Soils Old Exam 2s Compilation

In an average soil, approximately (25% / 50%) of the soil as a whole is pore space shared by air and water.

50%

(Humus / hummus) is the stable portion of organic matter remaining after major portions have decomposed.

humus

The process of (photosynthesis / decomposition) recycles nutrients from organic matter for plant use.

decomposition

Soil air has far (less / more) concentrated carbon dioxide than atmospheric air.

more

(Diffusion / mass flow) drives the majority of gas exchange in soils

mass flow

Soil physical properties which readily change on short time scales and can be altered by management are (static / dynamic) properties

dynamic

B horizons are primarily colored by (iron oxides / parent material).

iron oxides

A (low / high) chroma indicates a duller soil color.

low

Water flow most quickly through (prismatic / single-grained) soil structure

single-grained

Soil (consistence / consistency) is a term used by engineers to describe ease of penetration of soil by an object.

consistency

(Particle / bulk) density is an expression of soil density which includes the volume of the soil solids only.

particle

(Micropores / macropores) are most important for water movement into and through the soil.

macropores

(Clayey / sandy) soils are likely to have the larger specific surface area

sandy

Aggregates with (high / low) stability are more prone to slaking and dispersion.

low

(Cohesion / adhesion) is the tendency of water to cling to itself.

cohesion

Dark colored soils have a (higher / lower) albedo than light colored soils.

lower

The process of water moving through the soil and carrying solutes with it is (percolation / leaching).

leaching

Exposure of an unproductive subsoil is an example of an (on-site / off-site) effect of erosion.

off-site

(Fungi / bacteria) are the most abundant organism in soil.

bacteria

Soil organisms tend to (increase / decrease) in abundance with depth.

decrease

Which of the following materials will decompose the slowest?
a. Fats
b. Cellulose
c. Sugar
d. Starch
e. Protein

b

Aggregate stability is most directly related to which soil organic matter function?
a. Provides the distinct black color of soil
b. Source of essential nutrients
c. Habitat and food source for most soil organisms
d. Contributes to retention of nutrients and contaminants
e. Improves soil physical properties

e

Which of the following is not a soil physical property?
a. Water content
b. Texture
c. Microbial activity
d. Structure
e. Temperature

c

The capacity of the soil mass to withstand stress without rupturing or becoming deformed is most directly…
a. Consistence
b. Soil bearing strength
c. Shrink-swell potential
d. Consistency
e. Density

b

Which of the following is not a means of decreasing bulk density?
a. Reduce compaction
b. Increase porosity
c. Add organic matter
d. Increase soil bearing strength
e. Improve soil structure

d

Which of the following accurately represents the size range of silt particles?
a. 0.05 to 2.0 mm
b.

d

Which of the following coarse fragments is the largest?
a. Boulders
b. Gravels
c. Stones
d. Pebbles
e. Cobbles

a

Presence of the following structure types is most likely to result in reduced air, water, and root movement?
a. Granular
b. Prismatic
c. Angular blocky
d. Platy
e. Columnar

d

Which of the following water content status indicates the lowest soil water contents?
a. Permanent wilting point
b. Field capacity
c. Oven-dry
d. Saturation
e. Gravitational

c

Which of the following water content statuses is reached once all gravitational water has drained from the pores?
a. Saturation
b. Gravitational
c. Field capacity
d. Permanent wilting point
e. Oven-dry

c

Which form of water erosion is not driven by surface runoff?
a. Rill
b. Gully
c. Splash
d. Sheet
e. All of these are driven by surface runoff

c?

Which of the following erosion controls involves the use of vegetation to slow down runoff and trap sediments?
a. Terracing
b. Retention pond
c. Sediment traps
d. Addition of soil conditioners
e. Bioengineering

e?

Which of the following is not a practice which increases soil roughness?
a. Conservation tillage
b. Wind breaks
c. Cover crops
d. Overgrazing
e. Ridging/ridge tillage

a

Which of the following forms of wind erosion involves transport of small particles over long distances vertically and horizontally?
a. Creep
b. Rill
c. Suspension
d. Saltation
e. Sheet

c

Which of the following soil organisms is capable of performing photosynthesis?
a. Cyanobacteria
b. Fungi
c. Actinomycetes
d. Protozoa
e. Nematodes

a

Which of the following soil organisms is the largest?
a. Bacteria
b. Fungi
c. Nematodes
d. Protozoa
e. Archaea

c

Which of the following describes a symbiotic relationship between a fungus and algae?
a. Mycorrhizae
b. Lichen
c. Actinomycetes
d. Cyanobacteria
e. Archaea

a

Is a dead possum lying on the soil surface considered soil organic matter? Why or why not?

no - too big

List the three steps of erosion. Which step is most important to control and why?

detachment, transportation, deposition
detachment - w/o 1st step no further erosion can occur

bulk density formula

Db = Ms / Vt

particle density formula

Dp = Ms / Vs

porosity formula

f = 1 - (Db/Dp)

gravitational water formula

water content @ saturation - water content @ field capacity

max paw formula

(WC@FC) – (WC@PWP)

current PAW formula

(current water content) – (WC@PWP)

When soil color becomes lighter, color value has (increased / decreased).

increased

A bare soil will have (more / less) dramatic temperature changes than a vegetated soil.

more

The soil (series, order) is the most inclusive (most general) grouping of soil taxonomy.

order

As soil color becomes more diluted by grey (less pure), chroma of the soil has (increased / decreased).

decreased

Water has a (higher / lower) specific heat than air.

higher

Bulk density and porosity are (directly / inversely) related.

inversely

Capillary movement is more likely when the pores are (smaller / larger) in diameter.

larger

Hydraulic conductivity is (higher / lower) when the soil is saturated than at field capacity.

higher

Soil air has a (higher / lower) concentration of carbon dioxide than atmospheric air.

higher?

Coarse textured soils have (higher / lower) specific surface area than clays.

higher?

Slaking is more likely to occur with (low / high) aggregate stability.

low

(Macro / micro) pores are most important for effective water and air flow through soil.

macro

(Consistence / consistency) means ease of penetrability of soil by an object.

consistency

When density at the surface increases, infiltration rate is likely to (increase / decrease).

decrease

A soil with a lot of organic matter at the surface will have a (lower / higher) albedo than a soil with less organic matter.

lower

Soil with more organic matter and fungal growth is likely to have (high / low) aggregate stability.

high

Soil color is always read in the order value/chroma hue.

false

Chroma refers to the purity of the soil color.

true

The three size separates which make up soil texture are sand, silt, and clay.

true

The organic fraction is the same as the mineral fraction of the soil.

false

The C horizon is most likely to be colored by parent material.

true

The coarse fragments of soil are included in soil textural determination.

false

Presence of soil crust will promote infiltration.

false

Gravitational water is available for plant use.

false

Albedo refers to the fraction of solar radiation which is reflected back to the atmosphere.

true

What is the state soil series of Texas?
a. Sunnyside
b. Port
c. Houston Black
d. Austin
e. None of the above

c

If a soil is composed of 20% sand and 60% clay, what is the % silt?
a. 10%
b. 20%
c. 30%
d. 40%
e. Excuse me…math?

b

An “ustifluvent” is found in which soil order?
a. Entisol
b. Ustisol
c. Ultisol
d. Histisol
e. None of the above

a

A “durixeralf” is found in which soil order?
a. Oxisol
b. Alfisol
c. Inceptisol
d. Aridisol
e. Entisol

b

Aridisols are known for ______.
a. Being very young
b. Shrinking and swelling
c. Forming in arid regions
d. Forming in grasslands

c

What is the size range for sands?
a.

b

How many soil orders are there?
a. 10
b. 12
c. 15
d. 22
e. None of the above

b

Which of the following is not a function of soil organic matter?
a. Source of essential elements
b. Contributes to retention of contaminants
c. Provides dark color of soil
d. Buffers against pH change
e. All of the above are functions of OM

e

Which soil order is known for being a very young soil?
a. Vertisol
b. Inceptisol
c. Aridisol
d. Ultisol
e. Oxisol

b

Which of the following terms refers to water movement through the soil carrying solutes?
a. Infiltration
b. Percolation
c. Leaching
d. Hydraulic conductivity
e. None of the above

c

When the soil is saturated, soil air is assumed to be ___.
a. 0%
b. 10%
c. 25%
d. 50%
e. 100%

a

Which soil order is known for possessing a “mollic” horizon?
a. Histisol
b. Aridisol
c. Vertisol
d. Mollisol
e. Inceptisol

d

Field capacity is typically reached…
a. Immediately following a rain event
b. 2-3 days after a rain event
c. When sunflowers wilt
d. When there is no water remaining in the soil
e. None of the above

b

What percentage of area in an average soil is comprised of air?
a. 0%
b. 10%
c. 25%
d. 50%
e. 100%

c

Which soil property refers to the water content at which soil will become like a viscous liquid?
a. Liquid limit
b. Plastic limit
c. Bearing strength
d. Plasticity
e. Stickiness

a

Which structure type is taller than wide with flat tops?
a. Granular
b. Subangular blocky
c. Columnar
d. Prismatic
e. Granular

d

Which structure type is equally wide and tall with rounded edges?
a. Angular blocky
b. Subangular blocky
c. Granular
d. Prismatic

b

Which structure type is composed of small, rounded peds?
a. Granular
b. Angular blocky
c. Columnar
d. Platy
Prismatic

a

Which of the following coarse fragments is the smallest?
a. Cobbles
b. Boulders
c. Gravels
d. Stones
e. These are all the same size

c

The A horizon is most likely to be colored by…
a. Iron oxides
b. High water table
c. Organic matter
d. Parent material
e. Crayons

c

relation ship between bulk density and compaction?

direct

Soils which are structureless are more likely to flood.

true?

You are most likely to find prismatic structure in the A horizon.

false

Plowing the soil is likely to destroy peds/aggregates.

true

A soil with high mean aggregate stability will have higher infiltration rates.

true?

A soil crust which forms at the surface is primarily composed of sand particles.

true

A soil with a higher clay content will likely have a higher consistence.

true

Soil bearing strength has little impact on structural integrity of buildings.

false

Bulk density is likely to be higher than particle density.

true

High bulk density is most desirable for crop growth.

falsw