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Soils as the foundation of a forage program
part of test 1
218
Agriculture
Undergraduate 4
01/15/2017

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Term
some functions of soil
Definition
-Anchor medium for plants; provides support to the plant
-Water reservoir for plant growth
-Exchange site for nutrients required for plant growth
Term
the 5 factors of soil formation
Definition
-Parent material
-Climate
-Living organisms
-Topography
-Time
Term
depiction of how rock is weathered to form soil
Definition
[image]
Term
Metamorphic rocks formed by...
Definition
heat and pressure
Term
Igneous formed by...
Definition
magma
Term
Sedimentary rocks formed by...
Definition
cementing of sediment
Term
Silica combines with ______ in oxides
Definition
Fe
Term
Glacial escarpment
Definition
a steep slope or long cliff that occurs from faulting and resulting erosion and separates two relatively level areas of differing elevations
Term
Moraine
Definition
Any glacially formedAny glacially formed accumulation of unconsolidated glacial debris (soilAny glacially formed accumulation of unconsolidated glacial debris (soil and rock) which can occur in currently glaciated and formerly glaciated regions
Term
water's rome in forming soil
Definition
The hydraulic effects of flowing water, such as in rivers and streams, will break down rocks to parent material for soil formation.
Term
some types of soils
Definition
-residual
-transported
Term
residual soils
Definition
-Piedmont soils
-Formed in place from the rock-derived parent material
Term
transported soils
Definition
-Coastal plains, river beds
-Particles are transported from their origin to a new geographic location
Term
loess soil
Definition
wind transported; forms sand dunes
Term
alluvial soils
Definition
soils transported by water
Term
why mollisols are rich in OM
Definition
because of the decay of grass roots and such
Term
udults
Definition
humid ultisols
Term
the final stage of the decomposition of organic matter
Definition
humus
Term
Humus
Definition
the final stage of the decomposition of organic matter
Term
how natural vegetation can influence the type of soil
Definition
differences in the distribution of organic matter in the upper part of the soil profile
Term
description of the top layer of a forested soil
Definition
Forested soil exhibits surface layers (O horizons) of leaves and twigs in various stages of decomposition, along with a thin, mineral A horizon
Term
how grass affects the soil profile in grassland soil
Definition
Most of the organic matter in the grassland is added as fine roots distributed throughout the upper 1 m or so, creating a thick, mineral A horizon
Term
which soil is more acidic and more leached? forested or grassland?
Definition
forested
Term
which soil has more organic matter? that under grasslands or that under forests?
Definition
under grasslands
Term
Organic layer in forest soils made of...
Definition
leaves and twigs and such
Term
More organic matter in grassland thanks in part to...
Definition
grass having less lignin and lower C:N ratio
Term
why soils under forests are acid in nature
Definition
because of roots secreting acid
Term
why grasses are important in the environmental protection of soils
Definition
because grass roots hold soil in place, even sand
Term
one distinguishing characteristic of histosols
Definition
high OM content
Term
where histosols are often found
Definition
flooded places
Term
why histosols have such high OM content
Definition
because the flooded places they're found in have no air getting to the soil, such that the OM doesn’t decompose
Term
why Cecil soil aggregates better than Tifton soil
Definition
higher clay content
Term
why Cecil soil is red
Definition
high Fe
Term
why Tifton soil is yellow
Definition
high Al
Term
some physical properties of soil
Definition
-texture
-structure
Term
soil texture
Definition
mineral particle size
Term
some types of soil particles
Definition
-sand
-silt
-clay
Term
sand
Definition
macropores (coarse texture)
Term
silt
Definition
clay coated particles
Term
clay
Definition
fine texture
Term
soil structure
Definition
How particles are held together
Term
some types of cementing
Definition
-temporary
-permanent
Term
what causes temporary cementing?
Definition
-bacterial gums
-fungal mycelium
Term
what causes permanent cementing?
Definition
humus from organic matter
Term
the four major components of soils
Definition
-Minerals
‑Organic Matter
‑Water
‑Air
Term
chart showing the general composition of most soils (except for histosols)
Definition
[image]
Term
amount of soil mass taken up by minerals
Definition
95-100%
Term
amount of soil mass taken up by organic matter
Definition
0-5% (except for histosols)
Term
% of soil volume taken up by air and water
Definition
Air and water make up about 50% of soil volume – but this can vary from <40 to >60 depending on the soil.
Term
some functions of soil
Definition
-Anchor medium for plants; provides support to the plant
-Water reservoir for plant growth
-Exchange site for nutrients required for plant growth
Term
the 5 factors of soil formation
Definition
-Parent material
-Climate
-Living organisms
-Topography
-Time
Term
depiction of how rock is weathered to form soil
Definition
[image]
Term
Metamorphic rocks formed by...
Definition
heat and pressure
Term
Igneous formed by...
Definition
magma
Term
Sedimentary rocks formed by...
Definition
cementing of sediment
Term
Silica combines with ______ in oxides
Definition
Fe
Term
Glacial escarpment
Definition
a steep slope or long cliff that occurs from faulting and resulting erosion and separates two relatively level areas of differing elevations
Term
Moraine
Definition
Any glacially formedAny glacially formed accumulation of unconsolidated glacial debris (soilAny glacially formed accumulation of unconsolidated glacial debris (soil and rock) which can occur in currently glaciated and formerly glaciated regions
Term
water's rome in forming soil
Definition
The hydraulic effects of flowing water, such as in rivers and streams, will break down rocks to parent material for soil formation.
Term
some types of soils
Definition
-residual
-transported
Term
residual soils
Definition
-Piedmont soils
-Formed in place from the rock-derived parent material
Term
transported soils
Definition
-Coastal plains, river beds
-Particles are transported from their origin to a new geographic location
Term
loess soil
Definition
wind transported; forms sand dunes
Term
alluvial soils
Definition
soils transported by water
Term
why mollisols are rich in OM
Definition
because of the decay of grass roots and such
Term
udults
Definition
humid ultisols
Term
the final stage of the decomposition of organic matter
Definition
humus
Term
Humus
Definition
the final stage of the decomposition of organic matter
Term
how natural vegetation can influence the type of soil
Definition
differences in the distribution of organic matter in the upper part of the soil profile
Term
description of the top layer of a forested soil
Definition
Forested soil exhibits surface layers (O horizons) of leaves and twigs in various stages of decomposition, along with a thin, mineral A horizon
Term
how grass affects the soil profile in grassland soil
Definition
Most of the organic matter in the grassland is added as fine roots distributed throughout the upper 1 m or so, creating a thick, mineral A horizon
Term
which soil is more acidic and more leached? forested or grassland?
Definition
forested
Term
which soil has more organic matter? that under grasslands or that under forests?
Definition
under grasslands
Term
Organic layer in forest soils made of...
Definition
leaves and twigs and such
Term
More organic matter in grassland thanks in part to...
Definition
grass having less lignin and lower C:N ratio
Term
why soils under forests are acid in nature
Definition
because of roots secreting acid
Term
why grasses are important in the environmental protection of soils
Definition
because grass roots hold soil in place, even sand
Term
one distinguishing characteristic of histosols
Definition
high OM content
Term
where histosols are often found
Definition
flooded places
Term
why histosols have such high OM content
Definition
because the flooded places they're found in have no air getting to the soil, such that the OM doesn’t decompose
Term
why Cecil soil aggregates better than Tifton soil
Definition
higher clay content
Term
why Cecil soil is red
Definition
high Fe
Term
why Tifton soil is yellow
Definition
high Al
Term
some physical properties of soil
Definition
-texture
-structure
Term
soil texture
Definition
mineral particle size
Term
some types of soil particles
Definition
-sand
-silt
-clay
Term
sand
Definition
macropores (coarse texture)
Term
silt
Definition
clay coated particles
Term
clay
Definition
fine texture
Term
soil structure
Definition
How particles are held together
Term
some types of cementing
Definition
-temporary
-permanent
Term
what causes temporary cementing?
Definition
-bacterial gums
-fungal mycelium
Term
what causes permanent cementing?
Definition
humus from organic matter
Term
the four major components of soils
Definition
-Minerals
‑Organic Matter
‑Water
‑Air
Term
chart showing the general composition of most soils (except for histosols)
Definition
[image]
Term
amount of soil mass taken up by minerals
Definition
95-100%
Term
amount of soil mass taken up by organic matter
Definition
0-5% (except for histosols)
Term
% of soil volume taken up by air and water
Definition
Air and water make up about 50% of soil volume – but this can vary from <40 to >60 depending on the soil.
Term
the soil texture triangle
Definition
[image]
Term
[image]
Definition
the soil texture triangle
Term
which soil texture is number 1?
[image]
Definition
clay
Term
which soil texture is number 2?
[image]
Definition
silty clay
Term
which soil texture is number 3?
[image]
Definition
sandy clay
Term
which soil texture is number 4?
[image]
Definition
clay loam
Term
which soil texture is number 5?
[image]
Definition
silty clay loam
Term
which soil texture is number 6?
[image]
Definition
sandy clay loam
Term
which soil texture is number 7?
[image]
Definition
loam
Term
which soil texture is number 8?
[image]
Definition
silt loam
Term
which soil texture is number 9?
[image]
Definition
sandy loam
Term
which soil texture is number 10?
[image]
Definition
silt
Term
which soil texture is number 11?
[image]
Definition
loamy sand
Term
which soil texture is number 12?
[image]
Definition
sand
Term
size of stone and gravel particles
Definition
>2 mm
Term
size of sand particles
Definition
0.05-2 mm
Term
size of silt particles
Definition
0.002-0.05 mm
Term
size of clay particles
Definition
<0.002 mm (colloidal)
Term
some properties of soil that can be affected by soil texture
Definition
-permeability to air
-water holding capacity
-nutrient holding capacity
-compaction potential
Term
how soil texture affects permeability to air
Definition
Sands are permeable; clays are not
Term
how soil texture affects water holding capacity
Definition
Sands low; clays high (lots of surface area)
Term
how soil texture affects nutrient holding capacity
Definition
Sands low; clays vary in nutrient holding capacity

this is largely a matter of CEC
Term
how soil texture affects compaction potential
Definition
Sands low; clays high (that is, clays are more likely to compact than sands)
Term
surface area per g of sand
Definition
0.1m2
Term
surface area per g of silt
Definition
1.0m2
Term
surface area per g of clay
Definition
10-10,000m2
Term
soil structure
Definition
Arrangement of individual soil particles
Term
why good soil structure is important
Definition
-adequate aeration
-water permeability (low runoff and erosion)
-good seedbed
Term
Main features of soil structure
Definition
-arrangement of particles into aggregates
-stability of aggregates when exposed to water
Term
why the arrangement of particles into aggregates is important
Definition
because this can form pores for water and air and channels connecting pores
Term
how organic matter improves soil structure
Definition
increases aggregate stability
Term
why lignin is hard to break
Definition
because of all the chains and no repeating structure
Term
Porosity or pore space
Definition
refers to the volume of soil voids that can be filled by water and/or air
Term
how soil porosity is measured
Definition
Measured as bulk density:
-It is inversely related to bulk density
-High bulk density = low porosity
Term
porosity vs. bulk density
Definition
inversely related
Term
effect of OM on bulk density
Definition
reduces bulk density
Term
how cultivation ruins soil structure
Definition
Generally, cultivation decreases porosity, breaks down aggregates, and increases decomposition of organic matter.
Term
chart showing the various porosities for various textures
Definition
[image]
Term
chart showing soil water content at different textures
Definition
[image]
Term
Field capacity
Definition
the amount of water retained in soil after infiltration; this is the water held against gravity
Term
Wilting coefficient
Definition
the point where the plant can no longer get water from the soil; this is the permanent wilting point; this is when the plant can no longer pump water into it
Term
why the wilting coefficient is higher in clay soils than in sandy soils
Definition
because clay particles hold on to water more tightly than sand
Term
why the water and air held in the macropores is more important
Definition
because the water and air in the macropores is more accessible to plants
Term
Effect of Organic Matter on Pore Space
Definition
increases macropores and decreases micropores
Term
something OM can improve in clays
Definition
aeration
Term
something OM can improve in sands
Definition
water holding
Term
Most clay minerals are described as...
Definition
hydrous alumino- silicates
Term
some types of clays
Definition
-silicate clays
-hydrous oxides
Term
some types of silicate clays
Definition
-kaolinite
-illite
-montmorillonite
Term
kaolinite
Definition
1:1 clay
Term
illite
Definition
2:1 non-expanding clay
Term
montmorillonite
Definition
2:1 expanding clay
Term
hydrous oxides are oxides of...
Definition
aluminum or iron
Term
when hydrous oxides persist in soils
Definition
after silica has leached out
Term
Clays are minerals made of...
Definition
silica and Fe and/or Al
Term
how clay is structurally
Definition
Structurally, the clay minerals are composed of planes of cations, arranged in sheets, which may be tetrahedrally or octahedrally coordinated (with oxygen)
Term
depiction of the general structure of clays between sheets of clay
Definition
[image]
Term
structure of a 1:1 clay like kaolinite
Definition
[image]
Term
how aggregation decreases porosity
Definition
because more large pores are present as compared to single clay and silt particles that are associated with smaller pores.
Term
why H bonds are strong enough between sheets of clay
Definition
because they're very small
Term
the structure of kaolinite as it relates to cations
Definition
[image]
Term
some characteristics of kaolinite
Definition
-Compacted clay lattices
-Held together by H bonds (-H….OH-)
-Little movement of other ions in and out of interior surfaces
-Creates thick particles
Term
picture of kaolinite
Definition
[image]
Term
[image]
Definition
kaolinite
Term
is kaolinite expanding or non-expanding?
Definition
non-expanding
Term
structure of montmorillonite
Definition
[image]
Term
what holds the sheets of montmorillonite together?
Definition
cations
Term
structure of montmorillonite as it pertains to cations
Definition
[image]
Term
what hydrated cations do to montmorillonite
Definition
expand the lattices
Term
what large cations do to montmorillonite
Definition
keep the sheets apart
Term
some characteristics of montmorillonite
Definition
-2:1 expanding clay
-Open clay lattices
-Loosely held together by cations and water
-A lot of movement of other things in and out of interior surfaces.
Term
picture of montmorillonite
Definition
[image]
Term
[image]
Definition
montmorillonite
Term
characteristics of illite
Definition
-2:1 non-expanding clay
-Clay lattices held together by K and H.
-K not plant available except by weathering
-Not as tight as kaolinite, but much tighter than montmorillonite
-Not much movement of other things in and out of interior surfaces
Term
why the K in illite is not plant available
Definition
because it’s part of the structure
Term
picture of illite
Definition
[image]
Term
[image]
Definition
illite
Term
why K can get into illite, but larger cations can't
Definition
because the clay lattices are close enough such that larger ions and water can not move in and out
Term
structure of illite as it relates to cations
Definition
[image]
Term
some things that can cause clay hard pans
Definition
tillage/compaction
Term
what too much compaction does to soil
Definition
creates a hard clay pan
Term
the texture typical Georgia soil has
Definition
sandy loam
Term
the type of texture typical Illinois soil has
Definition
clay loam
Term
the clay in typical Georgia soil
Definition
-kaolinite
-hydrous oxide
Term
the clay in typical Illinois soil
Definition
1‑2% kaolinite
60% montmorillonite
35‑38% illite
0% hydrous oxides
Term
why CEC occurs
Definition
-Silicate clays and humus are negatively charged
-Therefore, positively charged ions (cations) will bind
-If these ions are not bound too tightly, they can be exchanged with the soil solution and made available to plants
Term
CEC of humus (organic matter)
Definition
average: 200 meq/100g
range: 100-300 meq/100g
Term
CEC of montmorillonite
Definition
average: 80 meq/100g
range: 60-100 meq/100g
Term
CEC of illite
Definition
average: 80 meq/100g
range: 20-40 meq/100g
Term
CEC of kaolinite
Definition
average: 8 meq/100g
range: 3-15 meq/100g
Term
CEC of a soil depends on...
Definition
composition of the soil
Term
what minerals define soil pH?
Definition
hydrous oxides
Term
why pH is important in soil
Definition
because it affects the solubility of elements in soil
Term
why Al is a problem in soil
Definition
because it's toxic to plants
Term
chart showing solubility of certain elements at various pH's
Definition
[image]
Term
chart showing how pH affects Al c'tration in soil solution and root growth
Definition
[image]
Term
which element is number 1?
[image]
Definition
N
Term
which element is number 2?
[image]
Definition
P
Term
which element is number 3?
[image]
Definition
K
Term
which element is number 4?
[image]
Definition
Ca
Term
which element is number 5?
[image]
Definition
Mg
Term
which element is number 6?
[image]
Definition
S
Term
which element is number 7?
[image]
Definition
Mn
Term
which element is number 8?
[image]
Definition
Mo
Term
which element is number 9?
[image]
Definition
Zn
Term
which element is number 10?
[image]
Definition
B
Term
which element is number 11?
[image]
Definition
Cu
Term
which element is number 12?
[image]
Definition
Fe
Term
which element is number 13?
[image]
Definition
Al
Term
the relationship between forage legumes and pH
Definition
very dependent on pH; alfalfa tends to produce better at pH 6.5-7.5
Term
soil texture in which you need more lime
Definition
clay soil
Term
some macronutrients of interest in soil
Definition
-N
-P
-K
-Ca
-Mg
-S
-C
-H
-O
Term
some micronutrients of interest in soil
Definition
-B
-Cu
-Mo
-Fe
-Zn
-Mn
-Co
Term
examples of how OM can be actively manipulated by management
Definition
-tillage “burns up” OM
-perennial plants add OM
Term
what tillage does to OM
Definition
"burns up" OM
Term
how perennial plants can benefit soil
Definition
by adding OM
Term
the importance of OM in the nutritional sense
Definition
directly as source of nutrients
Term
the importance of OM in the biological sense
Definition
-stimulates macro- and microorganism growth and function
-indirectly affects plant nutrition
Term
the importance of OM in the physical sense
Definition
-improves soil structure – greater aggregate stability, improved porosity, greater aeration, better water holding capacity, improved infiltration
-improves soil cation exchange capacity
Term
something you can't expect w/o soil OM
Definition
microbes
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