A Brief Discussion of Soil Surveys

A Brief Discussion of Soil Surveys

December 10, 2020Edward Stephens, Soil Scientist

NCDA&CS Division of Soil and Water Conservation

Soil Survey

• Began in North Carolina in the late 1800s.• Raleigh to New Bern Survey covered a narrow area.• Surveys along railroad right of ways• Looking for better agricultural land and to establish test farms.

• NCDA and NCSU now have research stations across the state.

Raleigh to New Bern Survey From USDA Archives

Soil Survey Time Line

Tough Work on Bad Roads

• Early mappers were on horseback or mules.• No air photos• Soil Science was very young • Few Series to delineate into

•Still tracks with the modern surveys!

Comparing Surveys 100 Years Apart

Bladen County in 1914 Bladen County in 2020

Why is it important?

• The most effective way to communicate the properties of soil and the environment to other land users.

Standardized practices are used to insure accuracy and reduce human variation in data.

New methods are emerging as technology advances.

Air photos were a big deal post World War II.

Mapping and Classification

Soils are mapped consistently by using the soil survey manual. Lab Data helps determine texture, chemical properties, etc.

Cecil Series in Wake County, NC is the same in Iredell County, NC and in other states.

What are you talking about?

• Soils that have profiles that are almost alike make up a SOIL SERIES. • ex. Norfolk Series

• A Soil Series is divided into Soil Phases - similar soils that have different slope, stoniness, wetness, degree of erosion or other characteristics that affect their use.

• ex: Norfolk loamy fine sand, 0-2% slope

• Catena: a sequence of soils about the same age, derived from the same parent material and occurring under similar climactic conditions, but having different characteristics because of variation in relief and drainage. From Elements of the Nature of Soil Properties, Brady and Weil

NorfolkGoldsboroLynchburg Rains

Complex: Soils that are so intertwined that they cannot be separated on a map at this scale

Soil Systems in North Carolina

What is in the book?

•Generally Speaking:• A general description of the nature of the soil survey area

• A description of general soil map units and detailed soil map units.• A list of prime farm land • Information about land uses for the survey area• Soil Properties including engineering, physical properties and soil and

water information

What is in the book?

Soil series descriptions in narrative form Tables regarding crop yield, land use limitations, temperature, drainage and engineering properties. Full Taxonomic Names!

Cecil (our State Soil):Fine, kaolinitic, thermic Typic KanhapludultsExum (in my yard):Fine-silty, siliceous, subactive, thermic Aquic Paleudults

A few words about map scale

Scales can vary. As the soil surveys were completed over the years some counties used different scales. 1:24000 is common• 1 inch on the map is 24,000 inches in the field• 1 inch on the map is 2000 feet in the field• ¼ inch on the map is 500 feet in the field• 0.050” (Sharpie line) is 100 feet in the field• 0.025” (ball point pen line) is 50 feet in the field• 0.010” Soil Series dividing line is 20 feet in the field

Map LinesSharpie

Pencil

Ballpoint Pen

0.100” ( one tenth of an inch) is 200 feet

Red arrow shows start of intermittent stream which is very significant for NCDWR Stream Buffers in the Neuse and Tar-Pam river basins and others in the state.

Flood Hazard Soils

Hydric Soils

A pencil line is 50’, will that change your project?

Paper Sheet from Columbus Co.

Web Soil Survey

• Digital version of the original paper survey.• Goes offline during Federal Government Shutdowns• Scale can be tricky • Makes a good map to work with• Original paper copies of the soil survey and USGS 7.5 Quad maps are

the legally binding version of the maps in certain regulatory circumstances

Variations due to digitalization?

• "I hope the answer to your question is clearly indicated in what I have written. It is that the soil survey will never be completed because I cannot conceive of the time when knowledge of soils will be complete. Our expectation is that our successors will build on what has been done, as we are building on the work of our predecessors." R. S. Smith, Director, Illinois Soil Survey in September 27, 1928.

Leon Series

Cecil Series

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Norfolk Series

Coxville Series