NEW Dynamic Crop Coefficient feature

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 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 if when you find discrepancies; we’re committed to improving this feature and we want your feedback.

5 Likes

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.

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. (See ET and Weather Data → Turf Coefficients at https://texaset.tamu.edu/ for source.)

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.

Lastly, see the quality offset (Qf). This is the offset that could be added as a feature. Using this table, I set my Crop Coefficient at 0.36 for my Bermuda/St Augustine lawn during the growing season. This seems to pretty much put me in line with recommendations from A&M’s “Water My Lawn” update service.

Below is from Texas A&M:…

Turf Coefficents

Potential Evapotranspiration, ETo (also abreviated as PET), is an estimate of the water requirements of a 4-inch grass growing in a deep soil under well-watered conditions. A turf coefficent (Tc) is needed to relate pET to the water requirements of a specific turf. For established lawns, the Tc remains constant throughout the active growing season of the grass. For warm season grasses, such as St. Augustine, the Tc is 0.6 throughout much of the year, while the Tc for cool season grasses, such as rye, is 0.8.

However, we seldomly apply this amount of water to lawns. Why? Because we do not want maximum production of grass clippings. Instead, we want to maintain a healthy, attractive turf with as little water as possible. Thus, we modify the coefficent by specifying a Quality Factor.

The complete equation is:

ETo x Tc x Qf = turf water requirement

Turf Coefficient Values (Tc)

Warm Season 0.6
Cool Season 0.8

Quality Factor (Qf)

No Stress 1.0
Low Stress 0.8
Normal Stress 0.6
High Stress 0.5
Very High Stress 0.4
1 Like

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.

After implementing the variable Kc feature in Rachio, it moved what would normally have been the 0.6 Kc to 0.8. And you say you expect it to be higher in the summer. That sounds like it’s going to be a lot of water.

It’s also a bit confusing for the default warm season grass that your year-round value was 0.6, but it’s already set at 0.8 and will no doubt get higher. I’ve been told by lawn guys that I greatly overwater my lawn, but it sounds like Rachio will advise more, not less, in the future.

Can we obtain any of the variable grass Kc data throughout the year, to anticipate how this will affect our water usage?

1 Like

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 :slight_smile: We are permanently in some form of drought so overusing water is definitely not desirable.

I understand an awful lot of work has probably gone into this but I don’t think it can realistically cater for all the microsystems. Truthfully, having a single setting for warm season grass is not ideal since Bermuda, Zoysia, St Augustine all have differing needs which themselves differ in different areas - even in the same state. For my needs, a simple table where I can set (or override) the coefficient for each month would be more useful.

I have had my Rachio turned off all winter simply because the Bermuda/ Zoysia is dormant and the rain we get is adequate during the winter months. The aim (for me) is to apply just enough water to keep the lawn healthy without over-watering and wasting a precious resource.

Sometimes I think moving away from the Flex Daily and setting a Monthly (optimistic) schedule might work better for me. Then, if we don’t get the expected rain or the grass starts to look stressed I can just do a manual water to play catch-up.

EDIT: Which reminds me of something I have seen suggested many times which is a simple water more/less slider. I play with the coefficient which has to be done on each zone. It would be great if I could just reduce the intelligent watering at the top level by 10 or 20% most of the year and then increase it in the heat of summer.

1 Like

This would be a GREAT FEATURE.

1 Like

Okay, since the dynamic Kc is built into both the mobile apps, but NOT in web app (which I prefer using), I need to know what, if anything, I should avoid doing in the web app so as to not screw up the dynamic settings. Can I VIEW everything? But maybe not CHANGE anything? Or can I change things, but not the Kc value? I’d really like to know what my system is going to do. Any my other concerns and questions and concerned above have not been answered.