Before plants can absorb nitrate-nitrogen that originated from residue of a previous crop, the
following processes must have occurred: (Note: processes must be in correct sequence.)
Select one:
a. nitrification, denitrification
b. mineralization, nitrification, immobilization
c. leaching, denitrification, N-fixation
d. mineralization, immobilization, denitrification
e. mineralization, nitrification correct answers e. mineralization, nitrification
Isomorphism describes a phenomena in soils that produces
Select one:
a. acidity
b. cation exchange sites
c. high specific surface area
d. kaolinite correct answers b. cation exchange sites
Mycorrhizae primarily affect plant growth by influencing plant uptake of _____.
Select one:
a. carbon dioxide
b. nitrogen
c. phosphorus
d. water correct answers c. phosphorus
_____ is not a characteristic of soil colloids.
Select one:
,a. Low water holding capacity
b. High external surfaces
c. Ability to exchange ions with the soil solution
d. Very small size
e. Electronegative charges correct answers a. Low water holding capacity
When soil chemistry makes it more difficult for plants to grow because of zinc toxicity, the soil
is probably _____.
Select one:
a. basic
b. sodic
c. acidic
d. saline correct answers c. acidic
A 2:1 type silicate clay has one octahedral sheet sandwiched between two tetrahedral sheets.
Select one:
True
False correct answers True
Clay minerals have a net _____ charge and attract ____.
Select one:
a. negative, anions
b. negative, cations
c. positive, anions
d. positive, cations correct answers b. negative, cations
Soil phosphorus is associated with eutrophication of lakes.
, Select one:
True
False correct answers True
Active acidity has little to do with the pH of a soil sample.
Select one:
True
False correct answers False
The swelling/shrinking tendency of some silicate clay minerals is due primarily to ________.
Select one:
a. the presence of cations attracted by the negative charges on the internal surfaces
b. expansion in the width of the interlayers due to movement of larger ions such as K+
c. varying thickness of the film of water covering the external surface of the particles
d. the high Mg2+ contents in the octahedral layers
e. the movement of water molecules in and out of the interlayers of the crystal correct answers e.
the movement of water molecules in and out of the interlayers of the crystal
Liming materials neutralize soil acidity by converting the hydrogen ion into
Select one:
a. carbon dioxide
b. water
c. a basic cation
d. a reserve form of acidity correct answers b. water
The nutrient most often limiting the growth of aquatic plants and algae in unpolluted fresh water
lakes is _____.
Select one: