Hello, I live in south Florida and noticed that my Rachio will only schedule watering for my yard when the soil moisture nears zero. For my St Augustine grass, I have the following advanced settings:
Available water= .15 in/in
Root depth=6 in
Allowed depletion= 40%
Efficiency=80%
Crop coefficient=80%
Nozzle rate=0.5in/hr
These advanced setting numbers come from the University of Florida extension office for my area and grass type. Any suggestions? Thanks
So it is a bit misleading, but the 0% in the water journal is equal to the allowed depletion you have set. So 0% means that you are at the 40% depletion.
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Tap the Soil Moisture item in your zone display. The resulting Zone Soil Moisture graph indicates the recent available water capacity of the zone in a range between full (100% - can’t hold more water) and the allowed depletion setting (at the red line). Watering days are in orange.
Ah I get it now. The setting is a bit confusing but seeing the graph now it makes sense. Since I set my allowed depletion at 40%, zero means it reached that 40%. Thanks so much for that. Bu the way, I cant seem to find any info from extension office concerning allowed depletion. Anyone have solid intel on what is a good number for St Aug in zone 11? Thanks
Yes… you’ve got it. The “full” watering zone represents water holding capacity of the soil through the root depth (all the plant cares about). You never want it to dry out (no water anywhere in the root zone - certain death), so the “allowed depletion” lets you adjust how long to wait before watering again to resaturate the root zone. The smaller the number, the more frequent waterings (all other things being equal). Rachio has a default somewhere around 50% depletion. The “Soil Moisture” percentage is, as you’ve surmised, the percentage of water still available of the “depletable” supply until you refill the zone.
I have a flat, full-sun common Bermuda grass zone with a .65 (65%) crop coefficient, 80% efficiency, 6" root depth, allowed depletion 50%. Working great in Texas (zone 8) right now with 100º days - waters every 2 or 3 days, and I’m betting the roots are working hard to use the whole 6" profile.
I also have a flat, partial-sun St. Augustine zone with a .65 crop coefficient, 80% efficiency, 8" root depth (better soil), that also uses 50% allowed depletion. It’s working great too, though it waters every 3 or 4 days. It’s mowed higher, so it’s almost “succulent” growth in this weather.
You’ve probably already done this in Florida, but here in Texas, the U.S. Department of Agriculture and Texas A&M have soil type maps for every inch of the state, available online, free, that has more data than even a Rachio can handle. But, it does give crop coefficients for ground covers, water retention (Water Capacity and Available Water Capacity) and descriptions (sand, clay, organics, water, etc.) for the very ground you’re standing on. It’s pretty geeky to get this far into it, but the whole idea of responsible watering is to learn how to “balance” on the knife-edge of killing your grass. Good luck to us all with that!
Awesome! Geeky about my grass is right up my alley. Thanks so much for taking the time to help me out. Much appreciated
Any way you could share where/how you got those parameters from? as in, a link? Or which county in So Flo are you? I am in Palm Beach, although Broward is two traffic lights away 
From the Florida Department of Health - All about growing things in Florida. I’m in Texas (@JBTexas) , so the USDA’s Web Soil Survey (WSS) mentioned in the below is the most common way to look up what you need. This Florida piece even has instructions on how to use it.
Google search is your friend… Just “Florida soil info” put this item on the front page. 
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thank you!