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Finding the Correct Irrigation Module Settings


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Hi All, 


Can you someone help me out here.  I am trying to find the correct settings for the Irrigation Module and they just don't seem to make sense.  Maybe I don't understand them correctly?  


Here is what I think my settings should be:


-I have a local weather station bring in data through HAM.  

-Calculation Method = Penman-Monteith

-Interior Plains **I am in central Florida

-Absorbtion Factor = 80% level ground

-Crop Co./Plant Type = .6 warm season grass


Now under "water applied per irrigation cycle" is where I get confused.  What I know is each time a zone runs in my program it replenishes my grass by 1.00 inch of water.  Time of each zone various but I have set them to run long enough to replenish an inch of water.  Based on this thought process I would expect "water applied per irrigation cycle" to equal around 1.00 inch.  What am I missing here?  


Then when I click on Calculate I have set the following:


-Water Available/Soil Type = Sand

-Root Depth (inches) = 3"

-Managed allowable depletion = 60  ***I am not able to change this which I understand why.  Would be nice if this showed as a DISPLAY field only to avoid confusion

-Calculated allowable depletion = 0.036"  ***I am not able to change this which I understand why.  Would be nice if this showed as a DISPLAY field only to avoid confusion\


To me it does not make sense that it would only allow 0.036 inches before needing water.  If that were the case my irrigation would run everyday.  Even if I select "Silty Clay Loom" is still is only .30 inches.  I would expect it to be more like .50 inches or more based on typical watering instructions of grass.  


I know this is a lot of information but if someone could help me make sense out of this it would be greatly appreciated.  I guess in short I need direction on how to correctly set the "Irrigation Settings" know that I water an inch each time and that I would guess depletion of water before I irrigate should be over 50%.


Thanks for your thoughts!




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Yes I used that to determine how long the runtimes should be in my programs. That does not help maintain the irrigation module settings though. If I understand correctly, these settings are what drive irrigation requirement variable. Am I correct?



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 According to http://edis.ifas.ufl.edu/pdffiles/lh/lh01100.pdf


Watering Zoysiagrass responds to drought by turning brown and going dormant in a short period of time (within a week under typical drought conditions). In the absence of rain or irrigation, zoysiagrass stays dormant for extended periods of time. Once irrigation or rainfall resumes, zoysiagrass will regain its green color. Irrigating on an “as-needed” basis is the best way to water any established, mature grass as long as the proper amount of water is applied when needed. Irrigation is needed when leaf blades begin to fold up, wilt, or turn a blue-gray color, or when footprints remain visible after walking on the grass. Apply ½–¾ inch of water per application. This applies water to roughly the top 8 inches of soil, where the majority of the roots are. Be sure to follow any local watering restrictions. Refer to the EDIS publication LH025, Watering Your Florida Lawn (http://edis.ifas.ufl.edu/lh025), for additional information on proper watering techniques.


This site is also helpful.  The chart refers to St Augustine grass but the water is very similar, if not the same as zoysia.  At least in central florida anyway.  



More details:



USE COMMON SENSE if the grass looks dry (wilted or thin blades) it wants water. I manually water my personal Zoysia lawn using the manual setting on my timer-I leave it off until the grass looks like it needs water. IF IT RAINS MORE THAN ½” DON’T WATER THAT DAY! You may be able to get away with watering 1 day per week if you have the right soil type. MORE WATER LESS OFTEN ¾” of water per watering as needed. Zoysia loves to dry out and it helps eliminate fungus issues. Drier is better! Zoysia will turn solid brown after 3 weeks of no water and really tell you it wants water. Have no fear as it will green up in 1-2 weeks after watering has started again. It can go up to 6 weeks without water in the summer depending on soil type-(I wouldn’t try it.) Now knowing that Zoysia can go easily 3-4 weeks with no water and be fine hopefully you are less worried about watering less often. Generally speaking water 2 times a week in the summer and 1 time per week in the winter if you are not manually watering and just want to set the timer and forget about it. Another benefit to watering less often is that the fertilizers and fungicides last longer-they don’t get washed / flushed out as fast as they will in St. Augustines.

Hope this helps!
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Hi jellis,


Sincere apologies for tardy reply. I was looking up some information. Attached table describes what ISY is trying to accomplish. Please note:


Allowable depletion (inches) is a calculated output from the above.  This is provided as a “guide” on how much depletion to allow/water to apply.  


Root depth and Absorption Factor are both very important and will dramatically increase the allowable depletion. For instance, for my yard, I have:

1. Absorption Factor: 60% (on a steep slope)

2. Root Depth: 5 inches

3. Soil Type: Sandy Clay Loam

Allowable depletion is 0.375 and thus water applied per cycle is 0.625 (it's multiplied by Absorption Factor).


Hope this helps.


With kind regards,


Irrigation Map.png

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