Uark Soil Science Exam 2 Study Guide

1. The two groups of soil colloids that possess the largest cation exchange capacities are the

a) layer silicates and the oxides

b) amorphous colloids and the organic colloids

c) 2:1-type layer silicates and the organics

d)smectites and kaolinite

e)oxides and the amorphous (noncrystalline) colloids

d

2. Saturated water flows in soils

a) is more rapid than unsaturated flow

b) is driven primarily by the force of gravity

c) occurs when the soil water potential = 0

d) occurs when all soil pores are filled with water

e) all of the above

f)none of the above

E

3. When virgin soil is first put into cultivation, the soil's organic matter content

a) tends to increase if a sufficient line is applied

b) tends to increase if a crop rotation, including pasture is used

c) usually doesn't change much

d) declines rapidly at first, then moves more slowly

e) declines slowly at first, then more rapidly

D

4. The Single most important factor when determining a soils buffer capacity is

a) PH

b) color

c) structure

d) CEC

e) moisture control

D

5. In which of the following soils would you expect downward movement of water through the profile to be most rapid

a) a uniformly textured sandy loam

b) soil with a sandy loam texture in the upper layers with a clay band underneath

c) soil with a sandy loam texture in the upper layers with a layer of coarse gravel underneath

d) a uniformly textured clay

e) a soil with silt loam texture in the upper layers underlain by a sandy layer

A

6. All of the following are factors that effect the amount of plant available water a soil can hold, except

a)organic matter content

b) texture

c) shear strength

d) structure

e) presence of high salt in the soil

f) soil depth and layering

C

7. All of the following materials can be used to lower soil PH except

a) alum

b) calcite

c) Sulfuric acid

d) elemental sulfur

e) aluminum sulfate

B

8. Montmorillonite is a good example of

a) an oxide mineral

b) an amorphous (noncrystalline) colloid

c) a swelling 2:1 type crystalline silicate

d) a non-swelling 1:1 type crystalline silicate

e) a non-swelling 2:1 type crystalline silicate

C

9. Compared with AG lime, the major advantage of liming materials such as burnt lime and slaked lime is

a) are less caustic than ag lime

b) they bring about a more rapid change in soils PH

c) they are less expensive than ag lime

d) their odor is less offensive than that of ag lime

e) they are easier to store and handle than ag lime

B

10. Most plants grow poorly in low PH (

B

11. Organic matter tends to accumulate to higher levels in poorly drained soils than in well-drained soils because

a) anaerobic decomposition of plant residues proceeds much more rapidly than aerobic decomposition

b) plants that are adapted to poorly drained soils return more carbon to the soil each year than do plants that are adapted to well-drained soils

c)plants that are adapted to poorly drained soils have a wider C-N ratio than do plants that are adapted to well-drained soils

d)anaerobic decomposition of plants residues proceeds much more slowly than aerobic decomposition

e) plants that are adapted to poorly drained soils tend to have a much higher content of lignin than do plants that are adapted to well drained soils

D

12. Plant roots obtain water from the soil by the mechanisms known as

a) diffusion and mass flow

b) hysteresis and flocculation

c) dispersion and dissolution

d) capillary and root extension

e) attenuation and root volume fluctuation

D

13. The swelling behavior exhibited by some of the 2:1 phyllosilicate clays is caused by

a) the presence of interlayer potassium (K+) ions, which force adjacent 2:1 layers apart

b) the presence of an interlayer aluminum or magnesium octahedral sheet

c)heating of the minerals, which causes them to expand

d)lengthening of si-O and Al-O bonds within the clay crystal

e)movement of water into the interlayer spaces between adjacent 2:1 layers

E

14. Soil organic matter consists of

a) living biomass, detritus, and humus

b) the products of respiration

c) undecomposed plant residues

d) lignin, cellulose, and hemicellulose

e) the products of humification

A

15. Amorphous (non-crystalline) silicate colloiuds are particularly abundant in soils in the order

a) andisols

b) spodosols

c) histisols

d) gelisols

e) plasmasols

A

16. as a genetic rule pf thumb, when an organic material such as crop residue is added to the soil approximation, what proportion of the added carbon is respired by the soil microorganisms and subsequently lost as carbon dioxide, CO2

a) 10%

b) 25%

c) 33%

d) 50%

e)75%

E

17. All of the following factors affect a soils lime requirements except

A)Particle size distribution of the liming material

b) chemical composition and purity of the liming material

c) the desired change in soils PH

d) the soils buffer capacity

e) the phosphorous content of the soil

E

18. Most of the charge on the 2:1 type phyllosilicate (crystalline silicate) clays is best described as

a) permanent positive charge arising from isomorphic substitution of either si4+ for al3+ in the octahedral layer or Al3+ for Mg 2+ in the tetrahedral layer

b) PH-dependent positive charge arising from protonation of surface hydroxyl groups

c)permanent negative charge arising from the isomorphic substitution of either AL3+ for Si4+ in the tetrahedral layer or Mg2+ for Al3+ in the octahedral layer

D) PH-dependent negative charge arising from deprotonation of carboxylic acid and phenolic -OH groups

e) none of the above the

C

19. Water will rise in a capillary made of glass because

a) water has a higher dielectric constant than glass

b) of adhesion between water molecules and cohesion between water molecules and glass surfaces

c) of cohesion between water molecules and adhesion between water molecules and glass surfaces

d) water is a nonpolar molecule and adhesion between glass molecules

C

20. A matric potential gradient will cause soil water to move

A) from areas of high salt content to areas of low salt content

b) in response to gravity

c) from wetter to drier soils

d) from drier to wetter soils

e) by saturated flows

C

21. The equation which best describes cation exchange at a soil colloid surface is

a) m1+m2=M3^2+

b) colloid-m1+m1=colloid-2M1

c) colloud1+colloid2=colloid1-colloid2

d) colloid-m1+m2=colloid-m2+m1

e) colloid+m1=colloid-m1

D

22. The net rate of change in the organic matter content of soil is determined by the relative rates of what two competing processes

a) photosynthesis and respiration

b) oxidation and humification

c) oxidation and reduction

d) ozonation and carbonation

e)sublimation and adulation

B

23. At which pf the following soil water potentials (expressed as kPa) is the soil water held at least tightly

a) -1500

b)-100

c)-50

d)-10

e) 0

E

Which of the following is not a characteristic of all classes of soil colloids

a) high specific surface area

b) isomorphic substitution

c) adsorption of water

d)adsorption of solutes

e) charged surfaces

B

1. cation exchange takes place on a charge-for-charge basis. This means that

a) one K+ in solution will replace one Ca2+ on the colloid

b) two K+ in solution will replace one Ca2+ on the colloid

c) one ca2+ in solution will replace one k+ on the colloid

d) one K+ in solution will replace two Ca2+ on the colloid

e) a mole of K+ ions is equivalent to a mole of of Ca2+ as far as cation exchange is concerned

B

2. According to Hillel, the near eastern goat

a) is an incorrigible overgrazer

B) is a denuder of vegetation and promoter of soil erosion

c) causes desertification

d) is a menace to civilization

e) has been unjustly vilified and condemned too harshly

E

3. All of the following are properties possessed by all the classes of soil colloids except

a) very small size

b) charged surfaces

c) adsorption of water and solutes

d) carboxylic acid functional groups

e)very high specific surface area

D

4. the surfaces of organic colloids become charged due to

a) deprotonation of carboxylic acid groups

b) isomorphic substitution

c)protonation/deprotonation of surface by hydroxyl groups

d) a combination of A and B

e) none of the above, the surfaces of the organic colloids are not charged

A

5. All of the following will have some sort of effect on the magnitude of a soil CEC except

a)clay content

b) organic matter content

c) PH

d) gravimetric water content

e) the type of clay minerals present

D

6. Isomorphic substitution of _________ for Al3+ in the octahedral layer of some 2:1 type crystalline silicate minerals causes these minerals to have permanent negative charge

A) K+

b) Si4+

c)Mg2+

d) Ni2+

e) Ca2+

C

7. Imogolite is

a) a 1:1 type crystalline silicate

a 2:1 type crystalline silicate

c) an oxide

d) a non-crystalline silicate

e) uncharged

D

8. The class of soil colloids with the highest CEC is

a) the crystalline silicates

b) the organics

c) the oxides

d) kaolinite

e)the non-crystalline silicates

B

9. noncrystalline silicate materials are particularly abundant in soils in what order

a) histisols

b) mollisols

c) andisols

d) oxisols

e) gelisols

c

10. partitioning is the process whereby

a) organic compounds distribute themselves between organic colloids and soil solution

b) colloids accumulate in certain portions of the soil profile

c) one cation replaces another cation at a charged colloid surface

d) carboxylic acid functional groups on humus lose a proton

e) phosphate forms inner-sphere complexes on oxides surfaces

a

1. all of the following are factors which effect the amount of plant available water held by soil except

a) average particle density of each horizon

b) the soil water content potential relationship for each soil horizon

c) rooting depth

d) soil bulk density in each horizon

e) soil depth (depth to bedrock)

A

2/ The two mechanisms by which plant roots are supplied with water are

a) covalent and ionic bonding

b) adhesion and cohesion

c) capillarity and root extension

d) gravity and pressure

e) hydrogen bonding and van der Waals forces

c

3. The mutual attraction between water molecules is called

a) matric potential

b) cohesion

c) adhesion

d) capillarity

e) osmosis

B

4. Water moves from areas of lower salt content to areas of higher salt content in response to

a_ hysteresis

b) a matric potential gradient

c) telekinesis

d) an osmotic potential gradient

e) preferential flow

D

5. The nonuniform movement of water and its solutes through a soil along macroporous pathways is called

a) the matric potential

b) the osmotic potential

d) the saturated hydraulic conductivity

d) referential flow

e) percolation

D

6. According to Hillel, the primary cause of soil salinization in ancient Mesopotamia was

a) irrigation without proper drainage

b) frequent floods

c) overuse of fertilizer

d) irrigation using water with a high salt content

e) climate change

A

7. The attraction of water for soil particle surfaces is an example of

a) the osmotic potential

b) cohesion

C) adhesion

d) preferential flow

e) hysteresis

C

8. the process by which water enters the pore spaces and becomes soil water is termed

a) leaching

b) percolation

c) infiltration

d) hysteresis

e) wetting front

C

9. When all the soil pores are filled with water, the soil is said to be at

a) the wilting coefficient

b) saturation

c) field capacity

d) the hygroscopic coefficient

B

10. Plant available soil water is defined as that water held between

a) saturation and field capacity

b) 0 and -10 kPa

c) field capacity and the permanent wilting coefficient

d) -1500 and -3100 kPa

C

1. The charge on soil organic matter "molecules"

a) is always negative and results from isomorphic substitution of Mg for Al

b) can either be pos or neg and results from protonation/deprotonation of surface -OH groups

c) is always pos and results from double protonation of carboxylic acid functional groups

d) is ph. dependent, always negative, and results from deprotonation of -C=O groups

e) is always zero, the molecules are uncharged

D

2. The process by which one plant infuses the soil with a chemical that effects (rather pos or neg) the growth of other plants is called

a) allelopathy

b) soil respiration

c) slaking

d) humification

e) mineralization

A

3. All of the following soil properties are influenced by the level of organic matter in the soil except

a) CEC

b) tilth

c) water holding capacity

d) structure

e) mass water content

E

4. the greenhouse gases produced by the soil are

a) carbon dioxide, carbon monoxide, and hydrogen sulfide

b) methane, ethane, and propane

c) methane, carbon dioxide, and nitrous oxide

d) ozone, nitrous oxide, and CFCs

e) CFCs, nitrous oxide, and ethane

C

5. According to Hillel, Fatehpur Sikri, the capital city built by Akbar the Great in northern India in the late sixteenth century, was abandoned less than 20 years after its completion due to

a) a regional famine

b)an undependable supply of water

c) bubonic plague

d) its destruction by invading Mongols

e) a series of earthquakes that devastated the city

B

6. The mining of peat from histisols located in Canada, Russia, and other northern countries

a) is a sustainable practice because it takes only a couple of years for the histisols to reform

b) increases carbon dioxide gas emissions to the atmosphere

c) actually decreases greenhouse gas emissions

d) increases methane gas emissions to the atmosphere

e) has no effect on the composition of the atmosphere

b

7. all of the following factors influence soil organic matter levels except

a) climate

b) texture

c) tillage

d) depth to bedrock

e) native vegetation

D

8. the overall process that results in the release of elements in inorganic forms from organic compounds is called

a) allelopathy

b) soil respiration

c) slaking

d) humification

e) mineralization

E

9. All of the following factors affect the rate of decomposition of plant residues in soils except

a) moisture content of the soil

b) the C: N ratio of the residues

c)particle size of the residue

d) lignin content of the residues

e) average soil particle density

E

10. Detritus is defined as

a_ living biomass

b) dead roots and other recognizable plant residues

c) an amorphous, colloidal mixture of organic substances no longer recognizable as tissues

d) all of the above

e) none of the above

B