Modified: 9/29/98

Example Questions: Soil Science 230

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• Basic Soils
• Land Use
• Sustainability
• Pollution

Basic Soils

1. nutrient cycling
2. humification
3. mineral weathering
4. carbon fixation

1. dissolved salts
2. primary (rock) minerals
3. clays
4. plant minerals (ash)

1. rock minerals
2. humus
3. secondary (clay) minerals
4. colonies of bacteria

1. rock cycle
2. hydrologic cycle
3. energy cycle
4. all of the above

1. respiration
2. transpiration
3. hydrolysis
4. weathering

1. humification
2. photosynthesis
3. nitrification
4. respiration

1. Ion exchange is the "decay" process that releases nutrients essential for plant growth from humus.
2. Charged atoms or ions are attracted by and loosely held to humus and clay surfaces through ion exchange.
3. Ion exchange is the central process in the rock cycle, releasing nutrients from weathered rocks and their ultimate return to rocks through sedimentation and metamorphosis.
4. Plants absorb nutrients dissolved in water by ion exchange.

1. number and thickness of soil horizons
2. soil aggregate stability
3. moisture holding capacity
4. fertility

1. Soil is located at the Earth surface; which also happens to be the upper boundary of the lithosphere, the lower boundary of both the atmosphere and the hydrosphere, and the place where most living things are found.
2. The clays and humus found in soils have a very high surface area, coated with moisture and supporting colonies of microbes and other organisms and surrounded by a moist atmosphere rich in carbon dioxide.
3. The minerals and humus in soil form a porous matrix filled with the moist respiration from a teeming ecosystem of microscopic and macroscopic organisms.
4. All of the above.

1. insects and other arthropods
2. symbiotic bacteria and fungi
3. heterotrophic bacteria and fungi
4. autotrophic algae

1. insects and other arthropods
2. symbiotic bacteria and fungi
3. heterotrophic bacteria and fungi
4. autotrophic plants

1. Because plants use carbon dioxide and produce oxygen during photosynthesis, plant roots produce none of the carbon dioxide in the soil's breath.
2. About a third of the soil's breath comes from root respiration.
3. Plant roots actively alter the surrounding soil to make it more favorable to growth.
4. The actual structure of a plant root system is influenced by its competition with the root systems other plants growing in the soil, drainage, aeration, and physical obstructions.

1. oxygen in the soil atmosphere
2. moisture in the soil pores
3. the faint light filtering into the lower soil horizons
4. partially decomposed organic matter needed for energy

1. the quantity of humus in the soil
2. the mass of plant litter on the soil surface
3. the amount of carbon dioxide produced by the soil
4. the thickness of the A-horizon

1. the depth from soil surface to bedrock
2. the water-holding capacity of the whole soil profile
3. accumulation of clay in the B horizon
4. accumulation of humus in the A horizon

1. cementing of mineral grains in the C horizon
2. accumulation of humus in the A horizon
3. accumulation of clay in the B horizon
4. formation of aggregates in the B horizon

1. Humus contents would be lower because the rate of biomass production is slower.
2. Variations in soil temperature has virtually no effect on humus content.
3. Humus contents would be higher because microbial degradation is slower.
4. There would be no humus at all in cool-climate soils, only undecomposed plant residue.

1. Concept recall: mineral weathering
2. Definition recall: primary (rock) minerals
3. Definition recall: secondary (clay) minerals
4. Comprehension: all of the above
5. Concept recall: respiration
6. Concept recall: nitrification
7. Definition recall: Charged atoms or ions are attracted by and loosely held to humus and clay surfaces through ion exchange.
8. Comprehension: fertility
9. Definition recall: All of the above.
10. Definition recall: heterotrophic bacteria and fungi
11. Definition recall: autotrophic plants
12. Comprehension: Because plants use carbon dioxide and produce oxygen during photosynthesis, plant roots produce none of the carbon dioxide in the soil's breath.
13. Comprehension: partially decomposed organic matter needed for energy
14. Comprehension: the amount of carbon dioxide produced by the soil
15. Comprehension: accumulation of humus in the A horizon
16. Comprehension: accumulation of humus in the A horizon
17. Concept Recall: Humus contents would be higher because microbial degradation is slower.

1. Wetland plants absorb water flowing through the wetland, storing it in their tissue.
2. The accumulated plant residue (peat) in a wetland soaks up water like a sponge.
3. Wetlands typically occur wherever surface water can easily flow directly into underground rock formations.
4. Wetlands lie in depressions that trap runoff the same way reservoir holds water.

1. Biological activity decreases until it reaches a minimum near 30^oC (86^oF), then it steadily increases as temperatures continue to rise.
2. Biological activity decreases steadily as temperatures rise.
3. Biological activity increases steadily as temperatures rise because optimal biological activity occurs at about 50^oC (122^oF).
4. Biological activity increases until it reaches a maximum near 30^oC (86^oF), then it steadily decreases as temperatures continue to rise.

1. It would dramatically increase biological activity because moisture most often limits biological activity in a soil.
2. It would have no effect on biological activity because water does not prevent root growth the way compaction does and plant roots do not need air.
3. The level of biological activity would slow slightly because carbon dioxide respired by soil organisms would take longer to escape from a waterlogged soil.
4. Most soil organisms require oxygen and, therefore, flooding will sharply decrease the level of biological activity.

1. uniform bluish, greenish or purplish coloring of much of the soil profile
2. uniform red, yellow or orange coloring of much of the soil profile
3. abundant plant roots throughout the A horizon
4. deep loamy texture

1. 2 H⁺
2. 2 OH^-
3. H₂CO₃
4. 3 O₂

1. It is the amount of humus in a soil.
2. It is the water-holding capacity of a soil.
3. It is the vitality of the soil ecosystem.
4. It is the absence of stones, cobbles, gravel and other large rock fragments.

1. Compaction makes the soil acidic because it traps carbon dioxide it the soil.
2. Compaction decreases the water-holding capacity of the soil.
3. Compaction makes the soil less permeable to air, decreasing aeration.
4. Compaction reduces the soil water content by squeezing water out of the soil.

1. It would acidify the groundwater, making it too acidic to drink.
2. It would dissolve soil humus, eventually leaching all humus from the soil.
3. It would accelerate mineral weathering, causing soils to age abnormally fast.
4. The acidity would decrease the general level of biological activity because most organisms are not tolerant of extreme acidity.

1. It is the collection of soils within a single drainage pattern on the landscape.
2. It is a list of soils found in a particular region without regard to their relation to one another.
3. It is the predictable pattern in the landscape occupied by a group of soils.
4. It is idea that specific properties express the location of a soil in the landscape.

1. A sequence of soils extending from an upland position to a lowland position, representing the effect of landscape topography.
2. A sequence of soils encountered as one crosses a series of climate zones.
3. A group of soils that are essentially alike in all major profile characteristics.
4. A group of soils that occur in a predictable pattern on the landscape.

1. mottling or gleying in the upper soil profile
2. humus content of the B horizon
3. soil acidity
4. the abundance of plant roots in the A horizon

1. Comprehension: Wetlands lie in depressions that trap runoff the same way reservoir holds water.
2. Comprehension: Biological activity increases until it reaches a maximum near 30^oC (86^oF), then it steadily decreases as temperatures continue to rise.
3. Comprehension: Most soil organisms require oxygen and, therefore, flooding will sharply decrease the level of biological activity.
4. Concept recall: uniform bluish, greenish or purplish coloring of much of the soil profile
5. Concept recall: 2 H⁺ (this is the acid cation)
6. Definition: It is the vitality of the soil ecosystem.
7. Comprehension: Compaction makes the soil less permeable to air, decreasing aeration.
8. Concept recall: The acidity would decrease the general level of biological activity because most organisms are not tolerant of extreme acidity.
9. Definition recall: It is the predictable pattern in the landscape occupied by a group of soils.
10. Definition recall: A group of soils that are essentially alike in all major profile characteristics.
11. Application: mottling or gleying in the upper soil profile (soil is often waterlogged)

1. the saturated water content minus the unsaturated water content
2. the water content at saturation minus the water content at the wilting point
3. the water content at field capacity
4. the water content at field capacity minus the water content at the wilting point

1. wilting point
2. saturation
3. field capacity
4. oven-dry

1. gravity gradient
2. relative-humidity gradient
3. osmotic gradient
4. matric ("dryness") gradient

1. sunset
2. when the temperature is at a maximum
3. sunrise
4. when the saturation vapor pressure P_o is at a minimum

1. thermal diffusion
2. solar radiation
3. evaporation
4. long-wavelength radiation

1. The ice in frozen soil acts as a thermal barrier and prevents heat from moving upward from the soil depths.
2. Moist soil reflects solar radiation so well that the soil absorbs very little heat.
3. Moist soil conducts heat into the soil depths so rapidly, the surface temperature is slow to rise.
4. It takes more heat to raise the temperature of moist soil than needed to raise the temperature of dry soil.

1. short-wavelength (visible) radiant energy
2. long-wavelength (infrared) radiant energy
3. sensible heat
4. latent heat

1. carbon and iron cycles
2. iron and calcium cycles
3. carbon and nitrogen cycles
4. energy and water cycles

1. the soil surrounding a root
2. a bacterial spore
3. the nodule formed by rhyzobia
4. a spherical mass of fungal mycelia

1. biological nitrogen fixation
2. mineralization
3. humification
4. nitrification

1. potassium-K
2. nitrogen-N
3. calcium-Ca
4. iron-Fe

1. leaf color
2. plant tissue damage
3. abnormal leaf or stem growth
4. reduction on plant growth

1. runoff water flowing in rills cut into the soil surface
2. gravel particles rolling over the soil surface carried by runoff
3. runoff water flowing like a uniform sheet over the soil surface
4. raindrop splash

1. removal of the humus-rich topsoil
2. exposure of a subsurface horizon that either has a high clay content or that is cemented
3. removal of nutrients in the topsoil
4. removal of the root system within the topsoil

1. Only a small fraction of the total land surface is actually used in farming.
2. Rainfall intensity and wind speed vary considerably over the landscape.
3. Soil loss usually results from improper use of highly erodible soils.
4. Most landowners use effective erosion control practices.

1. The nutrient-rich sediments stimulate the rapid algae growth that absorb oxygen from the water, killing other aquatic organisms.
2. The nutrients have no direct effect on aquatic organism because the main effect is that sediments bury bottom dwelling organisms.
3. Phosphate bound to eroded sediments is highly toxic to fish.
4. The nutrient-rich sediments stimulate the rapid algae growth, whose subsequent decomposition by microbes robs water of oxygen needed by other aquatic organisms.

1. the water content at field capacity minus the water content at the wilting point
2. saturation
3. relative-humidity gradient
4. when the saturation vapor pressure P_o is at a minimum
5. evaporation
6. It takes more heat to raise the temperature of moist soil than needed to raise the temperature of dry soil.
7. long-wavelength (infrared) radiant energy
8. carbon and nitrogen cycles
9. the soil surrounding a root
10. nitrification
11. nitrogen-N
12. reduction on plant growth
13. raindrop splash
14. exposure of a subsurface horizon that either has a high clay content or that is cemented
15. Soil loss usually results from improper use of highly erodible soils.
16. The nutrient-rich sediments stimulate the rapid algae growth, whose subsequent decomposition by microbes robs water of oxygen needed by other aquatic organisms.

1. NSP pollution occurs on flood plains where contaminants are transported large distances, PS is pollution on stable landscapes.
2. PS pollution refers to cases where the responsible party has been identified, NPS are cases where the responsible party remains to be identified.
3. PS pollution is on-site, NPS pollution is off-site (because of erosion, groundwater leaching or discharge through sewer system).
4. NPS pollution is caused by wide-spread practices of a community, PS pollution is traceable to a specific source.

1. Phosphate (PO₄^3-) is usually the nutrient limiting the growth of aquatic vegetation in freshwater systems.
2. Nitrate (NO₃^-) is highly soluble and is rapidly transported by water percolating to the groundwater.
3. Eutrophication occurs because nutrient-rich water stimulates algae to deplete the water of oxygen.
4. Biological oxygen demand indicates the likelihood that microbial activity will deplete the water of oxygen.

1. Soil loss is the sole environmental impact associated with soil erosion.
2. Soil erosion strips away nutrient-rich soil particles and carries them into lakes and streams where they cause eutrophication.
3. Eroded soil particles remain suspended in water until they enter the ocean, where they silt up shipping channels.
4. Soil erosion benefits aquatic ecosystems by providing nutrients that stimulate increased biological diversity.

1. The mass of soil is so great (2 million lbs. for a volume 200' x 200' x 1'), it dilutes contaminants.
2. Contaminant release into the atmosphere or hydrosphere is too risky, making soil the only practical alternative.
3. The solum is the zone where contaminant retention by humus and degradation by microbes is most likely.
4. Water moves more slowly through soil than through underlying sediments & rock formations.

1. Abundant emission of methane.
2. Decomposition of organic contaminants by soil microbes.
3. Rapid depletion of oxygen dissolved in soil water.
4. A sustained warming of the soil by intense microbial metabolism.

1. It is easier to perforate a plastic sheet than a clay liner.
2. Clay can adsorb contaminants as well as restrict water movement.
3. Clay is more durable than plastic.
4. Clay liners have no advantages over plastic films.

1. 0.2 meters
2. 2 meters
3. 200 meters
4. 2,000 meters

1. Contaminant binding to soil colloids promotes biological availability, accelerating the rate of contaminant decomposition.
2. Adsorption to soil colloids promotes the chemical degradation of contaminants.
3. Contaminant sorption to soil colloids retards contaminant leaching.
4. Contaminant binding has no effect on contaminant movement because the rate of exchange between bound and mobile is usually very rapid.

1. Xenobiotics are more volatile (evaporate more readily) than petrochemicals.
2. Xenobiotics tend to be more soluble in water.
3. Xenobiotics are easier to detect because they have a distinct "chemical" odor.
4. Xenobiotics resist microbial degradation because they possess chemical structures or compositions unfamiliar to organisms.

1. 1-to-1
2. 10-to-1
3. 10,000-to-1
4. 1,000,000-to-1

1. to allow carbon dioxide generated by microbes to escape from the pile
2. to allow toxic vapors to escape from the waste pile
3. to permit air to enter the waste pile and promote aerobic digestion of the waste
4. to allow methane gas generated by anaerobic microbial digestion within the pile to escape

1. The content of organic matter at the site exceeds 15-30%.
2. The content of one or more toxic elements at the site has reached their specified loading limits.
3. The population of active soil microbes drops below 1 million bacteria per gram.
4. The yield of crops grown on the land shows a 10% decline below historic yields.

1. NPS pollution is caused by wide-spread practices of a community, PS pollution is traceable to a specific source.
2. Eutrophication occurs because nutrient-rich water stimulates algae to deplete the water of oxygen.
3. Soil erosion strips away nutrient-rich soil particles and carries them into lakes and streams where they cause eutrophication.
4. The solum is the zone where contaminant retention by humus and degradation by microbes is most likely.
5. Decomposition of organic contaminants by soil microbes.
6. Clay can adsorb contaminants as well as restrict water movement.
7. 200 meters
8. Contaminant sorption to soil colloids retards contaminant leaching.
9. Xenobiotics resist microbial degradation because they possess chemical structures or compositions unfamiliar to microbes.
10. 10-to-1
11. to allow methane gas generated by anaerobic microbial digestion within the pile to escape
12. The content of one or more toxic elements at the site has reached their specified loading limits.

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