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  • Use of UC Davis WebSoil app

    If you are growing figs in the ground, or soil, you may have asked yourself from time to time ‘How much water does my soil hold?’, ‘Is my soil acidic or alkaline and should I add lime?’, or ‘How fertile is my soil?’. Without having to take a soil sample and send it to a lab for analysis there is a web-based way to get a feel for the answer to these and other soil questions. What I want to do here is give a short intro to the Univ. CA Davis ‘SoilWeb’ app at: https://casoilresource.lawr.ucdavis.edu/soilweb-apps/.

    The information in the app was developed by USDA’s Natural Resource Conservation Service and their site is https://websoilsurvey.nrcs.usda.gov/...oilSurvey.aspx. I like UCD’s ‘SoilWeb’ because it is easy to use, has cool graphics, and it works on your phone if you find a fig while out scouting.

    Click on the UCD link above and it will take you to the app home page. The one we want to use is ‘SoilWeb’, so click on the underlined title. After clicking if you are at the right page, you should see a blue band at the top of a satellite map of Davis, CA with ‘SoilWeb’ in the center of the blue band.

    A ‘Menu’ button is on the left of the band and an ‘Outline Color’ button on the right side. Set the ‘Outline Color’ by clicking it and selecting ‘Light’ if it is on ‘Dark’. The soil boundaries should appear as yellow lines on the map with the soil name coded as a 2 to 4 letter code for each soil displayed on the map. Before I say more about the soil names lets go to a different location.

    To zoom to a different location, click on the ‘Menu’ button and select ‘Zoom to Location’ a drop-down menu appears giving you 3 choices. Let’s choose the middle one for street address and enter “1501 Circle Dr., Fort Worth, TX”. If you do that the map location should be just east (right) of I-35W and just north (above) of I-20. Zoom in on the map until you can make out 2 mostly empty parking lots just to the right of the map locator marker.

    Now move the crosshair cursor so that it is within the boundaries of the soil coded ‘AuE’ and click on it. This should bring up a menu panel displaying ‘Aledo-Bolar-Urban land complex’. Let’s look at the Bolar soil by clicking on its underlined name. This brings up the ‘Soil Profiles’ menu with a graphic display of the soil profile shaded in the colors of each profile horizon or layer.

    For example, at the top is ‘Ap’ shaded brown with numbers starting at 0 cm and going down in depth to 15 cm. Ah good ole metric to make life easy divide 15 cm by 2 (2.54 if you have to be precise) to get the approximate 8 inch bottom depth of the Ap horizon. Without getting into the details the major soil horizon labels are O, A, E, B, C, and R. O indicates an organic layer, A, E, and B, are progressively deeper mineral layers that exhibit properties distinct from the underlying parent material, R, for rock, and C is a transition layer between the layer above it and the parent material. The lower-case letters indicate special properties of the layer.

    Note the Bolar soil does not have layers for every symbol, as is the case with most soils, and it is approximately 45 inches to rock top. Soils are typically comprised of clay, sand, and loam. To get the clay percentage click on the ‘Clay’ button. Notice you get a graph with a blue line indicating 30% down to maybe 75 cm and if you click on ‘Sand’ you see a blue line to the same depth at about 35%, implying loam is 35%. It is rare to see the same percentages clay, sand, loam across all the soil layers and this is an average across all layers. I’ll tell you how to drill down for more detail, but first let’s continue looking at some of the Soil Profile buttons. Click on the ‘Org. Matter’ button to see an example of a graph that varies by layer. Note, this soil really has little organic matter, typical of hotter drier climates.

    The ‘AWC’ button is available water capacity. To get any one layer’s holding capacity multiply the layer’s depth by its average AWC. Or for the total of all layers go down and expand the ‘Hydraulic and Erosion Ratings’ bar. At the bottom it displays total plant available water as 10.4 cm or appx 4 inches. So, if all your plants were wilted and you got a nice slow 4-inch rain your soil would be full again. Empty soil moisture is measured as the moisture level when a plant begins to wilt.

    Next, let’s look at soil pH, by clicking on the ‘pH’ button. The graph tells us the soil is uniformly alkaline at a pH of 8 across all layers. One source of the alkalinity could be calcium carbonate, clicking on the ‘CaCO3’ button shows a difficult to see line at 50%, to confirm this click on ‘View Source Data’. So yes, CaCO3 in Bolar soils is a source of alkalinity. Certainly, no need for lime here, but the calcium and relative high pH tend to bind phosphorus making it unavailable to plants, so phosphorus needs management. One way is the regular addition of organic matter.

    A soils latent fertility also is indicated by its cation exchange capacity or CEC. CEC is a soil’s ability to hold cations that are a source of plant nutrients such as K+ (potassium cation), NH4+ (nitrogen as ammonium cation), and Ca2+ (calcium). CEC values less than 12 are poor at retaining cations, soils with 12-25 CEC are good, and soils above 25 have high nutrient retention. If your soil is in the low range you may consider multiple fertilizer applications to reduce leaching. The Bolar soil has a CEC of about 17. Notice that for all the buttons clicking on the ‘?’ displays a helpful explanation.

    The ‘Soil Profiles’ menu and the options below it give you a quick look at the soil you selected. There are several ways to get more details, I’ll mention just the ‘Soil Data Explorer’, which you can access by clicking on the ‘Soil Data Explorer’ text at the top left in the ‘Soil Profiles’ menu. The Official Soil Series Description appears which has some technical stuff but come on admit it this description of the Ap layer “[A] brown clay loam; dark brown moist; weak fine subangular blocky and granular structure; hard, friable; few fine strongly cemented calcium carbonate concretions; moderately alkaline; calcareous; abrupt smooth boundary.” is poetic.

    The Menu icon at the top right will bring down a set of tabs listing 8 other types of information. I like to look at the ‘Block Diagrams’ tab because it has some nice graphics showing where your soil sits relative to other soils in the landscape. The ‘Extent’ tab gives a map of your soil in the U.S. And the last I’ll mention the ‘Lab Data’ tab gives you a host of graphs with more details of some of the things we have just gone over.

    Remember, soils epitomize place, they are all local so yours may be a blend of two soils near one another in the landscape. There is a wealth of information here and now that you’ve been introduced I hope you use it to explore your figs unique subterranean world.
    Gary, Fort Worth, Tx Zone 8a

  • #2
    Very nice writeup. I'll give it a try.
    Alpine, Texas 4500ft elevation Zone 7


    • #3
      I heart Soil! Thanks for the app rec, I will give it a try. Soil is life 😀

      there's more co2 stored in soil than the oceans & atmosphere combined. Releasing it will prob be mankind's undoing... Utilizing or harnessing it might save us.
      wnc Z7a Hominy Valley
      wish list: a world without Invasive Pests


      • #4
        I tried it out at all the places I've grown things. It's very nice and easy to use. I'll use it again.
        Alpine, Texas 4500ft elevation Zone 7


        • #5
          Nice! I like this one much more than the website I used before. Thanks for the writeup!
          ░░░SoCal░ ░ ͡ i ͡ ░ ░Zone░ ░9A░░░

          W/L: La Joya, Ondata, Belvedere, Bebera Branca, Fico Giallo, Vernino, Asunta 5 Paco (DF)


          • #6
            I am going to give this a try, thanks for sharing 👍
            -- Zone 10a
            Documenting my fig addiction here