# Sti calculations



## STI_MECE (Aug 4, 2020)

So I got this, can I get a sanity check.

Root Depth = 6in
Soil - Silty Loam = 0.16in/in
Crop Factor - 0.8
Daily ET - 0.24

Daily Water Depletion
Full Sun = 0.192 = 0.8 * 0.24
Partial Shade = 0.144 = 0.6*0.24

Soil Capacity
100% = 0.96in = 6*0.16
50% = 0.48in = 0.5 * 0.96

Irrigation Frequency 
(0.5*6*0.16)/(0.8*0.24) = 2.5 days

is it fair to assume that to start this regimen I need to put 0.96in of water down on Monday as my starting point? My soil is dry.

If I start at 100% lets say I fully saturate the yard Monday with 0.96inch of water, with current ET, I lose 0.19in per day. So in 2.5 days I will be at 50% and lost 0.48 inches of water.

Do I have two plans of attack here or what?

I could either put 0.48inch of water down on Thursday and then again on Sunday.

Or I could apply 0.24inch of water Every other day? IE the yard is saturated on Monday, and I just put 0.24inch down on Wednesday/Friday/Sunday etc?

Or do I apply 0.24inch of water on Thursday/Sunday?

What is tripping me up is where the starting point of 100% is at (day wise) and how to account for ET on the days I am watering. Its like the amount of evap on a day is the same amount of water I am applying that day so I have like a zero next effect on my moisture balance.

Someone help me. I am overthinking this.


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