[edit] Copying discussion concerning this topic in another thread to keep everything together.Hi Steve-
I enjoyed your very thorough write-up, you must be an engineer with that kind of detail. I also enjoyed all of your other weather pics on your website, but I did have one question...what's with the rain bucket 'condom'? How does that work??
Anyway, I liked you idea with the dual zone soil moisture/temperature placement; makes lots of sense for deep root and shallow root placement. For my garden, I have some perennial flowers and carrots that are about the deepest roots, so I kept all my sensors in the 6-8" deep zone. Speaking of placement, I never went with the Davis idea of glueing the sensors to a PVC pipe and placing that in the ground. I have an idea I know what they're after, 1) visibility of the sensor so the cable doesn't get cut, and 2) to ensure the sensor has soil packed all around it to keep out and air pockets to lessen false readings.
For my setup, I buried the cable 6" deep all the way from the beds to the 4x4 post that the station is mounted on, then attached neon flags where they enter the garden and put the flags on the surface so I can retrieve the cables and sensors when I have to dig/till. I'm going to see how that setup goes this year to see if the lawn guys cut the flags so I may revisit this next year. As far as the sensors themselves, I also conditioned them before placement to ensure more accurate readings. Instead of the PVC pipe, I drove a stick (each about the same diameter as the sensors) into the ground at and angle at a spot that was tamped down and put the sensors there and back-filled them. So far that seems to work as I can watch the moisture levels on all 4 sensors fluctuate during wet/dry conditions. It appears from your photos that you have the moisture sensor pretty close to the 2x8 side. Did you give any thought of putting it a little further out into your bed where most of your roots are?
As far as the placement of the leaf-wetness sensor, I emailed Davis but got nothing definitive except basically "read the manual". So I looked at what was around the garden and settled on a height about 3.5' and placed it on the SW side of the 4x4. The thinking was that I was trying to replicate dew and I didn't want it 'burning off too quickly' by putting it on the NE side, after all, I've got lots of tomatoes that still have dew 'til late in the AM. Right now my leaf wetness sensor 'burn-off' time is around the same time as most everything else in the garden so this orientation works for me. An added plus with the leaf wetness sensor as you may have seen is it will pick up the slightest amount of rain, well before the rain bucket does it's first 'tip'.
Again, nice write-ups and good luck with your gardening this year.
Jeb
Thank you, Jeb. And, yes indeed, I did work in engineering for over 35 years before retiring.
The rain condom is a bollard cap for pilings in marinas. I use it as a cover for the Davis VP2 while I am watering my garden. I record the amount I water using the CoCoRaHS gauge and record it separately , but don't want the VP2 data to include artificial precipitation.
My two soil temperature probes are at the same depth, but in different gardens. The strawberry patch keeps the soil cool, only changing a few degrees during the day, while the more open patch under the tomatoes fluctuates up to 10 degrees during the day. We'll see how this works out with our crop yield. We've put black plastic down under the tomatoes in the past to keep the soil hot. I may experiment with this next season and see if there is a substantial difference.
I did consider the proximity of the probes to the side of the raised bed box. I may get a slight artificially higher moisture content as this concentrates the rain or sprinkler water that runs down the inside of the box. I am on very sandy soil, so I've assumed that it dissipates a little. I will be getting two more soil moisture probes, so next year I will plant them further out in the garden.
It looks like you've optimized your leaf wetness sensor for the most accurate results. I pointed mine north, as the very early morning sun is blocked by a tree to the east of the garden. So I figured north would be the last to "burn off". On the WXforum, I've read of folks placing two leaf sensors; one north and the other south. I definitely have noticed how great the leaf sensor works as a precipitation detector, peaking out when the very first drizzle starts. In a very light rain, this may be many minutes before the first bucket tip, if it tips at all.
Thanks for the nice comments. I'm going to quote your reply with my Soil Station thread here and on MacWeather.net to keep these comments together.
Thanks,
Steve