SOIL Flashcards
Define soil
a loose mixture of small rock fragments, organic matter, water and air that can support the growth of vegetation.
1st step of soil formation is
weathering of a parent rock
in soil formation, the parent rock is the source of
inorganic particles
soil forms where
directly above the parent rock
what breaks down the parent rock?
weathering
parent rock is broken into smaller pieces and mixes with what
organic matter
what two things form soil?
small pieces of parent rock + organic matter
what are two decomposers that live in soil
bacteria and fungi
the decomposers break down the remains of
plants and animals
the remains of decayed organic matter is called
humus
humus is found where
the top layers of soil
humus contains
the nutrients that plants need to grow
larger animals such as earthworms and moles do what to the soil
loosen and mix
when animal loosen and mix soil, what results
increases the air in soil and improves soil ability to drain water
what are the 4 main factors determine how long it takes for soil to form
rock type, climate, topography, plants/animals
rock types weather at different rates and different ways T or F?
true
weathering of the rock depends on the
structure and minerals that make up the rock
soil usually develops more quickly in what climate
warm and wet
soil develops faster in what topography
flatter (not steep slopes)
soil in areas with lots of plants and animals develop
FASTER than in areas without plants and animals
a vertical section of soil that shows layers is called
soil profile
each layer of soil have different physical properties called
soil horizon
what is A horizon?
the top of the soil profile
what is B horizon?
below horizon A
what is C horizon?
below the B horizon
in what layers do decomposers live
Horizon A
which layer has most decayed matter
Horizon A
what color is humus on Horizon A
very dark color
what layer is the most developed and rich?
horizon A
which layer has the most humus
horizon A
in what layer does leaching happen
horizon B
what causes horizon B to be reddish in color?
leaching
explain leaching
after it rains, water seeps from layer A to layer B and washes away minerals and clay from soil.
what layer is least developed
horizon C
horizon C lies directly above the what
parent rock
does horizon C have organic matter
NO
what layer has largest rock fragments
horizon C
what are 6 properties of soil
texture, color, chemistry, pore space, fertility, permeability
what describes the size of soil particles
texture
soil particles are classified
as sand, silt or clay
most soils have all three–sand, silt, clay T or F
TRUE
what is the largest soil particle
SAND
what is sand particle size?
.05mm to 2mm
soils with a lot of sand feel
coarse
silt particles are what size
0.002mm to .05mm
soil with a lot of silt feel
smooth and silky
clay particles are how big
less than .002mm
soil with a lot of clay feel
smooth and sticks together when wet
soil can be what colors
black, brown, red, orange, yellow, gray and white
what determines the color of soil
the amount of minerals and organic matter in soil
what makes soil orange or reddish
iron
what makes soil black or brown
lots of humus
color of soil can be a clue about
environmental conditions
what does gray soil mean
too wet and poor drainage
soils are usually what color
a mixture of alot of colors
soil PH is determined by
combination of minerals, sediment and organic matter in soil
the soil PH measures how
acidic or basic a soil is
soil PH is measured on a scale of what to what
0 - 14
if ph is less than 7, soil is
acidic
if pH is more than 7 soil is
basic
a ph of 7 means
neutral–nor acid or basic
the PH level is used to determine
whether or not soil can support different plants
soy beans grow best at what PH
6 and 7
peanuts thrive at PH of
5.3 and 6.6
pore space describes
the space between soil particles
what is found between the pore spaces of soil
water and air
water and air move more easily through soils with
many well connected pore spaces–good plant growth
what percentage of soil is pore space
between 25 and 60 percent
the best soil for growing has about ____ pore space
50% (equally divided between water and air)
how do you describe soil fertility
how well soil can support plant growth
factors than can affect fertility include
climate, humus, minerals, nutrients in soil and topography
what are best conditions for fertile soil
moderate rainfall and moderate temperatures
high soil fertility has small amounts of humus
FALSE
Proper proportions of minerals and nutrients = high soil fertility T or F
TRUE
soil in dry areas or steep hillsides have high fertility
FALSE
Name three ways farmers can improve soil fertility
- add chemicals
- grow certain crops to restore nutrients
- leave land unplanted for a season
define permeability
property of soil which allows water to pass through
some of the MAJOR problems of soil is connected to
permeability
Too much soil permeability can be
a disaster!
Permeability of soil is connected to the success of
the design of highways, airports, earth dams etc…
what will happen to plants if there is too much permeability
they will be transported
what happens to plants if soil has not enough permeability
plants cannot get the water/nutrients they need
If low permeability, it takes longer or shorter for soil to form
LONGER
what is porosity
the volume of spaces between soil particles
what is the definition of permeability
the ability to transmit or release fluids
