What role does humus play in soil fertility?
Humus provides the soil with nutrients that are necessary for plant growth. Humus is a
food source for worms that can aerate the soil. In addition, humus also retains that the
roots of plants can absorb. Humus keeps the soil from becoming too compressed. This
facilitates root growth and penetration.
5. Why is pH such an important aspect of soil fertility?
If soil is to acidic cations such as magnesium and calcium are leached and lost from the
soil. If the soil is to acidic or basic the soil will stunt root growth by direct tissue damage
to the root hairs. When the pH is close to neutral, both the cations and anions are
available for use by plants.
6. What are some natural sources of the nitrogen, potassium and phosphorous
found in soil?
Nitrogen enters the soil during the nitrogen cycle when nitrogen is fixed. Phosphorous
and potassium come from the weathering of rocks and marine sediment. Another source
of phosphorus is guano. All three nutrients also come from decaying organic mater.
7. How are the three primary plant nutrients used by living organisms?
Nitrogen and phosphorus help make up proteins, amino acids, RNA, and DNA.
Potassium is used carry out many functions in cell membranes. Phosphorus is a
component of ATP and phospholipids bilayer membranes.
Cookie Mining - Lab 3
Stephen Herr
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8. By what process is atmospheric molecular nitrogen (N2) converted into a form
that plants can readily absorb through their roots?
Atmospheric molecular nitrogen is converted into a form that plants can easily use
through the process of nitrogen fixation. Rhizobium bacteria and cyanobacteria are the
primary source of fixed nitrogen. They convert N2 to ammonia, which is then converted
to ammonium by the water in the soil. This ammonium is used directly by plants or
converted by bacteria to nitrates through the process of nitrification. The plant then uses
these nitrates.
9. What are some possible sources of error in this experiment?
If the water did not completely settle out before testing it, the water could be murky and
change the color of the test. The dividing line between the sand, silt, and clay was not
distinct. Therefore the percentages of sand, silt, and clay are very rough estimates. The
capsules containing the chemicals in the soil test kit were hard to open carefully. As a
result, not all of the powder made it into the container. This could make the color slightly
lighter and give an inaccurate reading.
10. Evaluate the fertility of the soil used in this lab activity based upon your results.
Summary and Conclusions – In this activity I evaluated and compared the composition
and fertility of soil from two locations in my yard, in Sylmar, California. The first site
was located on a hillside in our backyard, a aproximentaly 20 degree slope cut from the
side of a hill in the foothills of the San Grabirel Mountains. The second soil was taken
from our lawn, a flat surface at the base of this hill.
Both soils had a fairly good soil structure. The soil from the hill was a sandy clay loam
and the soil from the lawn was a clay loam. These soils are suitable for different types of
plants. Both soils contained ample amounts of potassium and phosphorus, but did not
contain enough nitrogen. The pH of both soils were slightly acidic, but not enough to
hamper plant growth.
I was surprised to learn that the nitrogen in both soils was depleted. After seeing the
nitrogen report, I fertilized the lawn with fertilizer that contained nitrogen and noticed a
dramatic increase the growth of the tall fescue grass that makes up our lawn.
Cookie Mining - Lab 3
Stephen Herr
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