Crop Coefficients, Basic Flex, Advanced


#1

Above is a link to an old discussion. I messaged Franz with the following message and he requested that the message go to this board so all can benefit. The message is as follows:

Hello! I know the link above is an ancient (in Rachio development terms) discussion, but I am hoping you might help me understand some things better.

I have read a great deal about crop coefficients etc. It seems that what is “ideal” for one month might not be for another and so things are generally averaged. In my case I must average things for late April-October (anything else, my sprinkler lines are blown out).

At anyrate, here are my questions:

In the post I linked to, you mentioned that with a flex schedule, the “Advanced” settings for crop coefficient are ignored. Is this still true? I run a basic flex daily schedule and have noticed that when I change the crop coefficient, I noticed that it does change the soil moisture (and therefore the watering frequency).

In that post, you noted different crop coefficients for different months. Does the Rachio include these adjustments automatically when running the basic flex daily schedule?

2.5) If so, why did changing the coefficient in “Advanced” change the measured data as I mentioned in questions 1?

Ultimately, I guess I want to understand how the system manages crop coefficient when running the flex basic schedule so that I can ensure my system is not only keeping my lawn green (which it is doing) but also encouraging the roots to go deep so to speak. How’s it work :slight_smile:?
Right now, it is certainly keeping the lawn green, but after I adjusted the crop coefficient to .87 (thinking it to be a reasonable average for the months I run), it seems to run quite a lot even when the temperatures are not particularly high (65-78 degrees). I have not kept up on the software changes of the last couple years where this matter is concerned.

Thank you for any help you can provide. I would have gone right to tech. support, but your old post with the monthly crop coefficients and the associated discussion really fit with my questions - and added a bit to them :wink: .


#2

As you mentioned that is an old discussion. The SW has been updated since then to allow users to modify the crop coefficient in the advanced settings, so as you noticed it will impact the watering time.
As far as watering frequency goes, crop coefficient isn’t the only thing that will impact frequency. Available water in the soil, root depth, and sun exposure will also impact the frequency. Have you modified those settings to be accurate? You can try posting those here and ask for feedback.


#3

Correct, they fluctuate based on time of year.

These are the values we previously used to dynamically change throughout the year. We do not do this any more and use the user adjustable value in Zone Advanced settings.

CROP_COOL_SEASON_GRASS, JANUARY, .61
CROP_COOL_SEASON_GRASS, FEBRUARY, .69
CROP_COOL_SEASON_GRASS, MARCH, .77
CROP_COOL_SEASON_GRASS, APRIL, .84
CROP_COOL_SEASON_GRASS, MAY, .90
CROP_COOL_SEASON_GRASS, JUNE, .93
CROP_COOL_SEASON_GRASS, JULY, .93
CROP_COOL_SEASON_GRASS, AUGUST, .89
CROP_COOL_SEASON_GRASS, SEPTEMBER, .83
CROP_COOL_SEASON_GRASS, OCTOBER, .75
CROP_COOL_SEASON_GRASS, NOVEMBER, .67
CROP_COOL_SEASON_GRASS, DECEMBER, .59

CROP_WARM_SEASON_GRASS, JANUARY, .52
CROP_WARM_SEASON_GRASS, FEBRUARY, .64
CROP_WARM_SEASON_GRASS, MARCH, .70
CROP_WARM_SEASON_GRASS, APRIL, .73
CROP_WARM_SEASON_GRASS, MAY, .73
CROP_WARM_SEASON_GRASS, JUNE, .71
CROP_WARM_SEASON_GRASS, JULY, .69
CROP_WARM_SEASON_GRASS, AUGUST, .67
CROP_WARM_SEASON_GRASS, SEPTEMBER, .64
CROP_WARM_SEASON_GRASS, OCTOBER, .60
CROP_WARM_SEASON_GRASS, NOVEMBER, .57
CROP_WARM_SEASON_GRASS, DECEMBER, .53

This is not correct. Crop coefficient values are absolutely used in “discounting” the raw evapotranspiration (ET) for the day.

No, we used to but wanted to give user’s access to that value. At some point we might have the option to adjust automatically.

In Colorado since we have cool season grass what I do is in cooler months (May/June/September/October) I will usually have it about 5%-10% lower (i.e. 70%-75%) than our default of 80%. I’ll adjust back up to 80% in July/August.

It’s by far the easiest lever to affect frequency since it doesn’t adjust watering durations.

Please let me know if you have any other questions, these are all great.

:cheers:


#4

Here is the specification some of the monthly default values came from.

:cheers:


#5

Thank you for the reply.

It is always important to be thorough and I appreciate that the Rachio community includes folks like you who want to be sure all the variables are considered.

Yes, I am familiar with the other elements that influence water frequency and have customized all of the settings I
needed to (including adjusting water/capacity based on realistic root depths instead of simply using the averages that are generally listed for geographic regions --and which happen to be taken at depths largely irrelevant for basic landscaping purposes —which results in a potentially very different numbers).

What my questions came down to related simply to fine-tuning the coefficient since it changes from month to month and I was not aware of if the Rachio made these adjustments automatically with the software in its current configuration. Franz got what I needed covered.

As a side – it would be fantastic if on the “advanced” side, users could set the crop coefficient for each month (a balance between letting the user choose AND not requiring the user to make adjustments to optimize during the watering season).

Thank you again.


#6

As usual, Franz… Thank you!