Soil Science Chapter 14 (R&B) Chapter 14 (Miller) Ch 21 (R&B) Some diagrams and information in this presentation have been used and/or modified with permission

Soil ScienceChapter 14 (R&B)Chapter 14 (Miller)

Ch 21 (R&B)

Some diagrams and information in this presentation have been used and/or modified with permission from Dr. Greg Pillar, Soil & Environmental Science professor at Queens University in Charlotte,

NC.

Your Responsibility!!!SOIL READING GUIDE

Major Soil GroupsSoil Problems

… in both R&B and Miller books!

The Rock CycleIGNEOUS

ROCK

SEDIMENTARYROCK

METAMORPHICROCK

SEDIMENT

Melt

Cool &

Harden

Heat & Pressu

re

Erode & Weather

MAGMA

Erode & W

eather

Com

paction &

Cem

entationMelt

Ero

de &

Wea

ther

MeltH

eat & Pressure

What is SOIL????The relatively thin surface layer of the Earth’s crust consisting of mineral and organic matter.

Soil is not DIRT!

Q: What’s the difference between soil and dirt?

A.Location, location, location!

Dr. Greg Pillar, Queens College

The 5 Soil-Forming Factors

• climate (water, wind, temperature)

• biology (macro- and microorganisms, plants)

• relief (topography)

• parent material (rocks/minerals)

• time

Which is the MOST important??CLIMATE!!!

Formed from parent material (bedrock) that’s slowly broken down through

weathering processes.

What is Soil?How would you describe soil?

Color• Texture


Texture

http://www.mii.org

Why the color?http://www.msstate.edu http://www.cs.cmu.edu

Hematite: red

Goethite: yellowish brown

Ferrihydrite:reddish brown

http://www.beg.utexas.edu

Calcite: off white

http://www.pitt.edu

Quartz:white

Organic matter:black

http://www.organicgardeninfo.com


• Did you know ??????There are more than 20,000 different soil types in the

United States

Soil Color Variation

….and each one tastes different



Soil Composition

Water (~25%)

Air (~25%)

Mineral(~45%)

Humus (~5%)

Mineral matter comes from parent material

Air & Water percents are interchangeable

Humus is organic matter!

Soil Composition continued…

Mineral Matter– Provides nutrient

minerals for plants– Provides pore space

for water & air

Older soils are:– More weathered– Lower in certain

essential nutrient minerals

Humus: black/dark brown organic material remaining after

decomposition– Leaf litter, animal dung, & decaying organisms– Increases the soil’s water-holding capacity by

acting like a sponge

POROSITY = amt of soil pore

spaces

Pore spaces occupy ~50% of a soil’s volume– Filled with varying

proportions of soil water and soil air

Soil Air contains the same gases as atmospheric air, but in different proportions.– More CO2 and less O2

(from organism respiration)– Some bacteria need

nitrogen (why??)– The CO2 can accelerate

weathering• CO2 + H2O H2CO3

(carbonic acid)

PorositySoil Composition continued…

Soil Composition continued…

As water infiltrates the soil, it can carry dissolved materials with it.

Leaching: Removal of dissolved materials from the soil by water percolating downward

Illuviation: Deposition of leached material in lower layers– Some substances completely leach out

of the soil because they’re so soluble that they migrate right down to the groundwater.

Observe this Observe this SOIL PROFILESOIL PROFILE through soil through soil

Soil layers are Soil layers are horizonshorizons and and assigned lettersassigned letters

O: Organic materialO: Organic material (may be absent)(may be absent)

A: A: TopsoilTopsoil - Organic - Organic material & mineral material & mineral grainsgrains

E: Leached zoneE: Leached zone (may be absent)(may be absent)

B: B: SubsoilSubsoil – rich in – rich in clay, iron, aluminumclay, iron, aluminum

C: Weathered bedrockC: Weathered bedrock

R: Bedrock R: Bedrock (parent material)(parent material)

Soil Pedon


A horizon: organic coatings

B horizon: Iron coatings

C horizon: little coating

Soil Color by Horizon

http://nesoil.com

Fun Fact: It takes 100 to 600 years to

form an inch of topsoil.


Soil Color – Variation by Geography

Red soils: Southeast US



Brown/black soils: Midwest


http://www.scienceclarified.com


White (gypsum) sands: New Mexico


Soil OrganismsEx: bacteria, fungi, algae, microscopic worms, protozoa, plant roots, insects, earthworms, moles, snakes, groundhogs, etc.

Soil organisms provide several Ecosystem Services (important environmental functions).– maintaining soil fertility– preventing soil erosion– breaking down toxic materials– cleansing water– affecting atmospheric composition

Earthworms & Ants: – Cycle minerals– Aerate the soil– Decomposing corpses

contribute organic matter– Assist plants in

reproduction by burying seeds

Mycorrhizae– Symbiotic relationship

between fungi and the roots of vascular plants

– Fungus absorbs nutrients from the soil, and provides it for the plant.

– Plant produces food (photosynthesis), and provides it for the fungus.

Dr.

Gre

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Physical Soil

PropertiesPHYSICAL properties:Texture (%sand, silt, clay)

Porosity & PermeabilityIonic Charge

Texture is determined by its % sand, silt, and clay.

Texture determines the type of soil, and the soil’s properties.

Physical Property: Texture

Loam: ideal for

agricultural soil

Soil Components

http://school.discoveryeducation.com

Q: What did the shy pebble say to the big

rock?A. Do you think I’ll ever be a

little boulder?


Fine Texture - Clay

https://www.soils.org/lessonsDr. Greg Pillar, Queens College

Course Texture - Sand

https://www.soils.org/lessonsDr. Greg Pillar, Queens College

Soil TextureThe relative portions of sand, silt, and clay-sized particles

Sand: 2.0 – 0.05 mm

Silt: 0.05 – 0.002 mm

Clay: < 0.002 mm


B

Soil Texture Diagram PracticeWhat type of soil has:1. 20% clay, 40% silt, 40% sand2. 40% clay, 10% silt, 50% sand3. 30% clay, 60% silt, 10% sand

Find the % of each particle at:

1. A2. B3. C

A

C

60%clay, 20%silt, 20%sand



(1) Loam(2) Sandy clay(3) Silty clay

loam

Property Sand Silt Clay

Water holding Low Med-high High

Aeration Good Med Poor

Nutrient supplying Poor Med-high High

Pollutant Filtering Low Med High

Why is Soil Texture Important?

SO

IL

TO

UC

HY

FEELY

TIM

E!

Physical: Porosity & Permeability

again… Think it is important??

Definition?– amt of soil pore spaces

Porosity

PermeabilityDefinition?

– ability of water to percolate through

____ porosity = ____ permeability

Physical: Ionic ChargeSoil minerals are often present as ions.Minerals ions are either positively or negatively charged.Clay particles have mostly negative charges on their outer surfaces.– Positively charged mineral ions are attracted

to the soil particles and are held for plant use.• potassium K+ and magnesium Mg2+

– Negatively charged mineral ions are repelled by the soil particles and are washed away from roots.

• nitrate NO3-

Physical Characteristics (review)

Why would 100% sand be undesirable for plants?Why would 100% clay be undesirable for plants?

Answer SAND / SILT / CLAY for the following:– A soil with a lot of _____ would have good drainage,

but poor nutrient-holding characteristics.– A soil with a lot of _____ would have poor drainage,

but good nutrient-holding characteristics.– A soil with a lot of _____ would have low porosity.– A soil with a lot of _____ would have high

permeability.

Two soil cores

Bottom of corecontains filter

paper and cheese cloth

Demonstration

Two unknownliquids

Pollutant #1

Pollutant #2

Demonstration

Liquids passedthrough soil

cores

Leachate collected below

What did you observe?

Demonstration

What happened to the original liquids?

What does a change or no change

in color mean?

To what extent did the soil contribute to

this change?

Soil Soil

Adsorption of Organic Dyes

S+

N

NN

Cl-

O

SO

O

HO

OH

Cl

Cl

Chlorophenol red

Methylene blue

CR-

MB+

Soil

CR-

CR-

CR-

CR-

MB+

MB+

MB+MB+

MB+

MB+

MB+

MB+MB+

MB+

Chemical Property: Acidity

Most soil pH is 4-8. Plants are happiest at 6-7. Plants are affected by soil pH.(1) The solubility of certain nutrient minerals varies

with differences in pH• Low pH = Al & Mn are more soluble, and can be

absorbed in toxic amounts.• High pH = some salts are less soluble, and are less

available to the plants.(2) Soil pH affects the leaching of nutrient minerals.

• Acidic soil = positively charged ions are less soluble and are unavailable for plants.

Soil Conditioners (Lime)CaCO3 or MgCO3

Soil amendment / conditioner… not a fertilizer!Important functions:

1. Corrects soil acidity2. Adds important plant nutrients— Ca & Mg3. Reduces solubility & toxicity of certain elements

in the soil Al, Mn, FeThis toxicity could reduce plant growth under acid conditions.

4. Promotes availability of major plant nutrients. Zn, Cu, P

5. Increases bacterial activity & mutualistic relationships.

http

://w

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htm

Soil Conditioners (Compost)

Decayed organic matterReplaces some nutrientsImproves soil structure

– The soil becomes more porous, increasing air circulation and the ability of the soil to absorb and hold moisture.

– Makes the soil more spongy!

http

://w

ww

.wvu

.edu

/~A

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Wh

at is

So

il?

Soil supports life

http://www.Istockphoto.comL. Clarke and Corbis, 2008

Why is Soil Important?

Fun Fact: 1 teaspoon of good soil contains more than 1 million bacteria!

Fun Fact: There are more living organisms in a cubic foot of soil then

all of China!

Fun Fact: There are more living organisms in a cubic foot of soil then

all of China!


Soil stores important nutrients

http://www.lesco.com/

Nitrogen (NH4+) (ammonium)

Potassium (K+)Calcium (Ca2+)

Magnesium (Mg2+)

Phosphorus (P) (PO4-3)

(PO4-3 combines with +charged

particles in soil)


Soil Holds Water


Soil provides support for buildings

http://www.pbase.comDr. Greg Pillar, Queens College

Soil

Soil filters, buffers, detoxifies….

http://extension.missouri.eduDr. Greg Pillar, Queens College

Inputs/OutputsAre these Soil Inputs or Soil Outputs?

Mass Movements (landslides, etc)Precipitation

Parent MaterialLeaching

InfiltrationUptake by PlantsOrganic Matter

Energy

I

I

I

I

O

I

O

O

Transfers/TransformationsRecall:

Transfers simply MOVE things… they reorganize the soil!

Transformations CHANGE things…they alter the soil’s makeup in some way.

Are these Soil Transfers or Transformations?Decomposition

ErosionDepositionWeathering

Nutrient Cycling

transfer

transfer

transformation

transformation

transformation

Soil PollutionPart II

Chapter 21 (R&B)

Soil Pollution= any physical or chemical change in soil that adversely affects the health of plants and other organisms living in and on it.

Many soil pollutants…– ARE MOBILE!

• move into groundwater, surface water, or air– ARE PERSISTENT!

• seep into tiny cracks called micropores and adhere to the soil particles

– COME FROM FERTILIZERS / PESTICIDES! – CAN ACCUMULATE!

Sustainable Agriculture practices can help…

…more on this later…

Salinization of Irrigated SoilIrrigation water soaks through the soil area where the plant roots grow, adding to the existing water. The additional irrigation water causes the underground water-table to rise, bringing salt to the surface. When the irrigated area dries & the underground water table recedes, salt is left on the surface soil. Each time the area is irrigated this salinity process is repeated. ALL IRRIGATION WATER CONTAINS SOME DISSOLVED SALTS.

Salinization of Irrigated Soil

Extra water flows through the soil, mixing w/ salt underground, and bringing it to the surface.

This is in Australia – occurred not from irrigation, but from lack of water-loving plants.

Irrigation salinization is basically the same concept, and the ground would look just like this.

Effects of Salinized Soil on Plants

Normally, the water concentration inside

plant cells is lower than that in the soil resulting

in a net movement of water into the root cell.

When soil contains a high amount of salt, its

relative water concentration can be lower than the water concentration inside

cells. This causes water to move out of the roots into the soil, even when

the soil is wet.

Salinization Lab 1. Answer Prelab Questions2. Gather Materials

– 4 ziploc bags– 20 radish seeds– 4 paper towels

3. Follow instructions on the lab sheet4. BE SURE TO LABEL YOUR BAGS!!!5. Leave them in the box in the front. 6. We’ll inspect their germination

progress and take data over the next week.

Soil RemediationUntil recently, the only way to remove soil contaminants was to…

Why is this a bad thing to do??– Impractical, kills all beneficial

organisms, creates waste, expensive…

DIG IT UP

& INCINERATE IT!

Soil Remediation Techniques

Small Groups: define these, then make a pro/con list. Use your book if necessary.

Dilution– Add lots of water; leach out pollutants

Vapor extraction– Inject air into soil to remove volatile organic

compounds

Bioremediation– Use microorganisms to degrade organic contaminants

(oil, sludge)

Phytoremediation– Use plants to absorb contaminants such as salts or

heavy metals.

Extraction well

Pollutant low sorption potential = not attracted to soil easily washed away

Pollutant high sorption potential = not easily washed

Water

DILUTION: Pump & Treat / Soil Washing

12 - 28

GROUND LEVEL

… But what’s the problem here?

Source Identification and Removal !!!!

12 - 30

How can this problem be fixed???

GROUND LEVEL

Bioremediation (Bioventing)

12 - 32

15.06.b

Activities that Threaten SoilActivities that Threaten Soil

Removing vegetationRemoving vegetation

OvergrazingOvergrazing

Soil contaminationSoil contamination

Erosion ControlErosion Control

• Agricultural: 10% of the worlds best agricultural land damaged due to soil erosion and overuse over last 50 years.

- contour plowing- no-till agriculture (no plowing)- terracing slopes- crop rotation - fallow

Preventing Soil Erosion

Your Responsibility!!!Soil Reading Guide

Major Soil GroupsSoil Problems

Soil Conservation & Regeneration

… in both R&B and Miller books!

Soil Pedon

USDA Soil Profile Activity:http://soils.usda.gov/education/resources/k_12/lessons/profile/

Documents

Soil Science Chapter 14 (R&B) Chapter 14 (Miller) Ch 21 (R&B) Some diagrams and information in this presentation have been used and/or modified with permission