Alternate freezing and thawing of soils results in the heaving of plants and the destruction of shallow building foundations. This effect is due primarily to:
A) the wetting and drying of swelling-type clays.
B) the breaking down of soil aggregates due to freezing and thawing.
C) pressure from upward movement of water from lower horizons.
D) the hydration of adsorbed cations on the soil colloids.
E) the expansion of water when it freezes.
Question 2In various parts of the world, soil phosphorus is associated with which of the following environmental problems?
A) soil degradation because of depletion of soil phosphorus
B) eutrophication of lakes because of a build-up of soil P in the watersheds
C) toxic levels of phosphate in groundwater supplies
D) both A and B
E) all of the above
Question 3Soluble organic N compounds are taken up by plants and are lost in leaching and runoff waters.
Indicate whether the statement is true or false
Question 4The redox potential of a soil is -250 mV. Which of the following forms of the pertinent elements would you expect to find in the soil?
A) CO2 B) Mn4+ C) Fe2+ D) SO42- E) NO3-
Question 5If you owned a dairy farm with poorly drained clay soils in a humid temperate region, which of the following would be most satisfactory from the standpoint of soil aeration and temperature?
A) no-till system
B) heavy organic residues
C) conventional moldboard plow system
D) ridge-till system
E) heavy chemical fertilization
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