Incomplete without soil moisture %?

Is Rachio incomplete without knowing soil moisture? Our weather forecasts are notoriously inaccurate. The extent to which large and micro cells grow and dissipate makes forecasting even a few minutes ahead somewhat difficult. Yesterday for instance we had a 90% chance of rain at 1pm according to WU. We didn’t get a drop though 1 mile south got 3/4" over a 2 hr period.

In many cases if my lawn soil is somewhat moist then taking a risk on a forecast would be warranted. If it’s quite dry though then how much confidence do I have in the forecast and the amount of rain that I’ll get? How much risk do I take?

A rain gauge can run in to problems if we get a lot of rain on top of fairly dry soil. While the gauge may have a considerable level of water in it, the ground was dry and much of the water ran off in to a rain garden or storm sewer rather than soaking in. At least the rain in the rain garden will eventually percolate to the aquifers rather than go down the storm sewer but it won’t help our still dry lawn very much.

How does Rachio compensate for the lack of knowing soil moisture?

@Quincy Which schedule type are you using. The answer varies dependant on that.

Not using a Rachio yet. Looking at alternatives. Current schedule is 2 waterings every other day (even days, other side of the street is odd) using a Toro controller. Toro soil meter skips watering if soil moisture is high enough.

My question is as much general as specific to me though.

@Quincy Well, Rachio Iro allows 4 scheduling options that trade off simplicity vs. optimum operation. For the ‘smarter’ schedules, take a look at Flex Monthly and Flex Daily. The 1st article here should answer your question, and the other 2 add some implementation options. The concept implemented is, as far as I can tell, quite standard for the agricultural industry and the associated irrigation specialty that applies. There’s a lot of published research papers from government and universities out there that’s behind all of it.

Flex (concept):

Flex Monthly

Flex Daily

Note that the system currently does not use a soil moisture sensor, but rather predicts MAD levels based on your precipitation, irrigation, soil type, root depth, crop type, etc.

As far as shopping around, be sure to take a look at the forums for all of the controllers that you’re looking at. You found this one so it sounds like you’re already going down that route. Anyway, it was striking to me to see the difference in how active the community is here vs. others. The customer support is hands-down the best I’ve ever experienced. Let us users know if we can help you in any other way.


Thanks @azdavidr. I’m somewhat familiar with MAD and read through those article and a couple of others. It still seems that Rachio is missing some very critical information in not knowing either actual precip or much better, actual soil moisture.

Even getting rain amounts from a NOAA or a PWS would seem wildly inaccurate unless the PWS is on my property or an adjacent property. Though even this could be misleading as I mentioned in my OP due to how localized rain events can be and how varied saturation or infiltration rates can be due to a number of factors.

BTW, this is a great community and thanks for your responses. This forum and participation by Rachio folks is an important bit that Rainmachine and Skydrop miss.


@Quincy The micro-climate issue can certainly be a factor if you don’t have a good PWS, depending on where you live. I’m in a desert climate, so the rain issue is of little consequence. The big factor for me is the quick rise and fall that we have in temperature extremes, and Flex Daily certainly seems to handle that well, even with using the airport’s station 15 miles away. It may be 110F there but 113F here, so no big deal. If I lived elsewhere that had more precipitation then I’d be looking much more seriously at a PWS to make things better for the reason that you noted.

The infiltration rate and saturation (available water) issues you mentioned are minimized by getting someone to do a good soil analysis for you. Apparently in places like Boulder the city does it for free. Here, it would cost me ~$75. The data can be put into your zone settings so that the algorithm can get you closer, but of course it won’t be spot-on since it’s still an open-loop system. The end-all here seems to be a good soil moisture sensor, or set of them, connected to the controller to give you a closed-loop system. The technical challenge is building good, reliable & durable wireless moisture sensors that won’t need a battery change every month, constantly drop connections, or get destroyed by a lawn mower or weed whacker. I imagine that might take a while, but I would think that the Rachio guys would be on it as that market develops. At least I hope so.

Thanks for sharing great, constructive comments, and good luck with the rest of your investigation!

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Isn’t a PWS simply an attempt at getting some data to do a very rough and somewhat inaccurate calculation of how much moisture is in the soil? Why not skip this and just use a soil moisture sensor that is more accurate and eliminate the guesswork?

Weather forecast info is great for forward looking planning to avoid watering when there will likely be rain to do the same thing. I’m not sure how valuable it is for base/current status.

You are correct except the estimate provide by rachio is pretty damned accurate for me, 2 seasons running.

I would like soil moisture sensors but it’s pretty expensive to get adequate coverage.

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Thought I’d update this regarding the reliability of soil moisture probes, cost and battery life since that is one concern raised.

The battery on one of my Toro Soil Moisture probes just died. I purchased 3 of these a bit over 4 years ago for $49/ea. This is the first battery replacement on any of them. The other 2 are still working with their original battery.

Though Toro recommends keeping these at soil depth for better radio xmission, I’ve got these slightly under the sod and reception has been good. None are line of sight. One is connected normally to my Toro controller. The other two are connected in-line on two zones that will sometimes remain extremely moist and so need to be watered less often.

I’d still prefer something like a Rachio and may yet get one yet (though the way v3 appears to have been rolled out concerns me) but I would feel much more comfortable if it had accurate soil moisture knowledge and could base decisions on that rather than guesstimating.

Can’t argue with you that soil moisture sensors would be the best way to determine if watering was necessary. I’ve toyed with the idea of grabbing a few of these and pairing them with a raspberry pi zero W and seeing what happens.

However, that would be a completely different commercial product than Rachio that would come with it’s own host of problems. Mainly connectivity / maintaining a connection to the base controller but also battery life. As you pointed out, if you have 10-20 moisture sensors planted throughout the yard, even replacing every 2-3 years becomes a chore.

I haven’t heard a lot about Spruce since it launched but it does what you describe -

Rachio’s method of calculating ET is pretty accurate if you get the zone settings dialed in correctly.

I don’t think the tech for soil moisture is that complicated - basic resistive measurement. Biggest issues are likely fine tuning for consistent reliable accuracy and packaging it for durability. The Toro packaging seems to work well as it acts as an umbrella of sorts to keep the battery & circuits dry. They also SEEM to have gotten accuracy down. Getting accurate soil moisture readings should not be difficult.

Davis also have soil and leaf moisture probes.

Maintaining connections has not been a problem, at least w/ my Toro’s across 1 acre, nor has changing the batteries. Even if I had to take 30 minutes to an hour every spring to change batteries in a dozen of them it’d not be a big deal.

Overall, to me anyway, moisture probes would be well worth it for greater accuracy and peace of mind.

How do you know how accurate Rachio is? Given that the average homeowner here is estimated to water 4 to 6 times more than necessary, a 50% reduction would still be 2 to 3 times more than necessary. The past 3 years I’ve used my system on more of a water-only-when-necessary basis with the entire system sometimes off for weeks at a time. This is Minnesota US so short growing season. Sometimes I’ve probably waited too long to turn them on but my grass and other plants have remained healthy. Last year I only ran grass zones 10 days. I’ll be curious to see how Rachio does.