Aquaponic Gardening

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Water chemistry: necessary elements for plant growth

I've read here that there are 13 elements necessary for plant growth, but I haven't seen a treatment of what those are. Thinking ahead, I'd like to learn more about this topic.

It seems to me that we talk a lot about NPK and Iron, and that the others are more or less trace elements that we don't talk about a lot but are noticed if missing.

It also seems that some plants (like lettuces) don't miss the trace elements much.

Further, as we harvest plants and fish, we deplete the system of its resources, just like we do in soil farming.

Where can I find a discussion of the lesser known aspects of water chemistry? Can we have one here?

Do you guys add the missing elements on a chemical level or do you try to do it through the worms breaking down organic matter? For example, it occurred to me that potatoes and bananas (among other things) that would end up in my trash are rich in many of these elements and could be buried in my GBs for worm processing/consumption.

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It depends on what you are growing, sometimes you could add epsom salt for magnesium, chelated iron for iron deficiencies or potassium bicarbonate when you need some potassium (also a PH buffer). In general most of the trace elements you need for plants are in your fish food and your source water. Over time Aquaponics becomes more productive because as the biological activity increases, nutrient profile gets richer.

Is there a resource that tells me that plants use what nutrients so that I can know what I need to supplement, if anything?

I was researching this and I'm thinking that I might have asked a graduate-level question for which people go to school to study optimizing nutrient inputs to maximize yield with minimum waste.

I've dosed  a couple of times with trace elements but don't really know if it was needed or what effect it had, if any.  See azomite.

This should give you a general guide about what deficiencies you develop. And yes if you are growing for business purposes a graduate degree will surely maximize your profits, but it is not required to start growing Aquaponicly.

Actually there are 16 plant essential elements...but three of the are structural elements...hydrogen, carbon, and oxygen...but who's counting :)  ?

There is a gazzillion good resources...books, papers, studies...from the 1950's onwards on how plants grow...both in soilless culture and in soil. Most of that information comes from hydroponic research/industry...On a physiological level, how plants grow and what they need is essentially the same, whether mineral hydro, organic hydro, or some type of bio-ponic method (vermiponics, aquaponics, pee-ponics etc...) The biggest glaring difference being that in some sort of bio-ponic system (like AP) most of your plant nutrient inputs come in the form of complex organic substances which need to be broken down by bacterial action in order to become plant bio-available (with some help from worms, gammarus, whatever detritovores you have floating about). While in 'classic' hydro, those plant essential element inputs are in the form of various mineral salts that are immediately bio-available and do not require a bio-filter or other organisms to break those elements down into their most basic ionic forms (which is the only way that plants can ever use them)...But how plants use those elements to grow is still the same.

So look to hydro research for your answers. Taking a hydro class at a community college would be a good start.

Hydroponics, A Practical Guide for the Soilless Grower by J. Benton, Jones Jr (2005 revision) is also a decent resource with tons of good citations/footnotes pointing the way for further reading...

Here is a decent begginer-ish type introduction by AP Papadopoulos from the Harrow Research Station. Particularly, Chapter 3 may be of interest to you.

http://www.hydro-gardens.com/PDF%20Files/Growing%20GH%20Tomates.PDF

And there are many, many, discussions in various threads here on this forum (BYAP is also an incredible resource) of the things you mentioned in your OP. It may take some time to go through and search for those old threads and actually read them, but such is life :)

Oh, and if you are counting...You'll notice that Papadopoulos only lists 15 plant essential elements instead of 16...For some reason he seems to have chosen to leave one out (Cl)...

Nice illustration Jonathan.  The carbon dioxide deficiency probably doesn't show up very often.

Jonathan Kadish NYC AA Chair said:

This should give you a general guide about what deficiencies you develop.

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