EDTA vs DTPA Fe

[Mitelog]

Hi,

I’m close to the end of my micro solution ( i made a little batch) and my fe DTPA stock is empty.

I have maybe 300 gr of Fe EDTA (13%) in stock and my question is can i use it instead of the DTPA for my micro mix ( that consist of sulfate salt, like Burr) ??

My water is between 1 and 2 DKH and ph is around 6,33 when CO2 is on.

Thank’s

 

[Unexpected]

I ran in to this same problem and had EDTA available. Works just fine so go ahead and use it. If I recall correctly, 6.8 and above is the dropoff point.

 

[Mitelog]

Great !

You use it at the same level as DTPA ?

 

[Unexpected]

Great !

You use it at the same level as DTPA ?

Yes.

 

[ElleDee]

What is you pH your CO2 is off though?

I am giving a presentation for my local club in a couple months and did some digging on iron chelates. There is a recent-ish review that has this to say about EDTA stability and pH:

Iron ethylendiaminetetraacetic acid (EDTA): Although Fe-EDTA has been the most commonly used chelating agent, it is a slightly toxic form of chelated iron to plants and may thus present challenges in aquaponic systems (Rakocy et al., 2006; Vadas et al., 2007; Ghasemi et al., 2014). It has the ability to form complexes with free metal cations (such as Zn, Cu, and Mn), thereby decreasing their availability for plant uptake (Albano and Miller, 2001; Vadas et al., 2007). Furthermore, EDTA is sensitive to photodegradation with a half-life under severe sunlight conditions of 11 min at pH 7.0 upon illumination in a Xenotest 1200 apparatus derived from the annual maximum of a solar spectrum (Svenson et al., 1989; Albano and Miller, 2001). It is stable in a pH range between pH 4.0–6.3 (Albano and Miller, 2001). Considering the requirements of fish and microbes in aquaponics, Fe-EDTA is effective in the narrow pH range of 6.2–6.3. Using this chelate necessitates regular replenishment (Rakocy et al., 2006).

If you are adding micros daily when your CO2 is on you can probably get away with it, but if you are front loading I would be worried about the stability of the chelate during higher pH periods. I don't know how quickly it degrades in higher pH without light, but it could be a concern.

There may be iron in your substrate that plant roots can make available, depending on what it is. That iron pool is obviously not an option for plants that are not rooted, and some species are better at freeing up iron than others.

 

[Mitelog]

The ph just before the CO2 is on is at 7,05 to 7,10, degazed water is at 7,5.

In the early 2000, i used DuplaPlant and duplaplant 24 and those were based on fe EDTA, and i have had great results with this combo in my hard tap water (if memory is right ph was at 7,8 and kh was 9 dkh from the tap)