Aquaponic Gardening

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Meir Lazar got me thinking...pee-ponics philosophy...

When he asked how to add P or K to his pee-ponic system(s) for his flowering fruiting plants, I gave him a "standard" answer coming from a organic hydro perspective...Rock of Phosphate, Bone meal blahblahblah...but suppose you were a vegan? Or, the idea of using an unsustainable post peak mineral did not appeal to you? OR, you really were trying to stay within the bounds (of an as of yet non-existent) "pee-ponic philosophy"...Many of us choose not to do things that we are 'philosophically' out of tune with...or at least do them less, and attempt to choose when and why we do them, wisely...

Dosing your system with (N-P-K 11-1-2) humonia in order to get the 'required' or desired phosphates for flowering just isn't an option because of the massive amount of N you would be simultaneously introducing. I'm sure everyone is well aware of why this is bad and whatnot, so we wont get into that here...But, if you could extract all those phosphates, without all the N... that would seem like a mighty fine addition to you arsenal of effluent. It turned out that this wasn't a 'new' idea or anything (but what is these days?), this is what I did...

After researching why my cat gets bladder stones, the idea came to me...I added Mg in the form of Epsom salt (MgSO4-7H2O) to humonia, stired, strained. The white gunk I strained off is drying in the sun. That white stuff is NH4MgPO4-6H20-ammonium magnesium phosphate and is called stuvite (it's the stuff that bladder stones are made of). It is basically a phosphate precipitate. Like the whitish grey gunk (Calcium Phosphate) that builds up in your mineral hydro system over time causing you to have to flush the media...only instead of CaPO4 this is MgPO4...and 'ya made it yourself..!

According to the Swiss, this struvite should have an N-P-K value of 6-29-0 (Mg-10). AND...

...the effluent (liquid) that is left over from the process has a lowered N value, very little to no P value, and a high K value. Seems like a match made in heaven. This should really open up your fertilizing options while sticking to using 'sustainable humonia'...A 3 part hydro nutrient all from humonia. Whoopie!

Struvite dissolves readily in even slightly acidic environments, and slower in slightly alkaline environs. (might be a nice slow release fertilizer for the garden too). [edit. since writing this, I've used the MAP crystals in both the garden as well as in a couple of small bio-ponic test systems. The phosphates appear to be immediately bio-available to the plants (unlike say, bone meal). The potassium rich leftover looks promising, but the weather has precluded me from being able to test that out much on cultivars that are real potassium hogs...So more to come on that next spring/summer.]

I pretty much just did this last night and this morning and am still testing out some details, but it looks promising. I'm keeping notes of weights, measures, time...and should have some conclusions soon. If Meir or any one is interested I can post a 'how to' with details, measurements, and pictures. I'm building a 12 litre 'struvite reactor' out of galvanized sheet metal and pipes I have lying around (cuz I have lots of humonia to process and building stuff is 'fun'). But really all you need is a bowl, a stick, and a piece of clothe...

(and no explosions or highly caustic stuff with this one either...and 'skill level' is as easy as it gets. If you can make sugar cookies, you can pretty much do this. For now, just getting to the idea, seemed harder than executing it).

For the (so far) theoretical math there is this thread...

And for some other struvite stuff there is this... one...

I'd like to keep this thread (hopefully by culling some of the cream of what comes out of those other two) about how to make and use struvite and the results when used to grow plants...

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Replies to This Discussion

thanks vlad. appreciate the help.

To be in the safe side I did 25ml yesterday. 

from all the aquaponics reading I've done all I can see is that folks are just supplementing wiht MaxiCrop + Chelated Iron. 

did I missed anything ?

Vlad Jovanovic said:

Hi Butch, I just now saw this...been kinda swamped with stuff lately...

Yes, all 13 plant essential elements are there.

Supplementation will be the same (less actually) as with fish. Iron and MaxiCrop/Azomite is fine.

You might want to cut back dosing to about 30ml twice a week, until nitrates come down a bit.

@ vlad nitrates still off the charts. how about duckweed ? it should be alright to place some duckweed in the tanks since it is fishless. right ?

also, my ph is steadily @ 7.5. I wonder since there is no nitrification action going on because there not much ammonia in the system that makes the ph on a steady 7.5 as opposed to naturally coming down because of the nitrification process. am I way off with this ?


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