Using GIS together with soils information for landuse planning will:

• Increase effectiveness of how land is used
• Decrease time spent on onsite investigations
• Maximize the output of limited funds
• Increase chances for grant approval by targeting areas that would be the most beneficial

Understanding the Tabular information

Soil tabular information downloaded is part of the Soil Survey Geographic (SSURGO) Database. The information has been approved by the NRCS by meeting all of their quality control standards.

Downloadable SSURGO metadata explains the tables and their column headings in the downloaded SSURGO information.

• Metadata Table of Contents (.pdf)
• Column Descriptions (.pdf)
• Tables (.pdf)

You can now identify and obtain the information you would like to incorporate into your GIS. See the basic steps above.

Soil map units are displayed and referenced by their map unit symbol (map unit symbol is referred to as a musym) as it appears as a field in the soil spatial layer attribute table shown in the image below. Musyms are displated in the image below.

Another way to understand map units and their components

Imagine this piece of Swiss cheese as the above Mc soil map unit.

Think of the entire piece of cheese (including holes) as the soil map unit Mc. The cheese is the major component (Melvin soils). The holes are the minor components (Newark soils and ultra acid soils).

Why is this important in a GIS?

• Component information will result in a one-to-many relationship which will not work.
• Soil properties are a part of component information.
• Distinguishing a major component from a minor component is essential in using soil information

After understanding components most soil attributes can be queried in an access template and then joined in a GIS.

After loading the tabular data, soil component information resides in an Access template. See Importing Digital Soils Information into Access.

• land capability
• crop yields
• pasture yields
• soil management
• prime farmland
• hydric soils

• woodland
• productivity
• management concerns
• trees to plant

• Wildlife Habitat
• Building Site Development
• Sanitary Facilities
  • septic tank absorption fields
  • sanitary landfills
• Construction Materials

• limitations for
  • ponds
  • embankments, dikes & levees
• features affecting
  • drainage
  • terraces
  • grass waterways

• USDA Texture
• Unified Classification
• AASHTO Classification
• Particle Size Distribution
• Liquid Limit
• Plasticity Index

• clay, silt, sand
• rock fragments
• bulk density
• permeability
• available water capacity
• soil reaction
• shrink-swell potential
• soil erodibility factors K and T
• wind erodibility group
• organic matter

• hydrologic group
• flooding hazard
  • frequency
  • duration
  • time of year
• depth to
  • bedrock
  • seasonal high water table
• risk of corrosion to
  • concrete
  • steel

Modeling soil information

Certain soil characteristics have greater impacts on the success of a best management practice (BMP). If these characteristics are used in prioritizing areas for land use and BMP implementation, they will be more effective.

This example shows how soil information can be taken one step farther. The map on the left displays national septic ratings and the map on the right shows those soils that are the most limiting within that area.

Which map is more useful?

Reports and ratings listed in a soil survey are developed from national and statewide standards.

These standards are well studied and are accurate and useful when comparing soils nationally or statewide. (Soil properties can be modeled as in the example above.) The usefulness and reliability of ratings can be improved at the local level by using Access Queries and GIS.