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  • Soil moisture opinion

    Hi Michael,
    no rush with this one, I understand you have lot of high priorities right now. I would like your opinion based on this Soil Moisture sensor. Right now it is currently a 7.5. It has been raining very little but enough to keep the lawn ok. I do not water the lawn too much (Every 3 months the water bill is about $600) so only when is necessary. AS FYI, I purchase another similar sensor to get random measurements of the soil in different zones.
    My questions are these, 1) is this value sounds good to you based on the above comments. Your app is indicating the soil to be -16 without considering this sensor. 2) How would I integrate this as part of your application?

    Again no rush, looking forward to your great suggestion,
    Aldo
    Attached Files

  • #2
    Volume of water in a pot of soil is easy to measure because the soil boundry is well defined by the pot. When the boundry is not defined such as in a lawn where the depth and area are unbounded. Migration of moisture in large areas channels (e.g. streams down a mountain) so some parts are wet and some are dry.

    mcsSprinklers soil moisture is calculated using an assumption that moisture is loss from the top of the soil due to moisture escaping from the surface and from the foliage. It is based upon what occurs at the top 1" and is not concerned with the volume of water that may exist at lower depths.

    The scheduling strategy is based upon allowing the top 1" of the soil to get dry so that the foliage will be encouraged to root at lower levels. This will make it more tolerant to the short term effects of the weather.

    With your soil moisture sensor your objective is to find the water volume reading that would reflect relatively dry soil at the top 1". You zone run time is set so that 1" penetration of the soil is achieved in a cycle.

    Many users commonly run more often with shorter durations. This will have a more immediate feedback of the soil always being moist, but it could also encourage the foliage to keeps its roots at the surface so when moisture is lost for whatever reason the foliage will be stressed.

    You need to be the engineer to assess the voltage threshold that works for you. You can setup an area controlled by sensor while you continue to use your current method. Perhaps even setup a virtual zone as a HS devices in this test area. Compare the irrigation actual scheduling intervals between the two and adjust the voltage trigger level on the Area Page to get a result you find useful.

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    • #3
      Thanks for the explanation, I think I understand what you are saying. From the picture attached with the arrows, that is where I will set the values. So if the sensor register 10 when it had 2 inches of rain and 6 when is very dry, I would set 100% (wet) to 10, trigger to 7 and 0% (Dry) to 6 and select Measured instead of ET (Calculated), Am I correct?

      Aldo
      Attached Files

      Comment


      • #4
        Essentially correct. In the graph you provided the low/dry level is 1.1 and the slope is sharp below it so using 1.1 in this case would be a good place to start as the trigger. In an earlier response I indicated that volume measurement in my lawn in the Northwest never changed significantly. I also had a gypsum-based one that changed more based upon surface temperature than actual moisture. Likley because it was a temporary decrease in surface moisture that became replenished from lower moisture during the night.

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        • #5
          Last question I promise :-)
          Why do you suggest 1.1 instead of 7 as I pointed out below? I think this sensor range between 7 and 9. I also do not see where I would put my sensor device id in your application, is it under the "Weather".

          I'm still experimenting with this, I put it below the grass level, while I was making the hole, I noticed that the soil was really good the first 3 inches and then became hard. When I first checked it and I put it in the plant I was registering range of values between 20 and 28. Now that is under the soil range between 7 and 8 with slow movements. Yesterday we had thunderstorms but it did not go higher than 7.8. It seems to be close to your soil moisture based calculation, yours is at 20% with the same thunderstorm.

          Thanks Michael,
          Aldo

          Comment


          • #6
            I was just using the data from the graph you showed to illustrate. Use whatever range your sensor actually delivers. When you select Measured as your control strategy then additional setup options will be available for measure control strategy. At the bottom will be things like csv, xml, HS, xap as to where the sensor reading will be obtained.

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            • #7
              You are a genius, every time that I think I know everything about your program there is always some new great feature hidden. I got it now, you were talking about V and I was referring about VWC, same thing, different values. I would need to get some extra values before I switch to this system to get what the min and max would be when it is dry or moist.

              Thank you again for all your help,
              Aldo

              Comment


              • #8
                Hi Michael, how much calculated moisture % should increase with a certain amount of rainfall (say 1/4 inch)?

                Should I adjust other settings (low moisture % to trigger watering and watering duration) so same amount of water, either from rainfall or sprinklers, increases moisture % by the same amount?

                Thank you.

                Comment


                • #9
                  If you have an area covered by foliage, say grass, then the amount of moisture being lost through the foliage is the ET or calculated moisture. 1/4 inch would be typical summer day depending upon conditions. 1/4 inch may also be typical rainfall. If you have sun during the day and a strong thunderstorm in the evening then the net moisture loss could be near zero.

                  All calculations are based upon a model of soil being able to hold 1 inch of moisture to which the foliage has access. Add via rain or loss via ET have the same relative effect. If your soil cannot hold 1 inch such as sand that may be able to retain only 1/3 inch then your trigger would be set to 0.67 (67%). This means that "dry" is 1/3 inch rather than 1 inch.

                  If more than 1 inch of rainfall occurs then mcsSprinklers assumes that excess above 1" is lost through runoff or similar. It will show % above 100% but when ET exceeds rainfall then it will start moisture calculation at 1 inch and continue until trigger or additional rain.

                  McsSprinklers also assumes that the duration you set for a zone run time is the time needed to replenish water from the "dry" level to 100%. If the volume of water is not sufficient then the foliage will typically wilt. If it is too much then it will be waste and it will tend to keep the surface moisture damp which discourages deep root penetration and encourages disease such as fungus

                  Comment


                  • #10
                    Michael, if watering is triggered, for example, when calculated moisture % is below 50%, is it better to set the moisture % to 100% after a full cycle or increase it by 50%? Think if watering is restricted for some reason, when watering does start moisture can be significantly below the 50% threshold.

                    Comment


                    • #11
                      I forget the history as to why this option was added. I set mine to 100% when cycle is done.

                      If you accept the model that the water volume added on a zone's cycle is 100% of the useful moisture that can be added then when the cycle is done the soil is at 100% moisture content. It does not matter if moisture started at -100% or started at 90%.

                      If there were inhibits that prevented a cycle from completing for a long period of time then some of the added moisture will have been lost between the start and end so the ending moisture will be less than 100%. I just cannot think right now for a realistic case when this would happen.

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                      • #12
                        Michael, does calculated moisture % increase linearly with rainfall (and regardless of rate of rainfall)? My moisture % was changing with rainfall earlier this week (with 1% for every 0.01 inch) but on Friday it went from 30% to 200% with 0.47 inch rainfall.

                        The low bound is 0% on this chart.
                        Attached Files

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                        • #13
                          Did you have an irrigation cycle during this time to have added moisture beyond that from rainfall?

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                          • #14
                            Originally posted by Michael McSharry View Post
                            Did you have an irrigation cycle during this time to have added moisture beyond that from rainfall?
                            I don't think so: run log didn't show any activity, I setup cycle to start when moisture drops to 0% and the lowest on that day was ~30%, the calendar didn't show watering on that day (July 14th) either.
                            Attached Files

                            Comment


                            • #15
                              On the 14th their was rain. Is there are rain or rain forecast inhibit to prevent on the 14th? Do you happen to have the debug log for the day that moisture went to 200%?

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