Adding ferts in the dark

[adechazal]

As I was adding my daily regimen of ferts this morning at 6:30am I began to wonder if there are any opinions/facts out there regarding adding ferts a good 6 hours before the lights go on?

I add my daily KNO3, KH2PO4 and Flourish (Iron and Complete) at 6:30am but my lights don't come on until 12:00pm. Additionally my aquarium is in the wall so it doesn't get much light until the fixtures turn on. So if my plants aren't photosynthesizing until 6 hours after the ferts are added am I losing some of the effectiveness of the ferts? In particular I'm wondering about the iron and other micros. The macros I figure are fine.

I'm new to dosing iron so I know very little about how long it stays available to plants once in the aquarium.

BTW, enjoyed the article/interview with Tom.
Interview with Tom Barr « Acuario rosa

Aaron

[Philosophos]

I've dosed at off hours and never noticed a difference. EI keeps the water so saturated that your plants should be non-limiting 24x7. Iron is a bit of a concern though; Fe EDTA disassociates relatively quickly with pH above 7(not sure how long) and Fe gluconate loses its bond rapidly no matter what. DPTA should be good and stable.

-Philosophos

[Biollante]

Hi Aaron,

I am with Philosophos, I have dosed at all kinds of strange hours and not really seen any difference.

The only problem I see is that SeaChem Flourish Iron is complexed with gluconate. The claim is that complexing the iron with gluconate, “the iron is maintained in the ferrous (Fe2+) state for an extended period” and “plants are able to extract iron with little physiological energy.”

My understanding is that gluconate complexes without strong bonds and tends to break down rather quickly, apparently being a sugar it is rather tasty to various little bugs. While complexed EDTA and DPTA are chelated, meaning strong ‘formal’ bonds.

The argument for gluconate complexed iron is that it remains in its ferric state, which is easier for the plants to absorb.

I have not used Flourish Iron for a very long time so I really cannot say one way or another. I dose iron principally via CSM+B and on Tom Barr’s advice add about a third DPTA iron. I have not done this long enough to say for sure, but I believe I am seeing improvement particularly in my Echinodorus that I have been studying and propagating, for another study.

For the time being I would advise using a chelated iron and with your early dosing routine, I would suggest at least adding some DPTA iron.

My other concern is the level of Manganese (Mn), which on the chart I have (May not be correct) shows SeaChem Flourish as 0.0118% Manganese, I don’t know that is enough to allow the iron, however complexed to be effective.

http://www.barrreport.com/barr-repor...manganese.html and Iron gluconate are in my ever so humble plant opinion worth the read.

I will try some Flourish Iron and see if I can see any difference, it may not be up to laboratory standards, but I like to get a sense of these things.

Are there any observations you would be willing to share?

Biollante

[ordloh]

Free iron in water is not really free, it's actually complexed with 6 water molecules. Whether something stays complexed with whichever ligand you're interested in depends on how stable the complex is compared to iron complexed with water. (water isn't a bad ligand btw)
EDTA complexes reallys strongly to iron so it never loses iron to water. Gluconate complexes really strongly with iron 3+ and since iron 3+ is still usable by plants i don't think there's anything wrong with it. Also, i don't think gluconate decomposes easily while it's still attached to iron, since it wouldn't be the right shape to fit into a hydrolytic enzyme, but that's just a guess.
Chelation bonds aren't 'formal' in the sense that they are covalent bonds, they are all the same however, no matter what the ligand. the strength depends on factors like which atom donates the lone pair and stuff like that. Nitrogen usually is much happier to donate lone pairs then oxygen.

[adechazal]

Thanks very much for the feedback guys. Ordloh, I'm afraid your explanation of the chemistry goes beyond me but I'm sure Biollante and Philosophos are right there with you.

Biollante and Philosophos, I'll check out the links but it looks like you both are indicating caution with the iron. At the very least I can simply dose the Flourish iron when I get home and 5:00pm, the lights are on till 10:00pm so that's a good 5 hours that the plants can use the iron dosing.

I know about the chelated iron (aquariumfertilizer.com) but admittedly I don't know about EDTA/DPTA. If you have a quick summary or a link on these it would be great but I am certainly capable of doing a search as well.

Biollante, regarding observations, I'm in the early stages of taking "the next step" in my 180g by getting some R. Macrandra, P Stellata, R. Wallichi and T. Rosefolia. To date I have only ever done the Nitrate, Phosphate and flourish complete but some reading and observations suggest I'm missing some nutrients. So I've added some root tabs (aquariumfertilizer.com) and have started dosing iron as indicated.

When my Flourish runs out I'll try the CSM+B since you guys seem to endorse it and from previous posts it looks like it has all the iron I may need.

Thanks again for the feedback team.
Aaron

[Philosophos]

Sorry that was DTPA not DPTA. If you switch over to CSM+B, you'll find it uses EDTA as well; most sources do because it's cheap. You can push it along with some DTPA though. When aquariumfertilizer.com starts stocking Tom's micro mix, we'll finally have a DTPA based replacement for CSM+B. If that's on hold for a while, I may start rolling my own DTPA based micro depending on the costs.

-Philosophos

[Biollante]

Hi Aaron, ordloh,

I confess I am rather ‘regurgitating’ iron information; it has been decades since O-chem l my last serious chemistry class and I think that was only sophomore level.

I have taken a couple of agricultural classes at a community college and though I (as I often do) may have confused some of the information. I am reasonable sure that the information regarding the difference between the EDTA and DPTA is correct.

For anyone interested in a simply explanation DTPA, EDTA, NTA ACID (CHELATING AGENTS).

I may have incorrectly used the term ‘formal’, I was not thinking in terms of covalent bonds. I also may have been incorrect in (by inference) equating gluconate with H2O or NH3, monodentate ligands that are easily broken. Glucanate, (I thought) may be closer to polydentate ligands as chlorophyll with magnesium or heme with iron.

My (weak) understanding is that the ‘complexing’ is stronger the more ‘rings’ it has.

Sorry for any misunderstanding I may have caused, I am out of my depth here.

My actual interest is in how to encourage these noxious weeds I grow, in a manner that can be easily replicated.

Biollante

[ordloh]

Polydentates are usually stronger ligands then monodentates because of entropy, freeing up 6 water molecules to float around increases the entropy of the system. The actual bonding between the metal and the ligand is the same.
I'm not sure what you mean about the rings. EDTA and gluconate don't have rings. I don't think the ring system of chlorophyll and heme has anything to do with bonding with the metal ions.

[Biollante]

Polydentates are usually stronger ligands then monodentates because of entropy, freeing up 6 water molecules to float around increases the entropy of the system. The actual bonding between the metal and the ligand is the same.
I'm not sure what you mean about the rings. EDTA and gluconate don't have rings. I don't think the ring system of chlorophyll and heme has anything to do with bonding with the metal ions.

Hi ordloh,

I think the "Polydentates are usually stronger ligands then monodentates because of entropy, freeing up 6 water molecules to float around increases the entropy of the system." part is where I was going with this, indeed I may have the entire thing wrong.

Some of the material I have suggests an equivalency between chlorophyll with magnesium and heme with iron with certain chelating agents. I muddled that, once again I apologize.

Apparently I have been flim-flamed into believing there is a difference in using water, glucanates, EDTA and DPTA with iron to make the iron more readily availible to plants, when no differences exists.

Biollante

[Biollante]

Hi All,

Didn't mean to be snotty.

I guess what I so ineptly tried to say is along the lines of SpringerLink - Journal Article and Re: iron gluconate.
Re: EDTA
Re: iron gluconate
Re: iron gluconate

With I suppose a SeaChem kind of reply Re: iron gluconate

I had, apparently incorrectly, according to ordloh, considered 'free iron' in water not to be particularly usable by plants, my meager understanding was that the availability of iron complexed by water was something like a decimal point followed by 25 zeros kind of value.

Having not seriously concidered the possibility that I could simply add iron filings to the water I (mistakenly?) used SeaChem Iron a long time ago, left it principally due to PMDD, which meant CSM+B containing EDTA Iron. Though over the years I occasionally dosed SeaChem Iron.

Never really seriously considered the gluconate issue until recently.

I had understood ETDA iron to be stable through pH 10 or so. Lately here I have understood EDTA not to be as stable as I had thought. I began adding DPTA iron to my CSM+B.

Purely subjective on my part, I think I have noticed improved growth, in particular Echinodorus spp., I have been growing in quantity, of course it could be my imagination. .

I had always thought I was dosing pretty high iron.

Honestly just trying to answer Aaron's as best I could, my fault for getting into an area I am obviously not qualified.

Biollante