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Quizzes - Soil Components          answers to online quiz

1. Mineral Components

The proportion of sand, silt and clay in a soil defines its:

(a)     structure

(b)     bulk density

(c)     texture

(d)     particle density

A mineral particle that has a mean equivalent diameter between 0.05 - 0.002 mm is called:

(a)     gravel

(b)     clay

(c)     silt

(d)     sand

(e)     cobblestone

Clay sized particles have a proportionally greater impact on soil properties than silt and sand sized particles because:

(a)     clay is sticky when wet and cloddy when dry.

(b)     soil porosity is higher in clay dominated soils.

(c)     clay particles have a high specific surface area

(d)     soil pores are smaller in clay dominated soils.

(e)     clay particles move through the soil

Using a textural triangle, determine the textural class name for three soils with the following particle size distribution:


% sand % silt % clay













What is the difference between particle density and bulk density of soils?

What is the relationship between the compaction of a soil and its bulk density?

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

(a)     release nutrients by mineral weathering

(b)     support bacterial growth

(c)     adsorb gases

(d)     adsorb pollutants

(e)     all of the above

Silicate minerals:

(a)     have SiO4 tetrahedron structure

(b)     have a net positive charge

(c)     are found in sand dunes only

(d)     have no impurities

(e)     have no permanent charges

Kaolinite and montmorillonite are similar in that they:

(a)     have similar CEC values

(b)     are both secondary minerals

(c)     are ferromagnesium minerals

(d)     are both feldspars

(e)     have similar shrink-swell properties

Isomorphous substitution in aluminosilicate minerals results in:

(a)     increase in positive charge

(b)     loss of K+ ions

(c)     weathering of the clay minerals

(d)     increase of cation exchange capacity

(e)     increase of internal surface area

As soils age and weather through the eons they may change from montmorillonite to kaolinite. Also, the amount of oxides increases. As soils age and follow this trend of weathering, the charge on the soil particles will:

(a)     increase

(b)     decrease

(c)     remain the same

(d)     fluctuate.


2. Organic Components

Give an example of an important member of macrofauna, mesofauna, and microfauna. Explain how their activities contribute towards an improvement of soil productivity.

Yeast are classified as _________:

(a)     bacteria

(b)     actinomycetes

(c)     fungi

(d)     algae

(e)     protozoa

Describe an activity carried out by fungi, bacteria, and actinomycetes (one for each group) that is beneficial for soil productivity.

How does soil drainage affect organic matter accumulation?

Greater microbial biomass will be found in a soil that is rich in:

(a)     montmorillonite

(b)     kaolinite

Each soil organism has an energy source. Using the lecture notes and your textbook make a list including at least six organisms you would likely observe and determine whether the organism you list is heterotrophic, autotrophic, or can be either. 

3. Soil Water

Water held in the soil between soil moisture potentials from -10 to -1500 kPa is _________ water.

(a)     gravitational

(b)     free

(c)     plant available

(d)     hygroscopic

(e)     plant unavailable

How does the structure of a water molecule influence its properties and behavior in soils?

Two soil samples, P and Q, at different soil moisture levels are placed in contact with each other. Water will more likely move from soil P to soil Q if their water potentials, expressed in kPa, are:

(a)     P= -5; Q= +5

(b)     P= -5;Q= -5

(c)     P= -20; Q= -10

(d)     P= -30; Q= -40

(e)     P= -100; Q= -50

Which soil would exhibit a higher water content at a water potential value of -1/3 bar, a sand or a clay loam? Briefly explain your answer.

Which soil would exhibit a greater hydraulic conductivity, a sand or a clay loam? Briefly explain your answer.

4. Soil Air

To increase soil aeration, it is necessary to use soil materials with:

(a)     A high content of silt size particles, and low clay and sand contents.

(b)     Equal amounts of clay, silt and cobbles.

(c)     A high organic matter and clay content, but low in sand and silt contents.

(d)     A low content of clay and silt size particles, but high content of sand.

In an ideal agricultural soil in good physical condition, approximately what proportion of the total volume is comprised of pores?

How are the proportions of soil air and soil water related?

If a soil has a bulk density of 1.4 Mg/m3 and a particle density of 2.6 Mg/m3, what portion of the soil volume is pores and what portion is solid particles?

How are soil aeration, water content and microbial activity related? 

Faculty of Land and Food Systems