Envirothon Soils

Dennis BrezinaUSDA-Natural Resources Conservation

ServiceResource Soil Scientist – Bryan Area

Conservation…Our Purpose; Our Passion.

What is Soil? Soil is the combination of air,

water, organic and mineral matter on the earth’s surface that is distinguishable from its parent material and can support rooted vegetation. 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 same at all times.However, if the soil is wet, the pore space will contain more water.As the soil dries, the pore space will contain more air.

1%

49%

25%

25%

Air

Water

Mineral

OrganicSoil is half solid and half pore space

TOPOGRAPHY – Soil-forming FactorSlope or configuration of the land

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

• Different soils will occur on different landscape positions- Soils on back and shoulder slopes are generally thinner than those on summits, footslopes and toeslopes

• Summit• Shoulder

• Backslope• Footslope

• Toeslope

Slope PercentageRise over Run

Slope PercentageRise over Run

Simplified Soil Profile

• A= Surface Horizon• (Most biologically active)

• B = Subsoil Horizon• (Typically has higher clay

content and blocky structure)

• C = Parent Material• (Residual, Colluvium, Alluvium,

Marine or Eolian)

A

B

C

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:• Largest of the soil particles• Feels gritty• Compare it to a baseball

Silt size particles are:• Intermediate in size• Smooth, talcum powder feel• Compare it to a marble

Clay size particles are:• The smallest in size• Sticky and plastic when wet• Compare it to a BB

Clayey Soils

High Shrink-Swell • Clay minerals expand when wet and shrink when dry.• Cause cracks in building foundations, sidewalks, etc.

MoreWater

• High organic content• High water holding

capacity • Slower permeability• Higher runoff• Agriculturally

productive• Difficult to work with

Sandy Soils• Larger pore space• Low water holding capacity• Rapid infiltration and

permeability• Higher leaching• Low organic matter• Low fertility• Generally better drained• Easy to work with

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.).

SOIL COLOR

Soil color name is on the left page, and the color notation is written as:

Hue Value/Chroma (10YR 6/3)HUE

CHROMA

VALUE

Most visible soil property

Color Name

Soil ColorMost visible soil property

Dark = high organic content• Humus and organic matter are

generally black or brown.

Light = low organic contentRed, yellow and brown are well

drained• Generally due to oxidation of iron

compounds in the soil.• Reds are highly oxidized. • Compare it to rust on iron. When metal

gets wet, as it dries (oxidizes) it turns a reddish-yellow color.

Gray could mean excessive wetness

• The iron in soil is either removed or reduced when oxygen is removed.

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

HUE

CHROMA

VALUE

Mottles/Redoximorphic Features

• Grays are iron depletions (reduced iron).

• Mottles and 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

Vegetation.Vegetation. 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.• In general, as rainfall

increases, pH decreases• pH >8.5 could mean high salt

content• pH<4 could mean Aluminum

and Iron toxicity• pH meters best tool for testing• Add lime for soils less than pH

of 5.5, and sulfur for soils above pH of 7.5.

Three Main Plant NutrientsN-P-K

Nitrogen (N) • Most commonly deficient nutrient• Above ground vegetative growth

Phosphorous (P)• Seed germination• Disease resistance• Root development• Plant maturation (flowering, fruiting,

seed formation)

Potassium (K)• Root development• Photosynthesis (especially root crops

and for starch formation)

ACMEFERTILIZER

N-P-K

Can plants use just any form of Nitrogen?

• Atmospheric Nitrogen gas (N2) is the most common gas, but it cannot be used by plants.

• Nitrogen is converted into plant-usable forms through the Nitrogen Cycle

• Nitrate (NO3) and Ammonia (NH3) are plant-usable forms

How can the Nutrients be put back

when used up?• Organic Fertilizer - lawn clippings, manure, mulch, cottonseed meal, guano, poultry litter wood ash, peat• Inorganic Fertilizer - chemically produced. Broad range of types. Easy to use, but easy to over-fertilize. 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

• So…How many pounds of this fertilizer (25-10-5) should you use on a 6000 square foot yard?

ACMEFERTILIZER

N-P-K25-10-5

How much Fertilizer for 6000 square feet?

• 25-10-5 25% N 0.25 lb N per lb FertilizerRule of Thumb

• 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

• 4 lbs Fert X 6000 sq ft =

1000 sq ft

24 lbs Fertilizer

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.

Types of Erosion

• Wind Erosion • Gully Erosion

• Sheet and Rill Erosion• Raindrop Splash

Planting Wind Breaks

No-TillStubble Mulch or Ridge-Till

Contour FarmingStrip Cropping & Terracing

Conservation Practices = Things that Prevent Erosion

Preventing Raindrop Splash

• Vegetative cover • Lawns, pasture or

rangeland• No-Till• Stubble mulch or

ridge till• 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 is transporting less topsoil, nutrients and pesticides.

Milan Experiment Station-Milan, Tennessee

No-Till field

Conventional tilled field

Preventing Sheet, Rill & Gully Erosion

• Slow the speed of surface water flow

• Vegetative Cover• Contour farming• Diversion Terraces• Strip Cropping• No-Till, stubble mulch or

ridge-till• Grassed waterways

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

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

• Grassed waterways are used to prevent all four types of erosion.

Preventing Wind Erosion

• Plant Wind Breaks

• Rotary hoes add surface roughness

• Strip cropping

• The perfect time to Break Wind http://www.ewrs.org/pwc/rotary.htm

• http://images.search.yahoo.com/

• Increased runoff

• Increase floodwater energy (trees and other vegetation help dissipate floodwater energy)

• Increase Streambank erosion

Removal of vegetation along creeks can cause:

How can Soils affect our Bays & Estuaries?

• Over fertilization can lead to Eutrophication - algal blooms, depleted oxygen

• Soil erosion can lead to sedimentation

• Reduce water clarity• Water temperature changes• Pesticides can attach to

sediments and cause toxicity• Can impact the pH of the

water Euthrophication in the Sea of Azov (Source: NASA)

What is a Watershed?

• Watershed is the area of land draining into a river, river system or other body of water.

• Generally it is a tributary stream or a creek.

Primary Stream

Tributary Streams

What is a River Basin?

• A River Basin is a large watershed.

• Area of land drained by a river and all of its tributaries.

• Whatever you put in the water affects those downstream.

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 people wanting information on soil resources for 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

• Map unit symbol & name

• Where it is mapped

• Thumbnail soil description

• Soil Properties Narrative

• Inclusions

• Land uses

• Soil Suitabilities and Limitations

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.

Inclusions are areas of a different soil that are too small to delineate at the scale of mapping.

Mounds

Lower wet spot as an inclusion in the landscape

Soil map unit (flats) with mound inclusions

What is a soil mapping INCLUSION?

These dark spots in this area are inclusions.They are slightly lower 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.

•Example: Oz Ozias-Pophers complex, frequently flooded

What is a soil mapping COMPLEX?

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

What is a soil mapping COMPLEX?

Soil map unit that has a combination of flats and mounds.

How to use the Soil Survey Tables

• Table of Contents has a Summary of Tables

• The Tables contain information on soil properties, suitabilities 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?• Given that a bushel of wheat will yield about 42

pounds of white flour, and that 1 pounds of white flour will yield about 1.7 loaves of bread; How many loaves of bread will 40 acres of HoB Houston Black yield?

• From the table, HoB Houston Black will produce about 45 bushels of wheat per acre.

• 45 bu X 42lbs X 1.7 loaves x 40 acres = Ac 1 bu 1 lb flour

• 128,520 loaves of bread per 40 acres!

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://www.tx.nrcs.usda.gov/► 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://soilcrop.tamu.edu/

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Helping People Understand Soils

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