Advanced Settings for Drip Irrigation

Hello,

I have 40 16" pots per zone, and have 3 zones setup on my Rachio system.

How should I enter the area, per pot or total area of all the pots? i.e. A=pi*r^2, so 3.14 x 8^2 = 201 sq in, or 1.4 sqft? Or should I multiple by 40, the number of pots? I suspect if I’m calculating the nozzle inches per hour for 1 emitter, then the area should be for 1 pot, yes?

Each pot has it’s own spray emitter (a bubbler that fans out the water to about a 3" diameter). The emitter puts out about 7GPH. How do I calculate “Nozzle inches per hour”? What is the diameter of a drip cup? Obviously the diameter of the drip cup determines the “inches” of water (small diameter, greater inches received).

How do I determine the available water (in/in) in the soil? Some of the pots are Self Irrigation Pots (SIP) so they store water in the bottom. Should I remove the SIP pans holding any extra water? The SIP is used to catch any extra rain water to reduce water usage.

What is “Crop Efficiency” and how do I determine this?

Each zone has different root depths (based off the age of the trees in each pot) and soil types, so that’s easy enough to tweak.

Thank you in advance for your insight.

P.S. it would really be great if Rachio would update their App to reset water usage. This has been a long time request by many users, which seems to go unanswered.

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Search “drip emitter calculator” posted by azdavidr to get his excel spreadsheet. It covers this quite well I think.

I’d use the diameter of the pot to calculate in/hr. That’s effectively your dripline, though I grant most pots taper toward the bottom. So you could use the bottom diameter to, maybe, prevent overwatering. Plug that in to the equation:

Precipitation Rate (in/hr) = (96.25 * (7 GPH * 0.016))/Total Square Footage

Where Total Square Footage is found with pi * r^2 and r is your diameter/2 in feet.

0.016 is the conversion factor from Gal/hr to Gal/min so that the constant 96.25 works. See https://support.rachio.com/hc/en-us/articles/115010379587-How-do-I-calculate-my-precipitation-rate-

I have no idea how to deal with SIP & rachio likely wasn’t designed with that in mind so you’ll need to get creative by experimenting and making changes. Perhaps the water reservoir can be simulated as additional inches of root depth?

I can’t provide much with respect to potting soil AWC except I suspect they tend to have high AWC with their high organic content so maybe select loam? Probably varies wildly based on quality and age of use.

The square footage setting in Rachio is only used to estimate water use. I ignore it.

Keep it simple because you’ll hit diminishing returns very quickly.

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Obviously I meant “diameter/2 in ft” :-p corrected that huge blunder in my post.

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@Kubisuro, I was tacking ya! Thank you so much for your feedback, it was VERY helpful.

Any ideas on how to calculate available water? I typically use a peatmoss / perlite blend (similar to a Miracle Gro) potting mix.

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Peat is insane… I almost feel that a AWC north of .5 in/in is reasonable. I can’t find any straight forward literature on holding capacity but that peat moss can hold orders of magnitude more water than most soils. You’ll need to experiment. Maybe 1.0 in/in is valid?