homework: bring some soil from your home.. chapter 5.2 soil characteristics of soil soil composition...

HOMEWORK:BRING SOME SOIL FROM YOUR HOME.

CHAPTER 5.2 SOIL

Characteristics of Soil

• Soil Composition• Soil Texture• Soil Structure

What is Soil?

Regolith = small pieces of weathered rock

MOON

MARS

EARTH

Soil Composition (pg. 133)

Mineral Matter 45%Water 25%Air 25%Organic Matter 5%

Soil Composition = what it’s made of

Soil CompositionDifferent compositions of soils:

HIGH % Organic Matter LOW % Organic Matter

Soil CompositionDifferent compositions of soils:

HIGH % Air & Water LOW % Air & Water

Soil Texture = proportions of different particle sizes

• U.S. Dept of Agriculture – categories based on amounts of clay, silt and sand.

• Soil-Texture Diagram (pg 134 Figure 11)

• Loam has equal parts clay, silt and sand.

• Loam is best for plant growth.

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10

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100 90 80 70 60 50 40 30 20 10 0

Clay

Silty Clay

Silty Clay Loam

Silty Loam

Silt

Sandy Clay

Clay LoamSandy Clay Loam

Sandy LoamLoamy SandSan

d

Soil-Texture Diagram

% C

lay

% S

ilt

% Sand

60% Clay; 10% Silt; 30% Sand

Soil StructureTo clump or not to clump.

Soil Formation

1. Parent Material = source of minerals in soil.

2. Time = how long it took to form the soil.

3. Climate = did it form in dry or wet areas, under hot or cold temperatures, etc.

4. Organisms = what types of organisms are living or dead in the soil.

5. Slope = the angle of the land on which the soil forms.

Parent MaterialWho’s the mama?

Pg. 135 Figure 12

• Residual soil = forms on bedrock• formed on top of the parent material

• Transported soil = forms unconsolidated soil• moved from parent material to another location.

Parent MaterialHow did mama affect it?

1. Affects rate of weathering and rate of soil formation

Unconsolidated deposits are already weathered some, so they provide more surface area for chemical weathering.

2. Affects the soil’s fertilityMore plant material can grow – more organic matter – better fertility.

TimeHow long did it take to form?

• The longer it takes to form, the thicker it becomes.

• As time passes, weathering can reduce the influence of the parent material.

• Has greatest affect on soil formation.

• Temperature changes affect rate, depth, and type of weathering.

• Example: hot, wet climate produces a thick layer of chemically weathered soil.

• Example: cold, dry climate produces a thin layer of chemical weathered soil.

ClimateHow did and does

“neighborhood” affect soils?

ClimateHow did and does

“neighborhood” affect soils?

• Precipitation influences soil fertility.

• Climate affects what types and how many animals and plants can live on the soil.

• Climate can cause similar soils to be produced from different parent materials .

• Some soils named based on plants living in them.

• Prairie soil, tundra soil, forest soil, etc.

• Plants are main source of organic matter.

• Protozoans decompose organic matter in soil.

• Burrowing animals stir, pack and move soil.

OrganismsHow does the “family” affect

soil?

SlopeSoils on the edge?

• Slope varies greatly from location to location.

• The steeper the slope, the faster the erosion and the less water can soak in.

• Steep slopes have thin layers of soils or none at all.

• Flat slopes have thick layers of soils.

SlopeSoils on the edge?

• The direction a slope faces can affect soils.

• South-facing slopes receive more sunlight so are warmer and dryer.

• North-facing slopes receive less sunlight so are colder and wetter.

• All of these factors work together to affect the formation of soils.

Soil Formation – Summary

SOIL PROFILES = shows soil layers and composition of a section of earth.

A Horizon

• “topsoil”

• loose, partly decayed organic matter

• mineral matter mixed with organic matter

• insects, fungi, worms, microorganisms


B Horizon

• “subsoil”

• fine clay washed out of Horizon A

• sometimes packed into “hardpan” soil

• lower limit of plant roots and burrowing animals.


C Horizon

• partially weathered parent material

• still resembles the parent material


Rock

• parent material

• unweathered

SOIL TYPESThree common types of soil:

PEDALFER

PEDOCAL

LATERITE

SOIL TYPES: Pedalfer

• Temperate areas receiving > 63 cm/yr

• Rutherford County, NC

• B Horizon has lots of iron oxide and aluminum clay.

• Red or brown color

SOIL TYPES: Pedocal

• Areas with grasses and brush vegetation.

• Western USA

• B Horizon has lots of iron oxide and aluminum clay.

• Red or brown color

SOIL TYPES: Laterite

• Hot, wet tropical areas.

• Deeper than other soils.

• When dry, becomes very hard and almost waterproof.

•Used in brick-making.

Pg 139 Fig 15

• Red or orange color

SOIL TYPES: Laterite (cont.)

• Makes up much of the soil in rainforests.

• Plants decompose so rapidly in the rainforest there is no organic matter in laterite.

• Not fertile.

SOIL TYPES: Laterite (cont.)

SOIL EROSIONHow WATER erodes soil…

IMPACT erosion is a physical effect of water on soil.

When falling water hits soil it creates a tiny explosion that tosses soil into the air and displaces it.

FLOWING water picks up particles of soil and carries them with it.

This results in a deposition of soil from its original location to another location downstream.

This is an erosion bed. It is used to test the affects of running water on different types of soil.

Here is the bed BEFORE the water is released.Here is the bed AFTER the water is released.

SOIL EROSIONHow WATER erodes soil…

SOIL EROSIONRates of erosion…

• In the past soil erodes more slowly than it does today because more land was covered by plants.


• Human activities that remove natural vegetation have greatly accelerated erosion.


• Before humans, rivers carried 9 trillion kg of sediment to the oceans each year.


• Today rivers carry about 24 trillion kg of sediment to the oceans each year!


• Excessive erosion causes excessive sediment deposition in rivers.


• Wind can also carry displace large amounts of soil if the land becomes dry from a severe drought.

1930’s Dust Bowl

SOIL EROSIONControlling erosion…

Terracing

Erosion Walls and Fences

Windbreaks

Crop Rotation

Landscaping

homework: bring some soil from your home.. chapter 5.2 soil characteristics of soil soil composition...

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