PLS 366 FINAL EXAM REVIEW QUESTIONS
A dynamic natural body having properties derived from the combined effects of climate
and biotic activities as moderated by topography, acting on parent materials over time is
a definition of what? - Answers -Soil
As one moves from an A to a Bt horizon, what would you expect to happen to the clay
content? - Answers -Increase
This soil order would be formed on volcanic ash - Answers -Andisol
Chemical weathering occurs most rapidly at ___ temperatures, ___ precipitation, and
___ particle size. - Answers -High, high, small
The three most important soil properties used to characterize a soil profile and which
appear in a soil series description are: - Answers -Color, structure and texture
Which of the following soil orders is the YOUNGEST? Entisol Oxisol Spodosol Ultisol -
Answers -Entisol
The high impact area around a campsite has ___ bulk density, ___ infiltration, and ___
losses by surface runoff. - Answers -High, low, increased
Which of the following soil orders is characterized by a dark and thick surface horizon
containing >50% base saturation and is considered one of the most fertile soils in the
world? Mollisol Ultisol Alfisol Entisol - Answers -Mollisol
Which of the following would indicate a MORE weathered soil? - Answers -Low Si:Al
ratio
___ is the size range of a silt particle. - Answers -0.002 to 0.05 mm
Which of the five soil forming factors are most responsible for the differences between
Entisols and Inceptisols? - Answers -Time
___ vegetation leads to development of a thick, dark surface horizon with a uniform
organic matter content. - Answers -Tall grass
Which of the following does not contribute to soil acidification over time? - Answers -
Decreased leaching losses of exchangeable cations
Aggregate development first involves ___. - Answers -Flocculation
,From the list below, which of the following colloids would exhibit the greatest cation
exchange capacity (CEC)? Gibbsite Kaolinite Montmorillonite - Answers -
Montmorillonite
The structure of a 2:1 alumino-silicate clay includes: - Answers --One aluminum
octahedral sheet
-Two silicon tetrahedral sheets
-Isomorphous substitution for both Al and Si within sheets
One might expect the following suborder to appear in a description of a soil containing a
fragipan: Aquic Udic Xeric Ustic - Answers -Aquic
When a soil scientist, novice or professional, measures pH using KCl, they are
interested in specifically measuring what kind of acidity? - Answers -Exchangeable
What is the primary property of AL3+ which makes it able to contribute so much to
changes in pH? - Answers -It reacts with water to form protons (hydrolysis)
The hydrogen ion concentration of a solution is 10^-4. What is its pH? - Answers -4
Rank the following cations in ORDER of DECREASING effective flocculation power. -
Answers -Al3+, Ca2+, Na+
From the following list, the smallest soil organism would be: Algae Earthworms
Nematodes Bacteria - Answers -Bacteria
Under what circumstance will acid saturation of a soil be the highest? - Answers -Wet
pine forest
For most plants, the optimal range of soil pHwater would be: - Answers -6.0 - 7.0
A distinguishing feature which separates Alfisols from Ultisols is: - Answers -Greater
than 35% base saturation in the argillic horizon for an Alfisol
The percent organic matter in soils decreases as ___ increases. - Answers -
Temperature
Oxidation-reduction reactions during soil formation are examples of a(n): - Answers -
Transformation
The greatest annual turnover of soil organic matter (SOM) is for the ___ pool. -
Answers -Active
Positive contributions of earthworms to soil systems include: - Answers --Aeration
through construction of biopores
-Processing organic materials through their digestive tracts
, -Mixing of soil fractions
Growth and activity of microorganisms in soil is NOT promoted by: - Answers -Soil
temperatures near 2 degrees Celcius
Organisms capable of acquiring energy by enzymatic oxidation of inorganics are ___. -
Answers -Chemoautotrophs
Compared with aerobic decomposition, anaerobic decomposition of organic materials is:
- Answers -Slower
How would addition of an organic material with a C/N ratio of 200:1 influence plant
available nitrogen in the short term? - Answers -Decrease
Other things being equal ___ drained soils contain the greatest percentages of organic
matter. - Answers -Poorly
Relative to soil micropores, soil macropores: - Answers -Can be drained of water by
gravity
Which of the following would be good ways to try to maintain or increase soil organic
matter levels? - Answers -Plant winter cover crops like rye and hairy vetch
Which of the following N forms do plants take up from soils? - Answers -NH4+ and
NO3-
As a result of the process of immobilization, which of the following happens? - Answers
-Microbes obtain more N, and N in soil solution falls
Ammonium is lost to the atmosphere as ammonia gas (NH3) through the process of: -
Answers -Volatilization
The result of the microbial process of mineralization is a breakdown of organic matter
and the release of: - Answers -NH4+
Nitrogen leaching is environmentally harmful (resulting in, eutrophication of waters) but
can also hurt farmers by: - Answers -Reducing crop yields
Effective strategies to reduce nitrate leaching include: - Answers --Applying only as
much N as your crop needs
-Adjusting N applications based on pre-sidedress nitrate testing
-Planting cover crops as soon as you harvest your primary crop
Denitrification is favored by: - Answers --Anaerobic conditions
-Sufficient organic C for energy
-Abundant nitrate
A dynamic natural body having properties derived from the combined effects of climate
and biotic activities as moderated by topography, acting on parent materials over time is
a definition of what? - Answers -Soil
As one moves from an A to a Bt horizon, what would you expect to happen to the clay
content? - Answers -Increase
This soil order would be formed on volcanic ash - Answers -Andisol
Chemical weathering occurs most rapidly at ___ temperatures, ___ precipitation, and
___ particle size. - Answers -High, high, small
The three most important soil properties used to characterize a soil profile and which
appear in a soil series description are: - Answers -Color, structure and texture
Which of the following soil orders is the YOUNGEST? Entisol Oxisol Spodosol Ultisol -
Answers -Entisol
The high impact area around a campsite has ___ bulk density, ___ infiltration, and ___
losses by surface runoff. - Answers -High, low, increased
Which of the following soil orders is characterized by a dark and thick surface horizon
containing >50% base saturation and is considered one of the most fertile soils in the
world? Mollisol Ultisol Alfisol Entisol - Answers -Mollisol
Which of the following would indicate a MORE weathered soil? - Answers -Low Si:Al
ratio
___ is the size range of a silt particle. - Answers -0.002 to 0.05 mm
Which of the five soil forming factors are most responsible for the differences between
Entisols and Inceptisols? - Answers -Time
___ vegetation leads to development of a thick, dark surface horizon with a uniform
organic matter content. - Answers -Tall grass
Which of the following does not contribute to soil acidification over time? - Answers -
Decreased leaching losses of exchangeable cations
Aggregate development first involves ___. - Answers -Flocculation
,From the list below, which of the following colloids would exhibit the greatest cation
exchange capacity (CEC)? Gibbsite Kaolinite Montmorillonite - Answers -
Montmorillonite
The structure of a 2:1 alumino-silicate clay includes: - Answers --One aluminum
octahedral sheet
-Two silicon tetrahedral sheets
-Isomorphous substitution for both Al and Si within sheets
One might expect the following suborder to appear in a description of a soil containing a
fragipan: Aquic Udic Xeric Ustic - Answers -Aquic
When a soil scientist, novice or professional, measures pH using KCl, they are
interested in specifically measuring what kind of acidity? - Answers -Exchangeable
What is the primary property of AL3+ which makes it able to contribute so much to
changes in pH? - Answers -It reacts with water to form protons (hydrolysis)
The hydrogen ion concentration of a solution is 10^-4. What is its pH? - Answers -4
Rank the following cations in ORDER of DECREASING effective flocculation power. -
Answers -Al3+, Ca2+, Na+
From the following list, the smallest soil organism would be: Algae Earthworms
Nematodes Bacteria - Answers -Bacteria
Under what circumstance will acid saturation of a soil be the highest? - Answers -Wet
pine forest
For most plants, the optimal range of soil pHwater would be: - Answers -6.0 - 7.0
A distinguishing feature which separates Alfisols from Ultisols is: - Answers -Greater
than 35% base saturation in the argillic horizon for an Alfisol
The percent organic matter in soils decreases as ___ increases. - Answers -
Temperature
Oxidation-reduction reactions during soil formation are examples of a(n): - Answers -
Transformation
The greatest annual turnover of soil organic matter (SOM) is for the ___ pool. -
Answers -Active
Positive contributions of earthworms to soil systems include: - Answers --Aeration
through construction of biopores
-Processing organic materials through their digestive tracts
, -Mixing of soil fractions
Growth and activity of microorganisms in soil is NOT promoted by: - Answers -Soil
temperatures near 2 degrees Celcius
Organisms capable of acquiring energy by enzymatic oxidation of inorganics are ___. -
Answers -Chemoautotrophs
Compared with aerobic decomposition, anaerobic decomposition of organic materials is:
- Answers -Slower
How would addition of an organic material with a C/N ratio of 200:1 influence plant
available nitrogen in the short term? - Answers -Decrease
Other things being equal ___ drained soils contain the greatest percentages of organic
matter. - Answers -Poorly
Relative to soil micropores, soil macropores: - Answers -Can be drained of water by
gravity
Which of the following would be good ways to try to maintain or increase soil organic
matter levels? - Answers -Plant winter cover crops like rye and hairy vetch
Which of the following N forms do plants take up from soils? - Answers -NH4+ and
NO3-
As a result of the process of immobilization, which of the following happens? - Answers
-Microbes obtain more N, and N in soil solution falls
Ammonium is lost to the atmosphere as ammonia gas (NH3) through the process of: -
Answers -Volatilization
The result of the microbial process of mineralization is a breakdown of organic matter
and the release of: - Answers -NH4+
Nitrogen leaching is environmentally harmful (resulting in, eutrophication of waters) but
can also hurt farmers by: - Answers -Reducing crop yields
Effective strategies to reduce nitrate leaching include: - Answers --Applying only as
much N as your crop needs
-Adjusting N applications based on pre-sidedress nitrate testing
-Planting cover crops as soon as you harvest your primary crop
Denitrification is favored by: - Answers --Anaerobic conditions
-Sufficient organic C for energy
-Abundant nitrate
