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