Revisiting MAD/Dynamic ET

Hello All,

It’s blazing hot here in Texas and Rachio is running like a mad-man to keep up. I’ve done leg work to understand my soil, root depths, precip rates, slopes - basically everything that needs to be accurate for Rachio to be accurate. I have no doubt that Rachio is putting down the OPTIMAL amount of water for my zones…~2.56"/week.

My question is, what’s the best way to get to a “sub-optimal” level of watering, say, 1.5"/week.

A few reasons for this - given my very low precip rates (0.3-0.4 depending on zone), Rachio is running 4-5 times a week to get the required amount of water down. Primary concern is fungus with my grass being that wet that often. Secondary concern is the coming water bill. I’ve also started a PGR regimen which should further reduce my water requirements.

Historically I’ve seen that adjusting crop coefficient is the best way to accomplish this. But all those posts predate the dynamic crop coefficient feature, which I have enabled. And unfortunately, the crop coefficient feature doesn’t have an “offset” function, which would allow rachio to control the coefficient, but offset it by my stated amount (would help GREATLY with the “set it and forget it” ideal of flex daily).

In the moisture maps, I’ve seen the days are currently depleting 40-50% of the default 50% MAD value, meaning every other day I hit 0 and it waters. I’m wondering if bumping MAD to 60%, giving me that extra 10%, might be just what I need to give myself an extra day between waterings, and if this would be the most elegant solution, in my case, to decrease frequency.

I know all of the other settings that can be adjusted and how things are impacted as a result, but for all the values I’ve personally measured (soil, awc, root depth, slope, sun, precip rate), I’d like to keep them grounded in reality, rather than gaming the system.

Not sure if fungus is a concern when with current weather conditions, but the water bill could be a good enough reason…

If you want to keep crop coefficient locked, but want to reduce watering, you could go in and adjust nozzle inches per hour up. Rachio will think more water is being applied and adjust watering times down, but most likely won’t change frequency.

Or, just go into the schedule and manually adjust the times down from there. If each zone runs for 1 hour, lower to 45 minutes and see how it looks.

Like you mentioned, Rachio will optimize, so lowering that could put you on the ragged edge of stress for the grass.

Thanks tmchagey!

Given my precip rates, the schedules occasionally start at 2:30a, and i can still see water on the blades of sections that are watered until mid-day. Having wet grass for 10-12 hours 4-5 days a week concerns me a bit on the fungus front.

I’d rather not “fudge” my catch-cup results.

If I manually reduce watering times, won’t that just cause me to hit MAD more frequently, and thus up my watering frequency even more?

Logically to me, MAD seems to be the way, so I’m having trouble understanding why it’s so frequently cautioned against. For round numbers, lets say I have 8" roots. With MAD 50% that means when the top 4" of soil is dry, it will water to replenish, right? If my goal is to stress the grass a bit, ideally increasing root density/depth/resiliency, wouldn’t waiting until water is only in the 6-8" zone (MAD 75%) encourage roots in the 4-6" zone to grow deeper “hunting” for water? Is my understanding way off here?

Boy, your are making me go way back…

In theory, you are correct. So it has been probably 4 years since I tested it out, so I don’t recall with 100% certainty, but for some reason I remember my zone that I manually adjusted time stayed on cycle with the rest of the zones in the schedule. I guess I could test it out again to refresh my memory…

MAD would certainly be an option to stretch the time between waterings. Depending on the daily ET, that could save you a day here and there, but might not do as much as you think. You could test out dropping MAD 15% and see what that does. Again, be aware that you are flirting with the edge here, and “catching up” stressed lawn in blazing hot weather is tough…

Ah, I could see why it would work that way. I’ve got my 5 zones each on their own schedule. I assumed this would better allow Rachio to mix and match how and when it waters the zones. I guess theirs no harm in changing it to see what happens.

In looking at the moisture chart, it looks like if I just bumped it up an extra 10% that would be enough breathing room to give me an extra day between waterings while only increasing my watering time by ~15 minutes. Looks like this would put me at around .75" every 3-4 days, so ~1.5-1.75"/week rather than the 2.56" I’m getting right now. Definitely noted on the “catch-up” being rough when we’re sitting on the surface of the sun.

To simplify, there is no reason to NOT have all the grass in the same schedule. Rachio will juggle things around based on need, water some, not water others…

Try it out! Just keep an eye on things! Like I said, things can go south quick in this heat (In AZ myself).

So i went down a rabbit hole, which I’m known to do, in adjust crop coefficient and MAD, indepdently, all other settings being equal. What I found wasn’t what I expected, but glad I did it.

The more I increased MAD, the MORE water the grass was scheduled to get. While it did decrease frequency, as expected, the rate at which it extended watering times in the 3 week forecasted schedule exceeded the reduction in runs.

As expected, with adjustments to crop coefficient, watering duration stayed the same, while frequency decreased. We’re not talking a ton, but pushing my threshold from every other day to every 3rd day is what I was looking to do.

My current dynamic crop coefficient is 72%, which resulted in 2.67 scheduled waterings per week for the front over the 3 week forecast, and 3.33 waterings per week for the back. By running a -10 offset (62 crop coefficient, it reduced front run frequency to 2.33 runs over 3 weeks, and back to 2.33 runs over 3 weeks. This effectively reduces the amount of water the lawn is getting per week by ~.25" in the front and ~.5" in the back. I don’t trust the numbers for the back as much as the front right now, because my moisture level is sitting at 0% so it has a couple catch-up runs scheduled over the next few days.

I’m thinking of going down 1 of 2 paths - either just run a -10 offset that I configure at the beginning of every month, or in the warm months when the dynamic coefficient exceeds the old static coefficient of 65%, just locking at 65% through the warm months, then switching back to dynamic once it cools off and we fall below 65%.

Can you think of any pros/cons to either approach or have I gone totally off the reservation? This is my first house/first lawn, and we moved in late summer last year, so I haven’t had a full season to dial this thing in yet.