Deck 7: Soil Aeration and Temperature

Question 1

Forest fires result in sufficiently high soil temperatures to cause the vaporization and movement of certain organic compounds in soils. The main effect of these compounds is to _____.

A) reduce water infiltration and percolation through the profile
B) enhance soil structural stability
C) increase pH
D) decrease water losses by surface runoff
E) increase soil organic matter

Answer 1

A

Question 2

A mineral soil has a water content of 25 kg water per 100 kg dry soil. What is the approximate specific heat of this soil, expressed in calories per kilogram?

A) 250
B) 450
C) 640
D) 360
E) 590.

Answer 2

D

Question 3

Three rows of tomatoes were given different mulching treatments. Which of the following would result in the hottest soil in summer?

A) straw mulch
B) no mulch-bare soil
C) no mulch-living grass
D) black plastic mulch
E) clear plastic mulch

Answer 3

E

Question 4

The process of aerobic respiration is a significant source of which of the following gases?

A) methane
B) oxygen
C) nitrogen
D) carbon dioxide
E) ammonia

Question 5

The bulk of gaseous interchange in soils takes place by _____.

A) mass flow
B) partial pressure of N₂ C. diffusion
D) dissolution in water
E) respiration

Question 6

Which of the following is (are) considered necessary features for an area to be delineated as a wetland?

A) hydric soils
B) shallow standing water
C) aquatic vegetation
D) organic soils
E) all of the above

Question 7

The redox potential of a soil is -250 mV. Which of the following forms of the pertinent elements would you expect to find in the soil?

A) NO_3-
B) SO_42-
C) Fe²⁺
D) Mn⁴⁺
E) CO₂

Question 8

A well aerated soil is characterized by a relative abundance of _____.

A) micropores
B) Fe²⁺ions
C) NH₄₊ ions
D) NO_3- ions
E) methane gas

Question 9

Alternate freezing and thawing of soils results in the "heaving" of plants and the destruction of shallow building foundations. This effect is due primarily to _____.

A) the expansion of water when it freezes
B) the wetting and drying of swelling-type clays
C) pressure from upward movement of water from lower horizons
D) the breaking down of soil aggregates due to freezing and thawing
E) the hydration of adsorbed cations on the soil colloids

Question 10

Soil A has a redox potential of 400 mV, soil B -200 mV. Of the two soils, Soil A is more apt to be characterized by an abundance of _____.

A) Fe²⁺ ions
B) Mn²⁺ ions
C) H⁺ ions
D) S^2- ions
E) molecular oxygen

Question 11

The following is the reduced form of the essential element depicted

A) NH₄₊
B) Fe³⁺
C) CO₂
D) SO_42-
E) Mn⁴⁺

Question 12

Which of the following processes are most apt to encourage good soil aeration?

A) root respiration
B) organic matter decomposition
C) diffusion of oxygen from the soil to the atmosphere
D) creation of more macropores
E) reaction of oxygen with organic matter

Question 13

The redox potential is a measure of _____.

A) molecular oxygen content
B) the tendency of a substance to accept or donate electrons
C) carbon dioxide content
D) the ferric ion content
E) the balance between hydrogen and hydroxyl ions in solution.

Question 14

Which of the following actions would best assure good aeration in a soil?

A) increase the soil temperature
B) add organic residues
C) use a plastic mulch
D) use cover crops, especially legumes
E) remove excess water

Question 15

Compared to upland soils, wetland soils would be characterized by an abundance of _____.

A) methane
B) CO₂
C) NO_3-
D) SO_42-
E) Fe³⁺

Question 16

Which of the following is not a major factor in determining the soil aeration status?

A) redox potential
B) volume of macropores
C) nitrogen gas
D) carbon dioxide
E) oxygen

Question 17

If you owned a dairy farm with poorly drained clay soils in a humid temperate region which of the following would be most satisfactory from the standpoint of soil aeration and temperature?

A) no-till system
B) conventional moldboard plow system
C) ridge-till system
D) heavy organic residues
E) heavy chemical fertilization

Question 18

Which of the following practices would encourage higher soil temperatures in the spring in a humid- temperate area? 61

A) apply a thick mulch of straw
B) follow no-till practices with a killed cover crop
C) use a plastic mulch
D) irrigate the soil to leave it wet and dark colored
E) rototill the soil to leave it fluffy and bare

Question 19

The partial pressure of oxygen in the atmosphere is 0.21 bar and that of nitrogen 0.78. Which of the following partial pressure levels would you expect to find in the pores of a moderately well- drained soil?

A) 0.21 (oxygen)
B) 0.80 (nitrogen)
C) 0.30 (oxygen)
D) 0.50 (nitrogen)
E) 0.15 (oxygen)

Question 20

The primary characteristic of subsoils that accounts for the ability of ground circulating heat pumps to moderate temperatures in houses in both summer and winter is _____.

A) the high redox potential of the soil
B) the high heat of the evapotranspiration
C) the ready conduction of heat in the soil
D) the high specific heat of the soil
E) the low oxygen content of the subsoil

Question 21

A soil on the south facing slope in Canada is likely to be drier and warmer than a comparable soil on a north facing slope.

Question 22

In acid soils you would be concerned if the redox potential was low since it could mean a deficiency of some plant nutrients such as iron and manganese.

Question 23

If the CO₂ content of soil air is 3.5%, it is 100 times higher than that of the atmosphere.

Question 24

22 Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes carbon dioxide.

Question 25

The great bulk of gaseous interchange between the soil pores and the atmosphere occurs by mass flow of the concerned gases.

Question 26

The most important management factors influencing soil aeration in well-drained soils are those that determine the volume of the soil's macropores.

Question 27

In natural wetlands one would expect the redox potential to be high because of the low oxygen content.

Question 28

An abundance of macropores in soils helps assure an abundance of oxygen in the soil.

Question 29

Some 40 to 50% of the solar radiation in humid regions is used to heat the soil.

Question 30

Soil temperatures under an organic mulch will likely be lower than that of bare soils in the summer but higher than that of bare soils in the winter.

Question 31

Anaerobic conditions commonly prevail in liberally watered flower pots with mineral soil as the growing medium even though the containers have holes for drainage in the bottom of the pot.

Question 32

The partial pressure of CO₂ in the soil pores is higher than the partial pressure of this gas in the atmosphere.

Question 33

The alternate freezing and thawing of soils results in the upward heaving of plants and building foundations.

Question 34

The redox potential is a measure of the tendency of a substance to accept or donate electrons.

Question 35

Reduced forms of iron and manganese along with soil organic matter largely control the color of well-drained soils.

Question 36

A wildlife biologist in South Africa notes that the soils on south-facing slopes are wetter and deeper than those on north-facing slopes, and therefore support more wildlife. What likely accounts for this difference?

A) differences in rainfall from one area to another
B) more rapid plant growth on the south slopes
C) higher soil temperatures on the north slopes
D) more solar radiation on the south slopes
E) sandier soils on the north slopes

Question 37

Wildfires in forested areas result in the formation of organic compounds that enhance the percolation of water through the soil.

Question 38

Conservation tillage is not practical in some areas of the Northern part of the United States because the practice lowers the surface soil temperature in the spring of the year.

Question 39

The specific heat of soil solids is significantly higher than that of water.

Question 40

Heat pumps can take advantage of the fact that subsoils are generally warmer in the winter and cooler in the summer than the atmospheric air.

Question 41

An increase of 5 ^oC in soil temperature is likely to increase shoot growth on most plants much more than a similar increase in the air temperature.

Question 42

You would expect the installation of an effective tile drainage system in a naturally poorly drained soil in Iowa to increase soil temperatures in the spring of the year.