chapter five: soils Flashcards
percentages of optimal soil conditions
50 % solid:
-45% mineral matter from rocks
-5% organic matter
50 % pore space
-25% H2O
-25% air
there are ___ soil orders
12
layers of the soil that are part of the biosphere; interact with living things
fertile zone
which three horizons are contained in the fertile zone
O
A
E
soil horizon that contains humus and organic matter
O horizon
the O horizon is where soil bacteria and fungi break down ___
organic matter
organic matter that is partially broken down
humus
a layer of topsoil
A horizon
eluviation layer, where leaching occurs, the bottom of the topsoil
E horizon
layers of the soil that are not part of the biosphere do not interact with living things
infertile zone
4 soil horizons in the infertile zone
I
B
C
R
illuvial layer; zone of accumulation for minerals/elements, top of subsoil
I horizon
subsoil; mixture of sand, silt, and clay; impenetrable to most things
B horizon
unconsolidated parent material
C horizon
regolith layer; solid parent material (bedrock); where minerals come from
R horizon
the percent sand, silt, and clay in a given soil
soil texture
sand, silt, and clay are ___ identical; they are defined by ___
chemically
diameter of particle
ideal soil with balanced parts of sand, silt, and clay (one third of each)
loam soil
clay particles are ____ in diameter
< 0.002mm
what is the shape of clay particles
flat, not globular
individual clay particles are called ___
micells
clay particles (micells) have a ___ charge
negative
micells will permanently suspend in water, so they are known as ___
colloids
shape of silt particles
globular
silt particles are ___ in diameter
0.002-0.05mm
sand particles are ___ in diameter
0.05-2.0mm
sand types in order from smallest to largest particles
very fine sand
fine sand
medium sand
coarse sand
very coarse sand
can you change soil texture
no
the appearance of soil when it clumps together
soil structure
can you change soil structure
yes, by mixing
5 soil forming factors
- parent material
- climate
- topography
- living organisms and organic composition
- time
rock that the mineral matter in the soil is made from
parent material/regoliths
___ and ___ are the most common regoliths
granite and basalt
parent material accumulates through weathering of these 3 types of rock from these sources
- igneous rock from volcanic activity
- sedimentary rock from depositing by glaciers, water, or wind
- metamorphic rock from changes in igneous or sedimentary rocks from extreme pressure, heat, or both
___ and ___ are the two most important factors for climate
temperature and rainfall
lay of the land
topography
in steep land, soil may ___ or ___ because of wind, water, and ice
wash away or erode
in flat land, ___ and ___ may appear when it rains
pools and ponds
what is the topography in East Tennessee called that contains mostly foothills
rome formation
an ideal topography for soil formation is one that permits ___ without ___
drainage
erosion
the most important soil forming factor
time
it takes ___ years for one inch of topsoil to develop
1000
3 types of water found in soil
- hydroscopic water
- gravitational water
- capillary water
what is hydroscopic water
water chemically and permanently bound to the soil
hydroscopic water is ____, no matter how dry the soil seems
always present
is hydroscopic water available to the life in/on the soil
no
can hydroscopic water be removed under natural conditions
no
how is hydroscopic water removed in a lab
baked at 400 degrees for days
what is gravitational water
water that passes through the soil system into the water table by gravity
underground water that can be shallow or deep
water table
gravitational water is ___ in the soil after rainfall
temporarily
gravitational water is ___ available to life in/on the soil
temporarily
what is capillary water
water help against gravity in pores of the soil
capillary is the ____ to life in and on the soil
most available
the amount of capillary water and area can potentially hold
field capacity
___ is the most important factor in determining field capacity
soil density
is soils heavy in clay reach a field capacity of ___, plants reach a permanent wilting point
less than 15%
if sandy soils reach a field capacity of ___, plants reach a permanent wilting point
less that 4%
the most important biological parameter of all
pH
____ in soil causes certain minerals (like copper, iron, and manganese) to become less available to plants
alkalinity
acidity in soil inhibits the growth of ____
nitrogen-fixing bacteria
adding ___ to soil makes alkaline soils more acidic
sulfur
“black earth” in the midwest
mollisols
black pigments in soil come from ___
organic matter
red pigments in soil come from ___
iron and aluminum oxides
white pigments in soil come from ___
silicates and salt
found in the midwest where deserts meet grasslands
cryptobiotic soils
cryptobiotic soils have a ___ on the top of the ground that is ___ and will ___ underneath the foot
crust
cake-like
crunch
cryptobiotic soils are ___ in color
light (mosaic)
cryptobiotic soils are rich in ___ and ___ that are only found in this soil
bacteria and fungi
cryptobiotic soils are the ___ soils on the planet
rarest
cryptobiotic soils contain rare compounds that could be ___
medicinal
