Soil Science midterm

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

Clouds.

Which of the following is (are) essential plant nutrients?

Cu (Copper)

Compared to a similar soil under native vegetation, a soil with a long history of conventionally tilled cropping would have less micropore space.

False

Flocculation is the process by which certain chemicals in the soil stabilize large soil aggregates.

False

For most soils, plowing and harrowing every year improves soil tilth in the long run.

False

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

Spodosols

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

Which of the following is not true with respect to the hydrologic cycle?

There is a net migration of some 40,000 km3 of water in clouds from the land area to the ocean areas.

Fungal hyphae play an important role in stabilizing surface soil aggregates.

True

Histosols generally have higher organic matter contents than Mollisols.

True

If the CO2 content of soil air is 3.5%, it is 100 times higher than that of the atmosphere.

True

Mollisols are characterized by a deep epipedon that is high in organic matter

True

More than ninety-eight percent of the earth's water does not take part in the annual cycling known as the hydrologic cycle.

True

Organic matter distribution in the profile is a significant criterion for differentiating epipedons.

True

Oxisols are more highly weathered than are the soils of any other order.

True

Russian scientists were the first to develop the concept of soils as natural bodies

True

Soils of good tilth and high productivity are usually characterized by stable aggregation and a high percentage of macropores.

True

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

True

The great bulk of gaseous interchange between the soil pores and the atmosphere occurs by mass flow of the concerned gases.

True

The matric potential is due to the attraction of water molecules to soil solid surfaces.

True

Hydraulic redistribution or hydraulic lift dries out shallower soils during dry periods, allowing trees to take advantage of water deeper in the soil profiles.

False

The average residence time for water in clouds over the ocean is about one year.

False

The element most often involved in oxidation reactions as minerals weather is _____.

Iron

The following are true characteristics of a water molecule.

It has a positive and a negative side.

A well aerated soil is characterized by a relative abundance of _____.

NO3- ions

Organic matter accumulation is most pronounced in the ____.

O horizon

The polarity of water helps account for the attraction of water molecules for each other.

True

The pollution of ground water is often increased by the presence of macropores in soils.

True

The redox potential is a measure of the tendency of a substance to accept or donate electrons.

True

The water potential at the field capacity for most soils is in the range of -10 to -30 kPa.

True

Tillage when the soil is too wet is likely to increase the soil bulk density.

True

When preparing a surface soil seedbed, the soil should generally be in the loosest, least dense soil condition in the row where the seed is placed.

True

You would be more apt to find a Gelisol in Alaska than in Iowa.

True

Typical well drained, well developed soil in Northeast Tennessee will most likely be classified as a:

Ultisol

Glacial till is a term used to describe parent materials that:

contain a heterogeneous mixture of mineral debris dropped by receding glaciers.

Soils high in organic matter commonly hold more 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

The matric potential of soil water is _____.

not influenced appreciably by the force of gravity

Unsaturated water flow _____________.

occurs on soils that are at field capacity

The most important management factors influencing soil aeration in well-drained soils are those that determine the volume of the soil's macropores.

True

The partial pressure of CO2 in the soil pores is higher than the partial pressure of this gas in the atmosphere.

True

The following is the reduced form of the essential element depicted

NH4+

Which of the following pH values represents the most acid condition?

1.0

Which color would be typical of a well drained, low-organic matter sandy surface soil?

10YR5/8

In a field experiment you noted that 300 tons of water was transpired to produce 1 ton of corn (dry weight). If alfalfa had been grown in the same field instead of corn, which of the following would most likely have been the amount of water transpired?

500 tons

Which of the following pH values represents a neutral condition?

7

Topsoil is generally equivalent to which soil horizon?

A Horizon

Which of the following would you expect to have the highest leaf area index?

Alfalfa just before harvest

Subsoil is generally equivalent to which soil horizon?

B Horizon

Silicate clay accumulation is most common in the ____.

B horizon

Secondary minerals are most prominent in the fraction of soils.

Clay

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

Entisols

A friable soil is usually more likely to be indurated.

False

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

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

In acid soils you would be concerned if the redox potential was low since it could mean a deficiency of some plant nutrients such as iron and manganese.

False

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

False

Plant roots gain access to soil water primarily by the growth of the roots into moist soil.

False

Recent research with annual crops such as wheat, sunflower and sorghum in the Great Plains region suggests that, compared to continuous cropping, soil quality, crop productivity and farm profitability are likely to be greater when crops are grown in a field only every second year with the soil kept free of weeds in the non-crop year by repeated cultivation of herbicide application.

False

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

False

Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes carbon dioxide.

False

Soils classified as Inceptisols have the least well developed profiles of those in any order in the Soil Taxonomy system.

False

Some 60 percent of the water that is actively involved in the hydrologic cycle worldwide is found in soils.

False

Some two-thirds of the solar energy reaching the earth is absorbed by water on or near the earth's surface.

False

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

False

Subsoiling is a primitive deep tillage technique that results in extremely high subsoil bulk density.

False

The effect of soil organic matter on the amount of water available to plants is due to organic matter influence on total soil porosity as well as to the water-supplying power of the soil organic matter.

False

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

False

The property of cohesion in water stems from the attraction of water molecules for soil solids.

False

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

There is a net movement of clouds from land areas to the ocean areas in the hydrologic cycle.

False

Plant transpiration efficiency at a given location is markedly influenced by _____.

Fertilization practices used The plant species being grown Both C and D

Soil order characterized by permafrost is known as:

Gelisols

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

Histosols

Wind blown silt sized materials is known as:

Loess

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?

Mollisol

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

Munsell

Plant roots obtain access to soil water in which of the following ways?

Roots extend into moist soil area. Water flows to the roots by capillarity. both B and D

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

Russia

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

Soil Solution

An abundance of macropores in soils helps assure an abundance of oxygen in the soil.

True

Anaerobic conditions commonly prevail in liberally watered flower pots with mineral soil as the growing medium even though the containers have holes for drainage in the bottom of the pot.

True

Andisols are found mostly near recently active volcanoes.

True

Capillary movement is made possible by the processes of cohesion and adhesion.

True

Corn plants are generally more efficient in the use of water than is alfalfa.

True

Drip irrigation would more likely be used in the production of apples or peaches than in the production of wheat.

True

Early snowfall that arrives before the cold winter weather has frozen the soil generallyincreases the penetration of water into the soil.

True

Eutrophication is enhanced by the presence of pesticides in the water draining from agricultural soils.

True

Soil order characterized by high swelling capacity clays is known as:

Vertisols

A soil pedon is ____.

a category of Soil Taxonomy

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

a desert region of Arizona

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

a furrow-irrigated cotton field in Arizona

Argillic horizons are characterized by ___.

accumulation of silicate clays

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

adding straw mulch to the soil surface the use of no-till culture stubble mulch farming plastic mulch NONE OF THE ABOVE

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

adsorb water adsorb gases release nutrients by mineral weathering support bacterial growth1) ALL OF THE ABOVE

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

ancient seas

The process of aerobic respiration is a significant source of which of the following gases?

carbon dioxide

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

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

colluvial

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

contains organic compounds contains mineral nutrients is restrained in its flow by attraction to particle surfaces all of the above

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

creation of more macropores

Urban development of land under natural vegetation or agriculture usually greatly _____ soil infiltration capacity and therefore greatly increases _______.

decreases stream bank erosion.

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

diffusion

The expression, P - ET -SS estimates the ________ a watershed.

discharge volume from

Which of the following irrigation systems produces the most biomass per unit of water applied?

drip irrigation

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

Which of the following means of estimating soil water levels gives a direct measurement of the water content?

gravimetric determinations

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

gravitational

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

horizons

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

increase the soil's water holding capacity

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

Using a textural triangle chart, it can be determined that a soil with 45% sand and 20% clay belongs to the ___textural class.

loam

Dull gray colors are characterized by _____.

low chromas

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

macropores

Residual parent materials are best described as __________.

materials formed by weathering of rocks and minerals in place.

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

methane

Soil A has a redox potential of 400 mV, soil B -200 mV. Of the two soils, Soil A is more apt to be characterized by an abundance of _____.

molecular oxygen

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

nitrogen gas

The transformation of gneiss into mica, quartz, and feldspar crystals is an example of

physical weathering, disintegration, both A and C

If 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?

ridge-till system

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

Alluvial fans are usually characterized by ______ soils.

sandy and gravelly

Which of the following is not a textural class name?

sandy silt

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

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

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

texture

Mechanical weathering processes result in:

the disintegration of rocks due to differential expansion of minerals

Soil tilth refers to _____.

the physical suitability of a soil for plant growth

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

Igneous, sedimentary, and metamorphic are three _________.

types of rocks

In which of the following situations would you expect downward movement of soil water through the profile to be most rapid?

uniformly textured sandy loam profile

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

use of organic mulches use of green manure crops growing grass sod minimizing tillage ALL OF THE ABOVE

Which of the following is not considered one of the five major factors influencing soil formation?

valence state

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

water content of a soil with water potential of about -10 kPa