SSC 200 Exam 1

argillic

(Bt) Silicate clay accumulation

what are the three mechanisms by which plant roots acquire nutrients from the soil system?

1. root interception- roots continuously grow into new, undepleted soil 2. mass flow- dissolved nutrients are carried along with the soil water flowing towards a root that is actively drawing water from the soil 3. diffusion-from areas of high concentration to low concentration

how many soil orders are currently recognized?

12

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

which of the following pH values represents a neutral condition?

7

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. What are the other 4 master horizons and what are the features that distinguish each?

A- dominated by minerals, darkened by organic matter "topsoil" E- (some soils) intensely weathered and leached, no organic matter B- underlying, less organic matter, silicate clays, iron and aluminum oxides, gypsum, calcium carbonate. washed down or weathering C- least weathered, caused by extended plant roots and microorganisms "parent material"

rank the following 4 moisture regimes from wettest to driest: ustic, aquic, udic, aridic

Aquic, udic, ustic, aridic

Which of the following is considered to be a plant macronutrient? (4)

C, P, S, N

A, B, C, and E horizons can be found in any true soil.

False

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

False

Kandic

Fe and Al oxides kaolinite clays low cation exchange capacities form in areas of intense weathering

Oxic

Highly weathered, high in Fe and Al oxides, 10% weather able, humid areas

For any soil in which it is present, the C horizon is the parent material for the B horizon.

True

what is a soil series?

a class of soils (basic units)

what is humus?

a collection of very complex organic compounds that accumulate in soil because they are relatively resistant to decay (black or brown)

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

what is a polypedon?

a group of similar pedons

What is a soil individual?

a polypedon that is of sufficient size to be recognized as a landscape component

what are the distinguishing characteristics of each of the different soil orders?

alfisols- argillic, natric, or kandic, high to medium base saturation andisols- volcanic ejecta, dominated by allophone or al humic complexes aridisols- dry, ochric epipedon, sometimes argillic or natric entisols- little development, ochric common gelisols- permafrost, cryoturbation histosols- peat or bog, high organic matter inceptisols- embryonic soils, ochric or umbric mollisols- high base saturation, dark oxisols- oxic, highly weathered spodosols- Fe, Al oxides and humus accumulation ultisols- argillic or kandic horizon, low base saturation vertisols- high in swelling clays, deep cracks when dry

How are soil series different than soil individuals?

all of the soil individuals in the world that have in common a suite of soil profile properties and horizons that fall within a particular range are said to belong to the same soil series

list the important aspects of the following diagnostic subsurface horizons: cambic, argillic, spodic, and albic

argillic- subsurface accumulation of silicate clays that have moved downward from the upper horizons or formed in place spodic- illuvial, accumulation of colloidal organic matter and aluminum oxide albic- light colored eluvial that is low in clay and oxides of Fe and Al

what are some of the benefits of organic matter in the soil?

binds mineral particles into a granular soil structure increases amount of water soil can hold and proportion of water available for plant growth major source of phosphorus and sulfur primary source of nitrogen supplies carbon and energy to soil organisms

how does the soil surveyor determine which soils are found in different locations in a particular mapping area, and the locations of the boundary lines surrounding these soils?

bring up soil material from numerous small boreholes

Which six macronutrients are obtained primarily from the soil?

calcium magnesium nitrogen potassium phosphorus sulfur

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

clay

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

colluvial

alfisols

combo of Al and Fe

the water in the soil typically differs from pure water because the soil water (3)

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

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

cryolls

what is the difference between dark colored and light colored igneous rocks? what are examples of each? which are more easily weathered?

dark colored contain more iron and magnesium and are typically more easily weathered light- quartz dark- granite

How is the soil important in the life and death of many organisms?

death leads to organic waste which the soil converts and uses to create new growth, all while releasing carbon dioxide

what are the three basic tasks associated with mapping soils?

define each soil unit to be mapped compile information about the nature and classification of each soil delineate the boundaries where each soil unit occurs in the landscape

aridisols

dry arid

why is water such an important component of the soil?

essential for the survival and growth of plants and other soil organisms

why is an understanding and appreciation of the differences among soil orders valuable?

essential for understanding the nature and function of soils in different environments

what is the purpose of describing exposures of individual soils? what properties does the soil surveyor usually describe?

facilitates communication with other soil scientists and comparison with other soils colors, texture, consistency, structure, plant rooting patterns

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

false

Alluvial parent materials are those that have been laid down in former lake bottoms.

false

Epipedons are diagnostic subsurface horizons that are one of the primary means of classifying soils in the United States.

false

Most, if not all, of the nutrient supply stored in a fertile soil is in forms readily available to plants.

false

Soils in the Oxisols order are deeply weathered and have deep subsurface horizons of calcium oxide.

false

Spodosols are generally less acidic and less sandy than are Alfisols.

false

The C horizons are generally more completely weathered than the other horizons.

false

glacial till is laid down by melt waters gushing out from the front of glaciers

false

the parent materials for most coastal plain soils are residual in nature

false

gelisols

freeze

how does temperature contribute to physical weathering?

heat causes expansion which leads rocks to crack exfoliation- the peeling away of outer layers

what are the differences among igneous, metamorphic, and sedimentary rocks?

igneous= formed from molten magma. composed of primary minerals such as quartz metamorphic= formed from other rocks through metamorphism, harder and more crystalline sedimentary= form when weathering products released from other older rocks collect under water as sediment and eventually reconsolidate into new rock. most common type of rock

calcic

illuvial accumulation of carbonates CO2 or bubbles

spodic

illuvial horizon characterized by colloidal organic matter, aluminum oxide and iron highly leached areas

why do we classify things, including soils?

in order to make sense of our world

why are soil pores important?

in pores air and water circulate, roots grow, and microscopic creatures live

what are diagnostic surface horizons? (epipedons)

includes upper part of the soil darkened by organic material, the upper eluvial horizons, or both. It may include part of the B horizon if the latter is significantly darkened by organic matter

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

increase the soil's water holding capacity

ultisols

last ultimate

what is regolith and how is it related to soil?

layer of unconsolidated debris overlying the hard, unweathered rock

albic horizon

light colored eluvial horizon, low in clay and oxides (E)

residual parent materials are best described as

materials formed by weathering of rocks and minerals in place

what are the five crucial ecological roles of soil in our environment?

medium for plant growth recycling system for nutrients and organic waste system for water supply and purification engineering medium habitat for soil organisms

What are the defining properties of a mollic epipedon?

mineral surface horizon noted for dark color associated with organic matter, thickness, and softness even when dry. high base saturation > 50%

what are the four major components of the soil?

minerals, organic matter, water, air

What types of information are used to differentiate among the soil orders?

moisture and temperature regimes

how are soil series named?

named after a geographic feature near where they were first recognized

what are some of the benefits of using a geographic information system (GIS) to manage soil survey information?

new information about soil in an area can easily be downloaded online

particularly in terms of plant nutrient availability, why is the interaction of the soil solution and soil solids so important?

nutrients are released from solid forms to replenish those in the soil solution, which is the way plants collect nutrients

entisols

of recent origin

what are the six categories of classification in soil taxonomy?

order, suborder, great group, sub group, family, and series

what criteria are used to distinguish among soils in soil taxonomy?

organic matter thickness softness

oxisols

oxide, most highly weathered

What is pH, and why is it considered a master variable in the soil environment?

pH is a logarithmic scale used to express the degree of soil acidity or alkalinity considered the master variable because it is of great significance to nearly all aspects of soil science

five major factors of soil formation

parent materials climate biota topography time

What are the two major weathering pathways? What is the primary difference?

physical disintegration and chemical decomposition physical is simply the break down of rocks into small rocks and eventually silt

what essential needs for plant growth are supplied by the soil? (6)

physical support air water temperature moderation protection from toxins nutrient elements

While the topsoil is where the majority of plant roots are located, why is an understanding of the subsoil and its properties important for proper soil management?

plant growth problems are often related to lower levels control the amount of plant available water construction and excavation sewage disposal pollutants

how to plants and animals contribute to physical weathering?

plant roots enter cracks in rocks and pry them apart burrowing animals

how does the soil contribute to the regulation of water supplies?

purifies and controls amount of water entering larger body of water at one time

the lithosphere is made up of

rock

inceptisols

show the beginnings of a weakly developed 'B' horizon

what are the three general groups of minerals that tend to be found in well weathered soils?

silicate clays very resistant end products, including iron and aluminum oxide clays very resistant primary minerals, such as quartz

Natric

silicate clays and >15% exchangeable Na; columnar

cambic

slightly altered, not enough illuviation to become argillic (Bw)

What is a pedon?

smallest 3d sampling unit that displays the full range of properties characteristic of a particular soil (1 to 10 m^2)

mollisols

soft, grassland soils

what special properties of soil water distinguish it from other forms of water?

soil water is never pure but contains dissolved organic and inorganic substances (soil solution) resists changes in its composition (buffering capacity)

what is the difference between soil texture and soil structure?

texture: relative amount of different sizes of particles structure: the way particles are arranged together

The topsoil is roughly equivalent to the _____ horizon?

the A horizon

mechanical weathering processes result in

the disintegration of rocks due to differential expansion of minerals

what is a potential difference between a field mapping unit and a classification unit in soil taxonomy?

the mapping units may represent some further differentiation below the soil series level, such as phases of soil series

what is the rationale behind the unusual nomenclature used in soil taxonomy?

the names are combinations of syllables and are root words in several modern languages. the name automatically describes the general kind of soil being classified

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

what is weathering?

the physical and chemical breakdown of particles

histosols

tissue (organic)

what are the four general processes of soil genesis?

transformations translocations additions losses

Climate influences not only the rate of weathering but the type of native vegetation dominant in an area.

true

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

true

organic matter distribution in the soil is a significant criterion for differentiating epipedons

true

the broadest category of classification in soil taxonomy specifies 12 soil orders

true

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

How do umbric, ochric, and histic epipedons each differ from the mollic epipedon?

umbric= percent base saturation is lower ochric= too thin, too light in color, too low in organic matter histic= thick layer of organic soil materials overlying a mineral soil

why is knowledge of soil properties critical when considering building on or in the soil?

unstable soil can lead to hazardous and failed construction projects

What are diagnostic subsurface horizons?

used to characterize different soils, each provides a characteristic that helps place a soil in the proper class

vertisols

vertical cracking

andisols

volcanic ash

how does abrasion contribute to physical weathering?

when loaded with sediment, water has tremendous cutting power. windblown dust and sand moving ice masses embedded with sediment

spodosols

wood ash, ashy soils bh

what types of information are contained in a modern county soil survey report?

yield potentials, suitability for different irrigation methods, drainage requirements