Notwithstanding the importance of soil profiles in any model applications that involve water deficits or responses to nutrients, surprisingly few research sites have had their soils adequately characterized. Too often, even if data were taken, the information is limited to properties of the top 30 cm and at best, include only texture and key nutrients. Among options for obtaining more detailed data on soils within the US is to search for data related to the soil series of interest.

The SoilWed apps developed by the UC Davis California Soil Resource Lab (https://casoilresource.lawr.ucdavis.edu/soilweb-apps) can access USDA-NRCS soil data through user friendly interfaces. Two apps, SoilWeb and SDE: Soil Series Data Explorer, provide users searching for data on texture, soil pH, moisture retention and other traits for complete profiles. Mapping tools allow users to locate multiple sampling locations for a given soil series, possibly including the specific site of interest.

Option 1. If you know the soil series: the SDE: Soil Series Data Explorer

If you know the NRCS soil series name, the web app SDE: Soil Series Data Explorer (https://casoilresource.lawr.ucdavis.edu/sde/) allows users to enter a series name and then view lab data, a map of the series location, and other information.

1. Navigate to https://casoilresource.lawr.ucdavis.edu/sde/. An introductory panel appears with a box for entering the series name.
2. Enter the series name. We will use “Millhopper” as an example. As you type the name, options for names are suggested. The name does not include the texture description (e.g., “sandy loam”).
3. The official series description will appear. Across the top of the window, menu buttons to access other information are shown.
4. Among useful information presented in the official description is the Taxonomic Class (e.g., “Fine-loamy, mixed, superactive, hyperthermic Typic Natrargids”, which should be reported in any formal publication. Read through the description to get an idea of general features of this soil series.
5. Click on the button Lab Data to view a series of graphs showing data by soil depth. As explained in the description, the solid line is the median, and the width gives 5% and 95% intervals. The number of profiles used in preparing the graphs appears at the top center of the window, to the right of the name.
6. While the graphs are useful for understanding the variability in soil traits such as texture, DSSAT compatible soil profile descriptions require numeric values by layers. Scroll to the bottom of the screen to see the pedons used to create the lab summary. 
7. Click on “Primary” for the first pedon. A new tab opens showing the standard text-formatted report for NRCS soil laboratory data. This report contains data that can be used to create a DSSAT profile with SBuild. Useful data include the depths, layer designations, texture classes, pH, and CEC.
8. For some soil series, pedons may have been characterized for water retention parameters. The pedo 81FL001003 has data under “Water Retention”. Click on that pedon to view layer-by-layer descriptions of retention properties.
9. Returning to the tab for Lab Data, on the right, you will find the geo-coordinates for each pedon under Link To SoilWeb GMap. If you click on any entry, you will be taken to the SoilWeb mapping app.
10. The Soil Data Explorer has additional menu options that may be of interest. Notably, the Extent option displays a map of the full geographic extent of the series.

While we have outlined the basic steps to access soil data, this process does not guarantee a perfect characterization of soils at your desired location. The foremost constraint is that while the NRCS has a remarkable database of laboratory analyses, the data are far from providing complete geographic coverage of the United States. A further complication is that the NRCS laboratories characterize profiles for diverse reasons. Often, not all the properties needed for crop modeling are reported, most notably water retention characteristics. The SBuild application of DSSAT can estimate missing properties and output the data as an entry in a *.sol file formatted for DSSAT-compatible models.

Option 2: If you don’t know the soil series: SoilWeb

If you have a US location with no soil information, the SoilWeb app allows users to query by location name, geocoordinates (latitude and longitude) or map navigation. The app will display a soil map and if you click on a specific location, it then provides a menu listing soil series by composition (estimated percent of a given series within the selected map unit).

1. In your browser, navigate to:  https://casoilresource.lawr.ucdavis.edu/gmap/
2. Click on the Menu button and select “Zoom to Location”, which will display various options for choosing a location. For example, if you enter “Jay, FL”, the map re-centers to show the town of Jay, Florida and surrounding lands.
3. Click on a place of interest. The Menu area will display the Map Unit Composition, which corresponds to the NRCS soil series present in the map unit. For map unit 38, three series are shown: Red Bay, Organgeburg and Dothan.
4. If we click on “Red Bay”, the dominant series, a profile sketch is shown with horizon names and depths.
5. Clicking on “Series Extent Explorer” (top center of box for Red Bay), a new tab opens in the browser with a map that shows where Red Bay soils are found and where soil samples have been described by NRCS.
6. We are interested in the area around Jay, so we pan (drag) the map to place western Florida in the center of the displayed map. Then using the zoom toggle and the panning control, we zoom to Jay and the surrounding area.
7. The red dots indicate sampling sites. Clicking on a dot causes a pop-up menu to be displayed with seven options.
8. Return to the Series Extent Explorer tab. We are also interested in Water Retention, so click that option. Another tab opens. Most often, it will be blank because no data are available. For this series, the two pedons having water retention data are much further east, in Georgia:
   • 62GA193002 located west of Interstate 75 and southwest of Warner Robins, GA.
   • 85GA261001 located south of US 280 and southeast of Columbus, GA.
9. Select “Primary”. A new tab opens showing the lab data in the NRCS standard tabular text format. Several variables are used in DSSAT soil profiles:
   • Horizon
   • Depth
   • Totals for clay, silt, sand and rock fragments
   • Organic carbon (OC)
   • Cat ion exchange (CEC8)
   • pH in water and in buffer
10. For individual soil horizons, the depth appears in the upper left, and tables give soil texture and moisture retention data. For DSSAT, the values of interest are 33 kPa (considered the drained upper limit, SDUL) and 1500 kPa (lower limit, SLLL).

Troubleshooting

            The main menus appear to work robustly. We have encountered problems when the UC Davis web site sends a query the USDA NRCS web site but the USDA site is not working. In October-November of 2025, an outage occurred, but service was restored by 2025-11-06.