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NC State Soil Science: SSC–012: Principles of Soil Science

SSC 012 Practice Exam 4

Question #1: The relatively stable colloidal fraction of soil organic matter that contributes to the CEC of soil is called

A). plant residue
B). humus
C). animal waste
D). all of the above

Question #2: A tablespoon of fertile topsoil from a garden

A). is composed of only non-living material
B). contains millions of living organisms
C). contains only a few hundred living organisms


Question #3: Mineralization of organic matter is dependent on

A). soil organisms
B). soil texture
C). neither of the above

Question #4: The rate of decomposition of organic residue depends on

A). environmental conditions
B). the C:N ratio of the material
C). neither of the above
D). both a and b

Question #5: Which organic residue has the greatest C:N ratio?

A.). pine straw
B). cow manure
C). crimson clover


Question #6: Which plant residue would decompose more rapidly and release plant available N if incorporated into the soil?

A). pine straw
B). oak leaves
C). crimson clover

Question #7: Which plant nutrient could be added to accelerate composting of a pile of grain straw?

A). adding nutrients would have no effect
B). N
C). P
D). K

Question #8: An example of important soil macrofauna are

A). bacteria
B). fungi
C). earthworms
D). none of the above

Question #9: Examples of important soil microorganisms are

A). fungi
B). bacteria
C). actinomycetes
D). all of the above

Question #10: When plant residues with a high C:N residue (e.g. wheat straw) are incorporated into soil and decomposition begins

A). plant available N is temporarily increased
B). plant available N is temporarily decreased
C). there is no effect on plant available N

Question #11: Incorporating low C:N ratio residues like crimson clover into the soil results in

A). mineralization of N
B). immobilization of N

Question #12: Advantages of applying organic wastes to soils are

A). recycling nutrients
B). disposal of waste material
C). reducing the need for synthetic fertilizers
D). all of the above
E). none of the above

Question #13: Fixation of N by organisms that live in the nodules on the roots of legumes is

A). non‑symbiotic nitrogen fixation
B). symbiotic nitrogen fixation

Question #14: Symbiotic nitrogen fixation can produce as much as

A). 100-200 lbs/ac/yr
B). 10-20 lbs/ ac/yr
C). 1-2 lbs/ac/yr

Question #15: The rate of decomposition of organic matter in soils is more rapid when the soil is

A). saturated
B). well drained
C). excessively drained

Question #16: Denitrification occurs only if

A). ammonium is present
B). nitrate is present
C). ammonium nitrate is present

Question #17: Denitrification occurs only when soil conditions are

A). saturated
B). well drained
C). aeration does not affect denitrification

Question #18: Conversion of ammonium to nitrate (Nitrification)

A). requires aerobic soil conditions
B). results in more acid soil conditions
C). both of the above

Question #19: Nitrification requires

A). the presence of oxygen
B). the oxygen supply has no effect
C). the absence of oxygen

Question #20: The source of the plant nutrients C, H. and O is

A). slow release fertilizers
B). air and water
C). phosphate fertilizers

Question #21: The form of most of the nitrogen taken up by plants growing on well drained soil is

A). N2
B). NO3-
C). NH4+
D). all of the above

Question #22: The form of potassium taken up by plants is

A). K+
B). K2O
C). potash

Question #23: The form of nitrogen in soil that is most susceptible to leaching is the

A). organic form
B). NH4+ form
C). NO3- form

Question #24: Most of the nitrogen in soils is in the

A). organic form
B). mineral form

Question #25: Nitrogen fixation refers to

A). reaction with Fe to form insoluble compounds
B). conversion of NH4+ to NO3-
C). conversion of N2 to forms that plants can utilize

Question #26: Soil phosphorus is more available for plant uptake at pH

A). 4.5
B). 6
C). pH doesn't affect P availability

Question #27: The secondary nutrient that strengthens plant cell walls is

A). P
B). Ca
C). K

Question #28: The source of nitrogen for manufacturing fertilizer and fixation by rhizobia is

A). air
B). water
C). CO2

Question #29: Sources of calcium for plants are

A). dolomitic limestone
B). gypsum
C). calcitic limestone
D). all of the above

Question #30: Source of magnesium for plants are

A). dolomitic limestone
B). gypsum
C). calcitic limestone
D). all of the above

Question #31: Leaching loss from soils in the Piedmont is more of a problem with

A). nitrate
B). ammonium
C). phosphorus

Question #32: If a plant bed is fumigated to kill soil microorganisms, Nitrification would

A). not be affected
B). increase
C). decrease

Question #33: Phosphorus fixation is more of a problem on

A). soils high in Fe and Al
B). organic soils
C). golf greens

Question #34: Plant available phosphorus

A). accumulates in mineral soils when fertilizers containing P are applied regularly over a number of years.
B). cannot be maintained because it leaches out of the root zone

Question #35: Plant available nitrogen

A). accumulates in the soil when ammonium fertilizers are applied regularly over a number of years.
B). cannot be maintained because of leaching and other losses

Question #36: Which plant nutrient moves readily with the soil water when it is in the inorganic form?

A). N
B). P
C). K

Question #37: If a soil has a pH of 5, liming will

A). increase the availability of all micronutrients except Mo
B). decrease the availability of all micronutrients except Mo
C). have no effect on availability of micronutrients

Question #38: Phosphorus is taken up by plants as an

A). anion
B). cation
C). in the organic form
D). all of the above

Question #39: Sulfur is taken up by plants as

A). elemental sulfur
B). SO4-

Question #40: Nitrogen fixation by legumes is often increased by inoculating the seed with

A). mychorrizae
B). nematodes
C). Rhizobia

Question #41: Atmospheric pollutant contribute a significant amount of this nutrient for plant uptake.

A). Ca
B). Mg
C). S

Question #42: Potassium fixation refers to

A). atmospheric deposition of K+
B). trapping of K+ ions in the interlayer space of illite
C). reaction with iron

Question #43: The amount of plant available nitrogen in the soil could be decreased by

A). ammonification
B). nitrification
C). denitrification

Question #44: Most soil phosphorus is in the

A). organic form
B). inorganic mineral form

Question #45: How many pounds of NH4NO3 (34 % N) would be required to supply 150 lbs of N?

A). 150
B). 44
C). 441

Question #46: How many pounds of 5-10-10 fertilizer would be needed to supply 150 lbs of N?

A). 3000
B). 300
C). 150

Question #47: If you applied 200 lbs of 10-20-20 fertilizer, how many pounds of nitrogen would be supplied?

A). 500
B). 20
C). 100

Question #48: A soil test report recommended 1 lb of N per 1000 sq. ft. How many pounds 10-20-20 fertilizer should be applied to each 1000 sq. ft.?

A). 10
B). 5
C). 20

Question #49: The idea of decreasing excess carbon dioxide in the atmosphere by promoting practices that increase organic matter accumulation in the soil is more likely to succeed

A). in well drained soils
B). in frequently plowed agricultural fields
C). in soils that are saturated most of the year

Question #50: The form of nitrogen that may volatilize from hog waste lagoons is

A). ammonia
B). nitrate
C). organic N


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