Natural Resources Conservation Service (NRCS) GIS Data
A wide range of GIS data resources are available from the USDA Natural Resources Conservation Service. Highlights include gSSURGO soils data and the National Resources Inventory (NRI).
gSSURGO Soils Data
gSSURGO refers to a File Geodatabase of soils data, compiled for an entire US state. The geodatabase contains vector (MUPOLYGON), raster (MapunitRaster_10m), and relational attribute tables. The "Valu1" table is a compilation of 57 pre-summarized or "ready to map" attributes. For much more information, be sure to read the gSSURGO User Guide. gSSURGO data are the same as SSURGO, except gSSURGO refers to the file geodatabase product, while SSURGO data are available through Web Soil Survey, described further down.
Recommended method for using gSSURGO Soils Data in GIS software
Soils data are a very complex type of GIS data that includes hundreds of soil characteristic variables for each soil polygon. There is additional complexity due to some of the variables changing with depth, adding a form of third dimension to the data.
Below are example steps to find soil texture (percent sand, silt, clay), which demonstrate how you would also find other soil properties.
- Download and unzip the gSSURGO file geodatabase for the state(s) of your study area. NRCS does not provide county-level downloads, but watershed-level downloads are available from ArcGIS Online -- see below. Inside the file geodatabase, the MUPOLYGON feature class is the vector soil polygons. One of the attribute fields for this feature class is MUKEY, containing 6-7 digit key numbers.
- Using Google's AI help, ChatGPT, and/or this table, we can learn that texture values are in the "chorizon" table from the file geodatase. Use these same search tools to find the table(s) needed for other soil properties. The chorizon table uses COMPONENT KEY values as identifiers (8 digit numbers). To crosswalk the MUKEY and COMPONENT KEY identifiers, we can use the "component" table. Therefore, two tables need to be added from the file geodatabase (component and chorizon) and two table joins will need to be performed.
- First, join MUPOLYGON using the MUKEY field with the component table, MAPUNIT KEY field. Next, join MUPOLYGON using the newly added COMPONENT field (from the component table) with the chorizon table COMPONENT KEY field. These joins may take several minutes to complete.
- Once finished, you should have the two attribute tables joined. Each polygon will have attributes for sand, silt, and clay if you scroll about halfway through the table. They are shown as:- Total sand - representative value- Total silt - representative value- Total clay - representative valueThese values are percentages and will add to 100. Some texture values are further broken down by coarse, medium, and fine descriptions.
Data Sources
It is recommended that you use SSURGO and gSSURGO data only from one of the sources below because they have been certified by NRCS for accuracy and are regularly updated.
- Soils folder on Box - Used by NRCS for very large files.
- gSSURGO - download by state and entire conterminous U.S.
- gNATSGO - A composite database that provides complete coverage of the best available gridded soils information for all areas of the United States and Island Territories. It was created by combining data from the Soil Survey Geographic Database (SSURGO), State Soil Geographic Database (STATSGO2), and Raster Soil Survey (RSS) databases into a single seamless ESRI file geodatabase.
- Soil Color Maps - statewide tif images showing soil colors by depth. Color values "are translated from Munsell color notation to sRGB using the aqp library" within R statistical package.
- SSURGO Downloader - ArcGIS Online app for downloading soil data map packages (geo data combined with a lot of attributes) by river basin usable in ArcGIS Pro. Once open in ArcGIS Pro, it can be clipped to other extents and exported for use in other software.
- Geospatial Data Gateway - USDA data portal. Download state gSSURGO data, as well as a wide range of other map layers.
- Web Soil Survey - If you are interested in a small area of up to 100,000 acres (single farm, neighborhood, small watershed) and prefer to view and work with soils data in a browser (no additional software needed), then create an "Area of Interest (AOI)" and you can generate reports and maps within the online app.
REST Service
The North Carolina Dept. of Agriculture and Consumer Services provides NC statewide soils, forest, and farmland productivity data through an ArcGIS REST Map Service. Zoom in to a relatively large scale to see the data.
See also the Web-based data viewers, below.
Additional tools
NRCS maintains a Github site with tools for R and ArcGIS. From here, the Soil Data Development Toolbox is highly recommended for working with SSURGO and gSSURGO data in ArcMap 10.x (not compatible with ArcGIS Pro). Once installed, this toolbox will make it much easier to work with soils data. Contact Data Services for assistance getting started.
Web-based data viewers
Esri Living Atlas maps:
- USA Soil Map Units - Clickable soil units feature layer, with nice colors and attribute pop-ups.
- Image layers for various themes - Such as farmland, crop production, hydric, derived from attribute table fields.
Soil Surveys from the past
To better understand the soil maps and data, it may be useful to refer to the printed soil survey for your county of interest.
- PDFs of current and past print US soil surveys
- NC State University Libraries has soil surveys in print for all North Carolina counties, and many other counties in the US. Search the Catalog for library locations. The maps in these documents are considered to be superceded by current online SSURGO data.
Data that were digitized by NC CGIA (status graphic) in the 1990's from soil survey hardcopy maps 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.
Natural Resources Inventory
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 D. H. Hill, Jr. Library:
- 1992 - See Catalog Record
- 1997 - See Catalog Record
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.