Deck 4: Soil Architecture and Physical Properties

Question 1

Soil colors are scientifically described by ____ color designations such as 10YR3/4.

A)USDA
B)wavelength
C)Parson's
D)Munsell
E)structural

Answer 1

D

Question 2

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.

A)humus
B)iron
C)clay
D)silt
E)any of the above

Answer 2

C

Question 3

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

A)Clay generally promotes free water movement.
B)The subsoil may have an organic texture.
C)Prismatic structure may be well developed.
D)The water table may be present in the subsoil.
E)All of the above are common reasons.

Answer 3

C

Question 4

Which type of soil structure is typically found in surface soil (A horizons)?

A)platy
B)sub-angular blocky
C)prismatic
D)columnar
E)granular

Question 5

Because of their greater surface area per unit of soil mass,silt loams soils generally have a greater capacity than loamy sand soils to ___.

A)adsorb water
B)adsorb gases
C)release nutrients by mineral weathering
D)support bacterial growth
E)all of the above

Question 6

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

A)macropores
B)total porosity
C)bulk density
D)fineness of texture

Question 7

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)a well-aggregated surface soil

Question 8

The percentages of which soil components represent the minimum information necessary in order to determine the textural class of a soil?

A)gravel and sand
B)silt and sand
C)clay and organic matter
D)clay,water and air
E)sand,silt and clay

Question 9

A soil with a bulk density equal to 0.35 Mg/m³ is most likely what type of soil?

A)an Ultisol
B)a Vertisol
C)a compacted urban soil
D)a well-structured garden soil
E)a peat soil

Question 10

Brown and red colors in subsurface horizons are caused by __ in the soil.

A)manganese
B)aluminum oxides
C)organic matter
D)clay
E)iron oxides

Question 11

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

A)help to flocculate the soil colloids
B)stabilize macro aggregates
C)are active in the formation of soils crusts
D)create large channels that enhance water flow and aeration
E)all of the above

Question 12

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

A)10YR5/8
B)7.5YR6/2
C)2.5YR6/1
D)7.5YR2/2
E)10YR8/4

Question 13

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

A)sand
B)silt
C)clay
D)humus
E)none of the above

Question 14

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

A)humus
B)compost
C)clay
D)sand
E)either A or B

Question 15

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

A)sandy loam
B)loamy sand
C)sandy clay loam
D)loam
E)sandy clay

Question 16

Dull gray colors are characterized by _____.

A)gray hues
B)low chromas
C)high color values
D)low color values
E)mixed hues

Question 17

Which type of structure is typically found in sodium-rich sub-surface horizons?

A)platy
B)sub-angular blocky
C)prismatic
D)columnar
E)granular

Question 18

Texture describes the ____ of particles in a soil.

A)sizes
B)colors
C)arrangement
D)mineralogical makeup
E)roughness

Question 19

Colloidal properties are exhibited by the ___ fraction of soils.

A)gravel
B)sand
C)silt
D)clay

Question 20

Which of the following is not a textural class name?

A)sand
B)silt
C)loam
D)clay
E)sandy silt

Question 21

Roots of most plants have difficulty growing through soil if the bulk density is greater than 1.0 Mg/m³.

Question 22

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

Question 23

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

Question 24

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

Question 25

Soil tilth refers to _____.

A)the bearing strength of a soil under a given downward force
B)the moisture content at which a soil is best suited for tillage
C)ratio of bulk density to particle density
D)the physical suitability of a soil for plant growth
E)micro-aggregates produced as a by-product of tillage

Question 26

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 gley in the soil profile.

Question 27

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

Question 28

Fungal hyphae play an important role in stabilizing surface soil aggregates.

Question 29

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

Question 30

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

Question 31

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

Question 32

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

Question 33

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.

Question 34

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

Question 35

Proper timing of tillage is generally more difficult for a clayey than for a sandy soil.

Question 36

The plasticity index is used to determine soil texture.

Question 37

A friable soil is usually more likely to be indurated.

Question 38

Tillage when the soil is too wet is likely to increase the soil bulk density.

Question 39

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

Question 40

The difference between the liquid and plastic limits of a soil is _______.

A)that one is a moisture variable while the other is a density variable
B)that one is applicable to natural soils the other to artificial growth media
C)greater than the difference between the solid and liquid limits
D)the plasticity index
E)none of the above
True or False Questions
(Write T or F after each question. )

Question 41

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

Question 42

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

Question 43

Soil consistence changes with changes in soil water content.