NEW Dynamic Crop Coefficient feature

post by drew_thayer on Apr 20, 2022

Hello all, we’ve just released a new feature we call Dynamic Crop Coefficient, and we’re excited to already see interest in the feature. We build this in part using feedback from the community in these forums, so I’m posting this here as a starting point to get more feedback from the feature as customers use it.

We’ve written up an FAQ document that will address many of your questions, here: Dynamic Crop Coefficient FAQ

Beyond the FAQ, I’ll take some time here as to address specific questions that have come up in the community.

In a nutshell, this feature generates a new crop coefficient (Kc) value every month for all crops, for every zone. When you turn the feature on, you’ll get that value for your zone and cannot edit the value. You can toggle the feature on and off as much as you like. The values are local to your climate, and will change every month.

Our hope is that this feature will help avoid the heat-stress problems that many customers experience in peak summer. If you think about a sinusoidal curve vs a flat line, it’s clear that the static Kc values we used to provide were really only accurate some time in Fall and Spring, and were likely leading to over-watering in the shoulder seasons and under-watering in summer for a lot of controllers (they did for my yard).

The Kc values for turfgrass are regional, varying by high-level climate types, for example a Mediterranean climate on the west coast will have different values that steppe/semi-arid climates in the Rockies, southwestern deserts, eastern humid regions, etc. I’m sorry I can’t be any more specific at this time.

The Kc values for garden-type crops will vary slightly across even smaller climate micro-regions, roughly the size of western counties. This is because we fit expected growing season Kc values to the local growing season timing, and we can do this at a finer spatial resolution.

Data sources: we compiled the Kc curves for turfgrass from peer-reviewed research where available and other academic published documents (Master’s theses, Ag school department materials, etc) where needed. For other crop types, like vegetable and flower gardens, we’ve taken average seasonal values from the U.N. Food and Agricultural Organization (FAO) tables, which are extensive, and fit them to the local growing season (link to FAO tables is in the support document).

You have already provided some great concepts for improving this feature. To get this to market quickly we did not build an offset or an enter-your-own function, and those are good ideas. If you want to apply an offset this season, you can activate the feature on the first of the month, note the value, turn the feature off, and set the value with whatever offset you want. I realize that is a hack, and we really want to learn about the appetite for a feature like this so we can plan follow-up features.

You have also identified other changes made to the user interface. We combined the ‘Annuals’ and ‘Perennials’ classes into a ‘Flower beds’ class. It turns out a lot of customers didn’t know what those really meant, and even for those that do, our garden aesthetics often combine them. The root zone depth and Kc parameters for this new class is close to the average of the old classes, erring a bit on the side of more frequent watering. We have also made under-the-hood changes to “vegetable garden”, which will water more frequently, and changed “xeriscape” to “desert-adapted”, which will water less frequently and is a great choice for native steppe and desert plants that are becoming popular landscape elements in the southwest. In addition, if you set up new zones, you will find a cleaner and more informative zone setup process that we hope will lead customers to get it right more often the first time.

It’s worth saying that some of you have a really good intuitive and data-driven handle on how to tune a Rachio controller to get optimal results on your yard. We designed this feature as a finely discretized, yet generalizable solution that will work for most yards, most of the time. It could be that what you’ve learned through research and trial and error works better for your yard, and if so, keep doing what you’re doing! And please let us know when you find discrepancies; we’re committed to improving this feature and we want your feedback.

• Dynamic Crop Coefficient
• Adaptive Watering - Answers Please!

post by tmcgahey on Apr 21, 2022

I am really excited to see how this plays out! Previously, I didn’t do monthly adjustments, but I would make adjustments 2-3 times a year to account for winter/summer needs here in Arizona. It was clear that the Kc values were an “average” of sorts, and summer needed a bit of a boost, especially years when we had LOOONG stretches of 110+ degree days.

post by tlight on Apr 21, 2022

This is a followup to what I posted previously related to a “crop quality” offset to the new Dynamic CC feature. Texas A&M is looked to as the horticulture expert in our area as they have been involved in agriculture research in Texas longer than anyone. Below is their statement on Crop Coefficients, in Texas, for turf grasses.

First, note that the starting Tc of 0.6 is a lot lower than the one picked by the Rachio Dynamic Coefficient feature for my area (0.8). Second, note the statement that the Tc remains constant throughout the growing season for established lawns. A&M recommends no water during the dormant season for warm-weather grasses in my area. Rachio might want to somehow work with Texas A&M when developing their “proprietary” settings.

Turf Coefficient Values (Tc)

Quality Factor (Qf)

post by rraisley on Apr 21, 2022

This sounds like a great idea. Guess we’ll see. My concern is that while Rachio recommended 0.6 Kc for warm season grass (I’m in Columbia, SC), online sources recommend 0.85 for Centipede grass, which is what I have. I’ve used that since getting Rachio, and if anything, I think I’m overwatering.

post by gweston on Apr 22, 2022

My comments (and source of information) are basically in line with what tlight posted.

I was excited to see this feature but when it jumped the Crop Coefficient from the 0.6 I set straight to 0.8 which is as high as I would ever go when we get several weeks of over 100 deg F in August I’m afraid it is not going to work for me. Right now is our ‘rainy season’ in North Texas.

post by twin1 on Apr 22, 2022

This would be a GREAT FEATURE.

post by drew_thayer on May 23, 2022

Hi @rraisley, as a general trend we are not going to support new features in the web app, but you can still use it to view schedules and make adjustments that aren’t related to new features.

post by bug99 on May 25, 2022

I am a bit late to this new feature party, so I apologize if I miss something that has been previously posted.

My thoughts:

Assuming one has done a good job of dialing in the root depth and watering rate for their soil type for each zone, unless we have tons of adjustability and fine location data for the individual crop every week of the year, we are sort of stuck with cramming a lot of variables together.

The hard work is achieving 90% or 80% of that ideal lawn with far less water per year. Personally, this is my goal here in California.

It appears that this dynamic crop coefficient is actually convoluting ET and transpiration. The Rachio engine claims to do ET in the back end, but is basically a fixed ratio of evaporation (wind, heat, humidity).

For my needs, a simple table where I can set (or override) the coefficient for each month would be more useful.

post by Gerardv514 on Jun 3, 2022

Rachio definitely has a bug with the new dynamic crop coefficient. I have been seeing different durations among my 7 zones even though all settings are the exact same.