Soil Science Final
Primary minerals are most prominent in the ____ fraction of soils.
Sand
clear-cutting
The process of cutting down all the trees in an area at once
igneous rock
a type of rock that forms from the cooling of molten rock at or below the surface
Lacustrine
sediments in standing water; lake bottoms. lakes that get filled by incoming sediment
Most (usually 80% or more) of soil potassium and calcium can be found in the form of ______ .
structural components of minerals
As explained in Symphony of the Soil, how much of a yield improvement was witnessed from studies conducted in Africa on organic farming as compared to 'conventional' methods?
125%
An acid soil is known to contain toxic quantities of a certain plant nutrient. Which of these essential elements is it most likely to be?
manganese
Andisols
(young volcanic soils) • more than 60% volcanic ejecta (dominate rock is basalt)
soil porosity
1 - (bulk density/particle density(2.65))
Cover crop utilization can reduce nitrate release from the soil by up to ____ percent.
70%
Vermiculite
A 2:1-type silicate clay, usually formed from mica, that has a high net negative charge stemming mostly from extensive isomorphous substitution of aluminum for silicon in the tetrahedral sheet.
In which of the following horizons has the process of elluviation most likely occurred?
A Horizon
Dolomitic lime
A naturally occurring liming material composed chiefly of carbonates of magnesium and calcium.
Pedon
A three-dimensional soil body depicting the range of characteristics of a given soil.
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 the fastest if their water potentials, expressed in kPa, are:
A=-40; B=-50
riparian buffer
An area adjacent to a stream that is covered in vegetation in order to act as a buffer against runoff of sediment, pesticides, and excess fertilizer.
physical weathering
Any process that breaks rock down into smaller pieces without changing the chemistry of the rock; typically wind and water.
Silicate clay accumulation is most common in the ____.
B Horizon
Silicate clay accumulation is most common in the ____ horizon.
B horizon
Which of the following is not considered one of the five major soil forming factors?
Erosion
The soil water potential is a measure of the potential of a soil to hold water.
False
Which one of the following statements is true?
Glacial till contain a heterogeneous mixture of mineral debris dropped by receding glaciers
Which one of the following sentences is false? a. Many of the nutrients taken up by plants are in the form of compounds (not elemental forms). b. Micronutrients are those that account for approximately 1% of dry plant tissue. c. S is considered to be a plant macronutrient. d. Cu is considered to be an essential plant nutrient. e. Some plant macronutrients are derived from air and water.
Micronutrients are those that account for approximately 1% of dry plant tissue.
residual
Parent materials that have been formed in place from native rock
prismatic
Usually found in B horizons, where they promote drainage & aeration Because vertical shrinkswell does not require cracks to form (the soil surface just sinks or raises), flat tops
The attraction of water to solid surfaces is called _______.
adhesion
Adhesion
attraction between molecules of different substances
Polypedon
contiguous group of similar pedons
Aeolian
deposited by wind
In which soil orders would recent alluvium most likely be a common parent material?
entisols
alluvial fan
fan- or cone-shaped deposit of sediment (called alluvium) • created as flowing water interacts with mountains, hills, or the steep walls of canyons
Hydrostatic potential
forces acting on water due to PRESSURE from weight of water, only occurs in SATURATED SOILS
If the soils are to be used for crop production, for which soil order would land drainage be most critical?
histosols
What is the biogeochemical weathering process that combines hydrogen ions from water and carbon dioxide in air and/or from organism respiration?
hydrolysis
Increased compaction ______ .
increases bulk density
Capillarity in soils ________ .
involves adhesion and cohesion
Phosphorus availability in acid soils is constrained by the presence of significant quantities of reactive ______.
iron
Brown and red colors in subsurface horizons are caused by _____ in the soil.
iron oxides
Value
lightness and darkness of a color
secondary minerals
minerals whose ionic forms of their elements have been altered by chemical weathering
The matric potential of soil water is _______.
not influenced by the force of gravity
What is the most abundant mineral in most soils?
quartz
Igneous rocks can best be characterized as:
rocks formed when molten magma solidifies
Which of the following categories of Soil Taxonomy provides the greatest specificity of soil properties?
series
Soil texture describes the ______ of particles in a soil.
sizes
Texture best describes the ____ of particles in a soil.
sizes
Unsaturated water flow _______.
soils that are at field capacity or drier
Gelisols
soils with permafrost within 2 m of the surface
friable
term pertaining to soils that can be easily crumbled.
vadose zone
the aerated region of soil above the permanent water table. The unsaturated zone above the water table
Epipedon
the uppermost horizon or horizons of a soil that is used for diagnostic purposes (A horizon)
Endopedon
the uppermost horizon or horizons of a soil that is used for diagnostic purposes (B horizon)
Nitrogen fertilization is a significant cause of acidity in many cultivated soils.
true
To reduce evaportranspiration, it is best to _______ .
use efficient irrigation and keep the soil surface covered
Among the soils of which order would you most likely find the highest buffering capacities?
vertisols
______ are characterized by high levels of swelling-type clays.
vertisols
Mass Water Content
mass of water/mass of dry soil
glacial till
materials deposited by glaciers
E horizon
most commonly used to label a horizon that has been significantly leached of clay, iron, and aluminum oxides, which leaves a concentration of resistant minerals, such as quartz, in the sand and silt sizes • present ONLY in older, well-developed soils, and generally occur between the A and B horizons
mass flow
movement of nutrients with the flow of water to plant roots
Soil Organic Matter (SOM)
organic (carbon based) substances including living organisms, remains of organisms, and organic compounds produced by current and past metabolism in the soil
Colliod
organic and inorganic matter with a very small particle size and a correspondingly large surface area per unit of mass.
Humus
organic, dark material remaining after decomposition by microorganisms
Processes affected by soil temperature
physical, biological, and chemical processes: 1. Plant processes 2. Seed germination 3. Root function 4. Microbial processes 5. Freezing and thawing 6. Soil heating by fired 7. Contaminant removal
Hydrophytes
plants that have special structures (aerenchyma tissues and pneutophores) that allow them to thrive in saturated soils by obtaining O2 from the atmosphere
gully erosion
removal of layers of soil, creating channels or ravines too large to be removed by normal tillage operations
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
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.
secondary clay silicates
sedimentary rock
sediments that are deposited in water and consolidated (hardened into a mass of rock)
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
mica
silicate mineral that readily splits into thin, shiny sheets
hydric soils
soils that are water-saturated for long enough periods to produce reduced conditions and affect the growth of plants
Fungal hyphae have an important influence on soil structure because they ______.
stabilize macro aggregates
moriane
stony hills at the ice front of a melting glacier. Materials Deposited from Glacial Ice & Meltwater
field capacity
the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. Half of Porosity
nitrogen fixation
the chemical processes by which atmospheric nitrogen is assimilated into organic compounds, especially by certain microorganisms as part of the nitrogen cycle.
Hue
the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth
Mechanical weathering processes result in:
the disintegration of rocks due to differential expansion of minerals
tilth
the ease at which soil can be worked. Physical condition of the soil in relation to plant growth • Depends on aggregate stability, bulk density, soil moisture, rate of water infiltration
Osmotic potential
the effects of dissolved substances • Liquids move in response to differences in osmotic potential (the process of "osmosis"). The potential of water containing solutes (e.g. salts) is lower than pure water; thus ψs is always negative
biogeochemical weathering
the erosion or disintegration of rocks, building materials, etc., caused by chemical reactions (mainly with water and substances dissolved in it) rather than by mechanical processes
A soil profile consists of ________.
the general outline of a soil or group of soils when viewed from the side
Capillary mechanism
the movement of water up a surface (defying gravity). Two forces cause capillarity: Attraction of water for the solid (adhesion or adsorption) AND The surface tension of water (which is largely due to cohesion). The height or rise (strength of attraction) of water in a capillary tube is inversely proportional to the radius of the tube
Chemical weathering processes result in ______ .
the oxidation of iron and manganese compounds the hydrolysis of minerals through frost action
Soil tilth refers to _____.
the physical suitability of a soil for plant growth
Flocculation
the process by which colloidal (i.e. clay-size) particles join together into small clumps
Gravitational potential
the proportion of total Soil Water Potential that is due to differences in elevation of the reference pool of pure water and that of soil water. Usually Positive.
matric potential
the proportion of total Soil Water Potential that is due to the attractive forces between water and soil solids as represented through absorption and capillarity. Always negative.
Chroma
the purity, intensity, or saturation of a color
rill erosion
the removing of thin layers of soil as little rivulets of running water gather and cut small channels in the soil
Munsell Color Chart
took all colors and mapped them out in terms of lightness, darkness, and saturation; scale goes 0-100; saturation = level of greyness in a color. For example, a brown soil may be noted as: hue value/chroma (10YR 5/3).
A soil developed in residual parent materials will likely have properties related to the properties of the rock below the C horizon.
true
About one third of the readily accessible water in the hydrologic cycle is in the soil.
true
Andisols are found mostly near recently active volcanoes.
true
As shown in the film removing livestock animals from their natural ecosystem resulted in soil depletion, over production of manure, and farmer dependency on synthetic fertilizers.
true
Dr. Daniel Hillel, Professor of Soil and Hydrology, talks about the story of Adam and Eve in the Bible. The Hebrew word "Adam" is from "Adama", which means soil. Eve is translated as "life giver", so the combination of Adam and Eve is symbolic of soil and life.
true
Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants.
true
Histosols generally have higher organic matter contents than Mollisols.
true
More than 90% of land plants have a symbiotic relationship with mycorrhizae fungi. Throughout the Earth's evolution, there would have been no colonization of the land by plants from the ocean (and all the animals that rely on plants for food) without fungi.
true
Plants produce exudates for the purpose of growing bacteria and fungi that in turn benefit the plants.
true
Soil and crop management generally has a greater influence on evaporation from the soil surface (E) than on transpiration (T) from leaf surfaces.
true
Tillage when the soil is too wet is likely to increase the soil bulk density.
true
Vertisols are characterized by high contents of swelling-type silicate clays.
true
Gas Composition of Air
• Composition of air • 79% Nitrogen • 21% Oxygen • Trace amounts carbon dioxide, helium, argon, etc. • Water can be a factor depending on humidity
Exchangable cations
• potassium (K+) • sodium (Na+) • ammonium (NH4 +) • calcium (Ca2+) • magnesium (Mg2+) • hydrogen (H+) • aluminum dihydroxide (Al[OH]2 +) • aluminum (Al3+)
Limitations of Soil Tests
"Growers are used to taking soil samples and having them analyzed for available nutrients, pH, and total organic matter by a university or commercial lab. • The traditional soil test does not, however, make a comprehensive assessment of the health of a soil, which in fact probably fed the "chemical bias" in soil management. In other words, the widespread availability of good chemical soil tests, although a very useful management tool, may also have encouraged the quick-fix use of chemical fertilizers over the longer-term holistic approach promoted in this book."
Raindrop Erosion
(aka. splash erosion), the detachment and airborne movement of small soil particles caused by the impact of raindrops on soils.
Aridisols
(desert soils) • Lack of water reduces leaching, slows mineral weathering & allows accumulation of salts • Low SOM ; minerals make up most of these soils forming from parent rock
Alfisols
(fertile soils with subsoil clay) • Typically occur under hardwood forests that receive moderate precipitation to move clays downward • Have a clay-enriched subsoil; "Alf" refers to Al and Fe • Alfisols are one of the two most naturally productive soils used for crops
Ultisols
(highly leached soils with subsoil clay) • Warm humid-area soils • Have developed in humid climates, tropical to subtropical climates, and a forest or forest-savanna vegetation • Red-clay hills of southeastern U.S. • Clayey, often reddish
Oxisols
(highly oxidized soils) • Most intensively weathered of all soils • Found in old landforms in humid, tropical, or subtropical climates (weathering is accelerated by moisture and hot temperature) • Usually yellowish to bright red • Rich in Fe an Al hydrous oxide • Found in Hawaii, Guam, Puerto Rico, South America, and Africa
Mollisols
(prairie soils) • Dark colored soils of grasslands and hardwood forests • Deep, dark-colored, fertile A horizon • Tend to be the most fertile soil order - have higher contents of humus and nitrogen • Found in subhumid areas such as the Great Plains
Vertisols
(shrink-swell clays) • Expand and contract more than any other soils because of high clay content • Swelling and shrinking churn & mix the upper horizons • Resist degradation • Have 30%+ clay • Occur in humid, semiarid climates with noticeable wet and dry cycles • Develop from parent materials high in limestone and basalt
Spodosols
(soils with humus under sand) • Acidic soils of forested areas where coarse-textured parent material (sand) is present • High rainfall and easy leaching cause translocation • Characteristics: usually have O horizon, strongly acidic profile & well-leached E horizon • Found in cold wet climates and in Florida
Entisols
(soils with little or no horizon development) • Lack horizons because they are young or because weathering is ineffective • Slight soil development • Range from deep sand, stratified river-deposited clays, and recent volcanicash deposits to dry lake beds
Inceptisols
(soils with weak horizon development) • Have few diagnostic features - soil formation is in early stages • Lack a mature soil profile possibly due to: •Deposit may be recent (few decades) •Short weathering time to develop horizons
parent material
(unconsolidated material in which soil develops - this is the starting point for soil development) • Soil texture is often determined by the nature of parent materials • Parent materials may have been formed in place from native rock (residual) or they have been transported by water, ice, wind, or gravity
If porosity is 56% of a volume of soil, how much water is in 1 cm3 of that soil at field capacity?
0.56cm3
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 typical mineral soil in optimal condition for plant growth, approximately what percentage of the soil sample would be filled with water and what percentage filled with air?
25% water and 25% air
____ of U.S. soils are in the two most naturally productive soil orders, ______ and ______. This percentage is 2 to 3 times above the average that these soils are found globally, which is am important reason why the U.S. has experienced such high agriculturally productivity throughout its history.
40%, Mollisols, Alfisols
If porosity is 42%, how much of the volume of soil is filled with water at saturation?
42% bc saturation is when pore space is completely filled
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% air and 50% water
In a load of 12 cubic meters of topsoil, approximately how many cubic meters of the volume would be solid material? (in an average soil, assuming 50% pore space)
6
"Topsoil" is generally equivalent to which soil horizon?
A Horizon
In a given soil, the horizon with the highest organic matter content is generally the _____ horizon.
A Horizon
Montmorillonite
An aluminosilicate clay mineral in the smectite group with a 2:1 expanding crystal lattice, with two silicon tetrahedral sheets enclosing an aluminum octahedral sheet. Considerable expansion may be caused by water moving between silica sheets of contiguous layers.
Cohesion
Attraction between molecules of the same substance
Liming materials
Calcic limestone (CaCO3) • Dolomitic limestone (CaMg(CO3)2 ) • Lime from bottom of small freshwater ponds, soft limestone in ocean bottoms, furnace slag, ground oyster shells, wood ashes
Soil Forming Factors CROPT
Climate (temperature and precipitation) • Relief (slope, aspect, and elevation - called topography) • Organisms (living & dead/decaying organisms and residues) • Parent material (unconsolidated material in which soil develops - this is the starting point for soil development) • Soil texture is often determined by the nature of parent materials • Parent materials may have been formed in place from native rock (residual) or they have been transported by water, ice, wind, or gravity • Time
The mixed angular gravel, rock, and soil found at the foot of a steep slope is typical of what type of parent material?
Colluvial
factors effecting aeration
Drainage of excess water • Rates of respiration in the soil • The soil profile • Soil heterogeneity • Tillage • Pore sizes • Plant roots • Seasonal differences • Effects of vegetation
Where high-value crops, such as ornamental shrubs, are grown and water is expensive, the most efficient type of irrigation to use is _________ .
Drip or trickle
Which type of soil structure is typically due to biological activity found in surface soil?
Granular
_______ are organic soils found in wetlands.
Histosols
Which statements about igneous rocks are TRUE?
Igneous rocks can contain quartz. Types of igneous rocks include granite and basalt.
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 from the data given
blocky
In clayey soils, the horizontal cracking will form block peds Common in B horizons in humid areas (but may be in A)
Which of the following statements is correct? a. Nutrient cycling in forested areas contributes little to soil formation. b. Soils on hillsides tend to be deeper than those on level lands. c. Lacustrine parent materials have been subject to weathering for shorter periods of time than residual parent materials nearby. d. Calcium carbonate accumulation is more prominent in humid than in arid regions. e. Limestone parent materials enhance the process of acidification.
Lacustrine parent materials have been subject to weathering for shorter periods of time than residual parent materials nearby.
Loess
Materials Deposited from Wind Loess: wind-carried deposits dominantly silt sized (about 60-90% silt) • generally forms productive soils
______ are the most highly weathered of the soil orders, and are most prominent in the humid tropics where rain forest is the dominant natural vegetation.
Oxisols
compost
Partially decomposed organic plant and animal matter used as a soil conditioner or fertilizer.
Water Balance Equation
Precip (P) = Evapotranspiration (ET) + Soil Storage (SS) + Discharge (D)
Leaching
Process in which various chemicals in upper layers of soil are dissolved and carried to lower layers and, in some cases, to groundwater.
Kaolinite
Residues from extensive weathering in high-rainfall, acidic soils • One plane of O2 - layer is substituted by OH- which creates strong H bonding to adjacent layer that don't allow water penetration (non-expanding)
The lithosphere is made up of ______.
Rock. Plants
Which one of the following statements is FALSE? a. Sandstone and granite are examples of sedimentary rock. b. A mineral is a naturally occurring inorganic substance of definite chemical composition, and whose atoms are arranged in a pattern, such that crystalline structures may form. c. Parent materials are made up of rock that breaks down (weathers) over time and becomes the mineral fraction of soil. d. Marble is a metamorphic rock produced from limestone. e. A rock is an aggregate of one or more minerals.
Sandstone and granite are examples of sedimentary rock.
Colluvial
Sediments mostly moved by gravity • Colluvium: material that accumulates at the foot of a steep slope • Made up of poorly sorted rock fragments
Causes of water erosion
Soil peds disintegrated by direct impact of raindrops • Can move soils up to 1.5m • Soil moves into pores, clogging occurs reduces infiltration & increases runoff & suspended sediments become abrasive • Finer particles washed away • Irresponsible ag practices - removing plant cover with excessive plowing, burning crop residues, over-grazing, and clear-cutting forests • Erosion by water is classified as raindrop splash, sheet erosion, and rill and gully erosion
Soils in this order are commonly sandy in texture, quite acidic and develop primarily under coniferous trees in cool to cold climates.
Spodosols
Suspension
Suspension occurs when the wind takes fine particles of dirt and dust into the area and can move said particles over long distances
Which of the following statements about soil orders is true?
The broadest category of classification in soil taxonomy specifies 12 soil orders, 11 of which are for mineral soils.
Which one of the following statements is FALSE? a. The balance of nature in most soils is overwhelmingly in favor of organisms that provide ecosystem services essential to human welfare b. The composition of food does not reflect the composition and health of the soil in which it was grown. c. Soils play a greater role in curing diseases than causing them. d. In the video "The Other Side of the Fence", Dr. William Albrecht addresses the importance of soil for animal and human health.
The composition of food does not reflect the composition and health of the soil in which it was grown.
Evapotranspiration
The evaporation of water from soil plus the transpiration of water from plants.
Saltation
The movement of sand or other sediments by short jumps and bounces that is caused by wind or water
O horizon
The organic horizon at the surface of many soils, composed of organic detritus in various stages of decomposition
sheet erosion
The removal of a fairly uniform layer of soil material from the land surface by the action of rainfall and surface runoff.
Rhizosphere
The soil region close to plant roots and characterized by a high level of microbiological activity.
columnar
Usually found in B horizons, where they promote drainage & aeration Because vertical shrinkswell does not require cracks to form (the soil surface just sinks or raises), rounded tops
volumetric water content
Water content measure by volume. Volume of water/volume of soil. Requires bulk density to determine. 𝜃𝑣 = 𝜃𝑚 𝜌𝑏/𝜌𝑤
Which one of the following statements is false? a. The mineral fraction of soil does not include organic matter. b. Increasing the organic matter content of a soil is likely to increase the soil's water holding capacity. c. Most of the water in our rivers and lakes has come in contact with and has been affected by soils. d. Soil air usually has a higher carbon dioxide content than the air in the atmosphere. e. Where organic matter constitutes only 1 or 2 percent of the soil by weight, it has only negligible influence on soil properties.
Where organic matter constitutes only 1 or 2 percent of the soil by weight, it has only negligible influence on soil properties.
soil color
White colors are common where quartz, salts (Na+, Ca2+) or calcium carbonate CaCO3 (lime), gypsum (CaSO.2H2O) deposits exist. Red and yellow soils indicate high levels of iron (Fe) oxides formed under conditions of aeration and good drainage. Yellow-colored soils can indicate the presence of impure sulfur (such as jarosite, a potassium iron sulfate mineral). Grey and yellow-brown can be indicators of poor drainage. Dark brown or black color indicates high OM (e.g. presence of humus) or dark minerals (e.g. basalt, manganese oxide cause black color) ...and/or it indicates the presence of moisture, wet soil is darker than dry soil.
Smectite
a 2:1 type lattice structure silicate clay. high interlayer negative charge and high CEC
Top soil (A horizon)
a crumbly, dark brown soil that is a mixture of humus, clay, and other materials
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
soil water potential
a measure of the difference between the free energy state of soil water and that of pure water
primary minerals
a mineral that has not been altered chemically since deposition and crystallization from molten lava
A soil with a bulk density equal to 0.35 Mg/m3 is most likely what type of soil?
a peat soil
For which substance would the particle density equal the bulk density?
a quartz pebble
surface creep
a stage in the wind erosion process in which sand grains are moved along the ground surface by impact of other grains in saltation.
A soil pedon is ____.
a three-dimensional unit that embodies the primary characteristics of an individual soil
Which statements are true?
a. For any soil, the bulk density is always lower than the particle density. b. Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants.
Which statements are true? a. Soil plays a purifying role in ecosystems, for example soil microorganisms decompose toxins and pollutants in water. b. Most of the water in our rivers and lakes has come in contact with and has been affected by soil c. Where organic matter constitutes only 1 or 2% of the soil by weight, it has only negligible influence on soil properties. d. Soil air usually has a higher carbon dioxide content than the air in the atmosphere.
a. Soil plays a purifying role in ecosystems, for example soil microorganisms decompose toxins and pollutants in water. b. Most of the water in our rivers and lakes has come in contact with and has been affected by soil d. Soil air usually has a higher carbon dioxide content than the air in the atmosphere.
Ped
an aggregate formed by natural processes
Delta
an alluvial deposit formed where a stream or river deposits its sediment load upon entering a quieter body of water
Soil structure describes _____ .
arrangement of particles in a soil
R horizon
bedrock
B horizon
below A horizon • lower in organic matter but higher in soluble materials such as salts and clays • is an illuvial horizon
C horizon
below B horizon • deep enough to be unaffected by the migration of materials • includes parent material - the mineral material in which soils originated from the Earth's bedrock
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
Secondary minerals are most prominent in the _____ fraction of soils.
clay
The percentages of which soil components represent the minimum information necessary to determine the textural class of soil?
clay and sand
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
Permanent Wilting Point (PWP)
corresponds to the water content retained by the soil when the matric potential is about -1500 kPa. Water at PWP is held so strongly that plants are not able to extract it fast enough for their needs. One Quarter Of Porosity
fallow
cropland left idle in order to restore productivity through accumulation of nutrients, water, and OM
selective cutting
cutting down only some trees in a forest and leaving a mix of tree sizes and species behind
Urban development of land that was under natural vegetation or agriculture usually greatly _____ soil infiltration capacity and therefore greatly increases _______.
decreases; stream bank erosion
bulk density
dry weight of soil per unit volume of soil (g soil/volume of soil)
A Horizon
eluvial horizon. Enriched in decomposed OM
Nitrogen fertilizer runoff causes ________ in bodies of water, which results in a termination of aquatic life at that location.
eutrophication
The exchange complexes of strongly acid (pH 4.5) mineral soils are saturated mainly with _____.
exchangeable Al3+ ions
50% of grain production in China is dependent on irrigation.
false
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.
false
Eutrophication is enhanced by the presence of pesticides in the water draining from agricultural soils.
false
Fungi are much more sensitive to strong acid conditions than are bacteria or actinomycetes.
false
Hydraulic redistribution or hydraulic lift dries out shallower soils during dry periods, allowing trees to take advantage of water deeper in the soil profiles.
false
Hydrogen ions dominate the exchange complex of very acid soils (pH<5).
false
Living organisms affect soil formation primarily by their constraining the level of oxygen in the soil.
false
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.
false
Soils developed in wind-blown parent materials such as loess are generally of little agricultural value.
false
The acidity of "acid rain" can be traced to the reaction of CO2 in the atmosphere forming carbonic acid (H2CO3).
false
The drainage of some coastal wetland soils results in high pH due to underlying lime deposits.
false
Histosols
formed in cold or wet regions • found in swamps, marshes, bogs where the rate of new plant material production exceeds the rate of decomposition of old material • common in Alaska, Finland, Canada • contain at least 20-30% organic matter by weight
granular
glued together by organic substances and mixed by rodents, earthworms, frost, cultivation such that the edges are rounded; limited to surface horizons unless buried by sediment
Which type of soil structure is typically found in surface soil (A horizons)?
granular
metamorphic rock
igneous or sedimentary rocks hardened or altered by heat, pressure, or reactions with chemical solutions
Which of the following human actions is most apt to result in a long term increase in soil pH? a. application of NH4- containing fertilizers b. application of farm manure c. irrigation with high sodium salt-containing waters d. emission of gases from automobiles e. application of unlimed sewage sludge
irrigation with high sodium salt-containing waters
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
Compared to a clay soil, sand-sized soil particles are characterized by ______.
less capacity to hold nutrients and water
sub soil B Horizon
located below topsoil, this layer of soil contains clay and iron oxides washed from and absorbed from the topsoil
Soils with high porosity have a _________ .
low bulk density