Available Water and Crop Coefficient


#1

I have searched for help on these two topics and can’t really find much other that they are changeable. So here is the question:

How do they get set by default? What drives it
How do you determine what they should be - that seems a mystery to me

There are so many variables that interact, that it is hard to figure out each piece. It would be really helpful to have a basic FAQ for the advanced zone setting since it seems these drive everything. There is one that covers some topics but not these two. Ideally for each element it would:

Explain what it is
Explain how it is set by default
how you determine optimal
Does order matter? Is one more important than the other


#2

Quite a bit of information here: Zone Setup


#3

I finally found crop coefficient buried in topic what kind of vegetation do I have, but it is not discoverable by search strangely.
I went through the various sections and can’t find anything on how to determine optimal available water or how it is automatically calculated. It may be fine, but I can’t tell.


#4

For available water, I would recommend researchin pwp (permanent wilt point). That will provide a good deal of clarity.

You are not going to find any type of chart that tells you what to set it to,because many things go into it. If you have a warm season ryzome, you can lower it from the default, I’m currently at .1 (tif 419) to encourage deeper roots. so this means that the last .1 inches of my root zone will no longer supply enough water to transpire and the plant will transpire all of the water in leaves until they dry out. Once that process begins, it is irreversible hence the name. But with most grasses, the root system will burn starches to make a growth run to reach water. Some call this training.

If, I understand it correctly from my own reading.


#5

@garmanmd, available water automatically calculated by soil type; I wouldn’t recommend changing it unless you’ve done your research as @plainsane noted.

We’ll add on; apologies this data wasn’t easy to find or understand.


#6

I don’t know if this stuff is faq-able. I mean these are set to statistically valid values but are expert topics.