SSC200 Final Exam

(T/F) Where organic matter constitutes only 1 or 2 percent of the soil by weight, it has only negligible influence on soil properties.

FALSE

(T/F) A polypedon or individual soil is a group of closely related pedons that conceptually approximates what in the United States is called a soil series.

TRUE

(T/F) A significant portion of the global production of methane comes from the activity of termites.

TRUE

(T/F) A soil developed in residual parent materials will likely have properties related to the properties of the rock below the C horizon.

TRUE

(T/F) Algae are single-celled plants that function principally as primary producers in the soil ecosystem.

TRUE

(T/F) An aquic soil moisture regime connotes a higher degree of soil moisture saturation than an ustic one.

TRUE

(T/F) Capillary movement is made possible by the processes of cohesion and adhesion.

TRUE

(T/F) The polarity of water helps account for the attraction of water molecules for each other.

TRUE

A soil pedon is ________.

a three-dimensional unit that embodies the primary characteristics of an individual soil.

Which of the following locations in the United States would have the highest evaporation (E) from the soil surface in July?

an irrigated cotton field in Arizona

Alcohols, methane and organic acids of various kinds often accumulate as a result of ________ decomposition of residues in soil

anaerobic

The presence of rocks such as shale and sandstone indicate the existence of __________.

ancient seas

Which type of structure is typically found in sodium-rich sub-surface horizons?

columnar

The subsoils horizons are important for plant available water storage, therefore they should have a high proportion of _____.

mesopores

Compared to upland soils, wetland soils would be characterized by an abundance of ________.

methane

Which of the following groups of organisms are responsible for greatest amount of organic matter decomposition in soils?

microflora

Humic substances consist of ________.

polymerized, non-identifiable molecules

Practices that add organic matter and reduce tillage can be expected to most significantly increase the ________ in a soil.

porosity

The addition of large quantities of plant residues to the soil generally ________ the incidence and severity of soil-borne plant diseases.

reduces

(T/F) Soil, like the concrete and steel, is a standard construction material. Its properties are well characterized and predictable so that standard building foundation designs can be used uniformly as all building sites of a given topography.

FALSE

Which mineral is more resistant to weathering under humid temperate conditions?

Gibbsite

Which type of structure is never found in subsoils?

Granular

Which of the following is a direct measurement of water content?

Gravimetric determination

If the soils are to be used for crop production, for which soil order would land drainage be most critical?

Histosols

Igneous, sedimentary, and metamorphic are three _________.

types of rocks

A soil has a thick black A horizon, a distinct B horizon, has reasonably stable soil structure, and was formed under grassland natural vegetation. In which suborder is it most likely classed?

udolls

Soil occupies the _______ part of the regolith.

upper

The evapotranspiration (ET) from a pine forest was found to be 50 cm during a growing season. If the evaporation from the soil surface during this period of time was 5 cm, what is the level of loss from leaf surfaces?

45cm

In a given soil, the horizon with the highest organic matter content is generally the ________ horizon.

A

Conceptually, a soil might progress in development through which list of soil orders?

Alfisol, Ultisol, Inceptisol

The E horizon is

All of the above

Silicate clay accumulation is most common in the _______.

B horizon

Which soil structure is most likely to be found in the B-horizon of a mature soil profile?

Blocky

Foot traffic in a lawn on wet soils may cause _____.

Bulk density to increase

In soils of which great group would you most likely find wide surface cracks during periods of dry weather?

Calciusterts

The mixed angular gravel, rock, and soil found at the foot of a slope is typical of what type of parent material?

Colluvial

Loose, hard, plastic and firm are terms that describe _____.

Consistence

Soils in which of the following suborders would be more likely to occur in Minnesota than in Texas?

Cryolls

There are six soil master horizons, each designated by a different capital letter. The O horizon is a highly organic layer that forms at the soil surface, e.g.,under forest vegetation. The R horizon is the bedrock horizon. Which of the following is not one of the other four master horizons?

D

Which soil profile horizon will be formed as a result of intense eluviation processes and be typical of Spodosols?

E

In which of the following soil orders would recent alluvium most likely be a common parent material?

Entisols

In which soil orders would recent alluvium most likely be common parent material?

Entisols

(T/F) Roots of most plants have difficulty growing through soil if the bulk density is greater than 1.0 Mg/m3.

FALSE

(T/F) Sandstones are good examples of igneous rocks.

FALSE

(T/F) Sandy soils generally are higher in organic matter than fine textured soils.

FALSE

(T/F) Soils classified as Inceptisols have the least well developed profiles of those in any order in the Soil Taxonomy system.

FALSE

(T/F) The plasticity index is used to determine soil texture.

FALSE

(T/F) For agricultural use in a given region, a soil with an ochric epipedon could generally be expected to be more productive than one with a mollic epipedon.

FALSE

(T/F)Earthworms generally are most abundant in sandy, acid soils typically under coniferous forest vegetation.

FALSE

The categories of Soil Taxonomy can be listed from the broadest (first) and most specific (last) as: order, suborder, great group, subgroup, series, family.

FALSE

While many organisms depend on the soil for nutrients and water, only a few very specialized organisms live in the soil itself.

FALSE

(T/F) Light colored surface soils are likely to be warmer than dark-colored surface soils if soil moisture and other conditions are the same.

False

(T/F) Termites tend to enrich soils in the tropics much the same way as earthworms do in temperate region soils.

False

Investigating the soils of northern Canada on summer, you dig a soil pit easily through fairly uniform peat material until, at 75 cm deep, your shovel hits a layer that is frozen solid. Into which type of soil are you most likely digging?

Histel

Select the appropriate soil order: Organic soils that are not frozen.

Histosols

Soils with thick horizons consisting mainly (> 30% by weight) of organic matter and that form in topographic depressions or low-lying places usually belong to the order ________.

Histosols

If the average transpiration (T) loss from leaf surfaces in a particular watershed is 10 mm/day, you expect the evaporation (E) from the soil surface to be ________.

Impossible to calculate from the data given

The following are characteristics of a water molecule.

It has a positive and a negative side.

Which of these properties about a tillage pan is false?

It is permanent and cannot be corrected with deep tillage.

Select the correct order of increasing bulk density (low B.D. to high B.D.) _____.

Loose clay, loose sand, compact sand, compact clay

Plant macronutrients

N P K Ca S Mg B Cl Mn Fe Zn Cu Mo Ni

Which six macronutrients are obtained primarily from the soil?

N, P, K, Ca, Mg, S

Soil colors are scientifically described by ________ color designations such as 10YR3/4.

Parson's

Select the appropriate structure: Vertical orientation. Can be found in the subsoils in humid regions. Lacks the salt "cap" typical of a similarly shaped unit of structure. Not ideal for plant growth.

Prismatic

Soils in this order are commonly sandy in texture, quite acidic and develop primarily under coniferous trees in cool to cold climates.

Spodosols

(T/F) A soil on the south facing slope in Canada is likely to be drier and warmer than a comparable soil on a north facing slope.

TRUE

(T/F) Examples genetic horizons include Ap, E, & Bt.

TRUE

(T/F) Water molecules have polarity because the electrons are not uniformly shared between the two H atoms and one O atom.

TRUE

(T/F) Water will move from one site in a soil with a higher water potential to an adjacent site with a lower water potential.

TRUE

(T/F) Well aerated soils enriched with organic amendments can help reduce the methane load in the atmosphere.

TRUE

Soils in which of the following soil suborders would most likely have a prominent E horizon under the A horizon?

Udalfs

Of these suborders listed below, which would be representative of a mature soil.

Udult

Argillic horizons are characterized by ________.

accumulation of silicate clays

Which of the following diagnostic horizons would likely not restrict root growth in soils?

albic

Which of the following is (are) major sources of the carbon dioxide now being added to the atmosphere in excess of the amount taken out by plants?

all of the above

Which of the following describes a soil that likely exists and contains a significant content of low activity clays?

an Ultisol in the Congo River basin in Africa

Residual parent materials would most likely be found _____.

at the summit of a steep hill

Many members of which group of soil microorganisms are anaerobic heterotrophs?

bacteria

Brown and red colors in subsurface horizons are caused by _____ in the soil.

clay iron oxides

Which of the following sources of water have the shortest average residence time?

clouds

One would expect well drained soils to have the highest organic matter contents where the climate is ________.

cool and humid

Which of the following processes are most apt to encourage good soil aeration?

creation of macropores

Soil detritivores feed principally on ________.

dead tissues

Detritus consists of ________.

dead tissues and wastes

If you wanted to find a soil where physical weathering dominated over chemical breakdown you would be most apt to find it in _____________.

desert region of Arizona

The bulk of gaseous interchange in soils takes place by ________.

diffusion

Pesticides, excess plant nutrients and waste chemicals most likely to move through soils in the _____ water.

gravitational

The greatest chemical weathering occurs on soils located in what climate?

hot & moist

One method for determining the percent sand, silt and clay is called the _____ method.

hydrometer

Capillarity in soils ________.

involves both adhesion and cohesion

Brown and red colors in subsurface horizons are caused by ________ in the soil.

iron oxides

Land drainage is beneficial because ________.

it increases the depth of root penetration in the soil

Biomass consists of ________.

living organisms and cells

Compared to the bulk soil in which the earthworms live, earthworm casts contain ________.

more of most plant-available nutrients

Which of the following is not a major factor in determining the soil aeration status?

nitrogen gas

The matric potential of soil water is ________.

not influenced appreciably by the force of gravity

Which of the following subsurface diagnostic horizons would you expect to find in a highly weathered soil of the humid tropics?

oxic

Which of the following actions would best assure good aeration in a soil?

remove excess water

Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the use of a drying oven and balance?

requires "destructive sampling" for each measurement

A landscaping contractor wants to change the texture of a silt loam soil to meet the specifications for a loam. S/he would most likely do so by adding ________ to the soil and mixing it well.

sand

Which of the following categories of Soil Taxonomy provides the greatest specificity of soil properties?

series

The percentages of which soil components represent the minimum information necessary in order to determine the textural class of a soil?

silt and sand

Texture describes the _____ of particles in a soil.

sizes

Compared to finer textured rocks, those with coarser texture (larger crystals) are expected to have

slower rates of weathering

Which of the following pools contain the largest amount of the world's carbon?

soil

Most of the different nutrients essential for growth are supplied to plants directly from the __________.

soil solution

The amount of different sizes or mineral particles in a soil defines the soil _______.

texture

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 ________.

the expansion of water when it freezes

The likelihood of polluting groundwater with pesticides and plant nutrients is enhanced by ________.

the presence of macropores in the soil

The redox potential is a measure of ________.

the tendency of a substance to accept or donate electrons

Which of the following will not increase the efficiency of water use by plants in an irrigation system?

the use of flood irrigation for forage crops

If you dug a deep hole in your back yard and water started to seep into the hole it would fill the hole up to ________.

the water table

Which of the following statements concerning applications or capabilities of soil moisture measuring devices is (are) true for the electrical resistance block?

used to turn on irrigation when soil moisture potential reaches -200 kPa

Which of the following best characterizes the field capacity of a soil?

water content of a soil 24 hours after a saturating rain

In a typical mineral soil in optimal condition for plant growth, approximately what percentage of the pore space would be filled with water and what percentage filled with air?

50% water and 50% air

Soil organic matter consists of ________.

All of the above

(T/F) Plant roots gain access to soil water primarily by the growth of the roots into moist soil.

FALSE

(T/F) Polysaccharides produced by soil microbes and similar synthetic polymers applied to soils are largely responsible for the crusts that form when rain follows tillage.

FALSE

(T/F) Practices that increase the soil organic matter level generally have favorable effects on the chemical and biological properties of soils, but have little or no effect on soil physical properties.

FALSE

(T/F) Reduced forms of iron and manganese along with soil organic matter largely control the color of well-drained soils.

FALSE

(T/F) Removing all the straw with the harvest of paddy rice would increase the amount of methane produced by the paddy soil microorganisms.

FALSE

(T/F) Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes carbon dioxide.

FALSE

(T/F) The topmost horizon in the most cool-humid forest soils is the A horizon.

FALSE

(T/F) The water potential in soils is generally considered lower than that in the atmosphere.

FALSE

(T/F) Vapor loss from a south-facing slope in Australia would likely be higher than from a north-facing slope.

FALSE

(T/F) Subsoil is typically equivalent to the O horizon.

FALSE

The nomenclature of Soil Taxonomy is characterized by all but which one of the following statements?

The names give a clear indication of the modes of genesis of the soil.

The atmosphere is made up of

air

Which soil moisture regime has the highest soil moisture levels?

aquic

Nearly all organic compounds from which living beings are made have as their backbone, chains or rings of ________ atoms

carbon

A sticky, putty-like feel indicates a high percentage of which soil separate?

clay

Urban development of land that was previously natural vegetation or farm lan usually greatly ________ soil infiltration capacity and therefore greatly increases ________.

decreases; stream bank erosion.

Where high-value crops or individual ornamental shrubs are to be grown and water is expensive, the most efficient type of irrigation to use would be ________.

drip or trickle

Increasing the organic matter content of a soil is likely to ___________.

increase the soil's water holding capacity

Dull gray colors are characterized by ________.

low chromas

In which of the following epipedons is the organic matter level generally lowest?

ochric

Select the appropriate soil order: A true B horizon is present. The subsoil has a base saturation greater than 35%.

Alfisols

Organic parent materials are formed under the following conditions:

All of the above

(T/F) A pedon is a three-dimensional field unit occupying about 10,000 square meters (1 hectare) of land area.

FALSE

(T/F) All but a few nematodes are pests, attacking either economic or wild plants.

FALSE

(T/F) All particles greater than 2.0 mm in diameter are collectively called silt.

FALSE

(T/F) Allelopathic chemicals, once added to soil, usually make the affected soil unsuitable for any plant life for periods of years.

FALSE

(T/F) Alluvial parent materials are those that have been laid down in former lake bottoms.

FALSE

(T/F) Although the total soil water content of a clay soil is about the same as a nearby well structured silt loam, the clay will likely provide more available water to plants because of its higher volume of small pores.

FALSE

(T/F) Aridisols generally contain more organic matter than Mollisols.

FALSE

(T/F) As decomposition of added organic material proceeds, the C/N ratio in the remaining undecomposed material steadily increases.

FALSE

(T/F) Because soil development is just beginning in Entisols, these soils are generally less variable in properties than are those in the Andisol or Ultisol orders.

FALSE

(T/F) Certain soil fungi and actinomycetes are known to produce specialized organic compounds that inhibit or kill other, competing microorganisms in the soil, but so far scientists have not been able to put any of these compounds to practical use.

FALSE

(T/F) Epipedons are diagnostic subsoil horizons that are one of the primary means of classifying soils in the United States.

FALSE

(T/F) Examples genetic horizons include kandic, spodic, ochric, mollic and oxic.

FALSE

(T/F) Except for some kinds of foods, modern industry has made human dependence on soils a thing of the past.

FALSE

(T/F) For any soil, the bulk density is always lower than the particle density.

FALSE

(T/F) For most soils, plowing every year improves soil tilth in the long run.

FALSE

(T/F) Hysteresis is the phenomenon whereby a soil has the same water content/potential relationship when it is being dried as when it is being wetted.

FALSE

(T/F) In most B horizons one of the dominant processes of soil formation has been eluviation.

FALSE

(T/F) Mycorrhizae do not normally kill their host plants, but merely reduce the efficiency of the plant root system.

FALSE

(T/F) Mycorrhizae involve a symbiotic combination of certain bacteria and plant cells.

FALSE

(T/F) Natural soils (as opposed to modern farm soils) can recycle organic compounds, but not inorganic elements.

FALSE

(T/F) Organic matter is more resistant to decay than iron oxides.

FALSE

(T/F) Research has shown that most herbicides and insecticides used in agriculture drastically reduce the numbers of living meso- and microorganisms in soils for several years after the application of these chemicals.

FALSE

(T/F) Soils in the Oxisols order are deeply weathered and have deep subsurface horizons of calcium oxide.

FALSE

(T/F) Spodosols are generally less acidic and less sandy than are Alfisols.

FALSE

(T/F) Sprinkle irrigation is generally more efficient in the use of water than drip irrigation, especially for high valued crops.

FALSE

(T/F) Subsoiling is a primitive deep tillage technique that results in extremely high subsoil bulk density.

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.

FALSE

(T/F) The great bulk of gaseous interchange between the soil pores and the atmosphere occurs by mass flow of the concerned gases.

FALSE

(T/F) The hydrogen end of a water molecule is attracted to positively charged cations such as Na+ and Ca2+.

FALSE

(T/F) The property of cohesion in water stems from the attraction of water molecules for soil solids.

FALSE

(T/F) The soil water potential is a measure of the potential of a soil to hold water.

FALSE

(T/F) The tenacity with which water is held in soils is directly related to the soil moisture content, the higher the moisture level the greater the attraction of the water to the soil.

FALSE

(T/F) Weathering rocks usually is most intense in the center of a rock fragment, and gradually decreases toward the outside.

FALSE

(T/F) Where conditions are favorable, earthworms are known to add several hundred kg/ha of several important nutrients to the soil system.

FALSE

The following is a list of elements required for the completion of a plant's life cycle. Which element is shown in its reduced form?

NH4+

A soil with 45% sand will _____.

No way to determine with the data provided

In many soil profiles, the subsoil is high in clay, but is also quite permeable to percolating water. Why?

Prismatic structure may be well developed.

Soil scientists from which country first conceived the idea that soils were natural bodies?

Russia

(T/F) An argillic horizon is a diagnostic horizon characterized by the subsurface accumulation of silicate clays.

TRUE

(T/F) Animals, insects and worms affect soil formation primarily by mixing the soil, which increases the porespace where air and water move.

TRUE

(T/F) Climate influences not only the rate of weathering but the type of native vegetation dominant in an area.

TRUE

(T/F) Conservation tillage is not practical in some areas of the Northern part of the United States because the practice lowers the surface soil temperature in the spring of the year.

TRUE

(T/F) Drip irrigation would more likely be used in the production of apples or peaches than in the production of wheat.

TRUE

(T/F) Due to differences in soil drainage, proper timing of tillage is generally more difficult for a clayey than for a sandy soil.

TRUE

(T/F) Early snowfall that arrives before the cold winter weather has frozen the soil generally increases the penetration of water into the soil.

TRUE

(T/F) Evaporation from the soil surface (E) is determined to a large degree by soil surface wetness.

TRUE

(T/F) Examples of genetic horizons include R, E, O, B, C & A.

TRUE

(T/F) Flocculation is the process by which certain chemicals promote the aggregation of small, clay-size particles into larger particles.

TRUE

(T/F) Histosols generally have higher organic matter contents than Mollisols.

TRUE

(T/F) Humus is an important nutrient, essential for healthy plants.

TRUE

(T/F) In humid regions most rainwater that soaks into the soil and is not used by plants eventually flows into rivers and streams.

TRUE

(T/F) Microbial metabolism in the guts of termites and in waterlogged soils are two major sources of excess methane that is contributing to the global greenhouse effect.

TRUE

(T/F) Mineralization of soil organic matter results in the addition of inorganic nutrient ions to the soil solution.

TRUE

(T/F) Mollisols are characterized by a deep epipedon that is high in organic matter.

TRUE

(T/F) Most anaerobic organisms in soils are bacteria.

TRUE

(T/F) Most irrigation systems are very inefficient with less than half the water that is taken from streams ever reaching the plants.

TRUE

(T/F) Most of the water flowing in the rivers passed through a soil profile or over soil surfaces before reaching the river.

TRUE

(T/F) Most soil organisms are heterotrophs.

TRUE

(T/F) Of all the groups of soil organisms, bacteria have the most diverse metabolic capabilities.

TRUE

(T/F) Organic matter distribution in the soil is a significant criterion for differentiating epipedons.

TRUE

(T/F) Osmotic and matric potentials are commonly negative because the soil water has a lower energy level than that of pure water.

TRUE

(T/F) Plant roots are an important source of carbon for many soil organisms which are beneficial to plants.

TRUE

(T/F) Plants can be grown without soil.

TRUE

(T/F) Poorly drained soils generally contain more organic matter than well drained soils.

TRUE

(T/F) Residual parent materials have formed in place and have not been transported from one area to another.

TRUE

(T/F) Russian scientists were the first to develop the concept of soils as natural bodies.

TRUE

(T/F) Soil air usually has a higher carbon dioxide content than the air in the atmosphere.

TRUE

(T/F) Soil and crop management generally has a greater influence on evaporation from the soil surface (E) than on transpiration (T) from leaf surfaces.

TRUE

(T/F) Soil consistence changes with changes in soil water content.

TRUE

(T/F) Soil microorganisms often compete with higher plants for mineral nutrients, such as nitrogen.

TRUE

(T/F) Soils of good tilth and high productivity are usually characterized by stable aggregation and a high percentage of macropores.

TRUE

(T/F) The A horizons are more apt to be cultivated than the E horizons.

TRUE

(T/F) The adsorption of water on soil surfaces encourages capillarity.

TRUE

(T/F) The alternate freezing and thawing of soils results in the upward heaving of plants and building foundations.

TRUE

(T/F) The broadest category of classification in Soil Taxonomy specifies 12 soil orders, 11 of which are for mineral soils.

TRUE

(T/F) The drainage class of a soil (the degree to which the soil becomes water-saturated during the year) can be judged by the presence and location of gley in the soil profile.

TRUE

(T/F) The family category focuses on properties affecting plant roots and suitability for engineering uses of soils.

TRUE

(T/F) The leaf area index significantly affects the solar radiation reaching the soil surface.

TRUE

(T/F) The matric potential is due to the attraction of water molecules to soil solid surfaces.

TRUE

(T/F) The most important management factors influencing soil aeration in well-drained soils are those that determine the volume of the soil's macropores.

TRUE

(T/F) The osmotic potential is dependent upon the presence of salts and other solutes in the soil.

TRUE

(T/F) The partial pressure (i.e. concentration) of CO2 in the soil pores is higher than the partial pressure of this gas in the atmosphere.

TRUE

(T/F) The pollution of ground water is often increased by the presence of macropores in soils.

TRUE

(T/F) The soils of the world contain more carbon than all the world's vegetation and the entire atmosphere, combined.

TRUE

(T/F) The two most significant characteristics of the classification system used in the United States are a unique system of terminology and focus on measurable soil properties as a primary basis for the classification.

TRUE

(T/F) Tillage when the soil is too wet is likely to increase the soil bulk density.

TRUE

(T/F) Total soil water potential is a function of gravitational potential, osmotic potential and matric potential.

TRUE

(T/F) Vertisols are characterized by high contents of swelling-type silicate clays.

TRUE

(T/F) You would be more apt to find an Gelisol in Alaska than in Iowa.

TRUE

(T/F) If supplied with a suitable nutrient solution and a mechanism for physical support, plants can grow normally without any soil at all.

TRUE

(T/F) Oxisols are more highly weathered than are the soils of any other order.

TRUE

(T/F) Practices that tend to increase the amount of organic matter in soils would be expected to reduce the global greenhouse effect.

TRUE

Weathering of primary minerals to form secondary minerals is an example of what type of soil-forming process?

Transformations

There are four general developmental processes that result in the genesis of soil. Which process best describes eluviation?

Translocations

(T/F) Fungal hyphae play an important role in stabilizing surface soil aggregates.

True

A soil with a bulk density equal to 0.35 Mg/m3 is most likely what type of soil?

a peat soil

Disease suppressive soil often results from ________.

adding organic materials to the soil that stimulate diverse microorganisms

Because of their greater surface area per unit of soil mass, silt loams soils generally have a greater capacity than loamy sand soils to ________.

all of the above

The water in the soil typically differs from pure water because the soil water __________.

all of the above

Which of the following is a greenhouse gas contributed to the atmosphere by soils?

all of the above

Which of the following practices is(are) useful in stabilizing surface soil structure?

all of the above

Soil scientists generally map the soils in a landscape by sampling the soil in _________.

auger holes made mostly near expected soil boundaries

Organisms which use carbon dioxide or carbonates for their carbon source and either sunlight or inorganic chemicals for their energy source are called ________.

autotrophs

Colloidal properties are exhibited by the ________ fraction of soils.

clay

If a dry soil high in certain types of ________ is moistened, it is likely to swell up with enough force to crack pavements and building foundations.

clay

Secondary minerals are most prominent in the _______ fraction of soils.

clay

Which type of soil structure is typically found in surface soil (A horizons)?

granular

In which of the following "forms" of soil water are pesticides, excess plant nutrients and waste chemicals most apt to move through soils?

gravitational

Soils high in organic matter commonly hold more plant-available water than comparable soils with lower organic matter levels. This is most likely due to what characteristics of the high O.M. soils?

higher field capacity

A wildlife biologist in South Africa notes that the soils on south-facing slopes are wetter and deeper than those on north-facing slopes, and therefore support more wildlife. What likely accounts for this difference?

higher soil temperatures on the north slopes

The layers of contrasting material found when one digs a hole in the ground are called ________.

horizons

Residual parent materials are best described as __________.

materials formed by weathering of rocks and minerals in place

Which of the following will increase the evaporation (E) from the soil surface?

none of the above

The most common form of on-site waste water treatment for homes not hooked up to sewer lines is the ________.

septic tank and drain field

In most soils the overall population (numbers) of microorganisms changes with time, generally following changes in the ________.

supply of decomposable organic matter

Exfoliation is caused by changes in _____.

temperature

An organism that subsists by eating predators would function as a(n) ________ in the soil ecosystem

tertiary consumer

Soil structure probably does not have much influence on _____.

texture