Soil Science Midterm

Calcium carbonate accumulation is more prominent in humid than in arid regions. (T/F)

F

Eutrophication is enhanced by the presence of pesticides in the water draining from agricultural soils. (T/F)

F

Filling the bottom half of a flower pot with gravel will greatly improve the aeration of the soil-mix in the top half. (T/F)

F

Living organisms affect soil formation primarily by their constraining the level of oxygen in the soil. (T/F)

F

Micronutrients are those that account for approximately 1% of dry plant tissue. (T/F)

F

Nutrient cycling in forested areas contributes little to soil formation. (T/F)

F

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

Which of the following are categories of rock?

sedimentary, metamorphic, igneous

Most (usually 80% or more) of soil potassium and calcium can be found in the form of ______ .

structural components of minerals

In a load of 5 cubic meters of topsoil, approximately how many cubic meters of the volume would be solid material?

2.5

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

A

Silicate clay accumulation is most common in the ____ horizon.

B

Soil texture is defined as the way soil feels. (T/F)

F

Every drop of water in rivers, lakes, estuaries, and aquifers has either traveled through the soil or flows over its surface, except for the relatively small amount of precipitation falling directly onto surface water. (T/F)

T

Secondary minerals are most prominent in the _____ fraction of soils

clay

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

peat

The map units on a detailed soil map in a county soil survey report are most likely to be labeled with names from which category of Soil Taxonomy?

series

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 50% air

"Topsoil" is generally equivalent to which soil horizon?

A

Two soil samples, A & B, at different soil moisture levels are placed in contact with each other. Water will more likely move from soil A to soil B if their water potentials, expressed in kPa, are:

A=-20; B=-30

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. (T/F)

F

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

F

Limestone parent materials enhance the process of acidification. (T/F)

F

Minerals are mixtures of rock. (T/F)

F

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. (T/F)

F

Soils developed in wind-blown parent materials such as loess are generally of little agricultural value. (T/F)

F

Soils on hillsides tend to be deeper than those on level lands. (T/F)

F

Soils that are grey and mottled are found in arid areas. (T/F)

F

Soils that have good aggregation have a cookie crumble structure and form crusts on the soil surface. (T/F)

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. (T/F)

F

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

F

The ___ soil horizon includes undecomposed to decomposed organic matter on top of the soil surface.

O

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

T

About one third of the readily accessible water in the hydrologic cycle is in the soil. (T/F)

T

Andisols are found mostly near recently active volcanoes. (T/F)

T

Color is an important physical property of soil because it can give an indication of what minerals may be present. (T/F)

T

Cu is considered to be an essential plant nutrient. (T/F)

T

Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants. (T/F)

T

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

T

In the video we watched in class, rancher Gabe Brown talked about armor on the soil surface, which involves protecting the soil by not leaving the soil surface bare. (T/F)

T

Increasing the organic matter content of a soil is likely to increase the soil's water holding capacity. (T/F)

T

Lacustrine parent materials have been subject to weathering for shorter periods of time than residual parent materials nearby. (T/F)

T

Many of the nutrients taken up by plants are in the form of compounds (not elemental forms). (T/F)

T

Matric potential is always negative. (T/F)

T

Most of the water in our rivers and lakes has come in contact with and has been affected by soils. (T/F)

T

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

T

S is considered to be a plant macronutrient. (T/F)

T

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

T

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

T

Soil organisms, like fungi, are critical to aggregating soil particles. (T/F)

T

Some plant macronutrients are derived from air and water. (T/F)

T

The composition of food reflects the properties of the soil in which it was grown. (T/F)

T

The mineral fraction of soil does not include organic matter. (T/F)

T

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

T

Understanding soil physical properties is important because it improves our ability to manage soils. (T/F)

T

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

T

Water molecules are held together in soil by the forces of adhesion and cohesion. (T/F)

T

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 in Arizona

For which substance would the particle density equal the bulk density?

a quartz pebble

A soil pedon is ____.

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

The osmotic potential would likely be lowest in which one of these soil orders?

aridisols

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

clouds

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

colluvial

When a soil's bulk density increases, its porosity _____ .

decreases

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

decreases, stream bank erosion

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

entisols

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

granular

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

higher field capacity

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

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 with given info

Capillarity in soils _____.

involves both adhesion and cohesion

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

iron oxides

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

is restrained in its flow by attraction to particle surfaces, contains organic compounds, contains mineral nutrients

The solid portion of a volume of average soil is mostly made of:

minerals

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 ______ is the outermost layer of the Earth that is composed of soil.

pedosphere

One of the most abundant minerals in the Earth's crust that is also very resistant to weathering is______.

quartz

The lithosphere is made up of ______.

rock

Igneous rocks can best be characterized as:

rocks formed when molten magma solidifies

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

roots extend into moist soil area and Water flows to the roots by capillarity

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

Texture best describes the ____ of particles in a soil.

sizes

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

spodosols

Fungal hyphae have an important influence on soil structure because they ______.

stabilize macro aggregates

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

A soil profile consists of _________.

the set of layers seen in a vertical cross section of a soil

Water flow that moves through soil (not due to gravity) is specifically called _____ flow .

unsaturated

The dominant order of our region (in San Marcos area) that shrinks and swells is ______ .

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