Crop Coefficients and Plant Type - Schedules & Zones / Flex Daily - Rachio Community
Crop Coefficients and Plant Type
post by ECOBEARD on Feb 14, 2021
How do you know what crop coefficient should be used for each plant type? I have a 1 zone wonder with shrubs and trees on the same zone. I have my crop coefficient set at 70%?
Why is 50% recommended for shrubs and 75% for trees? They are similar plant types. There is a grey zone between tall shrubs and small trees.
Shouldn’t crop coefficient change throughout the year? I thought Deciduous plants and Evergreen plants have different water needs relative to each other based on the season.
post by Kubisuro on Feb 15, 2021
You’ll want to look up the crop coefficients if you have the time. In Rachio they’re in Percent but everywhere else they’re not (times by 100 for input to Rachio advanced settings). You’re right deciduous trees have vastly different needs especially in the winter. The coefficients do change over the year but Rachio simplifies it with defaults to be something like annual averages for the USA. I have been known to set reminders to change crop coefficients for my stone fruit trees-spring, summer, late summer, fall, winter. Your university extension may have crop coefficients or plant factors for your local area; these can be different depending on your climate.
post by rraisley on Feb 15, 2021
A search of the Internet will give you decent values for Crop Coefficient for most plants. Basically, that just says that trees, with their deeper roots and high foliage, require 50% more water than shrubs. And yes, there’s a lot of gray area here.
Some do change throughout the year, others are fairly constant. Remember that Crop Coefficient is not an absolute value for water required; it is a multiplier of the value of FRET (Forecast Reference crop EvapoTranspiration), which basically is the amount of water evaporated out of a shallow tray per day or week which varies with the temperature, humidity, sunlight, wind speed, etc.
post by ProWater on Feb 19, 2021
Crop Coefficient = Kc
This is a quick reference from my Cal Poly notes for PF Plant Factor which is used for a guide.
| Plant Type | Plant Factor |
|---|---|
| Tree, Shrubs, Vines, Groundcovers | 0.5 |
| Herbaceous Perennial Plants | 0.5 |
| Desert Adapted Plants | 0.3 |
| Annual Flowers & Bedding Plants | 0.8 |
| General Turfgrass Lawns, cool-season | 0.8 |
| General Turfgrass Lawns, warm-season | 0.6 |
| Home Fruit Crops, Deciduous | 0.8 |
| Home Fruit Crops, Evergreen | 1.0 |
| Home Vegetable Crops | 1.0 |
| Mixed Plantings | PF of the planting is that of the plant type present with the highest PF |
post by ECOBEARD on Mar 28, 2021
Does a crop coefficient twice a large water twice as frequent? For example will a plant at 60% Crop Coefficient need to be watered twice as often as a plant with a Crop Coefficient of 30%? The weather and soil conditions are assumed to be the same.
post by Kubisuro on Mar 28, 2021
Not exactly but that is one approximate way to look at it. The crop coefficient scales the day’s ET0 or reference evapotranspiration, and that changes day to day.
post by ECOBEARD on Jun 17, 2021
Should I increase the crop coefficient in excessive heat? My shrubs and trees are on the one zone wonder. I use the shrub watering depth of 16 inches and the crop coefficient of 0.75, which is the standard tree recommendation.
post by rraisley on Jun 17, 2021
You shouldn’t have to. The calculated ET (Evapotranspiration) value takes the heat, humidity, sun, wind, etc. into account, so that’s what does it. Now, if you find your crops drying out too much, you might increase it just because it probably needs it to fine-tune, as hot weather will bring a lack of water to light sooner than cool.
post by ECOBEARD on Jan 11, 2022
It appears crop coefficients might change throughout the year for certain plants. If so, can Rachio make it an option to have automatically adjusting crop coefficients?
post by drew_thayer on Jan 12, 2022
Good news! We are currently developing a “dynamic crop coefficient” feature we will release this spring (2022) that will automatically provide specific crop coefficients for each month of the year for all crops. We’ve combed the available research to come up with crop coefficient curves that are specific to months, plants, and regions.
post by ECOBEARD on Jan 13, 2022
I’m interested in how that will work so it won’t change the crop coefficient too much or too little. How would one change the crop coefficient up or down a little from the default if it’s dynamic? Would this new dynamic crop coefficient feature save more water than the static crop coefficient?
post by tmcgahey on Jan 13, 2022
I wonder if the dynamic crop coefficient will also account for different types of plants in the same zone?
post by spaceman_spiff on Jan 14, 2022
@drew_thayer Is this a feature that will be automatically turned on or will it require user input to activate it? If so, I’d like to know more about how that activation process will work for existing users vs new users.
post by drew_thayer on Jan 14, 2022
The feature will not be turned on automatically when it launches; existing customers will have to opt into it and we’ll explain how.
post by ECOBEARD on Jan 15, 2022
Is there an option to get additional inputs or values regarding the dynamic crop coefficient settings? For example, will it be adjustable based on the region or the soil type?
post by spaceman_spiff on Jan 16, 2022
Looking forward to seeing the dynamic crop coefficient feature in action! It's great to see Rachio adapting and improving to better serve the users.