Chelated Iron Dosing - Is there such a thing as a preventive dosing?

[Roger Pilon]

Is there a specific dosing of chelated iron that one can add to his system as a preventive dosing!

I know that when you see yellow leaf appearing it is normally time to add chelated iron. This said, I would like to know if there a specific dose that you can add weekly, monthly to keep your AP system in a happy iron level?

Not too much, not too high... just enough to avoid a lack of iron!

Some specs:

1. I have a chelated iron EDDHSA 6% (Fe)
2. Using a IBC tote with 1000 liters water +/-
3. 2 x (4x8x12inches) Deep Floating Raft 
4. PH is at 6.8 / 7 range

Any advices would be welcome!

Roger Pilon

Costa Rica

[TCLynx]

There is no generalized "preventative" dose that would be appropriate for every situation since the need for iron will be affected by your source water, fish feed, type of system, media, type of plants etc etc.

So if you have had to use iron before to deal with a lack of iron.  Keeping track of how much you needed to use and how often you have needed to dose with it to combat the problem, then you should be able to figure out how much you might dose ahead of time.  Say you used x amount every 4 weeks.  Well perhaps you divide x by 4 and then you dose that amount weekly? 

[Roger Pilon]

Thanks for the answer.I can see that there is no specific answer.

I found this video from Murray - one teaspoon once a month http://www.youtube.com/watch?v=dcoc26YbTa8

Murray answered here http://www.aquaponics.net.au/forum/archive/index.php/t-999.html - once a month, not at all, not even once a month

It seems that there is no magic dosing that fit all systems.

I will go slowly with half a spoon every month. Should be safe!??

Roger

[TCLynx]

I'd say reduce the dosage until you see deficiency show up then go one increment up and see if it doesn't show up again.

Not everyone needs to use chelated iron and I wouldn't recommend spending the money on dosing with it all the time if you don't actually need it.

[Ryan Chatterson]

I would buy a test kit and stop guessing ;)

TCLynx said:

I'd say reduce the dosage until you see deficiency show up then go one increment up and see if it doesn't show up again.

Not everyone needs to use chelated iron and I wouldn't recommend spending the money on dosing with it all the time if you don't actually need it.

[Jon Parr]

What test do you use for iron, Ryan?

I read recently that iron is unique among the micro nutrients in that you cannot overdose. I looked but couldn't find the reference. If your tomatoes start rusting, cut back a bit.

[Jon Parr]

Ok. I should not have said "cannot" overdose. Please strike that statement from the record. I can say that iron overdose is rare, and generally not harmful to fish and plants. I found some accounts of 20-40 times the recommended dose with no ill effects, and likely the only result is a reduced availability of P. Also, iron deficiencies may be the result of high pH, not a shortage of iron. Maybe Nate will chime in, he knows his iron.

[Vlad Jovanovic]

Any references I've ever come across to iron toxicity in plants seemed to involve the DTPA chelate. It's now known that the Fe-DTPA is toxic to plants. (Usually described as a sort of bronze speckling of the leaves, all the journals I've read have been in black and white, including the photos, so unfortunately this verbal description is all I'd have to go on).

The iron chelate product I have is EDDHA chelate, and it comes with instructions for use. I generally cut back a bit on what the manufacturer suggests (as I tend to believe they over do things a bit). 

Also, some plants are more sensitive to iron deficiencies than others...Keep say, an oregano plant around in your system to use as your "canary in the mine"...or just follow the manufactures instructions for hydroponic concentrations (mg/L or a %).

[Roger Pilon]

Vlad,

I have the same type of iron i.e.EDDHSA. The instructinos in the box are about:

1. pulverization
2. soil application
3. drip irrigation

Question:

How do you safely convert any type of instructions to an Aquaponic Deep Water System?

Roger

[Vlad Jovanovic]

Well, I'm guessing that a 6%Fe EDDHA product is going to be similar to an EDDHSA product unless someone like Nate can tell us otherwise :)

Basically If we were to follow the manufactures instructions it would take 16.5 grams of product per 1,000 liters of water to achieve a 1mg/l (1ppm) solution. I would cut that in half (at least).  

As Jon stated, Iron deficiencies seem to almost always be pH related. In all likelyhood once your pH begins to fall (unless you have a buffering media or really hard top-up water) you may not need to dose preventatively,...only when you see a need....

I'd be wary of a general, blanket conversion...but if I had to give you one (for this type of product at least) it would be 1/10th of whatever the drip irrigation instructions were. (or 1/20th  - 1/15th since I'm cutting the dose in half anyways)...Again, doing this sort of 'conversion' thing may not be such a good idea, generally speaking...but see if it jives with what your instructions say. 

Oh yeah, is the yellowing on the newer leaves, or the older leaves?

[Roger Pilon]

Vlad,

My system is more than one year old, the PH now is 6.6 to 6.8 all the time...and I have no yellowing at all! From what I read, by the book should I say: no yellowing = no touch!

This said, I am searching a regular-maintenance-very-safe-no-question-ask-iron-dosing... IF SUCH a thing exists at all!

The drip irrigation intructions says: 

.1 to 1 gramme per liter. Safe side, very safe side should gives something like 1 gram / per 10 liters. An IBC tank of 1000 liters would give a dosing of 100 grams! Gee! This is a lot! (check my numbers...not very good at them)!

Roger

[Vlad Jovanovic]

1 gram per liter!!! Holy crap! Iron is like what?... the fourth most common element found in the Earth?.When the hell would someone ever need that much? Haha, a kg per 1000 liters no less...wow. Take their 'safe side' and divide by 10...

Hmm... as far as "...a regular-maintenance-very-safe-no-question-ask-iron-dosing..." ...your pretty much on your own there, as most micro-element dosing is advised on an "as needed" basis. But you've got a couple things going for you if you need to 'make one up' with the Fe...

1) Like Jon already said, it seems to be one of the rare elements that if you have an excess in solution, doesn't seem to mess with the uptake of other elements.

2) Plants store iron (mostly in the chloroplast) as a ferric phosphoprotein called phytoferritin, which will accumulate in plants without any apparent ill effects whatsoever. So unless you are using the toxic chelate DTPA, you probably don't have much to worry about, within reason. My 2cents...

Still though, if your not seeing Fe deficiency in your plants why bother? (I understand this is not the point, but)...

[Nate Storey]

As usual, Vlad beats me to the punch! Vlad's right- there's no easy way to translate CheFe instructions for regular application to AP, and most formulations are a bit high regularly. . . dosing is a tricky business because nothing is flow to waste and different crops have pretty varied rates of uptake.  Because it's expensive stuff, it is best to stay above the deficiency threshold but just slightly.  Plants can be hogs and uptake more iron than they really need, so you can save money by just meeting their needs plus some.

You do want to develop a dosing schedule- especially if you are engaged in commercial production.  My opinion is that if you notice deficiency symptoms you are already two weeks too late and the recovery period means you have a 3-4 week depression in production.  Bad news.  So, developing a dosing schedule can help.  Remember that if you are too high, plants will engage in "luxury consumption" and it is highly unlikely that you'll end up with a toxicity problem.  However you do want to just undershoot minimum requirements based on your crop, pH, algal components, etc.  At UVI the dosing was 2 mg/L every three weeks.  This is about the range most people will want to dose at to avoid problems.  Or, if you're really a cheapskate you could go to 100 percent foliar applications- when I'm being cheap this is what I do- you get better absorption and apply a lot less.  This is also a great way to beat deficiencies fast.