Crop Coefficient

I have some shrubs that are not getting enough water. They are currently scheduled to water again Nov 25. I watered them by hand to revive them and gave them a manual cycle as well. I went into the setup and thought changing crop coefficient would allow me to increase the frequency of watering so it would water before Nov 25. After experimenting, I found a crop coefficient of 0.92 or lower results in next watering Nov 25, but changing crop coefficient to 0.93 makes the next watering day Nov 14. That is a huge jump in days for a minimum change. Why does it change so much?

Here’s a sheet I put together to help me figure out what each of the parameters does for watering. I don’t know if it’s correct. It would be nice to get feedback on this and maybe some additional columns.

What happens when you increase:
Range Run time Frequency Total water
Plant type
Soil AWC Increases Reduces Same
Slope Divides Repeats Same
Sun (~shade) 0 100 — Increases More
heads Reduces — Same
Area 0? ?? — — More
Avail water 0? ?? Reduces — Same
crop Coefficient 0? ?? — Increases More
Root Depth 0 ?? Extends Reduces Same
Allowd Depletion0 100 Extends Reduces Same
Efficiency 0 100 Reduces — Less

Sorry, this is lined up nicely in the draft, but not when I post it.

@amerson - see these articles for information ->


If these are new shrubs or trees, don’t rely on overhead irrigation. Give them a good hose soaking until they are established.

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The link says Crop Coefficient is “the best lever for adjusting watering frequency.” What I don’t understand is why it is so sensitive at that one spot (.92-.93) and not elsewhere. I bumped it up to 3 to get water more often. For now that will be ok and I’ll monitor it.

First, that drastic change is an estimate, so it changing drastically with such a small variance seems to indicate that their could be a tiered approach. That co seems way too high, there are not many shrubs that te that high. My gut tells me that either your pr is too high or your root depth is too deep for the zone