SSC 200: The Cyclying of Water thru Soil
Although the total soil water content of a clay soil is about the same as a nearby well structured silt loam, the clay will likely provide more available water to plants because of its higher volume of small pores. Select one: True False
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. Select one: True False
False
Plant roots gain access to soil water primarily by the growth of the roots into moist soil. Select one: True False
False
Reduced forms of iron and manganese along with soil organic matter largely control the color of well-drained soils. Select one: True False
False
Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes carbon dioxide. Select one: True False
False
Sprinkle irrigation is generally more efficient in the use of water than drip irrigation, especially for high valued crops. Select one: True False
False
The great bulk of gaseous interchange between the soil pores and the atmosphere occurs by mass flow of the concerned gases. Select one: True False
False
The hydrogen end of a water molecule is attracted to positively charged cations such as Na+ and Ca2+. Select one: True False
False
The property of cohesion in water stems from the attraction of water molecules for soil solids. Select one: True False
False
The soil water potential is a measure of the potential of a soil to hold water. Select one: True False
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. Select one: True False
False
The water potential in soils is generally considered lower than that in the atmosphere. Select one: True False
False
Vapor loss from a south-facing slope in Australia would likely be higher than from a north-facing slope. Select one: True False
False
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. Select one: True False
True
An abundance of macropores in soils helps assure an abundance of oxygen in the soil. Select one: True False
True
Capillary movement is made possible by the processes of cohesion and adhesion. Select one: True False
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. Select one: True False
True
Drip irrigation would more likely be used in the production of apples or peaches than in the production of wheat. Select one: True False
True
Early snowfall that arrives before the cold winter weather has frozen the soil generally increases the penetration of water into the soil. Select one: True False
True
Evaporation from the soil surface (E) is determined to a large degree by soil surface wetness. Select one: True False
True
Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants. Select one: True False
True
Most irrigation systems are very inefficient with less than half the water that is taken from streams ever reaching the plants. Select one: True False
True
Osmotic and matric potentials are commonly negative because the soil water has a lower energy level than that of pure water. Select one: True False
True
Soil and crop management generally has a greater influence on evaporation from the soil surface (E) than on transpiration (T) from leaf surfaces. Select one: True False
True
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. Select one: True False
True
The adsorption of water on soil surfaces encourages capillarity. Select one: True False
True
The alternate freezing and thawing of soils results in the upward heaving of plants and building foundations. Select one: True False
True
The leaf area index significantly affects the solar radiation reaching the soil surface. Select one: True False
True
The matric potential is due to the attraction of water molecules to soil solid surfaces. Select one: True False
True
The most important management factors influencing soil aeration in well-drained soils are those that determine the volume of the soil's macropores. Select one: True False
True
The osmotic potential is dependent upon the presence of salts and other solutes in the soil. Select one: True False
True
The partial pressure (i.e. concentration) of CO2 in the soil pores is higher than the partial pressure of this gas in the atmosphere. Select one: True False
True
The polarity of water helps account for the attraction of water molecules for each other. Select one: True False
True
The pollution of ground water is often increased by the presence of macropores in soils. Select one: True False
True
Water molecules have polarity because the electrons are not uniformly shared between the two H atoms and one O atom. Select one: True False
True
Water will move from one site in a soil with a higher water potential to an adjacent site with a lower water potential. Select one: True False
True
Which of the following processes are most apt to encourage good soil aeration? Select one: a. diffusion of oxygen from the soil to the atmosphere b. creation of more macropores c. reaction of oxygen with organic matter d. organic matter decomposition e. root respiration
b. creation of more macropores
The bulk of gaseous interchange in soils takes place by ________. Select one: a. partial pressure of N2 b. diffusion c. respiration d. dissolution in water e. mass flow
b. diffusion
Capillarity in soils ________. Select one: a. is not involved in the process of water uptake from soils b. involves both adhesion and cohesion c. is independent of the matric potential in soils d. is enhanced by the symmetrical nature of the water molecule e. does not account for unsaturated water movement in soils
b. involves both adhesion and cohesion
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. Mn4+ c. Fe3+ d. CO2 e. SO42-
a. NH4+
The process of aerobic respiration is a significant source of which of the following gases? Select one: a. carbon dioxide b. ammonia c. oxygen d. methane e. nitrogen
a. carbon dioxide
Urban development of land that was previously natural vegetation or farm land usually greatly ________ soil infiltration capacity and therefore greatly increases ________. Select one: a. decreases; stream bank erosion. b. increases; groundwater recharge. c. increases; stream bank erosion d. decreases; groundwater recharge.
a. decreases; stream bank erosion.
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 field capacity b. larger micro pore space c. higher clay content d. lower permanent wilting percentage
a. higher field capacity
Which of the following actions would best assure good aeration in a soil? Select one: a. remove excess water b. use cover crops, especially legumes c. use a plastic mulch d. increase the soil temperature e. add organic residues
a. remove excess water
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. requires "destructive sampling" for each measurement
Which of the following best characterizes the field capacity of a soil? Select one: a. water content of a soil 24 hours after a saturating rain b. maximum water content of a soil c. the total water in the soil micropores d. a wetted soil prior to the removal of the gravitational water
a. water content of a soil 24 hours after a saturating rain
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 ________. Select one: a. the hydration of adsorbed cations on the soil colloids b. the expansion of water when it freezes c. the wetting and drying of swelling-type clays d. the breaking down of soil aggregates due to freezing and thawing e. pressure from upward movement of water from lower horizons
b. the expansion of water when it freezes
The likelihood of polluting groundwater with pesticides and plant nutrients is enhanced by ________. Select one: a. light tillage of the upper centimeter or so of soil b. the presence of macropores in the soil c. the use of tillage to control weeds d. the production of oats rather than wheat e. conventional tillage as a choice compared with conservation tillage
b. the presence of macropores in the soil
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. the infiltration rate b. the water table c. the liquid limit d. the percolation rate e. field capacity
b. the water table
The following are characteristics of a water molecule. Select one: a. The H to O to H angle is approximately 90°C. b. It is attracted to surfaces with negative but not positive charges. c. It has a positive and a negative side. d. It is held in soils by adhesion but not adsorption.
c. It has a positive and a negative side
Where high-value crops or individual ornamental shrubs are to be grown and water is expensive, the most efficient type of irrigation to use would be ________. Select one: a. basin flooding b. furrow c. drip or trickle d. center pivot
c. drip or trickle
Which of the following means of estimating soil water levels gives a direct measurement of the water content? Select one: a. tensiometer b. pressure membrane c. gravimetric determinations d. neutron scattering e. gypsum blocks
c. gravimetric determinations
The most common form of on-site waste water treatment for homes not hooked up to sewer lines is the ________. Select one: a. soil enrichment process b. active composting method c. septic tank and drain field d. electrical induction sterilization e. chemical "flush" system
c. septic tank and drain field
The redox potential is a measure of ________. Select one: a. the balance between hydrogen and hydroxyl ions in solution b. molecular oxygen content c. the tendency of a substance to accept or donate electrons d. carbon dioxide content e. the ferric ion content
c. the tendency of a substance to accept or donate electrons
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. 10 cm b. Impossible to calculate from the data given c. 55 cm d. 45 cm e. 50.0 cm
d. 45 cm
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. 5 mm/day b. 10 mm/day c. 15 mm/day d. Impossible to calculate from the data given e. 100 mm/day
d. Impossible to calculate from the data given
Which of the following locations in the United States would have the highest evaporation (E) from the soil surface in July? Select one: a. an unirrigated soil in South Carolina growing cotton b. a corn field in New York c. a forest woodland in Illinois d. an irrigated cotton field in Arizona e. a bare, unirrigated dry land soil in Colorado
d. an irrigated cotton field in Arizona
Which of the following sources of water have the shortest average residence time? Select one: a. groundwater b. oceans and ice caps c. soil moisture d. clouds
d. clouds
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. differences in rainfall from one area to another b. sandier soils on the north slopes c. more solar radiation on the south slopes d. higher soil temperatures on the north slopes e. more rapid plant growth on the south slopes
d. higher soil temperatures on the north slopes
Land drainage is beneficial because ________. Select one: a. it increases the water-to-air ratio in the soil pores b. it increases the availability of iron and manganese in acid soils c. it increases the alternate of expansion and contraction due to freezing and thawing of 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. it increases the depth of root penetration in the soil
Compared to upland soils, wetland soils would be characterized by an abundance of ________. Select one: a. Fe3+ b. SO42- c. CO2 d. methane e. NO3-
d. methane
The matric potential of soil water is ________. Select one: a. influenced greatly by the content of salts in the soil b. is little affected by soil solids c. is generally higher than that of pure water outside the soil d. not influenced appreciably by the force of gravity
d. not influenced appreciably by the force of gravity
Which of the following will not increase the efficiency of water use by plants in an irrigation system? Select one: a. the use of drip irrigation for fruit trees b. the use of herbicides to control weeds c. the use of concrete-lined delivery ditches d. the use of flood irrigation for forage crops e. the use of crop residues to reduce evaporation
d. the use of flood irrigation for forage crops
The osmotic potential would likely be lowest in soils of which of the following orders? Select one: a. Histosols b. Spodosols c. Ultisols d. Oxisols e. Aridisols
e. Aridisols
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. both B and D
The process of aerobic respiration is a significant source of which of the following gases? Select one: a. oxygen b. nitrogen c. ammonia d. methane e. carbon dioxide
e. carbon dioxide
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. capillary b. unsaturated c. hygroscopic d. available e. gravitational
e. gravitational
Which of the following is not a major factor in determining the soil aeration status? Select one: a. carbon dioxide b. oxygen c. redox potential d. volume of macropores e. nitrogen gas
e. nitrogen gas
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. none of the above
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 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 e. both A and D
d. used to turn on irrigation when soil moisture potential reaches -200 kPa
