nc state university department of soil science nc state university department of soil science...

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE


Getting the Dirt on Soils



What are 4 things we cannot live

without?



SOILSOIL AIRAIR

WATERWATER SUNLIGHTSUNLIGHT



Does Soil=

Dirt?



NO!Dirt is the stuff under your

fingernails or that you sweep off the floor



Soil Facts• Topsoil is the most productive layer

• Five tons of topsoil spread over an acre is

only as thick as a dime

• Soil supplies water and nutrients for plants

• Most of our food comes from soil

• It can take more than 500 years to form one

inch of topsoil



Soil Facts• An acre of corn gives off 4000 gallons of

water a day in evaporation

• Soil Scientist have identified over 70,000

different soils in the U. S.

• Erosion of soil clogs rivers and lakes

• Soil influences the life spans of roads



Soil Facts• Soil is alive….

• 1 gram of soil contains up to a billion bacteria

• There many thousands of types of bacteria

in soil

• 15 tons of soil per acre pass through

earthworms each year



Soil Facts• Soil is the largest single wastewater

treatment unit in North Carolina

• 4 million North Carolinians rely on soil to

treat and disperse wastewater

• Soil is extremely effective at wastewater

treatment

• Best of all…



Soil makes Soil makes

great mud piesgreat mud pies

……and is just and is just

plain fun!plain fun!



A soil is a porous natural body of mineral, air, water and organic

matter that changes, or has changed, in

response to climate, topography, time, and

organisms.



What do you see in these photos?What do you see in these photos?



What is soil made of?

Soil is composed of Soil is composed of

minerals, minerals,

organic matter, organic matter,

air, air,

waterwater



Soil is made of:

• Solid material– Minerals– Dead organic material– Living organic material

• Pore space– Air– Water



Factors of Formation



Factors of formation

• Parent Material

• Topography

• Vegetation/Biology

• Climate

• Time



The soil forms through the interaction of these

factors.



Parent Material



Parent Material• Transported materials

• Bedrock or residual material

• Organic materials



Transported Sediments• Water transported or deposited

– Marine– Fluvial– Lacustrine

• Wind transported– Aeolian

• Gravity transported– Colluvium

• Ice transported– Glacial



Topography



Slope Names

• Summit or Ridge top

• Shoulder

• Back or side slope

• Foot slope

• Toe slope

• Terrace

• Drain way or channel



SummitSummit

Drainage wayDrainage way

Side or back slopeSide or back slope ShoulderShoulder

Foot slopeFoot slopeToe slopeToe slope



Soils on a slope



Vegetation/Biology



Grass Vegetation

• Thick top soil (A horizon)

• Stable soil structure



Forest Vegetation

• Thin top soil (A horizon)



Coniferous Vegetation

• Acidic

• Highly leached by organic acids

• Low fertility



Mixed Forest Vegetation

• In general more fertile

• In general less acidic



Climate



Humid Climate

•High rainfall

•Obvious horizons

•Illuviation/eluviation process dominant

•Organic matter accumulation at surface

•Clay accumulation



Arid Climate

•Low rainfall

•Little organic accumulation

•Salts or carbonates may accumulate

•Horizons less obvious



TimePast, present, and future



Newly Deposited Material



Undisturbed to DisturbedUndisturbed to Disturbed

nc state university department of soil science nc state university department of soil science...

Documents

wastewater soil

tons of soil

lakes soil

gram of soil

evaporation soil scientist

dime soil supplies water

erosion of soil clogs

year slide