Quiz 5: The Cycling of Water Through Soil
The matric potential of soil water is ________. Select one: a. is little affected by soil solids b. not influenced appreciably by the force of gravity c. influenced greatly by the content of salts in the soil d. is generally higher than that of pure water outside the soil
b
Which of the following best characterizes the field capacity of a soil? Select one: a. maximum water content of a soil b. water content of a soil 24 hours after a saturating rain c. a wetted soil prior to the removal of the gravitational water d. the total water in the soil micropores
b
Plant roots gain access to soil water primarily by the growth of the roots into moist soil (T and F)
False
Reduced forms of iron and manganese along with soil organic matter largely control the color of well-drained soils (T and F)
False
Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes carbon dioxide (T and F)
False
Sprinkle irrigation is generally more efficient in the use of water than drip irrigation, especially for high valued crops (T and F).
False
The great bulk of gaseous interchange between the soil pores and the atmosphere occurs by mass flow of the concerned gases (T and F)
False
The hydrogen end of a water molecule is attracted to positively charged cations such as Na+ and Ca2+ (T and F)
False
The property of cohesion in water stems from the attraction of water molecules for soil solids (T and F)
False
The tenacity with which water is held in soils is directly related to the soil moisture content, the higher the moisture level the greater the attraction of the water to the soil (T and F)
False
The water potential in soils is generally considered lower than that in the atmosphere (T and F)
False
Vapor loss from a south-facing slope in Australia would likely be higher than from a north-facing slope (T and F)
False
Hysteresis is the phenomenon whereby a soil has the same water content/potential relationship when it is being dried as when it is being wetted (T and F)
False Hysteresis is the phenomenon whereby a soil has the different water contents as the result of drying followed by re-wetting. Its is common in soils where a macropore is connected to a micropore at the top and one at the bottom. During draining, water stays in the macropore due to the capillary attraction in the micropore at the top. The adhesive and cohesive forces in the micropore prevent the macropore from draining. As the soil continues to dry, eventually, the soil macro and micropore will be void of water. During rewetting, capillary action draws water up to the macropore but adhesive forces are not strong enough to overcome gravity, and macropore never fills. Refer to lecture slides "Cycling of Water Through Soil" for a graphical description.
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 (T and F)
True
An abundance of macropores in soils helps assure an abundance of oxygen in the soil (T and F)
True
Capillary movement is made possible by the process of cohesion and adhesion (T and F)
True
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 (T and F)
True
Evaporation from the soil surface (E) is determined to a large degree by soil surface wetness (T and F)
True
Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants (T and F)
True
Osmotic and matric potentials are commonly negative because the soil water has a lower energy level than that of pure water (T and F)
True
Soil and crop management generally has a greater influence on evaporation from the soil surface (E) than on transpiration (T) from leaf surfaces (T and F)
True
The adsorption of water on soil surfaces encourages capillarity (T and F)
True
The alternate freezing and thawing of soils results in the upward heaving of plants and building foundations (T and F)
True
The leaf area index significantly affects the solar radiation reaching the soil surface (T and F)
True
The matric potential is due to the attraction of water molecules to soil solid surfaces (T and F)
True
The most important management factors influencing soil aeration in well-drained soils are those that determine the volume of the soil's macropores (T and F)
True
The osmotic potential is dependent upon the presence of salts and other solutes in the soil (T and F)
True
The partial pressure (i.e. concentration) of C02 in the soil pores is higher than the partial pressure of this gas in the atmosphere (T and F)
True
The polarity of water helps account for the attraction of water molecules for each other (T and F)
True
The pollution of ground water is often increased by the presence of macropores in soils (T and F)
True
Water molecules have polarity because the electrons are not uniformly shared between the two H atoms and one O atom (T and F)
True
Water will move from one site in a soil with a higher water potential to an adjacent site with a lower water potential (T and F)
True
Which of the following means of estimating soil water levels gives a direct measurement of the water content? Select one: a. pressure membrane b. gravimetric determinations c. tensiometer d. neutron scattering e. gypsum blocks
b
The evapotranspiration (ET) from a pine forest was found to be 50 cm during a growing season. If the evaporation from the soil surface during this period of time was 5 cm, what is the level of loss from leaf surfaces? Select one: a. 50.0 cm b. 45 cm c. 10 cm d. 55 cm e. Impossible to calculate from the data given
b.
In which of the following "forms" of soil water are pesticides, excess plant nutrients and waste chemicals most apt to move through soils? Select one: a. gravitational b. capillary c. hygroscopic d. unsaturated e. available
a
The following is a list of elements required for the completion of a plant's life cycle. Which element is shown in its reduced form? Select one: a. NH4+ b. CO2 c. Mn4+ d. SO42- e. Fe3+
a
Which of the following actions would best assure good aeration in a soil? Select one: a. remove excess water b. add organic residues c. use a plastic mulch d. increase the soil temperature e. use cover crops, especially legumes
a
Which of the following is not a major factor in determining the soil aeration status? Select one: a. nitrogen gas b. redox potential c. oxygen d. volume of macropores e. carbon dioxide
a
Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the use of a drying oven and balance? Select one: a. requires "destructive sampling" for each measurement b. used to turn on irrigation when soil moisture potential reaches -20.0 kPa c. good to turn on automatic irrigation at -5.0 kPa d. is an indirect measurement of soil water
a
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? Select one: a. sandier soils on the north slopes b. differences in rainfall from one area to another c. higher soil temperatures on the north slopes d. more rapid plant growth on the south slopes e. more solar radiation on the south slopes
c
Capillarity in soils ________. Select one: a. is not involved in the process of water uptake from soils b. does not account for unsaturated water movement in soils c. involves both adhesion and cohesion d. is independent of the matric potential in soils e. is enhanced by the symmetrical nature of the water molecule
c
If the average transpiration (T) loss from leaf surfaces in a particular watershed is 10 mm/day, you expect the evaporation (E) from the soil surface to be ________. Select one: a. 100 mm/day b. 15 mm/day c. Impossible to calculate from the data given d. 10 mm/day e. 5 mm/day
c
If you dug a deep hole in your back yard and water started to seep into the hole it would fill the hole up to ________. Select one: a. field capacity b. the liquid limit c. the water table d. the percolation rate e. the infiltration rate
c
Soils high in organic matter commonly hold more plant-available water than comparable soils with lower organic matter levels. This is most likely due to what characteristics of the high O.M. soils? Select one: a. higher clay content b. larger micro pore space c. higher field capacity d. lower permanent wilting percentage
c
The following are characteristics of a water molecule. Select one: a. It is attracted to surfaces with negative but not positive charges. b. It is held in soils by adhesion but not adsorption. c. It has a positive and a negative side. d. The H to O to H angle is approximately 90°C.
c
The most common form of on-site waste water treatment for homes not hooked up to sewer lines is the ________. Select one: a. electrical induction sterilization b. soil enrichment process c. septic tank and drain field d. chemical "flush" system e. active composting method
c
The osmotic potential would likely be lowest in soils of which of the following orders? The osmotic potential would likely be lowest in soils of which of the following orders? Select one: a. Oxisols b. Histosols c. Aridisols d. Ultisols e. Spodosols
c
The redox potential is a measure of ________. Select one: a. carbon dioxide content b. the ferric ion content c. the tendency of a substance to accept or donate electrons d. the balance between hydrogen and hydroxyl ions in solution e. molecular oxygen content
c
Which of the following processes are most apt to encourage good soil aeration? Select one: a. organic matter decomposition b. root respiration c. creation of more macropores d. reaction of oxygen with organic matter e. diffusion of oxygen from the soil to the atmosphere
c
Which of the following sources of water have the shortest average residence time? Select one: a. oceans and ice caps b. groundwater c. clouds d. soil moisture
c
Land drainage is beneficial because ________. Select one: a. it increases the water-to-air ratio in the soil pores b. it increases the alternate of expansion and contraction due to freezing and thawing of soils c. it increases the availability of iron and manganese in acid soils d. it increases the depth of root penetration in the soil e. it slows down the rate of soil warming in the spring
d
Urban development of land that was previously natural vegetation or farm lan usually greatly ________ soil infiltration capacity and therefore greatly increases ________. Select one: a. increases; stream bank erosion b. decreases; groundwater recharge. c. increases; groundwater recharge. d. decreases; stream bank erosion.
d
Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the electrical resistance block? Select one: a. would give the same reading for both a loamy sand and a silt loam if both contained 15% moisture b. good to turn on automatic irrigation at -50 kPa c. requires "destructive sampling" for each measurement d. used to turn on irrigation when soil moisture potential reaches -200 kPa e. both A and D
d
Plant roots obtain access to soil water in which of the following ways? Select one: a. Water vapor moves from the wet soil areas to the root surfaces. b. Roots extend into moist soil area. c. The roots contract and leave room in the pores for the water to move in. d. Water flows to the roots by capillarity. e. both B and D
e
The bulk of gaseous interchange in soils takes place by ________. Select one: a. respiration b. mass flow c. partial pressure of N2 d. dissolution in water e. diffusion
e
The process of aerobic respiration is a significant source of which of the following gases? Select one: a. methane b. nitrogen c. oxygen d. ammonia e. carbon dioxide
e
Which of the following locations in the United States would have the highest evaporation (E) from the soil surface in July? Select one: a. a forest woodland in Illinois b. a corn field in New York c. an unirrigated soil in South Carolina growing cotton d. a bare, unirrigated dry land soil in Colorado e. an irrigated cotton field in Arizona
e
Which of the following will increase the evaporation (E) from the soil surface? Select one: a. the use of no-till culture b. adding straw mulch to the soil surface c. plastic mulch d. stubble mulch farming e. none of the above
e
Compared to upland soils, wetland soils would be characterized by an abundance of ________. Select one: a. CO2 b. NO3- c. Fe3+ d. SO42- e. methane
e
