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USDA-NRCS Has a Very Useful Tool in Web Soil Survey

Corey Moffet, Ph.D.

By Corey Moffet, Ph.D.

Posted May 3, 2011

The Web Soil Survey is one of the most useful tools a producer, consultant or agricultural scientist will find for obtaining soils information on a particular land area. The interface is clean and easy to use - just click the green "START WSS" button to begin. Locating the land area you are interested in is simple. For me, the easiest way to find a land area is to use the zoom tool (magnifying glass with the + symbol), just above the map panel. The background map will change as you zoom closer from a simple state map showing interstate highways, to a county map with lakes, rivers and more highways until, finally, the base map will be fairly recent color or black and white photography.

Once you have found your area on the map, you must select an area of interest (AOI). You do this by using either the rectangle or polygon AOI (area of interest) tool. The polygon tool is useful if the area boundary is irregular or the land survey was not perfectly north-south aligned. When using the polygon AOI tool, double click or ctrl-click to select the final vertex and close the polygon. Once you have selected the AOI, the panel to the left will give AOI acreage and soil data sources on which the maps will be based. Some locations still do not have modern soil survey data available. If your area does not have data available you are through, but soil mapping in Oklahoma and Texas appears to be mostly complete.

Ecological site mapEcological site map for a portion of the Noble Research Institute's headquarters property

Now that you have selected your area of interest (AOI), you can produce a soil map by clicking on the Soil Map tab near the top of the Web page. The table to the left is a map legend. Click on a map unit name to get detailed information such as map unit composition, slope, soil depth, typical profile, drainage class, frequency of flooding or water pooling, available water capacity and assigned interpretive groups. Click on the Soil Data Explorer tab, near the top of the page, to select a characteristic you would like to map. For example, a yield map for non-irrigated improved bermudagrass is produced by clicking on the Suitabilities and Limitations for Use tab, then on the left panel, under Vegetative Productivity, select the Yields of Non-Irrigated Crops tab, and, if available for your area, select Improved bermudagrass from the crop drop-down list. Finally, click View Ratings to produce a colored productivity map. The map is colored according to the estimated average yield per acre (1 AUM = 780 lb forage) that can be expected of the selected crop under a high level of management. A table of the map units and the yield rating will follow below the map.

More basic soil properties such as pH, clay content and organic matter can be mapped by making similar selections under the Soil Properties and Qualities tab. The Ecological Site Assessment tab allows users to map the ecological sites. This has information about the historical plant community including annual production, plant species composition and a growth curve that indicates the monthly distribution of production. For a growing number of ecological sites, data are also available for alternative states and phases. Modern range science recognizes that past management may have altered the plant community and now is better represented with a different state or phase, but that discussion is for another day.

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