Topic: Davis Instruments Watermark Soil Moisture Readings Behavior....

[scudwatcher]

Greetings from The CSRA!  I currently have deployed in the field, a Davis Vantage Pro 2 Plus with 24 Hour FARS, Davis AIRLINK sensors and a Wireless Leaf Wetness and Soil moisture/Temperature Station.  The Leaf and Soil Moisture/Temperature station has two tandem WATERMARK moisture and stainless steel temperature sensors at 4" and 8" below sandy loam sod, respectively.  For the last several months, the soil moisture sensor readings spike upwards in the centibar range (between 100 to 200 cb) upon the onset of liquid precipitation.  During the next several days, the moisture sensor readings lower towards adequate to saturated soil moisture readings.  I have spoken with DREW of Davis Instruments Tech Support.  He has several soil moisture sensors that are behaving in the same way as my sensors.  Could this be a normal sensor reaction upon introducing wetness after a dry spell?  Have not received a response from Tech Support yet.  Any Ideas of what is being observed?  Thank You in advance!

[Aardvark]

I had soil sensors out there in the garden for about 20 years.  What I found was that the soil can pull away from around the sensor and give strange readings. then after a bit they settle down.  You can try to reset the sensors in the ground.  Watermark has a website with information about their sensors.  They suggest pouring bentonite into the hole then sitting the sensors. I didn't do that, but after a while I was ok.
 

[scudwatcher]

Aardvark,
  Thank you for your response!  Yeah, I had an inclination of this condition, due to the nature of the native soils being sandy.  I will research the WATERMARK website as well.  I don't understand the BENTONITE setting.  I would be more inclined to forming a paste of the native sandy soils to create a representative setting of the sensor.  Thanks again!