Soils Exam II Questions

In a field experiment you noted that 300 tons of water were transpired to produce 1 ton of corn (dry weight). If alfalfa has been grown in the same field of corn, which of the following would most likely have been the amount of water transpired? A. 500 tons B. 300 tons C. 275 tons D. 250 tons E. Depends on the climate in the area of the experiment

A. 500 tons

The osmotic potential would likely be lowest in soils of which of the following orders? A. Aridisols B. Histosols C. Oxisols

A. Aridisols

Colloidal properties are exhibited by the ______ fraction of soils. A. Clay B. Sand C. Gravel D. Silt

A. Clay

Which type of structure is typically found in sodium-rich sub-surface horizons? A. Columnar B. Granular C. Sub-angular blocky D. Platy

A. Columnar

The bulk of gaseous interchange in soils takes place by ________. A. Diffusion B. Respiration C. Partial pressure of N2 D. Mass Flow E. Dissolution in Water

A. Diffusion

In which of the following forms of oil water are pesticides, excess plant nutrients and waste chemicals most apt to move through soils? A. Gravitational B. Unsaturated C. Available

A. Gravitational

The following is the reduced form of the essential element depicted A. NH4+ B. Fe3+ C. CO2 D. SO4 2- E. Mn4+

A. NH4+

The partial pressure of oxygen in the atmosphere in 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

0.15 Oxygen

Which color would be typical of a well drained, low-organic matter sandy surface soil?

10Y5/8

The heat of vaporization of water is 540 cal/g. A soil containing 30 kg water per 100 kg soil solids lost one sixth of that water by evaporation. If one tenth of the energy needed to evaporate the water came from the soil solids how much would the temperature of those solids be lowered?

13.5ºC

The transpiration ratio of a native meadow is 550 kg per kg of dry matter produced. If 4Mg of dry matter is produced on a hectare of land, how many centimeters of water will be required (rounded to the nearest cm)?

22

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?

360

Which of the following expressions in kPa is most apt to characterize the gravitational potential of a clay loam surface soil? A. -5 B. -30 C. 0 D. +5 E. -3100

D. +5

The water potential at the leaf surface expressed in kPa is most likely to be _______. A. -10 B. 33 C. -33 D. -500 E. -31,000

D. -500

Two soil samples, A and B, at different soil moisture levels are placed in contact with each other. Water will more likely move from A to soil B if their water potentials, expressed in kPa are: A. A= -5 ; B= +5 B. A= -5 ; B= -5 C. -A= -20 ; B= -10 D. -A= -30 ; B= -40 E. -A= -100 ; B= -50

D. A= -30 ; B=-40

What is (are) the major factor(s) that influence soil color(s)? A. Organic Matter Content B. Water Content C. Presence and oxidation states of iron and manganese oxides D. All of the Above

D. All of the Above

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 macro pores E. Reaction of oxygen with organic matter

D. Creation of more macro pores

Which of the following means of estimating soil water levels gives a direct measurement of the water content? A. Gypsum blocks B. Neutron scattering C. Pressure membrane D. Gravimetric determinations

D. Gravimetric determinations

Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the neutron probe? A. Requires "destructive sampling" for each measurement B. Good to turn on automatic irrigation at -50 kPa C. Used to turn on irrigation when soil moisture potential reaches -200 kPa D. Would give the same reading for both a loamy sand and a silt loam if both contained 15% moisture

D. Would give the same reading for both a loamy sand and a silt loam if both contained 15% moisture

The expression, P -ET - SS estimates the ________ a watershed.

Discharge volume from

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 ___________.

Drip or trickle

At which of the following soil moisture potentials is the soil water held most lightly? A. +5 B. 0 C. -31 D. -1500 E. -3100

E. -3100

At which of the following soil moisture potentials is the waters' energy level lowest? A. +5 B. 0 C. -31 D. -1500 E. -3100

E. -3100

A soil with a bulk density equal to .35 Mg/m^3 is most likely what type of soil? A. A well-structured garden soil B. A compacted urban soil C. An Ultisol D. A vertisol E. A peat soil

E. A peat soil

Because of their greater surface area per unit of soil mass, silt loams soils generally have a greater capacity than loamy sand soils due to ______. A. Absorb gases B. Release nutrients by mineral weathering C. Support Bacterial growth D. Absorb water E. All of the Above

E. All of the Above

What is (are) the aspect(s) affecting soil temperature? A. Albedo B. Aspect C. Rain D. Soil Cover E. All of the Above

E. All of the Above

Which of the following practices is (are) useful in stabilizing surface soil structure? A. use of organic mulches B. use of green manure crops C. growing grass sod D. minimizing tillage E. All of the above

E. All of the above

Which of the following is not a textual class name? A. Sand B. Silt C. Clay D. Loam E. Sandy silt

E. Sandy silt

Texture describes the _____ of particles in a soil. A. Arrangement B. Mineralogical makeup C. roughness D. Colors E. Sizes

E. Sizes

The primary characteristic of subsoils that account for the ability of ground circulating heat pumps to moderate temperatures in houses in both summer and winter is ____________. A. The low oxygen content of the subsoil B. the ready conduction of heat in the soil C. the high redox potential of the soil D. The high specific heat of the soil E. the high specific heat of the evapotranspiration.

E. the high specific heat of the evapotranspiration.

A chroma greater than 4 generally indicated a soil in good tilth.

False

A friable soil is usually more likely to be indurated. T or F

False

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

False

Atmospheric vapor pressure has little effect on the vapor losses from soil surfaces. T or F

False

Compared to a similar soil under native vegetation, a soil with a long history of conventionally tilled cropping would have less micropore space. T or F

False

Conservation tillage can have a significant effect on transpiration of water from a rapidly growing crop of corn.

False

Eutrophication is enhanced by the pesticides in the water draining from agricultural soils. T or F

False

Filling the bottom half of a flower pot with gravel will greatly improve the aeration of the soil-mix in the top half. T or F

False

Flocculation is the process by which certain chemicals in the soil stabilize large soil aggregates. T or F

False

For most soils, plowing and harrowing every year improves soil tilth in the long run. T or 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.

False

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. T or F

False

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

False

Light-colored surface soils are likely to be warmer than dark-colorded surface soils if soil moisture and other conditions are the same. T or F

False

Plant roots gain access to soil water primarily by the growth of the roots into moist soil. T or F

False

Polycacchrides produced by soil microbes and similar synthetic polymers applied to soils are largely responsible for the crusts that form when rain follows tillage. T or F

False

Reducing forms of iron and manganese along with soil organic matter largely control the color of well-drained soils. T or F

False

Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes CO2.

False

Roots of most plants have difficulty growing through soil if the bulk density is greater than 1.0 Mg/m^3. T or F

False

Some 2/3 of the solar energy reaching the earth is absorbed by water on or near the earth's surface. T or F

False

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

False

Some 60% of the water that is actively involved in the hydrologic cycle worldwide is found in soils. T or F

False

Sprinkle irrigation is generally more efficient in the use of water than drip irrigation, especially for high valued crops.

False

Subsoiling is a primitive deep tillage technique that results in extremely high subsoil bulk density.

False

The average residence time for water in clouds over the ocean is about one year. T or F

False

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

False

The hydrogen end of a water molecule is attracted to positively charged cations such as Na+ and Ca 2+. T or F

False

The percent of total pore space in a soil can be calculated if only the particle density and the organic matter content are known. T or F

False

The plasticity index is used to determine soil texture. T or F

False

The property of cohesion in water stems from the attraction of water molecules for soil solids. T or F

False

The soil water potential is a measure of the potential of a soil to hold water.

False

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

False

The water potential in soils is generally considered lower than that in the atmosphere. T or F

False

There is a net movement of clouds from the land areas to the ocean areas in the hydrologic cycle. T or F

False

Vapor loss from a south-facing slope in Australia would likely be higher than from a north-facing slope. T or F

False

Water molecules have polarity primarily because each contains two H atoms and only one O atom

False

When preparing a surface soil seedbed, the soil should generally be in the loosest, least dense soil condition in the row where the seed is placed.

False

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

False

Plant transpiration efficiency at a given location is markedly influenced by __________.

Fertilization practices used and the plant species being grown

Unsaturated water flow occurs on soils that are at what?

Field capacity

Soils high in organic matter commonly hold more available water than comparable soils with lower organic matter levels. This is most likely due to what characteristics of the high O.M. Soils?

Higher field capacity

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 ______.

Impossible to calculate from the data given

The water content in a soil is known to be .2m^3/m^3 and the potential of pure water outside the system is assumed to be 0. If the soil is a clay loam you would calculate the soil water potential to be:

Impossible to calculate with data given

Capillarity in soils _______.

Involves both adhesion and cohesion

Using a textual chart, it can be determined that a soil with 45% sand and 20% clay belongs to the ____ textural class.

Loam

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

NO3- ions

Which of the following will increase the evaporation (E) from the soil surface? A. Adding a straw mulch to the soil surface B. The use of no-till culture C. Stubble mulch farm D. None of the above

None of the above

The matric potential of soil water is _______.

Not influenced appreciably by the force of gravity

In many soil profiles, the subsoil is high in clay, but is also quite permeable to percolation water. why?

Prismatic structure may be well developed

Plant roots access to soil water in what ways?

Roots extend into moist soil area and Water flows to the roots by capillarity.

A landscaping contractor wants to change the texture of a silt loam soil to meet the specifications for a loam. She would most likely do so by adding ______ to the soil and mixing it well.

Sand

Fungal hyphae have an important influence on soil structure because they ______.

Stabilize macro aggregates

Soil tilth refers to ______.

The physical suitability of a soil for plant growth

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 or F

True

An Increase of 5C in soil temperature is likely to increase shoot growth on most plants much more than a similar increase in the air temperature. T or F

True

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

True

Anaerobic forms of iron and manganese along with soil organic matter largely control the color of well-drained soils. T or F

True

Capillary movement is made possible by the processes of cohesion and adhesion.

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 or F

True

Corn plants are generally more efficient in the use of water than is alfalfa. T or F

True

Drip irrigation would more likely be used in the production of apples or peaches than in the production of wheat. T or F

True

Early snowfall that arrives before the cold winter weather has frozen the soil and generally increases the penetration of water into the soil.

True

Evaporation from the soil surface (E) is determined to a large degree by soil surface wetness. T or F

True

Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants.

True

For any soil, the bulk density is always lower than the particle density

True

Fungal hyphae play is an important role in stabilizing surface soil aggregates. T or F

True

Gypsum or nylon blocks are most useful in estimating the soil water content if the soil is quite dry. T or F

True

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

True

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

True

More than 98% of the earth's water does not take part in the annual cycling known as the hydrologic cycle.

True

Most irrigation systems are very inefficient with less than half the water that is taken from streams ever reaching the plants. T or F

True

Osmotic and matric potentials are commonly negative because the soil water has a lower energy level than that of pure water.

True

Proper timing of tillage is generally more difficult for a clay than a sandy soil. T or F

True

Soil and crop management generally have a greater influence on evaporation from the soil surface (E) than on transpiration (T) from leaf surfaces.

True

Soil consistence changes with changes in soil water content. T or F

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. T or F

True

Soils of good tilth and high productivity are usually characterized by stable aggregation and a high percentage of macropores. T or F

True

The adsorption of water on soil surfaces encourages capillarity

True

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

True

The drainage class of a soil, the degree to which the soil becomes water-saturated during the year, can be judged by the presence and location of gluey in the soil profile. T or F

True

The effect of soil organic matter on the amount of water available to plants is due to organic matter influence on total soil porosity as well as to the water-supplying power of the soil organic matter. T or F

True

The leaf area index significantly affects the solar radiation reaching the soil surface.

True

The magnetic resonance technique of estimating soil moisture levels can also be used to estimate salt contents. T or F

True

The matric potential is due to the attraction of water molecules to soil solid surfaces.

True

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

True

The osmotic potential is dependent upon the presence of salts and other solutes in the soil.

True

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

True

The plasticity index is the difference between the plastive limit and the liquid limit.

True

The polarity of water helps account for the attraction of water molecules.

True

The pollution of ground water is often increased by the presence of macropores in soils. T or F

True

The water potential at the field capacity for most soils is in the range of -10 to -30 kPa. T or F

True

Water will move from one site in a soil with a water potential of -5 kPa to an adjacent site with a water potential of -40 kPa. T or F

True

When the soil is too wet tillage is likely to increase the soil bulk density. T or F

True

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.

True

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

Use a plastic mulch

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? (more than one) A. Requires "destructive sampling" for each measurement B. Good to turn on automatic irrigation at -50 kPa C. Used to turn on irrigation when soil moisture potential reaches -20.0 kPa D. Gives same readings for loamy sand and silt loam if both contained 15% moisture

A. Requires "destructive sampling" for each measurement D. Gives same readings for loamy sand and silt loam if both contained 15% moisture

The difference between the liquid and plastic limits of a soil is ________. A. The plasticity index B. That one is a moisture variable while the other is a density variable C. that one is applicable to natural soils the other to artificial growth media D. Greater than the difference between the soil and liquid limits E. None of the Above

A. The plasticity index

In which of the following situations would you expect downward movement of soil water through the profile to be most rapid? A. Uniformly textured sandy loam profile B. Sandy loam in upper layers with a clay band underneath C. Clay texture throughout the profile D. Silt loam in upper layers underlain by a sandy layer

A. Uniformly textured sandy loam profile

Which of these would you expect to have the highest leaf are index? A. Bare fallowed area B. Corn, knee high C. Alfalfa just before harvest D. Corn three weeks after planting

Alfalfa just before harvest

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 lead surfaces? A. 55cm B. 45cm C. 50.0cm D. 10cm E. Impossible to calculate from the data given

B. 45 cm

The process of aerobic respiration is a significant source of which of the following gases? A. Ammonia B. Carbon Dioxide C. Nitrogen D. Methane E. Oxygen

B. Carbon dioxide

Which of the following sources of water have the shortest average residence time? A. Soil moisture B. Clouds C. Oceans and ice caps D. Groundwater

B. Clouds

Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the tensiometer? A. Requires "destructive sampling" for each B. Good to turn on automatic irrigation at -50 kPa C. Used to turn on irrigation when soil moisture potential reaches -200 kPa D. Gives same readings for loamy sand and silt loam if both contained 15% moisture

B. Good to turn on automatic irrigation at -50 kPa

Which type of soil structure is typically found in surface soil (A horizons?) A. Columnar B. Granular C. Sub-angular blocky D. Platy E. Prismatic

B. Granular

Which of the following is considered necessary features for an area to be delineated as a wetland? A. Organic soils B. Hydric soils C. Shallow standing water D. Aquatic vegetation

B. Hydric soils

Brown and red colors in subsurface horizons are cause by ____ in the soil. A. Clay B. Iron Oxides C. Manganese D. Organic Matter E. Aluminum Oxies

B. Iron Oxides

Which of the following actions would best assure good aeration in a soil? A. Increase the soil temperature B. Remove excess water C. Use a plastic mulch D. Add organic residue E. Use cover crops, especially legumes

B. Remove excess water

Which is not true to respect to the hydrologic cycle? A. More than 85% of the water evaporated from the earth's surface comes from oceans B. There is a net migration of some 40,000 km^3 of water in clouds from the land area to the ocean areas. C. The average residence time of water in clouds is about 10 days D. Some 78% of the total precipitation falls onto the oceans E. About one third of readily accessible water in the hydrologic cycle is in the soil.

B. There is a net migration of some 40,000 km^3 of water in clouds from the land area to the ocean areas.

Which of the following best characterizes the field capacity of a soil: A. Maximum capacity of a soil to hold water B. Water content of a soil with water potential of about -10 Pka C. The total capillary water in a soil D. A wetted soil prior to the removal of the gravitational water E. Soil with water potential of -1000 Pka

B. Water content of a soil with water potential of about -10 Pka

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. Large amount of water B. The expansion of water when it freezes C. The cold climate

B. the expansion of water when it freezes

For which substance would the particle density equal the bulk density? A. An organic soil B. A wet soil C. A quartz pebble D. A soil clod E. Well-aggregated surface soil

C. A Quartz pebble

Which of the following locations in the United States would have the highest evaporation (E) from the soil surface in July? A. A bare, unirrigated dry land soil in Colorado B. An unirrigated soil in South Carolina C. A furrow-irrigated cotton field in Arizona

C. A furrow-irrigated cotton field in Arizona

Which of the following irrigation systems produce the most biomass per unit of water applied? A. Flood irrigation B. Furrow irrigation C. Drip irrigation D. Sprinkle irrigation

C. Drip irrigation

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. NO3- B. SO4 2- C. Fe 2+ D. Mn 4- E. CO2

C. Fe 2+

Which of the following characteristics of water molecule is true. A. The H to O to H is approximately 90C B. The two H atoms are on diametrically opposite ends of the molecule C. It has a positive and negative side D. It is attracted to surfaces with negative but not positive charges. E. It is held in soils by adhesion but not absorption.

C. It has a positive and a negative side

Dull gray colors are characterized by ______.A. Clay B. Iron Oxides C. Low Chromas D. Organic Matter E. Aluminum Oxies

C. Low chromas

Compared to upload soils, wetland soils would be characterized by an abundance of ________. A. Oxygen B. Carbon Dioxide C. Methane D. Nitrogren

C. Methane

Soil A has a redox potential of 400 mV, soil B -200 mV. Of the two soil, Soil A is more apt to be characterized by an abundance of _________. A. Fe 2+ ions B. Mn 2+ ions C. molecular oxygen D. S 2- ions

C. Molecular oxygen

Soil colors are scientifically described by _____ color designations such as 10YR3/4. A. Parsons B. Wavelength C. Munsell D. USDA E. Structural

C. Munsell

Which of the following is not a major factor in determining the soil aeration status? A. Redox potential B. Volume of macro pores C. Nitrogen gas D. Carbon dioxide E. Oxygen

C. Nitrogen gas

The percentages of which soil components represent the minimum information necessary in order to determine the textual class of a soil is what? A. Clay, water, and air B. clay and organic matter C. Silt and Sand D. Sand, silt, and clay E. gravel and sand

C. Silt and Sand

Which of the following will not increase the efficiency of water use by plants in an irrigation system? A. The use of concrete-lined delivery ditches B. The use of floor irrigation for forage crops C. The use of drop irrigation for fruit trees D. The use of crop residues to reduce evaporation E. The use of herbicides to control weeds

C. The use of drop irrigation for fruit trees

Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the electrical resistance block? A. Requires "destructive sampling" for each measurement B. Good to turn on automatic irrigation at -50 kPa C. Used to turn on irrigation when soil moisture potential reaches -200 kPa D. Would give the same reading fr both a loamy sand and a silt loam if both contained 15% moisture

C. Used to turn on irrigation when soil moisture potential reaches -200 kPa

The redox potential is a measure of the tendency of what? A. The balance between hydrogen and hydroxly ions in solution B. Molecular oxygen content C. the tendency of a substance to accept or donate electrons D. the ferric ion content E. Carbon Dioxide content

C. the tendency of a substance to accept or donate electrons

A sticky, putty-like feel indicates a high percentage of which soil separate?

Clay

If a dry soil high in certain types of _____ is moistened, it is likely to swell up with enough force to crack pavements and building foundations.

Clay

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?

higher soil temperatures on the north slopes

Groundwater _________.

is a major source of water for irrigation in the United States

Eutrophication __________.

is a process of enriching ponds and lakes with plant nutrients

Land drainage is beneficial because __________.

it increases the depth of root penetration in the soil

Practices that add organic matter and reduce tillage can be expected to most significantly increase the ______ in a soil.

macropores

Of various types of drain systems, open ditch systems are most practical and economical for use on ________.

poorly drained soils with sandy profile

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 _______.

reduce water infiltration and percolation through the profile

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 temptation?

ridge-till system

The most common form of on-site waste water treatment for homes not hooked up to sewer lines is the ______.

septic tank and drain field

The likelihood of polluting groundwater with pesticides and plant nutrients is enhanced by _______.

the presence of macropores in the soil

The redox potential is a measure of __________.

the tendency of a substance to accept or donate electrons

Drainage pipe come in 200 ft long rolls. The number of rolls needed to construct a uniform buried drainage system for a nearly level 20 hectare field will depend primarily on ___________.

the texture an structure of 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 __________.

the water table