A wide range of GIS data resources are available from the USDA Natural Resources Conservation Service. Highlights include the US General Soils Map (STATSGO2), SSURGO soils, and the National Resources Inventory (NRI) all of which are documented on this page.
US General Soils (STATSGO2)
The US General Soil Map (STATSGO2) consists of "state general soil maps made by generalizing the detailed soil survey data. The level of mapping is designed to be used for broad planning and management uses covering state, regional, and multi-state area. The original STATSGO (stands for State Soil Geographic Database) data were revised and updated in 2006, and hence renamed to version 2. Contact Data Services if you need a copy of the original STATSGO data for North Carolina. A copy of North Carolina's STATSOG2 data is archived on the Geodata Server under /fedgov/nrcs/statsgo2.
Full details, download options, and metadata about STATSGO2 data are on this NRCS website.
The Soil Survey Geographic (SSURGO) Data Base consists of 1:12,000 to 1:63,360 scale detailed local soils data. "SSURGO digitizing duplicates the original soil survey maps. This level of mapping is designed for use by landowners, townships, and county natural resource planning and management. The user should be knowledgeable of soils data and their characteristics."--(NRCS site).
SSURGO data is downloadable in various formats and projections for nearly all of the US (status graphic pdf) from the Web Soil Survey or Geospatial Data Gateway. It is recommended that you use SSURGO data only from one of these two sites because they have been certified by NRCS for accuracy.
When you go to the Web Soil Survey site, click the big green button to access data. There are two ways to use the site:
- If you are interested in a small area (single farm, neighborhood, small watershed) then create an "Area of Interest" and you can generate reports and maps within the online app.
- If you are interested in an entire county or a large portion of a county, you will need to download the county's file geodatabase and do your analysis with desktop GIS software. To access the county files, click the yellow "Download Soils Data" tab and then "Soil Survey Area (SSURGO)" link.
If you are using ArcGIS, working with SSURGO data is MUCH easier by using the NRCS Soil Data Viewer. This is an ArcMap extension that makes soil mapping unit attribute joins to the appropriate database tables. Analyses, mapping, and report generation has been made very simple with this extension. Installing the extension is a multi-step process and not so simple. Contact Data Services for assistance or google for online tutorials and videos.
To better understand the soil maps and data, it may be useful to refer to the printed soil survey for your county of interest. Current and past print versions of all US soil surveys are online in pdf. NCSU Libraries has soil surveys in print for all North Carolina counties, and many other counties in the US. Search the Catalog for library locations.
Older soils data that were digitized by NC CGIA (status graphic) in the 1990's are available in ArcInfo Coverage format and shapefiles on the Geodata server (see the Detailed Data Listing). This data is kept for archival purposes and only recommended for historical comparisons.
Other NRCS Data Resources
The National Resources Inventory "...is a statistically based sample of land use and natural resource conditions and trends on U.S. nonfederal lands. It is the most comprehensive database of its kind ever attempted anywhere in the world" (NRCS). Since 1982, the NRI was conducted every 5 years; but, beginning with 2001, it is conducted annually.
Two CD-ROM products have been released of the NRI and are available from DH Hill Library:
According to the NRI website, annual inventory data is only available via the website (limited summary) or the NRI Online Analysis System used by NRI Coordinators.