ESS 170 Exam 2 Study Guide

The key to preventing soil erosion by water on both farmland and landscaping job sites is ---. a. To keep the soil surface covered with vegetation. b. To provide adequate surface and subsurface drainage. c. To grade or till the soil until a smooth surface is achieved. d. To keep the soil moist (with irrigation if necessary). e. To practice good landscape sanitation by clearing away any weeds and old plant residues.

a. To keep the soil surface covered with vegetation.

Other things being equal, a soil with 30% clay of the ___ type world be expected to have the greatest phosphorus fixing capacity. a. allophanic b. 2:1 c. 1:1 d. crystalline iron oxide

a. allophanic

Phosphorus availability in acid soils is constrained by the presence of significant quantities of reactive ---? a. iron b. calcium c. magnesium d. sulfur e. boron

a. iron

Concentrated animal production as is practiced in modern industrial agriculture usually results in ---? a. nutrient excesses in the area of the livestock operation b. depletion of nutrients from the soils in the vicinity c. insufficient manure production to properly fertilize cropland on the livestock farm d. nutrient exports from the operation that exceed imports e. both c and d

a. nutrient excesses in the area of the livestock operation

The universal soil-loss equation (USLE) suggests that soil erosion loss is a product of all but one of the following factors: a. soil drainage b. climate c. slope length d. sloped steepness e. vegetative cover

a. soil drainage

When fresh plant residues are added to soils, the "priming effect" may result in the decomposition of _______. a. stable/stabilized OM b. sugars and starch c. waxes and fats d. lignin and cellulose e. proteins and other nitrogen-rich compounds

a. stable/stabilized OM

The principal form of sulfur taken up by plants is ---. a. sulfate b. sulfur esters c. sulfides d. elemental sulfur e. gypsum

a. sulfate

In most soils the overall population (numbers) of microorganisms chnages with time, generally following changes in the ---? a. supply of decomposbale organic matter b. supply of oxygen c. pore space d. avaliability or root infection sites e. concentrations of antibiotics

a. supply of decomposable organic matter

T/F: Algae are single-celled plants that function principally as primary producers in the soil ecosystem? a. true b. false

a. true

T/F: Most chemical fertilizers are inorganic salts. a. true b. false

a. true

T/F: Most micronutrients play essential roles in plant metabolism as enzyme activators. a. true b. false

a. true

T/F: Nitrogen fertilization is a signifcant cause of acidity in many cultivated soils. a. true b. false

a. true

Other things being equal, a soil with 30% clay of the ___ type world be expected to have the greatest potassium fixing capacity. a. allophanic b. 2:1 c. 1:1 d. crystalline iron oxide

b. 2:1

The sites in certain clay minerals which fix potassium ions are also capable of fixing which other ion? a. NO3- b. NH4+ c. H2PO4- d. Ca2+ e. H+

b. NH4+

Many members of which group of soil microorganisms are anaerobic heterotrophs? a. actinomycetes b. bacteria c. fungi d. both a and c e. all of the above

b. bacteria

Oxidation or reduction of inorganic soil constituents such as iron and sulfur is carried out by members of which group(s) of microorganisms. a. actinomycetes b. bacteria c. fungi d. a and c e. all of the above

b. bacteria

T/F: Mycorrhizae do not normally kill their host plants, nut merely reduce the efficiency of the plant root system. a.. true b. false

b. false

T/F: Mycorrhizae involve a symbiotic combination of certain bacteria and plant cells. a. true b. false

b. false

T/F: The cation exchnage capacities of alkaline soils are commonly lower than those of comparable soils in humid regions. a. true g. false

b. false

T/F: The deeper that they are placed in the soil, the more rapidly organic compounds such as pesticides are decomposed by the soil microflora. a. true b. false

b. false

T/F: The total number of microorganisms in a hectare of soil is far greater than the number of macroorganisms, but the reverse is true for biomass of the two groups. a. true b. false

b. false

Of the macronutrients, which can be most correctly said to be a renewable resource? a. potassium b. nitrogen c. phosphorus d. calcium e. iron

b. nitrogen

The electronegative charge on 2:1 type silicate clays is due primarily to ___. a. ionization of surface OH groups b. substitution of one metallic atom for another in the crystal structure of the clay c. the extremely small size of the individual colloid particles d. the effect of pH on the presence of H+ ions in the exchange complex e. the preponderance of tetrahedral sheets compared to octahedral sheets

b. substitution of one metallic atom for another in the crytsal structure of the clay

In humid regions repeat applications of limestone are needed after a few years primarily because of ---? a. the release of aluminum ions from the structure of silicate clays b. the annual loss of calcium and magnesium in drainage waters c. increases in soil acidity from acid rain d. increased rates of formation of carbonic acid (H2CO3) e. increases in phosphate fertilization

b. the annual loss of calcium and magnesium in drainage waters

The swelling/shrinking tendency of some silicate clay minerals is due primarly to --- ? a. the presence of cations atrracted by the negative charges on the internal surfaces b. the movement of water molecules in and out of the interlayers of the crystal c. varying thickness of the film of water covering the external surface fo the particles d. expansion in the width of the interlayers due to movement of larher ions such as K+ e. the high Mg2+ contents in the octahedral layers

b. the movement of water molecules in and out of the interlayers of the crystal

In explaining erosion processes to a friend, which of the following would you say about accelerated erosion? a. It refers to sediment carried by water flowing at even greater velocity. b. It involves a much less rapid process than geological erosion. c. It is greatly enhanced by the splash effect of raindrops impacting bare soil. d. It is increasing in intensity in the United States, especially in the past 10 years. e. It removes more nitrogen from the surface soil than calcium.

c. It is greatly enhanced by the splash effect of raindrops impacting bare soil.

Nearly all organic compounds from which living beings are made have as their backbone, chains or rings of --- atoms. a. aluminum b. oxygen c. carbon d. nitrogen e. none of the above

c. carbon

Loss of P to groundwater is likely to be most signifcant for which type of soil? a. highly weathered tropical soil b. silt loam soils formed in windblown loess c. cultivated organic peat soils d. sandy soils under pine forests e. calcareous soils

c. cultivated organic peat soils

You find that the CEC of a sandy loam soil at pH 5.0 is 8 cmolc/kg and at pH 8.2 it is 14 cmolc/kg. What is the most likely reason for this difference? a. increase in the pH-dependent charges on 2:1 type silicate clays b. removal of Al3+ ions from the exchange complex at higher pH c. ionization of carboxyl and phenolic groups to release H+ ions d. removal of Al atoms from the tetrahedral layers at low pH e. replacement of trivalent Al3+ ions with divalent Ca2+ ions at high pH

c. ionization of carboxyl and phenolic groups to release H+ ions

Which of the following human actions is most apt to result in a long term increase in soil pH? a. application of NH4- containing fertilizers b. application of farm manure c. irrigation with high sodium salt-containing waters d. emission of gases from automobiles e. application of unlimed sewage sludge

c. irrigation with high sodium salt-containing waters

If you were looking for a soil with high cation exchange capacity and were not concerned with the soil's physical properties, which of the following would most likley fit your needs. a. Aridisol b. Oxisol c. Vertisol d. Mollisol e. Ultisol

c. vertisol

A cover crop is usually grown for the purpose of ---? a. improving soil quality b. saving or recycling nutrients c. covering expenses for pollution control measures d. a and b e. all of the above

d. a and b

Members of this microbial group are responsible for a major proportion of the nitrogen fixed globally in symbiosis with higher plants. a. actinomycetes b. bacteria c. fungi d. a and b e. all of the above

d. a and b

The fungal symbiont generally benefits from the mycorrhizal relationship by obtaining --- from the higher plant. a. water b. phosphorous c. micronutrients d. a-c e. none of the above

d. a-c

Plants obtain nitrogen from the soil by taking up ---. a. soluble anions b. soluble cations c. soluble organic compounds d. all of the above e. none of the above

d. all of the above

The sulfur dioxide in the atmosphere ---. a. can be an important source of sulfur nutrition for plants b. is a major contributor to acid rain c. comes from fires such as fossil fuel burning, volcanoes and forest fires d. all of the above e. none of the above

d. all of the above

Which of the following is (are) major sources of the carbon dioxide now being added to the atmosphere in the excess of the amount taken out by plants? a. loss of soil organic matter b. burning of fossil fuels c. destruction of natural forests d. all of the above e. none of the above

d. all of the above

Which of the following is a greenhouse gas contributed to the atmospher by soils? a. nitrous oxides b. carbon dioxides c. methane d. all of the above e. none of the above

d. all of the above

Organisms which use carbon dioxide or carbonated for their carbon source and either sunlight or inorganic chemicals for their energy source are called ---? a. facultative anaerobes b. heterotrophs c. detritivores d. autotrophs e. actinomycetes

d. autotrophs

In order for nitrate to form from soil organic matter, ___ must be present in the soil. a. nitrosomonas b. nitrobacter c. either A or B d. both A and B e. none of the above

d. both a and b

In various parts of the world, soil phosphorus is associated with which of the following environmental problems? a. soil degradation because of depletion of soil phosphorous 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

d. both a and b

Compared to land that is not disturbed by tillage, conventionally plowed cropland usually loses much more ---. a. dissolved P b. particulate P c. total P d. both b and c are correct e. none of the above is correct

d. both b and c are correct

One would expect well drained soils to have the highest organic matter contents where the climate is ____. a. warm and dry b. warm and humid c. cool and dry d. cool and humid

d. cool and humid

Anaerobic decomposition of organic wastes in landfills results in the production of ___ gas which is often recovered and used. a. ethylene b. oxygen c. ozone d. methane e. all of the above

d. methane

Which of the following groups of organisms are responsible for greatest amount of organic matter decomposition in soils? a. macrofauna b. microfauna c. mesofauna d. microflora e. autotrophs

d. microflora

In nature, beneficial mycorrhizae form with the roots of ---? a. coniferous trees b. grasses c. legumes d. broad leaf trees e. all of the above

e. all of the above

The active fraction of soil organic matter largely accounts for which of the benefits of adding organic matter ot soils. a. increased CEC b. increased water holding capacity c. increased microbial activity d. increased aggregate stability e. both c and d

e. both c and d

Which of the following is not a characteristic of soil colloids? a. vary small size b. high external surfaces c. electronegative charges d. ability to exchnage ions with the soil solution e. low water holding capacity

e. low water holding capacity

The process of ___ releases soluble nitrogen as the result of the breakdown of nitrogen-rich organic compounds. a. nitrification b. denitrification c. symbiosis d. volatilization e. mineralization

e. mineralization

The great majority of nitrogen (95 to 98%) in soils can be found in the form of ___ ? a. primarly minerals b. secondary minerals c. dissolved cations d. dissolved anions e. organic compounds

e. organic compounds

Soils rich in which type of clay would provide the most troublesome site on whhich to build a home? a. Fe, Al oxides b. kaolinite c. fine-grained micas d. chlorite e. smectite

e. smectite