essential question- what is soil made of? how do soils differ in structure? warm-up- complete the...
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Essential Question- What is soil made of? How do soils differ in
structure?
Warm-up- Complete the soil anticipation Guide. When finished trade your paper with a partner and discuss.
What do these words make you think of?
http://www.flickclip.com/flicks/Wall-E.html
What is Soil?What is Soil?
Soil: Unconsolidated mineral or Soil: Unconsolidated mineral or material on the surface of the earth material on the surface of the earth
resulting from and influenced by resulting from and influenced by time, parent material, climate, time, parent material, climate, organisms, and topography.organisms, and topography.
Why are soils important?
Great integrator
Producer andabsorber of gases
Medium for plant growth
Medium of crop production
Home to organisms(plants, animals and others)
Waste decomposer
Snapshot of geologic, climatic, biological, and human history
Source material for construction, medicine, art, etc.
Filter of water and wastesEssential natural resource
What ‘stands out’ about the landscape?
Color is the most obvious characteristic of soil.
What are some colors encouraged by well aerated conditions?
REDRED YELLOWYELLOWBROWNBROWN
What are some colors encouraged by poorly aerated conditions?
GRAYGRAY BLUEBLUE
Soil color is influenced by the oxidation state of iron and manganese.
Soil ColorSoil Color
Soil Color, Soil Aeration or Drainage, and the Oxidation State of Iron
1. Iron is reduced1. Iron is reduced
2. Fe2. Fe++++
3. dull colors (grays, 3. dull colors (grays, blueblue))
4. poorly drained4. poorly drained
1. Iron is oxidized1. Iron is oxidized
2. 2. FeFe++++++
3. bright colors 3. bright colors ((yellowsyellows, browns), browns)
4. well drained4. well drained
POOR AERATION GOOD AERATION
Soil Color Tells A StorySoil Color Tells A Story
Well Drained
Poorly Drained
Drainage on this farm?
Soil HorizonsSoil Horizons
B
C
ApZone of highest organic matter content. The ‘p’ denotes that this soil has been plowed.
A layer of accumulation of iron and clays. Blocky structure is readily seen in this layer.
Unconsolidated material. Outside the zone of major biological activity and is not affected by soil forming processes.
Soil ProfileSoil ProfileWhat do we see?
• organic matter - surface soil is organic matter - surface soil is darker due to organic matterdarker due to organic matter
• iron oxides - subsoil has iron oxides - subsoil has brighter browns and tans due brighter browns and tans due to iron oxidesto iron oxides
• drainagedrainage
• horizons - layers of different horizons - layers of different color or texture; formed from color or texture; formed from the top downthe top down
. . . more on Soil Horizons. . . more on Soil Horizons
B
C
Ap
A
Average Soil Composition
{ }Pore space 50%
Solids 50%
25% Water
25% Air 5% Organic Matter
45% Inorganic (mineral materials)
Soil TextureSoil Texture• Determined by the relative
proportion of sand, silt and clay
Surface AreaSurface Area ChargeCharge
SandSand 50 cm50 cm22/g/g nonenone
SiltSilt 500 cm500 cm22/g/g nonenone
ClayClay 5,000,000 cm5,000,000 cm22/g/g negativenegative
Relative Size Comparison Relative Size Comparison of Soil Particlesof Soil Particles
Sand - feels gritty
Silt- feels floury
(2.00 - 0.05 mm)
(0.05 - 0.002 mm)(< 0.002 mm)
barrel
plate
coin
Clay- feels sticky
USDA system for determining soil separates
Clay
Silty Clay
Silty Clay Loam
Clay Loam
Sandy Clay
Sandy Clay Loam
LoamSilt Loam
Silt
Sandy Loam
Sand
Percent Clay
Percent Silt
Percent Sand
Fine
MediumCoarse
Loamy Sand
Sand Sandyloam
Siltloam
Clayloam
Clay
1
2
3
4
Inch
es w
ater
/ft s
oil
Plant Available Water
Rhoads and Yonts, 1984.
Available Water Holding CapacityAvailable Water Holding Capacity
Storage capacity
Silty clay loam 1.8Clay loam 1.8
Silty clay 1.6Silt loam 2.0
Sandy loam 1.4
Texture (in./ft.)
Comparison of Coarse Textured and Fine Textured Soils
Coarse Textured Soil
Less porespace but more macropores
Fine Textured Soil
More total porespace
Texture and Pore SpaceTexture and Pore Space
Exit ticket
• Fill in the graphic organizer of each soil horizon and the characteristics of each.