Today I’m continuing a series on sources of spatial data (see past posts on aerial images and DEMs). Soil maps are useful for all sorts of applications, like deciding where to place a trial in a larger field so that all the treatments are on the same soil type or determining the drainage class of the soil where a particular sample was taken. Fortunately, it’s easy to get free soil maps for the vast majority of the US through a dataset called SSURGO. These maps were generated using data collected by the federal government since the early 1900s.
The tool I use most frequently to access the SSURGO database is Web Soil Survey, an online tool hosted by NRCS. To get started, go to the WSS home page and click the green “Start WSS” button (see below).
When you launch WSS, you have two options– uploading a shapefile of your area of interest, or using the Quick Navigation menu and highlighted tools to draw your AOI manually. For this example, I zoomed in on Devil’s Lake in Wisconsin. After defining your AOI, you can see the soil map or use the soil data explorer to learn more about potential land uses and soil properties.
If you want to download the soil map to use in other software, go to “download soils data” on the main menu. There’s a “create download link” button in the bottom right hand corner. Click that, and a download link will appear on the left-hand side.
When you click the download link, you’ll get a zipped file. Extract the files and go to the “Spatial” folder. This will have a variety of shapefiles with the boundary of you AOI, the soil map units, and other attributes. There is also metadata that includes information about when the data was collected.
WSS not working for you? You can also get SSURGO maps from the USDA NRCS Geospatial Data Gateway, which works very similarly to WSS. There’s also an SSURGO Downloader application for ArcMap. Happy map making!
Spatially Challenged 