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. The sites quoted above should help.
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. So much more is used in summer than winter, meaning CC can be relatively constant and still result in variable rain.
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 (tall fescue, Ky. bluegrass, rye, bent) | 0.8 |
| General Turfgrass Lawns, warm-season (bermuda, zoysia, St, Augustine, buffalo) | 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 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. For example, the table you posted with the Meyer 1985 data provides coefficient values for cool and warm season grasses in a mediterranean climate, so most Rachio controllers in mediterranean parts of CA, OR, etc will get those coefficients.
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 ECOBEARD on Jan 26, 2022
Any updates on the dynamic crop coefficient function?
Post by drew_thayer on Apr 20, 2022
Hello all, we’re excited to see the interest in the Dynamic Crop Coefficient feature. We’ve written up an FAQ document that will address many of your questions, here: Dynamic Crop Coefficient FAQ
In a nutshell, this feature generates a new 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. The values are local to your climate, and will change every month.
Conclusion
The conversation about crop coefficients reveals complexities in plant water requirements and seasonal adjustments. The development of tools like the dynamic crop coefficient aims to simplify and tailor watering schedules to better match the specific needs of different plant types throughout the year.