Exam 1 Flashcards
Chapters 1-3
soil functions
soils deliver ecosystem services enabling life on earth
importance of soil
plant production, matter cycling, habitat for biological activity (biodiversity), filter and buffer for water, carbon sequestration
ten threats to soil sustainability
1) erosion
2) organic carbon loss
3) nutrient imbalances
4) acidification
5) contamination
6) waterlogging
7) compaction
8) soil sealing
9) salinization
10) loss of biodiversity
five concepts of soil
1) mixture of solids, liquids, and gases
2) various colors (iron gives soil a red color)
3) formed from parent materials
4) soil has structure
5) soil has horizons
ideal composition
25% air, 25% water, 45% minerals, 5% organic matter
six roles of soil
1) medium for plant growth
2) natural body
3) regulator of water supplies
4) recycler of raw materials
5) habitat for soil organisms
6) an engineering medium
uses of soil
Native Americans used earth colors as body paints; cosmetics
three types of soil degradation
physical, chemical, and biological
physical soil degradation
caused by tillage or compaction from heavy equipment
chemical soil degradation
overapplication or misuse of fertilizers and pesticides
biological soil degradation
overgrazing that leads to compaction, less perennial root systems, and introduction of invasive species
what percentage of soil degradation is caused by agricultural practices?
39% (which is the highest)
three strategies to prevent/reduce degradation
1) the use of soil cover
2) improve landscape biodiversity
3) the use of living roots in agricultural practices
high functioning soils
closely related to soil health
soil health
the continued capacity of a soil to function as a vital, living ecosystem that sustains plants, animals, and humans
four soil health principles
1) maximize living roots
2) reduced tillage
3) maximize soil covers / cover crops
4) maximize biodiversity
soil microbes have key roles in…
nutrient cycling
five benefits of soil
1) medium for plant growth
2) regulator of water supplies
3) recycler of raw materials
4) habitat for soil organisms
5) engineering medium
how does soil act as a natural filter for water?
1) the movement of water, minerals, and organic materials filter and detoxify precipitation
2) soil can clean sewage
3) microorganisms can consume wastewater in drained fields
why is soil considered a microecosystem?
soil provides a habitat for the greatest diversity of microorganism species than any other environment on the earth
what materials can be made from clays?
ceramics and drilling fluid that is used by the oil industry
soils are like fingerprints because…
every type of soil has unique properties and can be traced back to its origin
four basic aggregate shapes
granular, blocky, prismatic, and platy
soil color can be used to determine…
whether a soil has high or low OM, is wet or dry, has aerobic (oxidized) or anaerobic (reduced) condition, and has a high or low iron content
4 processes that make soils
1) transformations - weathering
2) translocations - moving
3) additions - organic matter input, soil from wind erosion
4) losses - leaching and erosion
soil horizon
roughly parallel layers in the soil with varying composition and properties
soil profile
2D rep. of a vertical section of soil from the surface to deepest layers
soil master horizons
O, A, B, C
A horizon
dark color, minerals, best for plant growth, decomposed OM, 90% food production from A horizon, zone of gas and water exchange, high biotic activity and plant roots
B horizon
lighter color, more clay, less OM, accumulates material lost from from above, zone of translocation, good soil structure, high reactivity, strong color (clay), illuvial
C horizon
weakly altered by soil forming processes, resembles parent material
E horizon
between A+B in Western KY - lighter color, leaching, zone of leaching, Fe + Al oxidizes, elluvial
five soil forming factors
1) parent material
2) climate
3) organisma (vegetation, fauna, and soil biota)
4) relief (landforms and topography)
5) time
five transported parent materials
1) water (alluvium)
2) wind (sand or silt)
3) gravity (colluvium)
4) ice (glacial drift - materials transported by ice or glaciers)
5) loess -> silt -> silt loam
what is the most common parent material in western KY
loess
glacial till
morianes, end moraine, drumlins
sorted parent materials
water (outwash and lacustrine=former lake bottom), wind, and sand
effect of temperature on soil formation
warmer = faster
cooler = slower
effect of precipitation on soil formation
higher rainfall = greater leaching
why does soil get older faster in tropical climates?
the rainfall amounts, leaching, and the fact that the soil never gets to rest because of year-round cropping, temperature
leaching zone
determined by the location calcium carbonate in the soil profile
evapotranspiration
the amount of effective rainfall that can cause soil leaching
four organism soil forming factors
1) animals - soil mixing
2) vegetation - addition of OM
3) prairie - OM added to upper 2 feet of soil due to fibrous roots
4) forest - OM added to upper 4 inches due to yearly leaf fall
three relief / topography soil forming factors
1) catena
2) drainage classes
3) erosion and deposition
catena
a series of soils with different horizons due to differences in their depth to the water table
four drainage classes
1) well-drained
2) moderately well-drained
3) somewhat poorly drained
4) poorly drained
summit
minimum erosion and maximum soil development
backslope
similar to summit unless slope is >20%
shoulder
greatest erosion, least water infiltration, greatest runoff, minimal soil development
footslope
dark soil color, good soil fertility, high amount of water, may have greatest leaching, deposition of materials from upslope
aspect
direction the slope faces
hillslope
N facing slopes = more soil development
S facing slopes = less soil development
the age of a soil is determined by its _________ not the actual ______________
development; number of years it has been developing
six young soils
1) Entisols - ent
2) Inceptisols - ept
3) Gelisols - el
4) Andisols - and
5) Aridisols - id
6) Vertisols - ert
three old soils
1) Ultisols - ult
2) Oxisols - ox
3) Spodosols - od
organic soil
Histosols - ist
*must have more than 20% OM
two mature soils
1) Mollisols - ol
2) Alfisols - alf
climate factors that slow soil formation
low rainfall, low humidity, cold temperature
biota factor that slow soil formation
mixing by animals or man
what four things happens to soil with time?
1) loss of nutrients (bases) = lower pH or soil becomes more acidic
2) increase in concentration of iron or soil becomes redder
3) increase in clay content or old soils have more clay
4) deeper weathering into parent material
oldest soil in the U.S.
Durixeralf (California) and/or Petroargid (New Mexico and Arizona)
R horizon
bedrock (limestone)
O horizon
too soft for crops to grow, primarily composed of organic matter, often called peat, extremely similar to potting soil
The most common parent material in western KY is loess (said like loss), where does it come from?
eolian transported by wind
soil formation leads to…
soil horizonation
the fragipan layer
- unique to western KY
- after B horizon
- the thicker the fragipan, the worse the crop production because it is hard for crops and water to penetrate it
- hard in nature but very brittle
seven criteria to characterizing soil horizons
1) color
2) texture- sandy loam, clay loam, etc.
3) density- how compact or loose
4) structure- granular, blocky, etc.
5) organic matter
6) mineralogy- presence of iron, calcium, etc.
7) chemistry- relates to pH
acronym for soil forming factors
CORPT
Hans Jenny
famous for soil forming factors/building processes
soil science criteria of soil profile
top 5 feet
solum
horizons A, E, and B
KY state soil series
Crider silt loam
a subhorizon
highly decomposed OM
e subhorizon
moderately decomposed OM
i subhorizon
slightly decomposed OM
g subhorizon
wet for long periods of time
h subhorizon
humic; organic matter accumulation
o subhorizon
Fe and Al oxide buildup
p subhorizon
plowing or disturbance
r subhorizon
bedrock is weathered or soft
s subhorizon
OM and Fe + Al oxides accumulation
t subhorizon
accumulation of clay
w subhorizon
changed by weathering
x subhorizon
fragipan
Ap (common in agriculture)
surface horizon with plowing or disturbance
Bg
subsoil that is wet for long periods of time
Bt
subsoil that has accumulation of clay
Ax
surface horizon with fragipan
Bx
subsoil with fragipan
Bw
subsoil that has been changed by weathering
seven categories of soil taxonomy
1) order
2) suborder
3) great group
4) subgroup
5) family
6) series- common name
7) phase or type
twelve soil orders
1) Andisols
2) Entisols
3) Inceptisols
4) Aridisols
5) Gelisols
6) Vertisols
7) Mollisols
8) Alfisols
9) Ultisols
10) Spodosols
11) Oxisols
12) Histosols
oldest soil order
Oxisols
two soil orders commonly found in tropical areas
oxisols and ultisols
soil order developed under grasslands
mollisols
soil order developed under forest
alfisols
soil order considered organic soil
histosols
soil order developed under volcanic eruptions
andisols
soil order that has crazy clay
vertisols
soil order developed in weathered areas
oxisols
older, weathered soils may have a _______ or ______ color below the surface of the soil
yellow; red
andisols
- young
- low bulk density
- high porosity
- wind erosion problem
- amorphous clays
- highly productive and good for rice farming
- Hawaii
entisols
- only A horizon over C, missing B
- found on or with: inert parent materials, very poor limestone, active floodplains, poor climate conditions
inceptisols
- immature but more developed than entisols
- weak development
- tundra, mountains, etc.
aridisols
- develop in areas with only short wet periods
- little leaching of base cations
- low OM, salt accumulations
gelisols
- young, little development
- cold, frozen most of the year
- missing A and B horizons
- permafrost
vertisols
- must have more than 30% montmorillonite
- high expansion and contracting, self mixing
- poor horizonation except for deep A horizon
- very difficult management
- gilgai topography
mollisols
- greater than 50% BS
- usually grassland soils
- subhumid to semiarid; cold to hot
- very fertile and productive, most prized soils in the world
- high OM
famers use…
soil series
alfisols
- mature soil
- well developed A, (E), B, and C horizons
- greater than 35% base saturation in Bt horizon
- forest soils
ultisols
- well developed horizonation
- found in southern states and tropical areas
- acidic, < 35% BS
- productive when managed well
- high in 1:1 clays and has crazy clays
- orange color
spodosols
- old soil
- high sand content
- highly leached
- very acidic, low % BS
- very infertile
oxisols
- highly weathered
- tropical soils
- low activity clays
- Fe and Al oxides
- very strong soil (good for engineering)
- very low % BS
- not much difference in horizons
histosols
- organic soils
- high OM, sometimes 0.001-60% clay
- usually saturated part of the year
- high water and nutrient holding
- low bulk density (very soft)
youngest soil
entisols
boralf
alfisols
argid
aridisols
fluvent
entisols
hemist
histosols
xerult
ultisols
aquert
vertisols
ochrept
inceptisols
udoll
mollisols
turbel
gelisols
vitrand
andisols
torrox
oxisols
aquod
spodosols
oldest soil suborder
Torrox
youngest soil suborder
fluvent
volcanic eruption
vitrand
high sand
aquod
crazy clays
aquert
needs drainage, too wet
hemist
permafrost and found in Alaska
turbel
older than the youngest one
ochrept
commonly found in TX
argid
Om > 60%
hemist
best for farming
udoll
from prairie
udoll
developed under forest
boralf
commonly found in Hawaii and Japan
vitrand
uniform layers
torrox
