chelated iron Question

[james davis]

Hello all. Ive been spending the night looking through old posts about chelated iron but havnt really seen any brands that someone recommends. if there is a brand that you all use that i can order online can someone please let me know what it is and maybe a website. im getting that yellow leaf right now and would like to correct it. thanks for any help and have a nice day.

[Charles Sublette]

Thanks!!

Scott Roberts said:

Btw - I used the Hannah checker iron meter - and it detects my FeDTPA and FeEDDHA perfectly.

[Charles Sublette]

Very interesting, and, amazingly, I completely understood all of it.

What are some plants that act like a good "canary" to detect low iron before the cash crop exhibits signs of low iron?

I have heard Oregano is a good iron "canary" crop. What others are there?

Vlad Jovanovic said:

Howdy 

The 2-3ppm number comes from standard hydroponic research. Much of that research inevitably has it's roots in the 1950's work of Dr.'s Aron and Hoagland - The Water Culture Method for Growing Plants Without Soil, Circular 347, California Agricultural Experiment Station, University of California, Berkeley, CA. 

I believe in Hoagland's "Solution No1" he used iron ammonium citrate, while in "Solution No.2" an iron chelate was used (to the tune of 2ppm). Personally I think that even this number is excessive (especially for lettuce and greens), but I suppose folks are in luck in terms of irons unique trait of not behaving antagonistically towards any of the other cations (within reason), that and the fact that plants can engage in "luxury consumption" of iron without any apparent deleterious effects. So excessive iron dosing (again, within reason) probably only impacts the pocket book negatively...and not so much the plants. But we should still calculate out an amount...as opposed to "just tossing some in there and seeing if the plants green-up"

mg/L = Solute (mg)                                                     

             Solvent (L)

I shoot for 1-1.5 ppm or because I'm a cheapskate. I only can really know with any certainty how much iron is in any given system the very first time that I add it. After that we top up our water, plants uptake some iron etc...and I can no longer say for certain how much iron is actually present. I do however like to have some iron sensitive plants in a system that will start to exhibit signs of iron deficiency (inter-venal chlorosis in the youngest leaves) before my cash crop does. This lets me know it's probably time to add iron soon.

I could not with any confidence refer you to a test kit or brand, since I've not used them. I'm not even sure that a titration type test kit even exists which could reliably detect levels of Fe-DTPA or Fe-EDDHA...Hence the initial calculating/measuring, observing plants, then (hopefully somewhat intelligent) 'guesstimation'...of additional iron dosing.

Charles Sublette said:

Howdy Mr. Jovanovic. from a first time poster here and long time reader of your posts, love'm!

You stated that, "would never need more than 2-3ppm of Fe in the system"... I am curious how you determine this...

It appears all iron tests are not created equal and only some iron tests will test for EDDHA and some will only test for DTPA and some will only test for non-chelated iron. Also, from the research I have done, it appears that most common aquarium iron test kits only test for chelated EDTA and non-chelated iron such as ferrous sulfate.

Can you provide a hyperlink reference to a test kit that can test for Fe(DTPA) and / or Fe(EDDHA) ??

Hope you can provide some clarity here. Thanks for sharing your time. :)

Vlad Jovanovic said:

EDTA has also been proven to be toxic to plants as well...the jury is still out on DTPA plant toxicity (but it appears fine in even remotely sane quantities). 

I've learned to live with the slight red tint that Fe-EDDHA causes in my water. Fe-EDDHA is a bit pricier and all...but well worth it (to me at least).

You would never ever need more than 2-3ppm of Fe in your system regardless of what you were growing.

[Vlad Jovanovic]

Oregano is a good one, basil as well (if your not growing it for money of course), petunias tend to get chlorotic pretty easily too...

Charles Sublette said:

Very interesting, and, amazingly, I completely understood all of it.

What are some plants that act like a good "canary" to detect low iron before the cash crop exhibits signs of low iron?

I have heard Oregano is a good iron "canary" crop. What others are there?

Vlad Jovanovic said:

Howdy 

The 2-3ppm number comes from standard hydroponic research. Much of that research inevitably has it's roots in the 1950's work of Dr.'s Aron and Hoagland - The Water Culture Method for Growing Plants Without Soil, Circular 347, California Agricultural Experiment Station, University of California, Berkeley, CA. 

I believe in Hoagland's "Solution No1" he used iron ammonium citrate, while in "Solution No.2" an iron chelate was used (to the tune of 2ppm). Personally I think that even this number is excessive (especially for lettuce and greens), but I suppose folks are in luck in terms of irons unique trait of not behaving antagonistically towards any of the other cations (within reason), that and the fact that plants can engage in "luxury consumption" of iron without any apparent deleterious effects. So excessive iron dosing (again, within reason) probably only impacts the pocket book negatively...and not so much the plants. But we should still calculate out an amount...as opposed to "just tossing some in there and seeing if the plants green-up"

mg/L = Solute (mg)                                                     

             Solvent (L)

I shoot for 1-1.5 ppm or because I'm a cheapskate. I only can really know with any certainty how much iron is in any given system the very first time that I add it. After that we top up our water, plants uptake some iron etc...and I can no longer say for certain how much iron is actually present. I do however like to have some iron sensitive plants in a system that will start to exhibit signs of iron deficiency (inter-venal chlorosis in the youngest leaves) before my cash crop does. This lets me know it's probably time to add iron soon.

I could not with any confidence refer you to a test kit or brand, since I've not used them. I'm not even sure that a titration type test kit even exists which could reliably detect levels of Fe-DTPA or Fe-EDDHA...Hence the initial calculating/measuring, observing plants, then (hopefully somewhat intelligent) 'guesstimation'...of additional iron dosing.

Charles Sublette said:

Howdy Mr. Jovanovic. from a first time poster here and long time reader of your posts, love'm!

You stated that, "would never need more than 2-3ppm of Fe in the system"... I am curious how you determine this...

It appears all iron tests are not created equal and only some iron tests will test for EDDHA and some will only test for DTPA and some will only test for non-chelated iron. Also, from the research I have done, it appears that most common aquarium iron test kits only test for chelated EDTA and non-chelated iron such as ferrous sulfate.

Can you provide a hyperlink reference to a test kit that can test for Fe(DTPA) and / or Fe(EDDHA) ??

Hope you can provide some clarity here. Thanks for sharing your time. :)

Vlad Jovanovic said:

EDTA has also been proven to be toxic to plants as well...the jury is still out on DTPA plant toxicity (but it appears fine in even remotely sane quantities). 

I've learned to live with the slight red tint that Fe-EDDHA causes in my water. Fe-EDDHA is a bit pricier and all...but well worth it (to me at least).

You would never ever need more than 2-3ppm of Fe in your system regardless of what you were growing.

[Charles Sublette]

Thanks again!!

Out of curiosity...

Is there a book or material talking about the "canaries" of hydroponically or aquaponically growing vegetables?

This would be an incredibly interesting read. It would be nice additional reading to the various companion planting guide books that are out there.

Vlad Jovanovic said:

Oregano is a good one, basil as well (if your not growing it for money of course), petunias tend to get chlorotic pretty easily too...

[Vlad Jovanovic]

No, no books that I'm aware of. 

[Jim Dell]

I didn't know about the sunlight degredation of DTPA. Didn't find any mail order sites for EDDHA. Anybody have one?

[Steve R]

My questions is how on earth are people testing there water using EDDHA when it stains teh water so bad? That will bork most test kits and make it unreadable. I went and got some to try and I'm never going to use it again i cant check my nitrogen because both my api and hanna test wont read it will the tint or its very hard to. If some one has a solution I'm all ears but I cant see this as a long term viable solution. 

[Vlad Jovanovic]

I've been using Fe-EDDHA for many years, and have no problems at all reading any of my reagent test results.

As I know others who have as well, with no problems reading their results.

[Scott Roberts]

What do you mean your API test won't read?

[Steve R]

I got curious after your post on DTPA inhibiting germination so i setup my tiny system to try using the other iron before trying it in my bigger systems and i couldn't read the ph or the nitrogens because when i added the EDDHA the water was so red i couldn't make out what the color the water was from the test kit. Thats all.