State EnvirothonSoils

Dennis Brezina

USDA-Natural Resources Conservation Service

Resource Soil Scientist – Bryan Area

Helping People Help Helping People Help the Landthe Land

What is Soil?

Soil: The combination of air, water, and organic and mineral matter on the earth’s surface that is distinguishable from its parent material and can support rooted vegetation.

What is Soil?

It is a product of the effects of CLIMATE, BIOTIC ACTIVITY, acting on PARENT MATERIAL as conditioned by TOPOGRAPHY over TIME.

Four Components of a Typical Soil

Air

Water

Mineral

Organic

Pore space remains about the sameIf the soil is wet>>>it contains more waterAs the soil dries>>>air takes its place

1%

49%

25%

25%

FIVE SOIL-FORMING FACTORSFIVE SOIL-FORMING FACTORS

• Climate• Biotic Activity (Living Organisms)• Parent Material• Topography• Time

CLIMATE• MOST INFLUENTIAL FACTOR• Weather over time• Temperature and precipitation in

particular• Determines the nature and

speed of formation and development

• High Heat, High humidity, abundant rain generally produces more development

• For every 10 degrees C rise in temperature, the rate of chemical reactions doubles

• Also micro-climates created because of topography

BIOTIC ACTIVITY• Plants and manipulation by animals• Especially Native Vegetation - Grasses vs. trees• Microorganisms

Soils under prairie vegetation hold more moisture, have higher pH and organic matter, and thus are generally darker in color, and have higher fertility

Soils under forest vegetation generally hold less moisture, have lower pH and organic matter, and thus are generally lighter in color, and have lower fertility

PARENT MATERIAL• Weathered fragments of

Organic or Mineral material from which soils form

• Related to Geology • Most of the eastern half of

Texas was influenced by the Gulf Coast as Coastal Plain Sediments ( At least 85% of Texas was under water at one time)

• Soils are derived from sandy, loamy and clayey sediments

TOPOGRAPHY• Nearly level vs. sloping –

- Water shedding vs. water receiving- Flat areas are generally wetter than steeper, sloping areas

• Different soils will occur on the ridge, side slope and foot slope of a hill - Soils on backslopes and shoulder slopes are generally thinner than those on summits, footslopes and toeslopes

Slope or configuration of the land

TIME• Soils on flood plains

and along the coast are “younger” or less-well developed

• Stable landscapes have “older” more developed soils

Takes about 500 years to form an inch of soil from hard parent material

Geologic Yardstick of Time

• The relative proportion of SAND, SILT and CLAY.

• The MOST IMPORTANT PHYSICAL PROPERTY of the soil because it determines the capacity of a soil to retain moisture and air.

• Essentially impossible to change unless you remove it, or add large amounts to it.

SOIL TEXTURE

The Three SOIL Particle Sizes

• Sand size particles are the largest of the soil particles - feels gritty - compare it to the size of a baseball

• Silt size particles are intermediate in size - has a smooth, talcum powder feel - compare it to the size of a marble

• Clay size particles the smallest - feels sticky and plastic when wet - compare it to the size of a BB

Clayey Soils• High Shrink-Swell – clay

minerals expand when wet and shrink when dry- Cause cracks in building foundations, sidewalks, etc.

• Many are called VERTISOLS• High Organic Content• High Water Holding Capacity

(High clay=high water)

• Slower permeability• Agriculturally productive• Difficult to work with

Air

Water

Mineral

OrganicMoreWater

Sandy Soil

• Larger pore spaces• Low organic matter• Low fertility• Low water holding

capacity• Rapid infiltration and

permeability• Generally better

drained• Easy to work with

Air

Water

Mineral

Organic

More Air

This doesn’t mean that sandy soils are not as “good” as clayey soils. Sandy soils are just good for different things (peanuts, timber production, etc.).

Loamy Soil• Somewhere in

between• Wide array of soils• Low to High Fertility• Low to High Organic

content• Low to High Water

Holding Content• Moderate to work with• Often have an Argillic

Horizon

Argillic Horizon

• Generally have a Sandy or Loamy surface

• Increase in Clay from the surface to the Subsoil

• This horizon is called an ARGILLIC horizon

• Sometimes called a “Claypan”

• Water often perches on top of the Argillic horizon

SOIL COLOR

Soil color is written as: Hue Value/Chroma (10YR 6/3)

HUE

CHROMA

VALUE

Most visible soil property

Soil Color

• Dark=high organic contentHumus/Organic Matter is generally black or brown; thus soils that are high in organic matter are generally darker in color

• Light=low organic content• Red, yellow, brown is well drained

Generally due to iron compounds. Reds are highly oxidized. Compare to rust on iron=metal gets wet, as it dries (oxidizes) it turns a reddish-yellow color

• Gray could mean excessive wetnessIron is either removed or reduced due to the removal of oxygen

Most visible soil property

1. HUE

3. CHROMA

2. VALUE

Two Basic Soil Epipedons or Surface Horizons

• 1. Mollic Epipedon

• Thick, Dark Surface

• Color Value of 5 or less (3 or less moist)

• Color Chroma of 3 or less (moist)

• Dark=high organic content

• Soil Order is either Mollisols or Vertisols

Two Basic Soil Epipedons or Surface Horizons

• 2. Ochric Epipedon

• Basically any other surface horizon

• Light Colored Surface

• Light=low organic content

• Soil Order is generally Entisols, Alfisols or Inceptisols

Mottles/Redoximorphic Features

• Grays are iron depletions (reduced iron)

• Mottles or redoximorphic features are caused by oxidized or reduced iron

• Red, orange and yellow colors are iron accumulations (oxidized iron)

Gray Could mean Wet

• Gray surface• Contains mottles

(oxidized or reduced iron) • Mottles indicate alternate

wetting and drying• Concave or Flat

landscape! The water cannot drain off the area

• Wet soils could be associated with wetlands!

3 Requirements for a Wetland3 Requirements for a Wetland

Hydric SoilHydric Soil More than 50 percent Hydrophytic More than 50 percent Hydrophytic

VegetationVegetation Hydrology indicating seasonal inundation, Hydrology indicating seasonal inundation,

ponding or ponding or saturationsaturation by water by water

Hydric Soil

• Soils that formed under conditions of saturation

• Soils developed under sufficiently wet conditions to support the growth and regeneration of hydrophytic vegetation

• Essentially a “gray” soil

More than 50 Percent Hydrophytic Vegetation

Water Marks

Hydrology

Soil pH

• Ideal pH range is 5.5 to 7.5

• Most U.S. soils have pH range of 4 to 8.5

• pH >8.5 could mean high salt content

• pH<4 Aluminum and Iron toxicity

• pH meters best tool for testing

• Add lime for soils less than 5.5 and sulfur for soils above 7.5

Three Main Plant NutrientsN-P-K

• Nitrogen (N) encourages above ground vegetative growth (makes the grass greener)

• Phosphorous (P) important for seed germination, disease resistance, root development and plant maturation (flowering, fruiting, seed formation)

• Potassium (K) important for root development and photosynthesis (especially root crops and for starch formation)

ACMEFERTILIZER

N-P-K

How can the Nutrients be put back

when used up?•Organic Fertilizer - lawn clippings, mulch, cottonseed meal, guano, manure, poultry litter, ash, peat•Inorganic Fertilizer - chemically produced. Broad range of types. Easy to use, but easy to over-fertilize--and with higher fuel costs, expensive $$•On lawns, Rule of Thumb is to put: 1 pound of Nitrogen per 1000 square feet. More is NOT always better.

How much do you use?

• N-P-K is expressed as a percentage of Nitrogen, Phosphorous and Potassium

• Rule of thumb: 1 pound of nitrogen per 1000 square feet

• Question???• How many pounds of this

fertilizer (25-10-5) should you use on a yard that is 6000 square feet ?

ACMEFERTILIZER

N-P-K25-10-5

How much Fertilizer for 6000 square feet?

• 25-10-5 25 percent N 0.25 pounds (lbs) of N per pound of Fertilizer

• 0.25 lbs N x ? lbs Fert = 1 lb N per 1000 sq ft

• 0.25 lbs N x ? lbs Fert = 1 lb N per 1000 sq ft =

0.25 lbs N 0.25 lbs N

• 4 lbs Fert per 1000 sq ft = 4lbs Fert/1000 sq ft

• 4 lbs Fert X 6000 sq ft =

1000 sq ft 24 lbs Fertilizer

How big is 1000 square feet?

• Square root of 1000 is 31.6 or

• About 32 feet x 32 feet

32 ft x 32 ft =1024 sq ft

Salinity

• Causes soil to become hard • Modifies and degrades soil

structure over time• Damages roots and stunts

plants• Reduces the water that is

available to plants (moisture can be in the soil, but the sodium “ties” it up to where it is not available to plants)

• Damages steel

Remember our Argillic Horizon?• Sodium makes a special type

of Argillic horizon called a NATRIC horizon

• The salts and sodium (especially Na, Ca and Mg) leaches through the surface and collects at the Argillic horizon (remember how water perches on top of the Claypan?)

• This modifies the soil structure over time

• The argillic horizon becomes hard

Natric Horizon• The Sodium starts to

coat and seal off the natural soil structure and water starts to perculate only through larger structure cracks called COLUMNS or PRISMS

• Damages roots and stunts plants• Reduces the water that is available to plants (moisture can

be in the soil, but the sodium “ties” it up to where it is not available to plants)

Blocky Structure

ColumnarStructure

Platy structure is associated with water lain sediments.Single Grain is generally your sands.Columnar structure is associated with high sodium.Massive is associated with compact, heavy clay soils.

Soil Structure

Erosion

• Wearing away or removal of the earth’s soil or land surface

• Soil moved by wind, water, ice or gravity

• Especially occurs on bare soil • Areas with more than 3 percent

slope are susceptible to water erosion

Why is Soil Conservation Important?

• Food (Fruits, vegetables, cereal grains, beef, chicken, pork, etc.)

• Cotton (clothes)• Leather (shoes, jackets)• Rubber (comes from trees)• Lumber• Paper• Paints, color dyes

What do we get from soil?

Why is Soil Conservation Important?

• Only 1/4 of the Earth is land, the rest water.

• 1/2 of that is mountains, deserts, or covered with ice (non-livable).

• Cut remaining 1/8 that is livable into fourths (Cities, too dry or too wet, too hot or too cold) .

• Only 1/32 of the Earth is farmable.

• Now, peel the skin off this 1/32 slice of the apple, and that is our soil that we are farming on.

Imagine the Earth as an Apple…

http://www.flickr.com/photos/

Types of Erosion

• Raindrop Splash• Sheet and Rill

Erosion• Gully Erosion• Wind Erosion

Planting Wind Breaks

No-Till Stubble Mulch or Ridge-Till

Contour FarmingStrip CroppingTerracing

Conservation Practices Preventing Erosion

Preventing Raindrop Splash

• Stubble Mulch or Ridge Till

• No-Till• Pasture or

Rangeland• Some type of

vegetative cover• Cover Crops

• No-Till intercepts Raindrop Splash almost like having grass cover.

• Soil structure improves with time, and more water infiltrates and percolates through the soil.

Comparison of No-Till to Conventional Tillage

The clear water from the no-till side of the field istransporting less topsoil, nutrients and pesticides.

Milan Experiment Station-Milan, Tennessee

Runoff from

no-till field on

the left and

Conventional

tilled field on

the right.

Preventing Sheet and Rill Erosion

• Contour Farming• Terracing• No-Till, Stubble

Mulch or Ridge-Till• Grassed Waterways• Slow the speed of

surface water flow

• Contour farming and terracing intercept and slow down the speed of surface water flow.

• Some crops do not leave enough residue and cover to use No-Till.

• Clayey soils also do not accept No-Till as well as loamy soils (hard to work).

Preventing Gully Erosion

• Grassed Waterways

• No-Till

• Vegetative cover

• Contour Farming

• Strip Cropping

• Terracing

• Grassed Waterways are used a lot all over the country to prevent all four types of erosion.

• Terraces are used on steeper land to intercept and slow down the downhill flow of water.

Preventing Wind Erosion

• Planting Wind Breaks• Rotary Hoe-adds

surface roughness• Strip Cropping• The perfect time to

Break Windhttp://www.ewrs.org/pwc/rotary.htm

Secondary Benefits of Preventing

Erosion

• Moisture Conservation leads to Increased Yields (especially in drier years).

• Improved Soil Structure leads to Moisture Conservation (see above).

• Preventing Fertilizer Loss leads to Increased Yields and saves money.

• Takes less horse power to use a spray rig than tillage (saves Fuel and money).

Soil Quality Indicators

• Soil organic matter: soil fertility, structure, stability, nutrient retention; soil erosion

• Physical: soil structure, depth of soil, infiltration and bulk density; water holding capacityChemical:  pH; electrical conductivity (salinity); plant available nutrients

• Biological: microbial biomass C and N; potential for mineralization of N; soil respiration. 

Soil Surveys

• An inventory of soils that includes maps, soil descriptions, photos and tables of soil properties and features

• Used by farmers, real estate agents, land use planners, engineers and others who desire information about the soil resources for use in general land use planning

The major parts of a soil survey publication...

• How to Use this Soil Survey• Table of Contents• Introduction and General

Nature of the County• General Soil Map & Block

Diagrams• Detailed soil map units• Use and management

and interpretive tables• Classification of soils• References• Glossary• Index to map sheets• Soil maps

Using a Soil Survey• Locate your area of

interest on the map index

• Identify all of the soil map unit symbols at your area of interest, and find the soil map unit on the soil legend

Detailed soil map unit description

• Probably the most important description

• Map unit symbol and name

• Description of where it is mapped

• Inclusions

• Thumbnail soil description

• Land uses

• Soil Properties Narrative

Compare a SOIL MAP UNIT to a red sorrel horse

What is a soil mapping INCLUSION?

What is a soil mapping INCLUSION?

Now compare a SOIL MAP UNITto a red sorrel horse with white points or “inclusions”It is still “Red,” but it has other colors

Mounds

Lower wet spot as an inclusion in the landscape

Soil map unit (flats) with mound inclusions

What is a soil mapping INCLUSION?

The white “splotches” in this area are inclusions.They are slightly higher than the surrounding landscape.

What is a soil mapping COMPLEX?

Soil map unit that has a combination of flats and mounds

Compare a soil mapping COMPLEX to this red paint horseWhat color is it?Is it white with red spots, or red with white spots?

Complexes are two or more kinds of soil occurring in such an intricate pattern that they cannot be shown separately on a soil map

What is a soil mapping COMPLEX?

The white spots in these map units on this aerial photograph are mounds (often called pimple mounds) associated with flats.

Depression and Mound areasDepression and Mound areas

Dry Mound areas

Wet depressional areas

How to use the Soil Survey Tables

• Table of Contents has a Summary of Tables

• The Tables contain detailed information on soil properties and their suitability and limitations as well as management and production

• Find the Table that has the information that you are needing

How to use the Soil Survey Tables

• Go to the table that contains the information you seek

• Find your map unit symbol

• Find the land use practice or yield data

• Table provides information on suitability for that soil for that particular land practice

HoB Houston Black will produce about 45 bushels of wheat per acre.

Question?• HoB Houston Black will produce about 45

bushels of wheat per acre. • A bushel of wheat weighs 60 pounds.• A bushel of wheat will yield about 42 pounds of

white flour.• 42 pounds of white flour will yield about 73

loaves of bread.• How many loaves of bread will 40 acres of HoB

Houston Black yield?• 45 bushels X 73 loaves x 40 acres = • 131,400 loaves of bread

ReferencesReferences

► Essentials of Physical Geography,Essentials of Physical Geography, by Gabler, by Gabler, Sager, Brazier and WiseSager, Brazier and Wise

► The Nature and Properties of Soils,The Nature and Properties of Soils, by Nyle by Nyle C. BradyC. Brady

► http://www.ewrs.org/pwc/rotary.htmhttp://www.ewrs.org/pwc/rotary.htm► http://soils.usda.gov/http://soils.usda.gov/► http://www.tx.nrcs.usda.gov/http://www.tx.nrcs.usda.gov/► http://www.flickr.com/photos/http://www.flickr.com/photos/► http://milan.tennessee.edu/http://milan.tennessee.edu/► http://photogallery.nrcs.usda.gov/Index.asphttp://photogallery.nrcs.usda.gov/Index.asp► http://soildatamart.nrcs.usda.gov/http://soildatamart.nrcs.usda.gov/► http://soilcrop.tamu.edu/http://soilcrop.tamu.edu/

ContactsContacts

►USDA-Natural Resources Conservation USDA-Natural Resources Conservation Service Service Dennis Brezina, Resource Soil ScientistDennis Brezina, Resource Soil Scientist

Bryan Area Office=979-846-0757 ext. 3Bryan Area Office=979-846-0757 ext. 31716 Briarcrest Drive, suite 5101716 Briarcrest Drive, suite 510Bryan, TX 77802Bryan, TX 77802dennis.brezina@tx.usda.govdennis.brezina@tx.usda.gov

Temple State Soils Staff=254-742-9850Temple State Soils Staff=254-742-9850

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Helping People Understand Soils

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