Soils (SPSS 2120) Homework Assignments

The highest T value (soil-loss tolerance limit) assigned for most soils in the USA by the USDA is ______ Mg / ha.

11

Which of the following added to a soil would be likely to result in the greatest level of SOM after several years of decomposition?

5 Mg of carbon in plant roots

Green manure crops and grass clippings generally have a water content of _____ % by weight.

75

After the O horizon, which horizon is rich in organic matter?

A horizon

Soils with thick organic-rich horizons (SOM > 30% by weight) that form in topographic depressions or low-lying places usually belong to which order?

Histosols

Which land use capability (LUC) class is most suitable for the production of row crops?

I

The ______ factor in the USLE will account for "living" terraces involving rows of deep rooted grasses planted on the contour.

P

The idea of describing soils as natural bodies was first introduced in which country?

Russia

Which land use capability (LUC) class is the suggested use restricted to non-production purposes, with only wildlife and recreational purposes being appropriate?

VIII

Kandic horizons are characterized by

accumulation of silicate clays

Detritus consists of

dead tissues and waste

A chroma less than 3 generally indicates a soil in good tilth.

false

Humus is an important nutrient and essential for healthy plants

false

Brown, red and orange colors in soils is caused by

iron oxides

Weathering of minerals

is faster in the presence of soil organic matter

Which of the following soil temperature regimes would provide the warmest and least variable soil temperatures?

isohyperthermic

A well‐drained soil in a tropical rain forest is likely to contain plenty of

kaolinite

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

series

Which of the following is likely to have the greatest surface area?

silty clay

Which has a greater capacity to adsorb water?

silty clay loam

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

soil

Smectite clays are more common in arid Nevada than in humid Georgia.

true

If an alkaline soil contains 3% humus (CEC = 200 cmolc/kg) and 20% clay (CEC = 40 cmolc/kg), what is the estimated CEC/kg value of the soil?

14

A soil with a high COLE value is rich in which type of clay?

2:1 clays

In conservation tillage practices, a system must leave at least _____ of the surface surface covered with plant residues.

30%

Wind erosion accounts for about ______ of the total soil erosion losses in the United States

35%

According to the USDA, about _______ of the total non-federal government owned rural lands in the USA is considered suitable for cultivation if appropriately managed

55%

Based on the plant residue analysis table below, which plant residue (A, B, C, D or E) is the highest quality residue in terms of suitability to support an active community of soil organisms and rapid nutrient cycling?

A (C/N ratio: 15, Polyphenol content: 0.5%, lignin content 10%)

In which state would you easily find soils rich in clay content, but low activity clays?

Alabama

Illuviation will most likely occur in the

B horizon

The accumulation of clay is most commonly found in which horizon?

B horizon

About 80% of a plant's dry weight consists of which two elements?

C and O

Soil colors are scientifically described by _________ color designations, such as 10YR 3/4.

Munsell

in the places listed below, where would you expect to see physical weathering dominating over chemical weathering?

a desert region in Arizona

If the bulk density of a soil is 0.35 Mg/m3, then the soil is probably

a histosol

A soil pedon is

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

SOM consists of

all of the above ( living organisms and cells, identifiable biomolecules, polymerized non-identifiable molecules, dead tissue and wastes)

Soil colloids

all of the above (are very small, can have a high ion exchange capacity, have a high water holding capacity)

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

all of the above (nitrous oxides, carbon dioxide, methane)

A soil with recent alluvium parent material is mostly likely

an entisol

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

anaerobic

residual parent materials

are formed by the weathering of rocks and minerals in place

Plastic limits and liquid limits refer to

are needed to calculate the plasticity index

Which soil order is not likely to be found in Connecticut?

aridisols

Colloidal properties refer to which soil fraction?

clay

If a dry soil swells up when moistened, then it probably contains

clay

If a soil feels sticky and putty-like, then this indicates a high percentage of which soil separate?

clay

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

clay

The texture of a soil containing 35% sand, 30% silt, and 35% clay is a

clay loam

The R factor in the USLE is concerned with

climate

The soil at the foot of a slope that consists of a mixture of angular gravel and rock is what type of parent material?

colluvial

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

columnar

In which climate would you expect to find a well-drained soil to have the highest organic matter content?

cool and humid

Coniferous forests are found mainly in

cool humid areas

To stabilize surface soil structure, you may

do all of the above (add organic mulches, minimize tillage, grow green manure crops)

. Yields of row corps on poorly drained soils are generally somewhat higher with no-tillage systems than with conventional tillage systems.

false

A pedon is typically about 2 meters deep and one hectare in land area.

false

Addition of organic polymers to soils will encourage formation of soil surface crusts when rain follows tillage.

false

An ustic soil moisture regime has a higher moisture content than an udic one.

false

As the decomposition of added organic material proceeds, the C/N ratio of the remaining undecomposed material steadily increases.

false

Assuming the soil pH and soil texture is the same in an Ultisol and an Aridisol, then you would expect the CEC to be the about the same value in both of these soils.

false

Calcium carbonate accumulation is more prominent in humid than in arid regions.

false

Eluviation is common in A horizons, while illuviation is common in B horizons.

false

Epipedons are diagnostic subsurface horizons that are also often found on the surface.

false

Epipedons are differentiated by the clay content distribution in the B horizon.

false

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

false

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

false

Fulvic acids are non-humic substances.

false

Glacial till is laid down by melt waters at the front of glaciers.

false

Humic sustances have not been shown to affect plant growth processes directly.

false

Hydraulic conductivity is commonly higher in soils with conventional tillage systems than in soils with no-tillage systems

false

Iron and aluminum oxides are major components of igneous rocks.

false

Kaolinite is very most common in Andisols.

false

Management practices that increase SOM improve soil chemical and biological properties, but have little effect on soil physical properties.

false

Pedoturbation is the mixing of soils by large animals.

false

Proper timing of tillage is generally more difficult for a sandy soil than for a clayey soil.

false

Removing all the straw with the harvest of paddy rice would increase the amount of methane produced by the paddy soil microoranisms

false

Saltation is the process of wind movement of salt-affected soils from one location to another in arid regions.

false

Sandstones and marbles are good examples of metamorphic rocks.

false

Slope length is generally of greater significance on erosion rates than is steepness of the slope.

false

Soils formed in wind-blown parent materials (loess) are generally poor agricultural soils.

false

Soils in Land Capability Class VIII areas are the least subject to erosion of all the classes.

false

Spodosols are generally less acidic and less sandy than Alfisols.

false

The CEC of humus is much greater than the CEC of silicate clays of equal volume.

false

The acidity of acid rain is mostly due to the formation of carbonic acid (H2CO3) from atmospheric CO2 and water.

false

The addition of neutral salts to an alkaline soil has a tendency to increase the pH of the soil.

false

The cation adsorption capacity of humus is higher at pH 5.5 than at pH 8.0.

false

The name of the soil series indicates the name of the family that it belongs to.

false

The plasticity index is used to determine soil texture.

false

The presence of iron in a mineral generally increases its resistance to chemical weathering.

false

The surface area of 100 grams of kaolinite is probably larger than the surface area of 50 grams of montmorillonite.

false

The surface soil pH is generally higher on no-tillage plots than on comparable conventionally tilled plots.

false

Well-aerated soils enriched with organic amendments will increase the methane load in the atmosphere

false

When native prairie soils are brought under cultivation, the fraction of SOM that disappears most quickly is the passive fraction.

false

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.

false

Which of the categories in Soil Taxonomy indicates properties that have implications for root growth as well as for the construction of building foundations?

family

Which of the following subsurface diagnostic horizons are common in Connecticut C-horizon soils due to the overburden of glaciers?

fragipan

Which type of soil structure is typically found in surface soil A-horizons in Connecticut?

granular

igneous rocks

have a salt and pepper appearance if the minerals in the rock are coarse

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

histic

Non-humic substances consists of

identifiable biomolecules

. The active fraction of SOM accounts for which benefit(s) to soils?

increased microbial activity and increased aggregate stability

The color of the soil is most often involved with the oxidation or reduction of

iron

Conservation tillage systems are advantages over conventional tillage systems in all the following ways except which one?

it involves the use of less toxic weed control practices

Which of the following is true about accelerated erosion?

it is greatly enhanced by the splash effect of raindrops impacting bare soil

Which type of clay is ideal for pottery?

kaolinite

Biomass consists of

living organisms and cells

Dull gray colors are characterized by

low chromas

Adding organic matter and reducing tillage can be expected to increase a soil's

macropores

Examples of igneous rocks do NOT include

marble

Which of the following epipedons would you expect to find in the Corn Belt?

mollic

The highest food producing soils and bread baskets of the planet are typically which soils?

mollisols

A soil rich in which type of clay is likely to have the greatest surface area?

montmorillonite

To maximize the quantity of vegetative cover on soil, which tillage practice should you use?

no-tillage

Which of the following changes in soil properties would you expect if a soil managed by conventional tillage operations was followed with 10 years of a no-till system?

organic matter content would increase

Under natural vegetation, about 70 to 90% of SOM is in which fraction?

passive

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

physical weathering

Humus consists of

polymerized, non-identifiable molecules

A subsoil high in clay will generally have a slow infiltration of water. Sometimes, however, it is not that slow. What may be causing this?

prismatic structure may be well developed

A soil suborder common near the ocean shores is

psamments

which of the following is NOT a major factor influencing soil formation?

redox conditions

Which of the following is true?

rill erosion channels can be removed by ordinary cultivation

To modify a silt loam soil into a loam, I would need to add _________ to the soil and mix it well.

sand

What is the minimum percentage information needed to determine the texture of a soil?

sand and silt

Alluvial fans are usually characterized by _______ soils.

sandy and gravelly

It is not recommended that you build a home on a soil rich in what type of clay?

smectite

The USLE suggests that soil erosion is a product of all but one of the following factors:

soil drainage

The P factor in the USLE is concerned with all but one of the following:

soil erodibility

Wind erosion is generally not affected by

soil pH

Adding fresh plant residues to soils can result in the "priming effect" decomposing _______

stable humus

The sizes of particles in a soil is described by its

texture

Silicate clay minerals will swell and shrink due primarily to

the movement of water in and out of their interlayers

Regarding nomenclature in Soil Taxonomy, which statement below is false?

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

Soil tilth refers to

the physical suitability of a soil for plant growth

Which of the following do not describe the role of aluminum hydroxyl ions in the soil?

they can be applied to help reduce the soil pH for acid-loving plants

. 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

A polypedon or individual soil is a group of closely related pedons that conceptually approximates a soil series.

true

A soil with an aquic soil moisture regime can exist in the state of New Mexico.

true

All organic compounds contain carbon.

true

All soils combined contain more carbon than all of the world's vegetation and the entire atmosphere combined

true

All soils must have a C horizon, the parent material horizon, at a minimum.

true

Allelopathic chemicals are released by plants, and can be beneficial or detrimental to other plants or organisms nearby.

true

An argillic horizon is characterized by the accumulation of silicate clays.

true

Climate influences rate of weathering, type of vegetation dominant in an area, and rate of soil formation.

true

Conservation tillage generally has positive effects on soil physical properties.

true

Conservation tillage systems rely more heavily on hebicides to control weeds, compared to conventional tillage systems.

true

Conventional tillage will decrease a soil's macropore space.

true

Dry dark-colored soils are warmer than dry light-colored soils.

true

Exfoliation is caused by changes in temperature.

true

Fine textured soils are generally higher in organic matter than sandy soils.

true

Funal hyphae play an important role in stabilizing soil aggregates.

true

Hydrated lime will increase the soil pH much faster than calcium carbonate.

true

Igneous, sedimentary and metamorphic are three types of rocks.

true

In Soil Taxonomy, a Gelisol can have a mollic epipedon

true

In soil taxonomy, "soil reaction" indicates the degree of acidity or alkalinity in a soil.

true

Inceptisols are common in Connecticut.

true

Iron and aluminum oxides are common in highly weathered soils.

true

Lacustrine parent materials have been subject to weathering for shorter periods of time than residual parent materials nearby.

true

Loblolly pine tolerates higher levels of acidity than beech or maple trees.

true

Mineralization of SOM result in the addition of inorganic nutrients to the soil solution.

true

Mollisols generally contain more organic matter than Aridisols

true

Mollisols generally have less organic matter than Histosols.

true

Oxisols are the most highly weathered soils of any other order.

true

Poorly-drained soils generally contain more organic matter than well-drained soils.

true

Soil colloids are very small, and generally require more magnification than that of an ordinary light microscope to be seen.

true

Soils formed in residual parent materials will likely have properties related to the properties of the R horizon rock below the C horizon.

true

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

true

Some N‐fertilizers are significant sources of soil acidity

true

The A horizons of soils are richer in nutrients than the E horizons.

true

The CEC of a soil is influence primarily by the kinds of colloids present and by the pH.

true

The O horizons of soils are generally found above the mineral horizons.

true

The RUSLE is more location specific, more accurate in predicting soil loss, and provides answers on alternative procedures more quickly than does USLE.

true

The T values are the maximum losses of soil by erosion that can be tolerated without a reduction in the soil's long term productivity.

true

The drainage class of a soil can be judged by the presence and location of gley in the soil profile.

true

The family category focuses on properties affecting plant roots and suitability for engineering uses of soils.

true

The majority of the surface area in expansible 2:1 clays is in their internal interlayer surfaces.

true

The moisture level will influence the amount of oxygen in a soil.

true

The name of the soil suborder indicates the name of the order that it belongs to

true

The percent of total pore space can be calculated from bulk density and particle density data.

true

The plasticity index is the difference between the plastic limit and the liquid limit.

true

The soil erodibility factor in USLE relates primarily to the soils infiltration capability and structural stability.

true

The topmost horizon in most forest soils is the O horizon.

true

The total global soil lost through sheet erosion is generally greater than from gully erosion.

true

Tilling a wet soil will likely increase the soil bulk density.

true

Vegetative barriers planted on the contour are low-cost "natural" terraces.

true

Weathering of rocks is usually from the outside toward the center of the rock fragments.

true

You can add sulfur to a soil to lower its pH, however you would need to add more sulfur to a Vertisol than an Alfisol. (Assume both soils have an initial pH of 6.5, and you seek to lower the pH on both soils to the same low pH value as needed for azaleas.)

true

Which soil moisture regime is most often found in Connecticut?

udic

A soil has a thick black A horizon, a distinct B horizon with reasonable stable soil structure, and was formed under grassland natural vegetation. What is its most likely suborder?

udolls

RUSLE differ from USLE in all but one of the following ways:

use greatly modified soil erodibility factors

Deciduous forests are found mainly in

warm humid areas