Soils 205 Spring 2002
1.
Explain
the relationship between soil and regolith.
2.
What is
the relationship between a soil profile and soil horizons?
3.
Pore
space makes up what % of the total volume of an average-textured surface soil in
good physical condition?
4.
What is
the difference between primary and secondary mineral constituents of a soil?
5.
What is
the “typical” organic matter content of mineral soils?
6.
How is
the term humus different from the more general term of soil organic matter?
7.
Why is
the make-up of the soil solution important when evaluating soil-plant relations?
8.
What are
the 18 plant essential macronutrient and micronutrient elements?
9.
How are
the relative amounts of CO2 and O2 in soil related to
plant growth, microbial activity and water content?
10.
If a soil
pH value goes from 7.2 to 5.5, has it become more acid or alkaline and has the
amount of H+ increased or decreased?
11.
What is
the difference between the texture of a soil and its structure?
12.
What is a
particle-size analysis of a soil and how is it obtained?
13.
How much
sand in % by weight must a soil contain to be classified in the sands group?
Likewise, how much clay must a soil contain to be classified in the clay
group?
14.
Explain
what is meant by a loam soil and the basis for the numerous subdivisions of loam
soils
15.
Using a
textural triangle, determine the textural class name for three soils with the
following particle size distribution:
|
Soil |
%
sand |
%
silt |
%
clay |
|
1 |
22 |
60 |
18 |
|
2 |
38 |
17 |
45 |
|
3 |
59 |
13 |
28 |
|
|
|
|
|
16.
Which is
more susceptible to modification by soil management:
soil texture or soil structure?
17.
Describe
the 7 types of soil structural units or peds and tell where each is most likely
to occur in the profile.
18.
What is
the difference between particle density and bulk density of soils?
19.
What is
the relationship between the compaction of a soil and its bulk density?
20.
If soils
A and B have bulk densities of 1.2 and 1.4 Mg/m3, respectively, which
soil has the highest pore space and which soil is the most compacted?
21.
What is
the approximate weight of an acre-furrow
slice and how is it related to bulk density?
22.
If a soil
has a bulk density of 1.3 Mg/m3 and a particle density of 2.6 Mg/m3,
what portion of the soil volume is pores and what portion is solid particles?
23.
To establish the impact of foot traffic on a camp ground area, a small
hole was dug and the soil placed in a plastic container.
The hole was lined with plastic and filled with water, requiring 675 ml. The soil and container were found to weigh 1.36 Kg.
The soil was dried at 110 C and lost 88 grams of weight.
The empty container weighed 140 grams.
When 2 liters of water was poured into the container of soil, there was a
total volume of 2416 ml.
a)
What was
the bulk density of the soil?
b)
What was
the particle density of the soil?
c)
What was
the % water in the soil in the field?
d)
What was
the pore space of the soil in the field in % by volume?
24.
A specially designed soil probe was used to remove an undisturbed soil
core from the field. The core was 6 cm high and 5 cm in diameter.
When saturated with water the probe, core and water weighed 268 grams.
After oven drying, the soil and probe weighed 211 grams and the empty
probe weighed 45 grams.
a)
What is
the bulk density of the soil?
b)
What is
the % pore space in the soil?
c)
What is
the particle density of the soil?
25.
Why is the pore space of subsoils often considerably less than the pore
space of surface soils?
26.
Why are the relative amounts of macropores and micropores important to
air and water movement in soils and how can these be influenced by soil
management?
27.
What is the difference between water polarity and hydrogen bonding of
water and why are they important to the behavior of water in soils?
28.
Explain how adhesion and cohesion are related to basic water properties.
29.
What is meant by capillarity or capillary rise and why is it important in
soils?
30.
Why is a knowledge of the relative free energy of water in soil important
to understanding its behavior?
31.
What is the reference point for the definition of total soil water
potential?
32.
What are the components of the total soil water potential?
Under what soil water conditions would each be the most important?
33.
Why are values for total soil water potential usually negative, i.e.
–140kPa or –15 bars?
34.
If a soil has a water potential of –5 bars, what is the potential in cm
of water and kPa?
35.
Draw a soil moisture-energy curve with water content on the x axis and
potential on the Y axis.
36.
If a soil sample weighed 280 grams when it was moist and 190 grams when
it was oven-dried, what is the gravimetric moisture content of the soil?
37.
How does the neutron probe evaluate the water content of the soil?
38.
What are the two common procedures used to obtain values for soil
moisture-energy relationships?
39.
What is the basis for measurement of soil moisture status by thermocouple
psychrometers?
40.
For each of the following techniques for measurement of soil moisture
status, list whether they measure i) total soil water, ii) soil water potential,
or iii) moisture content-tension relations and the moisture levels to which they
are limited:
a. tensiometers
b. neutron probes
c. pressure plates
d. thermocouple
psychrometers
e. resistance blocks
41.
What are the three types of water movement through soils?
42.
Compare the driving forces for movement of soil water by saturated flow
as compared to unsaturated flow?
43.
What are the soil/water conditions which favor water movement by
saturated flow?
44.
Explain how the following types of soil stratification influence the
movement of water through the soil profile:
a. buried clay layer
b. sand layer in contact
with free water
c. buried organic matter
layer
d. buried sand layer
45.
How can a buried sand layer in a medium textured soil result in an
increased water storage capability of the soil?
46.
Compare the rate of water movement by saturated flow, unsaturated flow,
and vapor equalization.
47.
Define the water relations in soils in terms of (i) type of movement,
(ii) plant availability and (iii) water potential at the following moisture
levels:
a. field capacity
b. permanent wilting point
c. saturation
d. hygroscopic coefficient
48.
What is the definition of available water holding capacity of a soil?
49.
How is the available water holding capacity of a soil related to its (i)
texture, and (ii) organic matter content?
50.
What is the volumetric water content of a soil that has a gravimetric (by
weight) water content of 22% and a bulk density of 1.26 Mg/m3?