BYU PWS 282 soil science exam 1

In stokes law V=kd2 1. What is k?

(gravity, temp, viscosity, drag force, denisty)

At which of the following soil moisture potentials (expressed as kPa) is the soil water held most tightly?

-3100

A cultivated soil....

.... has no O Horizon, and the A Horizon is plowed (shown as Ap)

What influences Soil color--

1. Organic matter content 2. Oxidation state 3. Water content

Electromagnet methods

1. capacitance probes measure electrical capacitance of soil and calibrates to water content 2. time domain reflectometry measures the dielectric constant of the soil and calibrates to water content.

Hans Jenny soil scientist developed.... Five Factors of soil formation

1. climate- humid vs. arid, frozen, precipitation 2. biotic activity- organisms or living functions in soil 3. topography- sloping landscapes 4. acting on parent materials- volcano? lake? 5. time- how weathered is it? (not how old)

6 reasons why soils are important

1. medium for plant growth 2. modifier of atmosphere 3. engineering medium 4. habitat for soil organisms 5. system for water supply and purification 6. recycling system for nutrients and organic waters

How to preserve soil structure:

1. minimize tillage and traffic 2. allow only necessary traffic, only when dry 3. use organic materials 4. practice crop rotation with sod crops 5. when needed, add soil amendments

Five epipedons occur naturally over wide areas:

1. mollic epipedon- mineral surface horzon with organic matter 2. umbric epipedon- same as mollic except the percentage base saturation is lower. 3. orchic epipedon- too thin, too light in color, too low in organic matter to be mollic or umbric, but not as deep as mollic or umbric 4. melanic epipedon- very black, high o. matter, extremely fluffy 5. histic epipedon-thick layer of o. soil materials overlying mineral soil, in wet areas, layer of peat or muck, low density, black or brown. MUOMH

Six hierarchical categories of classification in Soil Taxonomy:

1. order- the broadest category 2. suborder 3. great group 4. subgroup 5. family 6. series- the most specific cateory O,SO,GG,SG,F,S

The color of a soil reflects

1. organic matter content 2. presence and oxidation states of iron and maganese oxides 3. water content

Bulk density range

1.1 to 1.8

range for mineral soils

1.1 to 1.8 g/cm2 in density

2.5YR76

2.5 is hue YR means yellow red 7 is chroma 6 is value

Particle density mass per unit volume of soils

2.65 g/cm3

A hydrometer is used for what?

A glass instrument that floats in water; used to measure the density of a solution.

Soils with good tilth have.....

A. Stable aggregation B. High percentage of macropores C. High rate of infiltration

Two soil samples, A and 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=-30, B=-40

The property of ____________ in water stems from the attraction of water molecules to soil solids.

Adhesion

Flood Plains

An area of land adjacent to a stream or river which stretches from the banks of its channel to the base of the enclosing valley walls (terraces), and which experiences flooding during periods of high discharge. (Think of having a bath, and leaving rings along the sides of the tubs.)

Fine-loamy, mixed, superactive, frigid Calcic ARGIudolls

Argi indicates the Soil Great Group In this case, indicating the presence of an argillic diagnostic horizon

AWHC

Available Water Holding Capacity (volume water content at field capacity subtract volume water content at wilting point)

A clay bulge happens in which horizon?

B Horizon

Silicate clay accumulation is most commonly in the ______.

B horizon

Which soil horizon has the process of illuviation most likely occurred?

B horizon

Weathering involves....

BREAKDOWN ( physical disintegration and decomposition) and SYNTHESIS of secondary minerals forming new minerals

Lacustrine Parent Material

Beach ridges may be present where glacial lakes once washed up sand. Material is well sorted and fine-textured, having finer silts and clays.

Fine-loamy, mixed, superactive, frigid CALCIC Argiudolls

Calcic is the Soil Sub Group In this case it is a diagnostic subsurface horizon

Colloidal properties are exhibited by the _______ fraction of soils.

Clay

Marine (ocean) Parent Material

Collections of material that have been carried by rivers and streams to the ocean and eventually sink to the bottom. Such materials can vary in texture.

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

Cooler

Which trees, conifers or deciduous, cycle base forming soil cations, like magnesium and calcium?

Deciduous--- they have a better O Horizon because of the leaf litter each year Conifers suck magnesium and calcium out of the soil, making it acidic.

Glacial Outwash Parent Material

Deposit of sand and gravel carried by running water from the melting ice of a glacier and laid down in stratified deposits

Alluvial (or fluvial) parent materials

Deposited by moving water bodies such as rivers and streams. The texture of the deposit depends on the energy of the water body. Fast-moving water deposits only coarse material such as rocks and gravel. If the water velocity decreases, finer particles (sand and silt) are deposited, while fine silt and clay particles are deposited by slow-moving water such as that found associated with deltas.

Wind transported materials (Eolian)

Dunes- sandy, loess - silty textured

An albic horizon is a diagnostic subsurface horizon found in some soils. It is light in color and characterized by removal of most of the clay and iron oxides originally found in the parent materials. An albic horizon would be found in which of the master horizons?

E horizon

An albic horizon is light in color and characterized by removal (washing out) of most of the clay and iron oxides originally found in the parent materials. An albic horizon would be found in which master horizon?

E horizon (washing out)

The diagnostic horizons that occur at the soil surface are called...

Epipedons, which includes the upper part of the soil darkened by organic matter, the upper eluvial horizons, or both.

The surface soil is more likely to be acidic under which vegetation type?

Evergreen, coniferous forest

What is the name of the process by which positively charged ions in the soil cause clay particle to hold together?

Flocculation

Molisols

Formed in semi-arid to semi-humid areas, typically under a grassland cover. They are most commonly found in the mid-latitudes, namely in North America, mostly east of the Rocky Mountains, in South America in Argentina (Pampas) and Brazil, and in Asia in Mongolia and the Russian Steppes. Their parent material is typically base-rich and calcareous and include limestone, loess, or wind-blown sand.

What type of glacial parent materials would well-sorted, sand sized particles most likely originate from?

Glacial outwash

In this soil taxonomy: "Fine-loamy, mixed, superactive, mesic typic dystroxerepts", what does "dystro" indicate?

Great Group

Which of the following would be expected to have the deepest soil formation? a) an arid environment near the equator b) a humid environment at 30 degrees north latitude c) an arctic location

Humid environments will have more organic material and deeper soil formation. arid- means dry arctic- frozen with little or no growth

Which of the following are characteristics of a water molecule?

It has a positive and a negative side.

Lacustrine Sediments

Lacustrine deposits are sedimentary rock formations which formed in the bottom of ancient LAKES. They are poorly drained and well sorted.

Water transported parent materials ....

Lacustrine, alluvial fans, flood plains

What soil texture has the highest infiltration rate in cm/hr after 7 hours?

Loamy Sand

Think of two rainfall conditions, where location A has rain every month consistently, and location B has heavy rainfall six months of the year and then six dry months, but both locations have the same amount of precipitation annually. Which location would you expect the formation of a Bk horizon to be deeper? (k indicates accumulation of carbonates.)

Location B with six months of heavy rainfall has more accumulation

Colluvium Parent Material

Material that moves down slope due to gravitational forces (in some cases water may play a role in initiation of the movement). The material is heterogeneous, unsorted material of all particle sizes (from boulders to clay) with relatively little abrasion to round the particles.

Which of the following is a dominantly organic soil horizon existing above underlying mineral soil horizons?

O Horizon

Soil layers (top to bottom)

O Horizon- mostly ORGANIC matter, leaf litter A Horizon- TOPSOIL, dark-rich organic matter E Horizon- elluvial (out or exit), washed out B Horizon- SUBSURFACE, light-colored, rich in iron, aluminum, clay (zone of accumulation) C Horizon- SUBSTRATUM R Horizon- BEDROCK

The _________ potential is dependent upon the presence of salts and other solutes in the soil.

Osmotic

mottling

Oxidation or rusting of soil due to periodic saturation. Rust colored patches in soil.

What are the five major factors influencing soil formation?

Parent Material, Climate, Living Organisms, Landscape Position, and Time

Definition of Parent Materials

Parent material is the geologic material from which soil horizons form including....lacustrine, alluvial, marine, colluvial, till, outwash

Grassland

Puts energy in deep roots, dark A Horizon, little E horizon

Which is the most important means for plant roots to obtain water from the soil?

Roots extend into moist soil area then water flows to the roots by capillarity.

Entisols

Soil order that forms on hillsides and deltas New & poorly developed Many soils that do not fit well into other soil orders are classified as this

Histosols

Soils that form in decaying organic matter. In low, wet places, like in bogs or marshes, organic matter accumulates below the water table and decomposes more slowly than it accumulates. Over time, thick accumulations of this material can form.

Describe soil horizons formed in grassland or forest vegetation

Soils under FOREST vegetation are likely to have an E HORIZON, while soils under grasslands have little organic matter, and no E horizon.

Stokes law assumptions

That all particles are rigid, smooth, spherical That all particles have the same density That particles don't interfere with each other as they settle

FINE-LOAMY, MIXED, SUPERACTIVE, FRIGID Calcic Argiudolls

The CAPITALIZED text is the FAMILY name: Fine-loamy describes the soil texture Mixed describes clay mineral content Superactive describes clay activity (CEC) Frigid describes soil temperature regime

What part of a water molecule is attracted to positively charged cations such as Na+ and Ca2+.

The Oxygen end

Weathering

The chemical and physical processes that break down rock at Earth's surface.

Soil Profile

The collective vertical exposure of a soil, showing the sequence of all pedogenic layers

Definition of SOIL

The layers of generally loose mineral and/or organic material that are affected by physical, chemical, and/or biological processes at or near the planetary surface and usually hold liquids, gases, and biota and support plants.

bulk density

The mass of dry soil per unit volume, including the air space

particle density

The mass per unit volume of soil particles, excluding pore space

Porosity

The percentage of the total volume of a rock or sediment that consists of open spaces. Equation 1 - x.xx g/cm3 2.65 g/cm3

What helps account for the attraction of water molecules for each other?

The polarity of water

How do you best describe soil texture?

The proportions of different mineral particle class sizes.

What describes the correct relationship of soils that are classified as XEROLL and an AQUOLL?

The soils are from the same order, but differ in soil moisture regime.

alfisols

These soils form in semi-arid to humid areas, typically under a hardwood forest cover. They have a clay-enriched subsoil and relatively high native fertility. They are widely used both in agriculture and forestry.

Glacial Till Parent Material

This parent material is found where glaciers have deposited material. Ice is a poor sorter of soil particles, so all sizes of particles are present.

soil compaction

When soil is pressed down tightly resulting in the removal of air pockets; therefore not allowing water to penetrate or plants to grow.

Alluvium

a deposit of clay, silt, sand, and gravel left by flowing STREAMS in a river valley or delta, typically producing fertile soil. (floodplains, aluuvial fans, deltas, terraces)

Name a substance where the particle density would equal the bulk density?

a quartz pebble, because there is no pore space

settling

a separation technique in which a "heavier" component sinks to the bottom of a liquid, lighter aggregates settle on top, and the liquid can be poured off

Dielectric constant-

ability to store charge-- soils grouped together with low charge, liquid water is high

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

ancient seas

Hue, Value, Chroma

characteristics of the Munsell Soil Color chart. Written like this: 10YR 5/3

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

clay

Which is more dense, sand or clay?

clay has micropores (air space), sand is dense or solid

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

colluvial

clods

compressed, cohesive chunks of soil that can form artificially when wet soil is plowed or excavated.

Glacial till is a term used to describe parent materials that _______.

contain a heterogeneous mixture of mineral debris deposited by ice from receding glaciers

Soil temp regimes

cryic frigid mesic thermic-- in this order

Current volume percentage of total plant available water

current water content subtract Volume water content at field capacity

plate-like

flat, usually found in compacted soil and the cracks are stretched more horizontally than they are vertically.

aridisols

form in an arid or semi-arid climate. Aridisols dominate the deserts and xeric shrublands, which occupy about one third of the Earth's land surface. Aridisols have a very low concentration of organic matter. Water deficiency is the major defining characteristic of Aridisols.

soil temperature regimes

frigid, mesic, thermic, cryic

the soil type has all sizes of minerals deposited

glacial till

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

Diagnostic Subsurface Horizons

horizons with specific characteristics that we use to place soil in its proper class in the system. Here are a few of the more common subsurface diagnostic horizons: Argillic horizon- accumulation of silicate clays Natric horizon-silicate clays and sodium Kandic horizon-clay accumulation, subtropical climates Oxic horizon-oxide clay presence, found in tropics Spodic horizon- iron and aluminum accumulation, coniferous forests Albic horizon- presence of E horizon, associated old/mature soil orders ANKOSA

peds or aggregates

individual particles of soil or material

gleying

intense chemical reduction (lack of oxygen) due to poor drainage. Colors range from grey to bluish green.

chroma

intensity or brightness (whiteness), chroma of 0 being gray

Capillarity in soils________.

involves both adhesion and cohesion

Series part of soil name

is usually a proper name.

value

light or darkness, 0 being black

Unsaturated water flow_______.

occurs on soils that are at field capacity

Fine-loamy, mixed, superactive, frigid Calcic ArgiudOLLS

oll indicates the soil order in this case, the soil is a Mollisoll

lacustrine

parent materials deposited in LAKES

alluvium

parent materials deposited in STREAMS

Glacial till is described as heterogeneous which means

particles and rocks of many sizes are deposited due to a glacier that melts all at once (in 10,000 years) and everything drops to the surface; there is no sorting. (Heterogeneous means diverse in content.)

Sand Silt Clay

particles smaller than 2 mm but larger than 0.05 mm particles smaller that 0.05mm but larger that 0.002mm particles smaller than 0.002mm

pedon, polypedon, landscape

pedon is one soil profile polypedon is an area with several soil profiles landscape includes many polypedons

CL,O,R,P,T by Hans Jenny refers to what?

process of soil formation CLimate, (living) Organisms, Relief (topography), Parent (materials), Time

hue

redness or yellowness in soils

Soil Moisture Regimes (SMR)

refers to the presence or absence of either water-saturated conditions or plant-available soil water during specified periods in the year. The five categories are: 1. Aquic-dry for half of growing season and moist for 90 consec days; arid regions, highest soil moisture level. 2. Udic- soil moisture high year round, meets plant needs (sounds like humid) 3. Ustic- between udic and aridic, some plant-available moisture during growing season, some periods of dourght. 4. Aridic- soil is dry for half of growing season, arid regions, soils hot and dry during summer. 5. Xeric- found in typical mediterranean-type climates, with cool, moist winters and warm, dry summers; long periods of drought in summer. AUUAX

spheroidal

round to oval

Alluvial fans are usually characterized by _____ soils.

sandy and gravelly

Forest

small A horizon, O horizon present, deep E horizon

In soil taxonomy, what do the terms 'mesic' and 'cryic' describe?

soil temperature regimes

Stokes Law V=kd2

speed at which particles of sediment drops based on radius of flask, density, gravity, buoyancy, drag force; bigger particles drop faster. V=velocity m/sec d= diameter k= constants (gravity, density, viscosity) The sum of all forces equals 0.

prism-like

tall, narrow. shrink-swell causes vertical cracks.

Measure water potetial-

tensiometers, electrical resistance sensors

Water Content

the amount of water in the soil, expressed as either percent by mass or by volume.

Mechanical weathering processes result in ______

the disintegration of rocks due to differential expansion of materials

Water Potential

the energy status of water in the soil.

block-like

the size of the soil will be large and cracks in it will go in a vertical and horizontal direction. Soil with a blocky texture has a good level of water penetration and a moderate level of drainage and aeration.

soil forming processes

transformation- chemically changing translocation- movement of materials by water additions- input of organic material, sediment dust, ions losses- erosion, leaching, gas fluxes

Fine-loamy, mixed, superactive, frigid Calcic ArgiUDolls

ud indicates the soil suborder In this case indicating a distinguishing udic soil moisture regime

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

uniformly textured sandy loam profile

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

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

Gravimetric soil water content calculation

wet mass - dry mass DIVIDED BY dry mass