Ren R 210 Module 2 practice questions

For which substance would the particle density equal the bulk density?

wet soil
organic soil
soil ped
well-aggregated surface soil
quartz pebble

quartz pebble

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

A: -100 B: -50
A: -20 B: -30
A: -5 B: +5
A: -50 B: -40
A: -5 B: -5

A: -20 B: -30

Crystalline minerals can be characterized using...

x-ray diffraction

Total cation exchange capacity can be determined using...

atomic absorption spectrophotometry

Organic matter content (% OM) in a given soil horizon can be calculated by multiplying the organic carbon (% Org C or % OC) of this horizon by...

1.72

Electric conductivity is a measure of the concentration of...

cations and anions in the soil solution

The water content of a soil at -0.033 MPa is referred to as...

field capacity

A landscape contractor wants to change the texture of a sandy clay loam soil to meet the specifications for a sandy loam. Which material should s/he mix into the soil?

silt

Particle size analysis using the hydrometer method requires two measurements: one after 40 seconds, and one after an hour. What particles are assumed to still be in suspension during the second measurement?

clay

Which factor would NOT misrepresent particle sizes during analysis?

organic matter >5%
re-suspending particles after the first hydrometer reading
taking the first hydrometer reading at 30 seconds
organic matter oxidized prior to suspension
flocculated clay particles

organic matter oxidized prior to suspension

The property of cohesion in water stems from the attraction of water molecules for soil solids.
True or False

False

The matric potiential of soil water is:
influenced greatly by the content of salts in the soil
not influenced appreciably by the force of gravity
little affected by soil solids
more negative in a sandy soil with 20 percent soil water than in a clay soil with the same water
content

not influenced appreciably by the force of gravity

For any soil, the bulk density is always lower than the particle density:
true or false

true

lsomorphous substitution in aluminosilicate minerals results in:
an increase in positive charge
a loss of K+ ions
weathering of the clay minerals
an increase of cation exchange capacity
an increase of internal surface area

an increase of cation exchange capacity

A typical example of isomorphous substitution is the substitution of:
a) two Na+ ions for one Ca2+ ion
b) one Ab+for one Si4+ in an tetrathedral sheet
c) one 02-for one OH- in a tetrahedral sheet
d) one Mg2+ for one Ab+ in an octahedral sheet
e) both answers b and d above

both answers b and d above

Raising the soil pH from 5.0 to 7.5 using limestone would produce the greatest increase in
cation exchange capacity if the soil colloids were mainly:
organic matter
smectite
kaolinite
vermiculite
all of the above would have their CEC respond equally to the same change in pH.

organic matter

The height to which water will rise in a soil above the water table is directly proportional to:
the number of negative charges in the soil colloids
the hydrogen ion concentration
the inverse of the radius (1/r) of the soil pores
the size (diameter) of the soil colloids
the amount of organic matter in the soil

the inverse of the radius (1/r) of the soil pores

The hydrogen end of a water molecule is attracted to positively charged cations such as Na+ and Ca2+:
true or false

false

Considering the soil water retention curves for a clay, a loam, and a sand, for which sample would the soil water content be the greatest at a water potential of - 3.1 MPa?

clay

The relative contribution of the pH-dependant charges to the total negative charges on a silicate
clay would be less for kaolinite than for montmorillonite:
true or false

false