A Community and Forum For Aquaponic Gardeners
Iron
I have been reading here where chelated iron is a major issue. Maybe not major as compared to the nitrification process, but significant anyway.
Is there a way to produce your own plant-available iron WITHOUT buying commercial supplements?
Replies to This Discussion
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Permalink Reply by Vlad Jovanovic on
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If by 'major issue' you mean the proven and known toxicity issues surrounding EDTA chelate, you can always opt for a EDDHA chelate. (I don't know why folks would still sell and buy Fe-EDTA...probably because it's cheap...and then not go through the 10 seconds of 'trouble' to figure out how much they should use and how often...but anyways)...
Yes there is Pat. I'm kinda swamped for time right now, and there is a BUNCH of info on that topic strewn throughout different threads here...but the skinny of it is...
Iron (Fe) is a 'Transition' metal. Because it easily changes it's valence shell from Fe3+ (called ferric iron, and not really plant usable), to Fe2+ (called ferrous iron which is readily plant available).
It's pretty 'easy' to turn rusty nail fillings (Fe3+) into Fe2+...but once it hits an oxygenated environment like our AP water, the Fe2+ reverts back to Fe3+ in a heartbeat. Temps and pH will play a role in how quickly this occurs.
Now, you can chelate (bind the Fe2+ to an acid) your Fe2+ yourself to keep it plant available much longer, to say, tannic acid (from Oak galls or even leaves)...and run things at a nice lowish pH.
None of this needs be complicated nor time consuming (no more so than running an AP system in the first place), but it will take a bit of knowledge and dedication to the process to do it right. I can't remember where all the threads are at...but...
http://community.theaquaponicsource.com/groups/group/show?groupUrl=...
http://community.theaquaponicsource.com/group/fish-less-systems/for...
There are a bunch more so dig around in the search field...
Of course you could always just use some of the very common compounds that hydroponicists used before commercial Fe chelates were readily available...
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Permalink Reply by Sylvia Bernstein on
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Great explanation, Vlad, as always. I'm curious about your statement about EDTA and toxicity. My understanding is that it is only begins to exhibit toxicity at extremely high levels - 100 ppm according to a study by Rengel (2002) - and that most hydroponic solutions keep it closer to the 1.5 - 3.0 ppm levels. I think most additives can become toxic to plants at extremely high levels, can't they?
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Yeah, I agree Sylvia...Just about too much of anything can be (and usually is) a bad thing. Yup, the Rengel study seems to be the one most often cited...there are some others I can dig up again if you need/want them, but if I recall, they too dealt with some pretty 'high' (all things being relative) numbers.
I guess one of the biggest problems with EDTA in my mind is, in an AP setting we do not run our water to waste, since it's a closed loop re-circulating system. So, some things that might be wholly appropriate in a classical hydro setting, might not be for an AP setting. Why 'risk it' if alternatives (like EDDHA chelates) exist? I mean after going through all the 'trouble' and spending thousands of dollars (or whatever) setting up an AP system, why crap out over a couple lousy extra bucks for a superior Fe chelate?
The other thing that comes to mind is the (apparently) totally haphazard way some posters here go about adding iron chelates to their systems...lots of folks don't know how to measure out say, 2ppm Fe-EDTA 13% (or whatever)...So they do the old "I'll just toss some in and see what happens" thing...That's just a bad idea (there's a difference between being 'adventurous' and plain 'stupid'...lest anyone get the wrong idea, I'm not picking on anyone in particular...I do some pretty 'stupid' stuff myself at times)...
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Well, if you should ever find yourself without internet service (and god forbid something like that should happen to anyone)...'ppm' (parts per million) is another way of saying 'mg/L' (milligrams per litre)...so to figure out ppm...
mg/L = Solute (mg)
Solvent (L)
Then just adjust for the strength (6%, 10%, 13% whatever) of the particular product you are using.
In this case the water is your solvent, and whatever you are adding is your solute. If you don't you your systems water volume in litres, multiply the gallons by 3.8
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Sure thing
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All fair points, Vlad, although it would be interesting to see if iron actually builds up in an AP system if added sparingly or if you can assume that at the points when the plants are looking chlorotic (sp?) again if the iron has been taken up and out of the system. Unfortunately those other forms of iron are very difficult to find...and very expensive. But we are looking. We've also been getting a lot of calls here about iron dosing so Matt Freshour and I started a project at the end of last week to figure out what to tell people...so this conversation is amazingly timely for us! Would you mind if we used your formula in a blog post we are writing about all this? And then Gina just put out a great blog post in here about their experience at Green Acres around all this. It seems to me that while iron testing kits haven't been a part of the standard AP tool kit, they probably should be. What are your thoughts? Do you use one?
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I wasn't so much referring to iron potentially building up in the system as I was to Ethylenediaminetetraacetic acid (EDTA) potentially building up in the system (this of course assumes that the operator is using the Fe chelate in a sane manner :)...
As far as I know, iron is rather unique among the metal cations in that it doesn't behave antagonistically towards the other base or metal cations (Mg, Ca, K, Zn, etc)...an excess of iron (within reason) doesn't really interfere with the uptake of other cations, and plants can engage in "luxury consumption" of iron with no ill effects (again within reason). The iron content of leaf mass can vary wildly in the same cultivar, as long as it's above a minimum threshold there doesn't appear to be a big problem. So, there's a good chance that it is actually the chelating agent that might be causing the problems when in excess...(btw...Diethylenetriaminepentaacetic acid, or DTPA, another common chelating agent, is also now suspected of being a plant toxin...although this has yet to be unequivocally proven. When I use chelates I use EDDHA and that is what I've recommended to others here.
Testing for iron is just a really, really good idea, for both your plants and your pocket book. But you can use "canaries in the mine" type plants that have a higher iron sensitivity than the cash crop you are rearing to let you know when iron in solution is getting low.
Waiting for Fe deficiencies to manifest in the crop you are trying to rear and sell in order to know when to add Fe would just be foolish...but having a few iron sensitive cultivars as 'indicator plants' has worked acceptably for me thus far. But really, in a 'commercial' setting, just sport the couple extra bucks, and test for iron for chrissakes :) By the time an iron deficiency makes itself visually manifest in your cash crop... so that you can go about correcting it, you've already lost at least a week or two of production time...So pick a 'canary' or buy an iron testing kit...or better yet both...
If the 'AP Gods' are wanting to add a few commandments...It'd be really keen to turn people on to kH testing as well as iron testing.
Sylvia Bernstein said:All fair points, Vlad, although it would be interesting to see if iron actually builds up in an AP system if added sparingly or if you can assume that at the points when the plants are looking chlorotic (sp?) again if the iron has been taken up and out of the system. Unfortunately those other forms of iron are very difficult to find...and very expensive. But we are looking. We've also been getting a lot of calls here about iron dosing so Matt Freshour and I started a project at the end of last week to figure out what to tell people...so this conversation is amazingly timely for us! Would you mind if we used your formula in a blog post we are writing about all this? And then Gina just put out a great blog post in here about their experience at Green Acres around all this. It seems to me that while iron testing kits haven't been a part of the standard AP tool kit, they probably should be. What are your thoughts? Do you use one?
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Permalink Reply by Beth Medeiros on
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Oh my....as a newbie to aquaponics, all this information just reminds me how much we have to learn! :)
Vlad and Sylvia, are there resources to tell us which vegetables need which elemental additions? And then to what amounts? I see that you have given 13% for the iron along with the equation. But how do we know what percentages each element needs? It's probably that I haven't found the different threads on this forum yet, so I apologize if this is something that you have posted on before.
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@Beth...13% is the just amount of iron that is contained in a particular iron chelate powder that some folks here use...the actual amount of iron you need present in solution for most plants at most phases of growth is 2-3ppm (parts per million)...'much' less for stuff like lettuce...There are vast resources for such information mostly coming from hydroponic research...aquaponics, vermiponics, pee-ponics, organic hydro...any such soil-less growing methods more or less piggy-back's on those numbers.
@Sylvia, no I don't mind if you use "my" formula...though honestly, it is just the relationship that exists between two numbers and it's use is neither 'mine' to permit or deny... (It is kind of you to ask though...being cited or credited is always nice though :) either that, or send five US dollars to the following address: ..........................
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LOL - your check is in the mail, Vlad. I know you aren't inventing the math, but you sure are saving me some trouble looking it up!
I just went to my greenhouse to feed the piggies...I mean fish...and poked around to see what I would consider to be iron "canary" plants. For me it is kale and basil. What are yours?
I'll look for the EDDHA iron, but honestly I've never seen it and have just been using EDTA for years. Where do you find it?
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Permalink Reply by Alex Veidel on
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Oh, chelated iron can be bad for your plants in large quantities. Just check out Tim Bolton's "iron chelate incident of 2013" post :) He's a good friend of mine and I was present for the effects of excess iron in his system. His plants looked like they were being eaten from the inside out. He spilled a little of the powder on his leaves when he added it to the system and it started to melt the leaves and turn them to goo :/ Everything in moderation, I guess...
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For me, Oregano has worked well on the iron side...and some of these brassicas like Chinese cabbage, or even kale seem like they start showing Mg deficiencies before most other plants. But sure Basil will work, just don't use your 'main' crop as an indicator...Hehe, many folks think of Basil as some kind of light feeding leafy green with plant essential element requirements akin to lettuce, but boy can it suck nutrients like a champ!
Sylvia Bernstein said:LOL - your check is in the mail, Vlad. I know you aren't inventing the math, but you sure are saving me some trouble looking it up!
I just went to my greenhouse to feed the piggies...I mean fish...and poked around to see what I would consider to be iron "canary" plants. For me it is kale and basil. What are yours?
I'll look for the EDDHA iron, but honestly I've never seen it and have just been using EDTA for years. Where do you find it?
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