UNIVERSITY OF THE WEST INDIES
DEPARTMENT OF GEOGRAPHY & GEOLOGY
GEOG1231: EARTH ENVIRONMENTS I: GEOMORPHOLOGY AND SOILS
SOILS PRACTICAL: SOIL PROPERTIES
1. The following relates to data extracted from a soil survey at 3 sites on differing soil types.
Refer to Table 1 and answer the following questions.
a. Use the textural triangles to plot the A,E,B and C horizons for the soil types at each site.
b. For each of the textural triangles, identify the soil type of the horizons in the space provided.
c. Which site is most suitable for agricultural activity? Justify your answer based on the A and B
horizons.
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Table 1: Soil Textural Characteristics at three sites.
Site
Number
1
1
1
1
Horizon
A
E
B
C
%
Sand
7
15
10
9
%
Silt
35
60
44
55
%
Clay
58
25
46
36
2
2
2
A
B
C
94
98
97
2
2
2
4
0
1
3
3
3
A
B
C
52
39
84
29
44
13
19
17
3
Site 1
Soil Textural Class:
(A Horizon) ---------------------------------------------(E Horizon) ---------------------------------------------(B Horizon) ---------------------------------------------(C Horizon) -----------------------------------------------
Site 2
Soil Textural Class:
(A Horizon) ---------------------------------------------(B Horizon) ---------------------------------------------(C Horizon) -----------------------------------------------
Site 3
Soil Textural Class:
(A Horizon) ---------------------------------------------(B Horizon) ---------------------------------------------(C Horizon) -----------------------------------------------
2. Soil texture can affect the ability of the soil to supply nutrients. Coarse textured soils tend to
be deficient in plant nutrients. Suggest two reasons for this observation.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3. Soil samples were collected at two sites. When the acidity was tested, it was observed that site
1 had a much lower pH than at site 2. Suggest two possible explanations for this observation.
Limit your answers to natural processes.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4. Table 2 shows soil moisture release curves for different tensions at three localities with
different soil types.
Table 2: Soil Moisture release curves for the three sites in Question one.
Applied Tension on
Drying (MPa)
0 (Saturation)
0.001
0.005
0.01 (Field Capacity)
1.0
1.60 (Wilting Point)
100.0
1000.0 (Oven Dry)
Soil A
Soil B
Soil C
39
37
13
10
8
4
2
0
50
45
39
20
13
10
5
0
55
53
52
50
33
28
10
0
a. Plot the data on a graph sheet or using a spreadsheet program such as EXCEL.
b. Calculate the values for the transmission water that would drain from the soil for 48 hours
after a saturating rainfall event to field capacity for the three soils.
Site A. -------------------------Site B --------------------------Site C ---------------------------c. Calculate the percentage of plant available water for the three sites.
Site A. -------------------------Site B --------------------------Site C ---------------------------d. Calculate the unavailable or residual water at the three sites.
Site A ----------------------------Site B -----------------------------Site C -----------------------------e. Each of the sites is equivalent to the three soil types in Question 1. But which one is which?
Site A ------------------------------Site B -------------------------------Site C --------------------------------