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Improve Soil Test Recommendations

2018 Soil Test Now Features Soil Series

The WVU Soil Testing Lab has introduced a fertilizer recommendation system that uses soil productivity groups for agronomic crops. West Virginia has 195 named soil series, and these are placed into five yield classes.

If you are submitting a soil sample where the intended crop is hay, pasture, corn, barley, wheat, soybeans, oats, small grain silage or grain sorghum, it is important to determine the predominant soil series within the boundaries of the field that you sampled.

If the sampled field has more than one soil series mapped in equal proportions, ask your county agent to assist with determining the best soil series for your crop.

Using the websites listed and following the directions, selecting your dominant soil series for a field should not be a difficult task. You will only need to do this once for each field.

The WVU Soil Testing Lab has an updated submission form that asks customers to select their predominant soil series. This box lists all the West Virginia soil series; just click on the one that best represents your sampled area.

When you select a predominant soil series on the sample submission form, the fertilizer recommendation will be optimized for your soil series and an expected or target yield will be provided.

If your historical yield records are higher or lower than the target yield, increase or decrease the fertilizer recommendation to align with the known yield potential from your harvest records.

How to Select Your Dominant Soil Series

  • Open your web browser and go to the “soil web” California Soil Resources Lab homepage or search for soil web – UC Davis.
  • Read the welcome and getting started information, then click the “ OK” button.
  • In the top left of the screen is a “Menu” button, click this and choose “Zoom to location.” Your location will automatically be shown on the map or you can enter an address in the box labeled “Enter a location.”
  • This will zoom to your location in West Virginia. You will see a yellow soils layer over an aerial photo of your location.
  • Roll your mouse to get closer to the ground so you can then find the field location.
  • Click on that location, and the soil series name is shown on the top left of the screen.
  • If you need to determine the dominate soil type for a larger area, like a field that is an acre or more, use the instructions for farmers.

How Farmers Can Determine the Dominant Soil Series and Field Size

Determining the treatable acres of a farm field is one of the essential parts of building a nutrient management plan. Knowing the field’s predominant soil series is needed for the WVU Soil Testing Lab to generate a custom fertility recommendation based on the planned crop and the predominant soil series. This field specific recommendation is generated using the productivity potential of a specified soil series. 

To receive this custom recommendation, the landowner who is submitting a soil sample must determine the sampled areas dominant soil series. If the landowner does not determine the dominate soil series and leaves that information blank on the submission form, the lab will provide a default recommendation to the landowner. This default recommendation may result in potential yield losses if the dominant soil has a higher productivity potential than the default soil series, or the recommendation may result in over application of nutrients that the crop will not use due to a lower productivity potential of the default soil. Either of which end up causing the landowner to lose money.

Web resources make it easy - with some practice - to determine field size and dominant soil type. The United States Department of Agriculture Natural Resources Conservation Service offers a useful tool called Web Soil Survey that can be used for these purposes.

How to Use the Web Soil Survey

  • Open your web browser, and go to the Web Soil Survey homepage (or search for Web Soil Survey).
  • Click on the green “START WSS” button.
  • On the left side of the Web Soil Survey page under Quick Navigation, click on “Address” and enter the farm address.
  • If the address does not work, you can also zoom into a state/county and locate the farm yourself by using the following tools at the top of the interactive map: An onscreen image of the web soil survey highlighting zoom and pan icons.
  • Once you are in the correct area, the interactive map will display an aerial photo with additional layers for reference such as roads, streams, etc. Zoom in on the map until you can see the entire field that you need to determine the soil series and size.

  • An onscreen icon representing area of interest in the web soil survey.Next, you will define an area of interest in order to extract soils information. The AOI will be an irregularly shaped polygon that you trace on the screen. Click on the “AOI Polygon” tool shown below, then apply the tool by clicking on the map to trace around the outline of your farm or field as best as you can.

  • An example is shown next. The AOI polygon tool is used to click once at each “corner” of the field. The example used eight clicks to delineate the field boundary. When you have completely defined the boundary of your field, double-click to end. You can also start over by pressing the Escape key. You may have to practice a few times before getting the field size correct. An onscreen image of the web soil survey area of interest highlighted by an arrow.

  • Once you have created an AOI, the Web Soil Survey tool will extract soils data for your polygon. Be patient! This process can take a few minutes. The final AOI will be outlined for you.

  • Once your AOI is created, at the top of the screen, click on the “Soil Map” tab (as shown in the following image) to switch to a view with individual soils, soil names and acreage information. An onscreen image of the web soil survey highlighting instructions.

  • Items to note:

    • Dominant soil: This is the soil type in your AOI with the highest percent of land area. In the above example, the predominant soil mapping unit is CcC, or Culleoka silt loams, 8 to 15 percent slopes. So you would write Culleoka down on the soil sample form. Or select this soil series from the drop down menu.

    • Total acreage for AOI: In this example, the field is 7.7 acres.

  • You can now save this information for future use by pressing the “Printable Version” button (at the top right of the map) and saving the file as a PDF document.

  • Having an aerial photo of the farm that includes tract numbers, field names or numbers and locations of sensitive features to be avoided is a standard part of a nutrient management plan. Use the web soil survey site to generate this map, and then draw in the field boundaries and highlight the sensitive or setback areas so the landowner has a visual record of the plan. You can also use the printed map to show locations where soil samples were extracted and the label you used for that sample.

Authors: Tom Basden, Retired WVU Extension Specialist, Ed Rayburn, Retired WVU Extension Specialist, Agriculture and Natural Resources and Jackie Strager, Assistant Director for Technical Services, Natural Resource Analysis Center, Davis College of Agriculture, Natural Resources and Design
Last Reviewed: August 2018