soil & media importance of soil - pvag.weebly.com · •made up mostly of inorganic materials...

1/4/2013

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Soil & Media Importance of Soil

A. Explain the importance of soil as a life-supporting layer

B. Describe agricultural and non-agricultural uses of soil

C. List and describe the components of soil

D. Describe the physical characteristics of soil

E. Describe the biological activity within soil

F. Describe the chemical properties of soil

G. List factors effecting the movement of water in soil

H. List components of soilless media

I. Define Soil Fertility and describe how it can be improved with

fertilizer

J. Identify symptoms of plant nutrient deficiency

K. Calculate fertilizer application rates & choose correct fertilizers

Properties of Soil

Soil Fertility


Importance of Soil • What is the difference between soil and

dirt?

• Why is soil a precious resource? List as

many reasons as you can

Earth as an Apple


Importance of Soil

What is SOIL?

• Loose surface of the earth

• Material that nourishes and

supports growing plants

• Foundation of every living thing


Importance of Soil

What is DIRT?

• Soil out of place and unable to

serve it’s purpose – On the floor

– Under your fingernails

– Stuck to your shoes

– etc


Importance of Soil Rank the following in order of importance:

___ a) to grow plants (for food, oxygen, paper, lots of things).

___ b) to filter out pollutants that may contaminate drinking

water.

___ c) to provide income for: farmers, food, companies, clothing

companies and grocers, to name a few.

___ d) as a surface for building roads, sidewalks, and the places

where we live.

___ e) to provide food for livestock.

___ f) to walk on.

___ g) to provide wildlife and insect habitat.

___ h) . . . make up your own


Uses of Soil

1- Plant Growth:

• Physical Support

• Nutrients, Water, Air

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Uses of Soil

2- Recycle Raw Material:

• Decomposes organic matter

• Returns nutrients to soil for use by

other plants

• Disposes of waste


Uses of Soil

3- Habitat for soil

organisms:

• Billions of organisms

– Producers & consumers live in soil


Uses of Soil

4-Engineering:

• Soil effects building & construction

• Foundation for roads and structures


Uses of Soil

5- Supports life:

• How do we depend on soil?

– Plants

– Animals

– Humans


Uses of Soil

6- Contains & Filters

Water:

• Absorbs and holds water

• Filters as it soaks through each layer


Components of Soil

Average soil contains:

• 50% Air & Water (depends on rain fall)

• 45% Minerals

• 5% Organic matter

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Components of Soil

Soil Formation Factors:

• Parent material available

• Climate – Temperature

– Rain

– Wind

• Elevation or slope

• Living Organisms present

• Time


Components of Soil

3 Soil Layers:

• Topsoil

• Subsoil

• Soil Bedrock


Components of Soil

3 Soil Layers: • Topsoil:

– Depth a field is plowed


Components of Soil

3 Soil Layers: • Subsoil:

– Deep rooted plants send roots into subsoil


Components of Soil

3 Soil Layers: • Bedrock:

– Rock layer


Components of Soil

Master Horizons: • O- Organic

– Forms above mineral soil

usually in forrested areas

• A- Topsoil

– dark humus layer where plant

rooting occurs

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Components of Soil

Master Horizons: • B- Zone of Illuviation

– Where material accumulates

from zones above

• C- Parent Material

– Wind blown silt (loess), river

deposits, glacial till

• R- Bedrock


Physical Characteristics of Soil

How is soil classified? • According to percentage of sand,

silt, and clay



Soil Textures: • Determined by proportion of 3 sizes

of soil particles

– Sand (large)

– Silt (med)

– Clay (small)



Soil Textures: • Soil Triangle


Practice: – 40% sand 22% clay and 38% silt


Practice: – 90% sand 10 % clay and 25 % silt

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Practice: – 30% sand 50 % clay and 15% silt



Sand: • Largest Particles

– Very Course

– Course

– Medium

– Fine

• Weathered grains of quartz

• Gritty to touch

• Do NOT stick together

• Little water holding capacity



Silt: • Medium sized particles

• Silky/powdery to touch

• Do NOT stick to each other

• HIGHEST water holding capacity



Clay: • Smallest particle size

• Holds MOST minerals/nutrients

• POOR drainage

• STICKS together (if 30% clay or more)



Loam: • Perfect soil

• Equal parts of sand, silt, clay



How to determine soil texture: 1- Testing in a laboratory

2- Work a sample in your hands and feel for

different sized particles

3- Sedimentation Test

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Why is texture important? • Water holding Capacity

– How fast will water pass through sand?

– How fast will water pass through clay?

• Ability of plants to grow

– Can roots push through soil?

– Will root system hold the plant up?



Soil Texture Lab: – Steps:

1- Get a small sample of soil

2-Add just enough water so that you can work the soil

sample into a ball

3- Feel the grit between your fingers

4- Try to “ribbon” the sample



How to determine soil texture: • Fine- Ribbon forms easily and

remains long and flexible.

• Moderately fine- Ribbon forms but

breaks into pieces ¾ to 1 inch long.

• Medium-No ribbon forms. The

sample breaks into pieces less than ¾

inch long. The soil feels smooth and

talc-like.

• Moderately coarse- No ribbon forms.

The sample feels gritty and lacks

smoothness.

• Coarse- No ribbon forms. The sample

is composed almost entirely of gritty

material.



Soil Sedimentation Lab – Place soil in a jar

– Mix soil and water

– Let it settle


Biologicial Activity in Soil

The Soil Ecosystem

• Interaction of biotic & abiotic factors in

soil

• Organisms growing and decomposing



The Soil Ecosystem

¼ teaspoon of fertile soil contains

approximately:

• 1 earthworm

• 50 nematodes

• 52,000 algae

• 111,000 Fungi

• 2,920,000 Actinomycetes

• 25,280,000 bacteria

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Earthworms

• Decompose organic matter

• Mix plant litter with soil

• Tunneling helps aerate soil



Nematodes

• Roundworms, threadworms, hair

worms

• Consumes microbial organisms

• Also found in plant roots



Algae

• Too small to be seen with naked eye

• In large numbers, can be seen on

soil surface giving green color



Fungi

• Mushrooms, mold, mildew, rusts,

yeast

• Grows on dead/decaying tissue

• Makes nutrients available by

decomposing organic matter



Actinomycetes

• Rod-shaped form of bacteria

• Decomposes cellulose

• Gives fresh tilled soil it’s smell



Bacteria

• Most numerous & MOST important

• Breaks down chemicals

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Chemical Properties of Soil

What are the effects? • Plant growth

• Availability of nutrients

• Dissolved mineral salts determine Ph • Acidic soil: < 7.0

• Alkaline soil: >7.0

• Neutral soil: =7.0



Cation Exchange Capacity: • Total # of exchangeable cations the soil

can hold

• More organic matter = more CEC

• The higher the CEC, the more nutrients

the soil can hold



Cation Exchange Capacity:

1/20,000 in

• Clay particles are stacked in layers

like sheets of paper.

• Each clay sheet is slightly separated

from those on either side.

• Each sheet has negative charges on

it.

• Negative charges have to be

balanced by positive charges called

cations.




Low pH, 4 - 5

(acidic soil)

Neutral pH

Hydrogen Nutrients

Increasing pH

increases cation

exchange capacity

of organic matter




• Soil CEC increases as – The amount of clay increases

– The amount of organic matter increases

– The soil pH increases


Water Movement

How much water will be

absorbed?

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Water Movement Factors effecting water absorption:

•Soil Texture –Sand

–Silt

–Clay



•Slope –Will water run off or absorb into ground?

–Soil texture also plays a role • Clay soil, steep slope= bad

• Sandy soil, steep slope= not so bad



•Soil Temperature –Warm= Water is absorbed

–Cold=Water stays on top til ground

thaws



•Plant Growth –Bare fields and slopes encourage water run

off instead of absorption


Water Movement

Factors effecting water absorption:

• Round 1: Measure the amount of

water that flows through different

soils

• Round 2: Measure the amount of

water that flows through different

soils after amending the soil


Preventing Erosion Methods of transporting soils:

• Gravity- colluvial

• Water – Streams

– Oceans

– Lakes

• Ice- glacial

• Wind-aeolian

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Preventing Erosion How does erosion effect soil quality?

• One of the largest environmental

problems that stems from

agriculture

• Lowers productivity from loss of

topsoil


Preventing Erosion How to decrease erosion:

• Terracing

–Plowing fields perpendicular to water

flow



• Minimum or no-til farming

–Leaves stubble in fields to hold soil



• Cover Crops

–Plant a crop after harvest to minimize

bare soil

H. List components of soil less media

Soil less Media How does it compare to soil?

• Found OUTSIDE in the

garden

• Heavy

• Little Air Space &

Porosity

• Made up mostly of

inorganic materials like

broken down rock

• Found INSIDE, in a

greenhouse or potted

plant

• Light

• Lots of Air Space &

Porosity

• Made up of mostly

organic materials like

bark, peat moss, etc.

Components of Soilless Media

•Sphagnum Peat Moss: – Grows in bogs and wet places

– Can absorb water up to 20x it’s weight

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•Vermiculite – Platy minerals that have been heated until

they explode like popcorn


•Perlite – Volcanic glass, similar to obsidian that has

been heated similar to vermiculite


• Bark Chips or Coconut Bark


•Fertilizer -Usually a slow release fertilizer

I. Define Soil Fertility and describe how it can be improved with fertilizer

Soil Fertility

Do plants eat?


Soil Fertility

Do all soils produce the

same??

• Soil Fertility= ability of a soil

to supply plant nutrients

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Soil Fertility

1- Water

• Most important plant nutrient

• Makes up 90% of plant’s

weight

• Transports other elements


Soil Fertility

2- Elements

• Macronutrients (major elements)

–Needed in relatively large amounts

–Found in fertilizer

oNitrogen (N)

oPhosphorus (P)

oPotassium (K)


Soil Fertility

2- Elements


Nitrogen

Phosphorus

Potassium

**always listed in this order**


Soil Fertility

2- Elements


15 % Nitrogen

5% Phosphorus

10% Potassium

*Remaining 60% is filler


Soil Fertility

2- Elements

• Micronutrients (minor elements)

o Calcium (Ca)

o Magnesium (mg)

o Sulfer (S)

o Iron (Fe)

o Manganese (Mn)

o Boron (B)

o Copper (Cu)

o Zinc (Zn)


Nutrient Deficiency

Nitrogen • Makes leaves GREEN

Not enough:

• Yellow/light green color

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Nutrient Deficiency

Nitrogen


Nutrient Deficiency

Phosphorus • Feeds the ROOTS

• Encourages cell division

Not enough:

• Purple color on underside of leaf

• Reduced flower/seed production


Nutrient Deficiency

Phosphorus


Nutrient Deficiency

Potassium • Increases disease resistance

• Develops chlorophyll

Not enough:

• Leaves appear dry and scorched with

irregular yellow areas


Nutrient Deficiency

Potassium


Choosing a Fertilizer

2 Types • Organic

–Naturally occurring

• Manure, worm castings, compost

• Inorganic

–Minerals/elements are

manufactured

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Choosing a Fertilizer

Types • 1 component

• Complete fertilizers (3 ingredients)


Applying Fertilizer

How to calculate • Follow instructions on package

• Every plant has different

requirements

"I’m no expert, but if we’re going to

save the Earth, the color of Dirt

makes a heck of a lot more sense

than the color of Envy. The way I see

it, if we really want to get clean and

green, we’re gonna have to get down

with brown. In other words, we’re

going to have to get our hands

dirty."

Mike Rowe

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