Dynamic Crop Coefficient FAQ

Last Update:Oct 19 2023 10:51pm • Est. Read Time:Est. Read Time: 3 MIN

Article Summary

We're excited to announce the latest upgrade to Rachio's scheduling software. This article will explain what the feature is, how it works, and how you can disable and enable it

FAQ


What does this feature do?

  • Dynamic Crop Coefficient is Rachio’s latest upgrade to our irrigation scheduling software. Crop coefficient helps us predict how much water is lost through evaporation and transpiration (evapotranspiration). Each crop type in the Rachio app has a different crop coefficient value (different plants have different water needs). A plant with a higher crop coefficient needs more water, and a plant with a lower crop coefficient needs less water. The crop coefficient helps Rachio calculate how frequently the plant should be watered.
  • Up until this point, the value in our app has been static year-round and based on an average for that crop type. 
  • The reality is that a plant’s crop coefficient changes each month. The value increases during the plants’ growing season (typically, the hotter months), and decreases during the dormant season and colder months. The crop coefficient value can be different for the same crop type based on the region where the plant is growing.
  • Rachio’s Dynamic Crop Coefficient will change the crop coefficient value each month to provide you with higher accuracy in our watering frequency calculations. The value will be updated on the first day of every month.


How do I turn this feature on and off?

Go to the zone's Advanced Settings (Tap Zones at the bottom, select that specific zone, and then go to Edit > Advanced) and toggle the lock icon next to Crop Coefficient.

What happens if I turn this feature off?

When you turn this feature (by selecting Static) off the crop coefficient value will revert to whatever you last had it set to. If you don’t change this yourself, it will be set to the system default.


How does Rachio calculate crop coefficients for my garden crops?

The U.N. Food and Agricultural Organization (FAO) publishes comprehensive tables of reference ET and crop coefficients for dozens of common vegetable and cereal crops. For Rachio “vegetable garden” zones we interpolate between average initial, peak, and end-season values from the FAO tables and set them to appropriate months for your growing season. FAO: https://www.fao.org/3/x0490e/x0490e0b.htm#chapter%206%20%20%20etc%20%20%20single%20crop%20coefficient%20(kc)


I’m an experienced Rachio user, and I’ve dialed in my crop coefficients via trial and error. I turned on this feature and the value is different, which should I use?

Our dynamic crop coefficient system is a generalized solution designed to meet the needs of most yards, most of the time. If you’re a dedicated gardener you know your yard better than us; keep using what you’ve discovered (And tell us what works for you! We love to hear how experienced users use our features; you can email support@rachio.com)


Is there an offset feature? I.e. I want to use your recommended value + 10%

We did not design an offset into the initial release of this feature. If you want to use the recommended value plus or minus some offset, activate the feature on the 1st of the month, note the recommended value, then turn the feature off and select the value you want. If you have any recommendations for improvement, please share this feature with us by emailing support@rachio.com or posting on the Rachio Community https://community.rachio.com/c/product-suggestions/5 


What climate zone am I in?

The exact way we define a controller’s local climate is proprietary, but it’s generally based on seasonal rainfall patterns, temperature patterns, and frost dates. We have distinct parameters for local climates at roughly a county level; for example, the western suburbs of Denver, Colorado have slightly different coefficients than the eastern suburbs, but watering schedules will be very similar. 


Where can I find the 12-month coefficient curves for grass in my region?

The system we use to interpolate coefficient values where there is no published research is proprietary but rest assured that we’ve combed available peer-reviewed research to find as much data as possible.

Rachio controllers in Mediterranean climates (mostly found in CA, OR, and WA) use coefficient values from a smoothed curve interpolated from a commonly cited research study performed in California in 1985 (Table 1, below)


What kind of grass do I have?

Cool and warm season grasses are generally distributed across the northern and southern U.S., respectively, with a transition zone that runs approximately West to East from central California to Virginia (Figure 2, below).


Figures and Tables


Figure 1. Turfgrass growing regions of the contiguous U.S. 


Table 1. Crop Coefficient values from the Meyer 1985 study in California


Data published by the University of California, Division of Agriculture and Natural Resources. https://ucanr.edu/sites/UrbanHort/Water_Use_of_Turfgrass_and_Landscape_Plant_Materials/Turfgrass_Crop_Coefficients_Kc/

Source: Meyer et al. 1985. Irrigation of turfgrass below replacement of evapotranspiration as a means of water conservation: determining crop coefficient of turfgrasses, pp. 357-364 in: F. Lemaire (ed.) Proc. 5th Intl. Turfgrass Research Conf., Avignon, France, July 1985. INRA Publications, Versailles, France.