John q
Member
Nope edta is good at pH 7 and below.
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Plant deficiencies and the Fe Experiment
- Thread starter KirstyF
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Mattant1984
Member
John q
Member
Probably the fe 3 turns into fe 2 which is still useful to the plants.
For the interest of this thread we watch and learn 👀
KirstyF
Member
I would recommend dosing 3xpw as a minimum. As it is potentially prone to precipitation, it is best to spread it out. In your case, opposite days to your current dosing would be good. The Fe EDTA you have in the Solufeed will also potentially offer some trickle feed.
As to downsides. There has been some commentary on here regarding certain types of algae and Fe, but I would feel fairly confident in saying that deficient plants are more likely to cause an issue and the levels we are talking about fall well within the ‘norm’ so I don’t believe you have much to be concerned about.
Mattant1984
Member
KirstyF
Member
I am more than happy to stand corrected, and my on-line research did turn up a bit of variation, but I’ve not really found anything quoting EDTA over 6.5ph and many as low as 6ph
Below is quoted from an article by the University of Michegan, but typically, I can’t re-find the article that I got my original quoted numbers from. 😂
There are four commonly used chelates: citric acid, EDTA (Ethylenediaminetetraacetic acid), DTPA (Diethylenetriaminepentaacetic acid) and EDDHA (Ethylenediamine di(o-hydroxyphenylacetic acid)). According to data presented by Norvel (Equilibria of Metal Chelates in Soil Solution, in Micronutrients in Agriculture, Soil Science of America, 1972) citric acid does not strongly bond with iron and is not effective at pHs above 6.0. EDTA strongly holds iron in solution up to pH 6.0, but by pH 6.5, almost one-half the iron is precipitated, and by pH 7.0, almost none of the iron is available to plants.DTPA is an excellent iron source up to media pH 7.0; however, 60 percent of the iron is precipitated and unavailable by pH 8.0. EDDHA is the strongest chelate of any of the commonly used materials and maintains iron availability to plants past pH 9.0. These chelates are ranked in the same order of effectiveness by Drs. Bill Argo and Paul Fisher in Understanding pH Management, Meister Publications.
John q
Member
KirstyF
Member
Trying to thrash out an explanation in layman’s terms here but happy for our scientific folks to do a better job. 😊
Fe, as a rule becomes insoluble in higher PH water, making it unavailable for uptake by plants (or at least less available - some plants have adaptions)
Chelates work by grabbing hold of the iron so that it doesn’t precipitate and ‘transporting’ it to plants for use.
The ‘stronger’ the chelate, the higher Ph at which it will remain effective, the more iron remains available.
Hence the wisdom behind using particular chelates (EDTA, DTPA, EDDHA etc) dependant on Ph.
Gluconate is not Chelated. It exists already in the form of Fe2, which is readily and preferably taken up by plants.
The theory behind gluconate being effective is that, in this form, plants have immediate and easy access to the iron. The downside is that it is likely to precipitate (become insoluble/unavailable) pretty quickly (particularly in high Ph water) as it is not ‘protected’ by a Chelate.
I am not aware of any specific negative to having precipitate in the water (though too much can cause clouding) but again, I’ll throw that out to folks who may know better.
My interest in the responses from use of gluconate in high Ph water is that it effectively contradicts the conventional wisdom of using stronger Chelates in these situations, and the testing is to establish whether it’s effectiveness can be reasonably evidenced.
Undoubtedly, it will precipitate, and certainly more quickly than a chelated source, but will it do a ‘better job’ for the plants whilst it’s there!
You are absolutely right here John, and I suspect the answer is not a huge amount. The questions that I ask myself are, what level will work effectively and what is the optimal delivery system.
But there is certainly logic behind the argument that all Fe type’s ultimately have the capability to provide adequate Fe to plants if enough is used.
Mattant1984
Member
Soilwork
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- 22 Nov 2015
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Interesting thread thanks. I suppose how quickly iron precipitates will also depend on how many other ions there are in solution to form insoluble compounds with. In hard water, this will probably occur much faster than in softer waters with less ions.
Whilst I appreciate that this is an experimental thread for learning purposes. It highlights the challenges we face when dosing iron directly in to the water column and suspect that a more successful approach to iron would be substrate addition and allowing the substrate to mature enough to become available to plants. The plants can take exactly what it requires in this way.
Regards CJ
Whilst I appreciate that this is an experimental thread for learning purposes. It highlights the challenges we face when dosing iron directly in to the water column and suspect that a more successful approach to iron would be substrate addition and allowing the substrate to mature enough to become available to plants. The plants can take exactly what it requires in this way.
Regards CJ
Hi all,
cheers Darrel
That was one of the reasons for using a floating plant for the <"Duckweed Index">, because they don't have access to the substrate they show you the nutrient status of the water column.
I think that is true <"Another microbial paper, this time looking at aquaponics and iron availability">and I'd guess <"that iron deficiencies are much less likely"> in plants rooted in a relatively undisturbed substrate, where zones of <"fluctuating REDOX"> surround the plant root.
cheers Darrel
_Maq_
Member
Iron citrate is not that simple issue, even for pros. The Fe-citrate chemistry seems to be much more complicated, a plenty of bonds occur. But practically, yes, Fe-citrate can be used as a rather weekly chelated iron.
Iron sulphate FeSO4 should not be used. Fe2+ readily oxidize to Fe3+ while creating ferric (oxi)hydroxides like FeOOH or Fe(OH)3 or so, again, there are about 15 forms, all of them poorly soluble and unsuitable as an readily available iron.
Ferric chloride FeCl3 works fine for me.
In my opinion, there are two main scavengers of iron in our tanks. The first is bicarbonates. These hinder uptake of iron by forming poorly soluble FeCO3, and secondly, inside the plant, bicarbonates deactivate some enzymes necessary for successful utilization of iron. The second problem is phosphates. If there is elevated concentration of either iron or phosphates in the water column, these react and form poorly soluble FePO4. Iron phosphate in the sediment may be reduced and dissolved (with active participation of microbes), and as such it may serve as a long-term reserve of both nutrients. However, before the tiny invisible particles settle in the sediment, they are often trapped in the filter (adsorbing to organic matter). There, in strongly oxidized environment, they seldom dissolve and both nutrients are lost.
I can live without chelated iron (using FeCl3) because following conditions are fulfilled:
1) I do not inject CO2, and because of that, to keep my water acidic, bicarbonate content [alkalinity] must be very low. (On the contrary, those who inject CO2 make the water acidic thanks to CO2, but their alkalinity may be high, i.e. well above 1°dKH.)
2) I keep phosphates low (0.1 mg/L or so) and take care not to dose phosphate simultaneously with iron (and other transition metals). Also, I do not use filters.
Hi all,
<"Iron availability for floating plants"> might be more of an issue.
cheers Darrel
Same for me. In <"oxygenated, alkaline, water"> the ferric iron ions (Fe+++) are mopped up by the bicarbonate (HCO3-), hydroxide (OH-) and dissolved oxygen (O2) to form <"insoluble ferric carbonate, hydroxides and oxides">. When you have phosphate (PO4---) ions <"present as well">? That is a double whammy. The <"water industry"> actually uses both these techniques to remove ions from solution.
I'd guess that for most of us some form of complexed iron will be required. I'm fine using FeEDTA, mainly because I use rainwater in the tanks, but other members will need a chelate <"more suitable for harder water">. I haven't tried iron (ferric) citrate (C6H5FeO7), ferric chloride (FeCl3) <"or iron (ferrous) gluconate">, but they may also be all right for me.
One reason I think it might be able to use non-complexed iron salts is that I don't tend to <"disturb my substrate very often">, so I'm guessing that<"natural processes"> (in the zone of <"fluctuating REDOX"> values in the rhizosphere) will make <"iron plant available">.
<"Iron availability for floating plants"> might be more of an issue.
cheers Darrel
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_Maq_
Member
I strongly believe this actually happens.
I've been experimenting with fertilizing by Chlorella and Spirulina powders. I reasoned that each and every single cell of these algae (cyanobacteria) must contain a complete set of enzymes common to photosynthesizing organisms, incl. vascular plants. In other words, it must be an excellent source of organically bonded transition metals. My results showed two things:
1) It worked. I didn't have to dose micronutrients for many weeks, even months. Obviously, microbes (with possible contribution of plants' roots) quickly decomposed those enzymes and other species to mineral nutrients available to plants. This presumably happened mainly within the substrate - in low redox zones.
2) Whenever I dosed any of these "organic fertilizers", algae temporarily proliferated. I take it for an argument supporting theory that not nutrients per se but organic pollution is the main cause of algae.
KirstyF
Member
Hi guys
And so the experiment continues:
I left you with these images following 3 weeks of DTPA at 0.3ppm (split into 3 doses per week) some signs of chlorosis visible.
The next test was the same ppm of Fe gluconate, also split into 3 doses.
Possibly some small improvement here over DTPA only but certainly not to a level I’d be happy with and not as good as the previous results with a DTPA/gluconate mix (albeit at a slightly higher ppm)
So 0.3ppm of DTPA is not a success and 0.3ppm of gluconate may be slightly better but is also not solving the issue.
This begs the question as to why those previous results were better:
1 - The slightly higher total ppm (could 0.1ppm make that much difference 🤔)
2 - The mix of gluconate/DTPA giving a benefit of some longer availability and some easy access.
3 - The impact of the subsequent increase in Po4 reducing efficacy (causing additional precipitation)
So, working through that, I think my next route will be to match the total ppm of that successful dosing, but with gluconate only to see how that works (increase by 0.1ppm pw) and then re-try the DTPA/gluconate mix to get a comparison.
If I can’t match the previous results then I may drop the Po4 back to previous levels, to see what difference that may be making.
In the interim I did a quick switch to 0.3ppm Fe only still, but split into 6 doses (0.05ppm per day) to see what more frequent dosing with the same weekly ppm would offer. The previous successful DTPA/gluconate mix was initially dosed over 6 days. 0.05ppm of DTPA per dose x 3 and around 0.08ppm of gluconate x 3 (Total 4ppm) The total daily dose is therefore not massively different, but the results certainly are.
I think we can safely say…not a raving success. 😏
The testing takes some time and there are a good few variables to consider but appreciate everybody’s patience in tagging along!
And so the experiment continues:
I left you with these images following 3 weeks of DTPA at 0.3ppm (split into 3 doses per week) some signs of chlorosis visible.
The next test was the same ppm of Fe gluconate, also split into 3 doses.
Possibly some small improvement here over DTPA only but certainly not to a level I’d be happy with and not as good as the previous results with a DTPA/gluconate mix (albeit at a slightly higher ppm)
So 0.3ppm of DTPA is not a success and 0.3ppm of gluconate may be slightly better but is also not solving the issue.
This begs the question as to why those previous results were better:
1 - The slightly higher total ppm (could 0.1ppm make that much difference 🤔)
2 - The mix of gluconate/DTPA giving a benefit of some longer availability and some easy access.
3 - The impact of the subsequent increase in Po4 reducing efficacy (causing additional precipitation)
So, working through that, I think my next route will be to match the total ppm of that successful dosing, but with gluconate only to see how that works (increase by 0.1ppm pw) and then re-try the DTPA/gluconate mix to get a comparison.
If I can’t match the previous results then I may drop the Po4 back to previous levels, to see what difference that may be making.
In the interim I did a quick switch to 0.3ppm Fe only still, but split into 6 doses (0.05ppm per day) to see what more frequent dosing with the same weekly ppm would offer. The previous successful DTPA/gluconate mix was initially dosed over 6 days. 0.05ppm of DTPA per dose x 3 and around 0.08ppm of gluconate x 3 (Total 4ppm) The total daily dose is therefore not massively different, but the results certainly are.
I think we can safely say…not a raving success. 😏
The testing takes some time and there are a good few variables to consider but appreciate everybody’s patience in tagging along!
Maq, you may find this product interesting. at some point i wanted to clone it using Chlorella and other needed acids but it was way too complicated and complex.
Kirsty, 0.3 ppm Fe Gluconate might be bit low considering all other factors in your tank. you can aim for up to 1 ppm Fe Gluconate and see if you see improvement. only if you further want to continue with the only Fe gluconate responses.
jaisol
Member
KirstyF
Member
You may be absolutely right and there is certainly space for testing higher levels of gluconate versus higher levels of chelated Fe but, for now, I’m aiming for comparative results in order to establish whether DTPA or gluconate or a combo will give different, (better or worse) results at similar ppm’s and/or dosing frequencies.
Knowing that a combo mix at 0.4ppm, (whilst dosing 2ppm of Po4) did a pretty good job, I’m trying to keep my mixes below that threshold for the moment and to figure out which works best.
If I can duplicate or improve on those results either with gluconate only (at 0.4ppm) or by re-using that combo again, but not increasing ppm’s any further, this starts to tell me what is offering the optimum response.
If, at that level, I cannot achieve comparable results, now that I’m dosing 6ppm of Po4, but succeed in doing so, if I go back to 2ppm of Po4, this evidences the negative reaction or interaction with higher Po4 dosing (potentially).
I could then slowly increase Po4 to see if deficiency pops up again and then see what level of Fe dosing is required to mitigate it. We shall wait and see!!
Ultimately the idea is to confirm whether using gluconate is of particular benefit, and, if so, as a gluconate only solution or as part of a combination mix….in addition to the total ppm levels required (possibly relative to Po4)
I’m aware that Po4 is not necessarily the only thing that can interfere of course, it’s just the primary other thing that has changed in my tank. I will not know what impact that has had until I repeat the combo test under the higher Po4 levels of course! 😊
Gluconate only at 0.4ppm starting this week so we’ll see how that goes.
And you may be absolutely right too! 😊
All of the testing that I am doing is based on column dosing and the subject plants are planted in sand which potentially emphasises that even more (not such alot of CEC going on here)
Whilst I’m a believer that most plants grow just fine in sand, it may be that, the harder your water is, the less true this becomes. As plants become more challenged by their environment, the value of having good nutrient availability at both root and leaf may increase so putting them in hard water and in inert substrate presents a greater challenge. Having said this, I still had issues with plants that were planted in aquasoil and in a tank that was probably 10months old at that stage. Having never used root tabs, I can’t, however, offer a direct comparison to supplemented substrate.
I have a couple of Blyxa ‘stands’ in the tank though so, once I’ve run through these column tests, I would be more than happy to do a comparison of one with root tab and one without. 😊
Mr.Shenanagins
Member
Any new updates? I’ve been following along because I have a feeling this was an issue in my tank. I have a low gH (2-3) and higher kH (~9) coming from my tap which I think may have been causing issues with iron uptake.
