# Iron, chelated or sulphate?



## Arte Et Labore 1875 (23 Mar 2010)

Hi, is dosing extra iron on top of tpn and tpn+ necessary?

If so what is the difference between chelated iron (this has different PH numbers next to it for some reason?) and iron sulphate and which should i get?

Finally how much and how often should i dose?

120L
30ppm, pressurised, stable.
2 x t5 tubes

here is the website i was looking at:

http://www.gardendirect.co.uk/fertilise ... -5_147_204

thanks.


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## ceg4048 (23 Mar 2010)

Hi,
   TPN+ contains exactly the same ingredients as TPN, therefore it is completely redundant to use both. 
The "+" in TPN+ means that they have taken TPN and added Nitrogen, Phosphorous and Potassium (NPK). 

TPN has only micronutrients such as Iron, Magnesium, and so forth therefore adding more iron is also completely redundant. If you plants have an iron deficiency by using TPN then it is likely they have a deficiency in the other micronutrients as well, therefore, simply add more TPN.

Chelation is a process by which, typically Iron (but any other metal/mineral as well) is held in a form that keeps it sequestered until it can be assimilated by the plant. In some cases chelation is used to bind toxic metal products in an innocuous form until it can be eliminated from the system. Normally, an amino acid is mixed with the product of interest. The most well known chelating agent is Ethylene Diamine Tetra-acetic Acid (EDTA) so you might see this included in the list of ingredients on chelated Iron products. In non-chelated iron products such as the one you listed the Iron will be in a form more difficult for the plant to assimilate.

Garden Direct sells dry powders (including chelated Iron powder) at the cheapest price except for possibly e-bay, but either you should stick with TPN+ or you should mix your own NPK and micronutrient. It's pointless to buy both unless there is a specific need or purpose.

If your plants are not suffering any form of nutrient deficiency, why spend more money than you need?

Cheers,


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## Arte Et Labore 1875 (25 Mar 2010)

Great reply Ceg, thankyou.

So would it be beneficial in any way to create my own macro solution and continue to use standard tpn for my trace elements?


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## ceg4048 (26 Mar 2010)

Yes, absolutely I would suggest that you buy the NPK from Garden Direct at a unit cost of at least 100X cheaper than any commercial NPK you can buy (you'll just not have the fancy bottle, but so what?). 

Even so, you can mix your own JamesC's homebrew TPN+ recipe  and save megabucks in the process.

Cheers,


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## Arte Et Labore 1875 (26 Mar 2010)

I'll give it a go, james' guide includes iron and i'm quite happy dosing trace elements via TPN for that as i have a few litres of the stuff, unfortunately his recipe page for just macro's isn't working. I did find this on the internet for a 2000ml solution although he said its no biggie if you miss out the KS04 and the addition of hydrochloric Acid would clear any cloudiness. Are these 2 statements correct and would this solution work?   :

[copied and pasted]
61 g (11 teaspoons) Potassium nitrate (KNO3) - "Stump remover" (Source of "N", and "K") 
5.2 g (1 teaspoons) Potassium monophosphate (KP04) - "Fleet enema" (Source of "K" and "P") 
10.8 g (2 teaspoons) Magnesium sulphate - (MgSO4) - "Epsom salts" (Source of "Mg") 
1.8 g (0.3 or 1/3 teaspoon) Potassium sulphate (KSO4) - (Source of "K")


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## ceg4048 (26 Mar 2010)

I'll pull some data verbatim from his DIY "all-in-one" recipe page for you - remember that this is not the TPN+ reproduction because TPN+ uses Ammonium Nitrate in lieu of Potassium Nitrate:

QUOTE
=====
*How do I make it?*

It depends on how you dose to what quantities of each chemical you add. The important thing to remember is that you must get the right amounts of the macro's and trace's mixed up especially if you currently dose different amounts of the solutions. Also it might be an idea not to make the solution too concentrated. What I do to make life easy is to adjust the levels so that one full fill (25ml) of my old Tropica bottle is enough to dose the whole of my 200 litre tank in one go.

As an example here is a formulation that is based on my PMDD+PO4 formula:

10g  Potassium Nitrate
1.2g  Potassium Phosphate (monobasic)
4.0g  Potassium Sulphate
8.0g  Magnesium Sulphate Heptahydrate (Epsom Salts)
0.5g  E300 Ascorbic Acid
0.2g  E202 Potassium Sorbate
6g  EDTA Chelated Trace Elements Mix
500ml distilled water

If you wish to change the amounts of ingredients then as long as the levels aren't changed too much you can leave the amounts of Ascorbic Acid and Potassium Sorbate the same.

Dosing is 5ml per 40 litres
Each 5ml dose adds:
1.5 ppm Nitrate
0.2 ppm Phosphate
1.5 ppm Potassium
0.2 ppm Magnesium

UNQUOTE
======

The recipe you quoted is a basic EI macro only (NPK) which does not include micronutrients. When dosing EI levels of nutrients as opposed to TPN+ type levels then it is true that you do not really need K2SO4 as you get enough K+ from the KNO3 + KH2PO4. Cloudines, first of all is not that big of an issues and secondly is not caused by macro mix per-se, but can be an issue dosing some micro powders in hard water. Hydrochloric Acid (Muriatic Acid) is typically used to etch hard surfaces like concrete or grout, so imagine what it does to your fish or to your face. It's not something I would recommend. 

If you want to learn more about the fundamentals of EI dosing check out the Tutorial EI DOSING USING DRY SALTS although there is certainly plenty of value in starting out with James' all-in-one listed above.

Cheers,


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## spider72 (27 Mar 2010)

ceg4048 said:
			
		

> Chelation is a process by which, typically Iron (but any other metal/mineral as well) is held in a form that keeps it sequestered until it can be assimilated by the plant.



I thought, that iron is not available directly for plants from the chelated complex, as chelators are usually organic compounds, and chelator need to be break down by light, bacteria etc. prior to plant uptake by leaves. I know that roots can reduce Fe3+ to Fe2+ prior to uptake or sometime will take Fe3+. I know that plant use internal chelators for iron transport from roots to leaves for example, but thought that for leaves uptake iron need to be in inorganic form of Fe2+ state.
Am I wrong, or just misinterpreted your explanation?

Edit: Ok, found it in Barr Report, and it looks like iron can be taken directly from chelator on the leaves surface. Iron is taken, chelator left behind.


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## ceg4048 (27 Mar 2010)

Hi Maciek,
             It was just a general statement regarding the concept of chelation. In our case, Iron can combine with other elements to form precipitates or otherwise non-bioavailable compounds. But I'm not sure the chelation has to necessarily be broken prior to uptake (as opposed to transport). One of the knocks on UV lights, for example, is that is breaks the chelate bond too early, allowing the Fe to combine with other ions such as PO4 to form Ferric Phosphate, which is almost completely insoluble.
Also, I don't think that plants "only" can use Fe2+. There are plenty of electron movement via reversible Redox reactions in both photosynthesis and respiration where Iron cycles between Fe2+ and Fe3+. There are a few strategies for root uptake of Fe:

Reduction Based Strategy (Protonation) - this does occur in the area of the rhizome where the plant pumps out protons (H+) into the surrounding area. Increased proton density means a drop in pH (by definition.) By acidifying the area, Fe3+ becomes more soluble. A "1 unit drop" in pH, say from pH 7 to pH 6 causes a 1000X increase in Fe3+ solubility. The proton (H+) pumping mechanism is no doubt controlled by some kind of ATP synthase type of enzyme.

Fe3+ Chelate Reduction Strategy - It just so happens that Fe2+ is very much more soluble than Fe3+. Some plants are efficient at producing enzymes referred to as a "ferric-chelate reductase". So their strategy would be to combine proteins that have a high Fe3+ affinity with this chelate enzyme. This is a heck of a lot more efficient than the proton pumping strategy, and that's why grasses, corn, wheat, rice and so forth tend to use this strategy.

So the issue about Fe2+ vs Fe3+ has less to do with "can a plant use one vs another", but has more to do with "Due to solubility issues Fe2+ is a lot more available than Fe3+ so why not optimize uptake mechanisms to account for this?".

Here's the long and short about Fe; While it is a vital element, at the same time it is extremely toxic. The reason that makes it vital is the very same reason that makes it toxic. Think about the Bohr model of the atom, where the atom is like a solar system composed of a central core (the Sun) and orbiting planets (electrons). Iron is a solar system with its outer planets far away and only loosely bound in its orbit. These outermost 2 or 3 planets can actually leave the solar system or return at will, based on the other forces surrounding the Fe solar system.

Energy production and consumption is dependent on the movement of planets across solar systems, i.e movement of electrons across the boundaries of atoms. So to get maximum efficiency out of a chemical process it's necessary sometimes to have an easy way to move these electrons. All metals such as iron give up their electrons easily while other substances, like PO4 readily accept electrons. The trick in biochemistry is to precisely control when this happens. If a free Fe2+ ion passes by a plant DNA molecule, for example, the "+2" means that is will pull 2 electrons from that nearby DNA - changing the very nature of that DNA. 99.999% of the time it will be a bad change. So the plant needs a way to stabilize the Fe2+ until it requires that "electron pull" capability, such as in photosynthesis where "electron pull" is an absolute must. That's why plants have developed sophisticated internal chelation and transport schemes. Then, just prior to cell entry the Fe will be unbound from the chelate or complex. The chelates do not enter the cell.

Iron therefore is a tightly controlled element within plants. They don't need a whole lot of it, so when there is excess they'll lower the uptake and when they need more they'll pull it using leaf uptake or either of the root uptake mechanisms discussed above. I don't really worry too much about whether Fe2+ (in chelate) or Fe3+ (in sulphate) is available as long as either is available and not locked up forever in some insoluble compound.

Cheers,


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## spider72 (27 Mar 2010)

Hi Clive

Yes I have found info about Fe uptake and forms available to plants in Barr Report. Most plants nutrients are usable in inorganic form, so I have extended this automaticaly to Fe.
I have basic knowlage about electron trasfer as I had chemistry course (but not biochemistry) in high school, but you explanation with solar system example is making things easy to visualize, you should be a teacher    , and on this forum you certainly are  .
It looks like "proton pump" mechanizm is used by plants more often, than I thought. I know some plants use this method to free CO2 from carbonates. They will pump protons to bottom side of leaves to bring pH of water down close to leaf surface and carbonate will give up CO2.

Thanks for your time and lesson  .

But, 


> ..or Fe3+ (in sulphate)..


Fe in sulfate (FeSO4) should be in Fe2+ state, not Fe3+, you probably mean phosphate, or may be I should go back to school  .


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## ceg4048 (27 Mar 2010)

Hi mate, 
            Glad you find the analogy useful. Still a lot of life left in the Bohr planetary model. No one is more more bummed out than me that it was obsoleted and replaced by the incomprehensible quantum model. Oh well, the truth is more important than convenience -  at least, that's what Richard Feynman used to say (he was one of the top eggheads in the development of Quantum Physics.)

In any case, you're right in that the stuff sold as fertilizer is typically Iron(II) Sulphate FeSO4 (the green powder) but one can also have Iron (III) Sulphate. The ferric form is Fe2(SO4)3, a yellowish powder. Tetra FloraPride reportedly uses the ferric form. Check out Aqua Botanic - Plant Fertilizer Comparisons by Ingredients

Proton pumping fascinates me to no end. You're absolutely right about CO2 sequestering in high KH water via this pumping mechanism. I think Vallis uses this method and that may be why it does so well in African Chiclid tanks. The most famous use of proton pumping from our perspective of course is in the chloroplast where the plant uses the high proton gradient induced by the pump to drive ATP synthesis from ADP. It doesn't stop there. ATP production is also performed in every cell. The centre of every cell is where energy production occurs. This area is called the Mitochondria. ATP production happens here and proton pumping is used here just as effectively as in the chloroplast. Amazing stuff!  

Cheers,


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## Lisa_Perry75 (27 Mar 2010)

ATPase is what kick started my fascination with biochemistry/structural biology. Had to do a presentation on it and was blown away.


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