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.