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Chelated Iron Dosing - Is there such a thing as a preventive dosing?

Is there a specific dosing of chelated iron that one can add to his system as a preventive dosing!

I know that when you see yellow leaf appearing it is normally time to add chelated iron. This said, I would like to know if there a specific dose that you can add weekly, monthly to keep your AP system in a happy iron level?

Not too much, not too high... just enough to avoid a lack of iron!

Some specs:

  1. I have a chelated iron EDDHSA 6% (Fe)
  2. Using a IBC tote with 1000 liters water +/-
  3. 2 x (4x8x12inches) Deep Floating Raft 
  4. PH is at 6.8 / 7 range

Any advices would be welcome!

Roger Pilon

Costa Rica

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Crap...sorry TC. I just now saw that you asked "how often", not "how"...oops.

They took samples every 21 days...Sorry...

TCLynx said:

Heck, I've read how different types of fish will provide you with different numbers in the waste.

All interesting.  Did they say how often they were scooping the sludge out?

Vlad,

I'm not familiar with the nutrient ratios used in hydroponic solutions. Thanks for pointing out the similarities. 

Vlad Jovanovic said:

Thank you Terri explaining that to us. It makes so much more sense now. That's a pretty darn good fertilizer At fist glance it looks like those Ca-Mg-Fe-Zn-Cu ratios jive with some different generally accepted hydro formulas. (yeah, I know that's kind of a generic thing to say, since there are a lot of them, but Barry (1996), Jones (1997), Yuste/Constincar (1999) are a few that I'm at least a little familiar with)...Good stuff. Thanks Terri.

Hi Nate,

I see you mention foliar application. Do you use a wetting agent? Do you use a nitrogen base as well? Do you use a mister?I am trying to fine tune my foliar spraying. Those hand sprayers are really not suitable, a lens, any lens, even one made by water magnifies light and causes leaf burn.I know its easier to maintain an average saturation between 1 ppm and 2 ppm       ( sufficient for most plants) by dosing in sys. water, but as you say very expensive when dealing with large water volumes. Do you notice a difference in plant growth between these two types of applications? Sorry for all the questions nate!

Hi Harold, 

We are including iron in our solution almost exclusively now as we are on a dosing schedule.  It's more important for us to maintain above-threshold iron levels than to fall below and slow plant growth.  If you see deficiency systems you're 2 weeks too late.  When we have applied chelated iron, we only spray at night- you should never spray any substance during the day or you run the risk of burning your plants.  You may choose to apply other compounds at the same time.  Misters will work best, but hand sprayers will suffice so long as you have it dialed back to apply lower volumes in smaller droplets.  The issue here is that you have to essentially spray until you have a response- it is very difficult to calculate how much iron you're actually applying to each plant- so it is more of a responsive measure than I like.

Anymore, we just apply it to solution.  As we grow larger, we spray regularly, but typically just for insect control.  It simplifies our life to just dose our solution.  We are over-dosing to some extent but the financial costs are insignificant compared to the costs of doing it another way (for us at least).  If we had a more capital intensive infrastructure with integrated sprayers and more automation, we could move primarily to foliar application- in fact, a design I'm working on how uses significant amounts of foliar-applied nutrients, but in most cases this isn't necessary or financially feasible.


Harold Sukhbir said:

Hi Nate,

I see you mention foliar application. Do you use a wetting agent? Do you use a nitrogen base as well? Do you use a mister?I am trying to fine tune my foliar spraying. Those hand sprayers are really not suitable, a lens, any lens, even one made by water magnifies light and causes leaf burn.I know its easier to maintain an average saturation between 1 ppm and 2 ppm       ( sufficient for most plants) by dosing in sys. water, but as you say very expensive when dealing with large water volumes. Do you notice a difference in plant growth between these two types of applications? Sorry for all the questions nate!

Thanks, as always Nate. I too spray at night.I get good results when i add some micro nutrients and a nitrogen base   (around .2 ppm), with a suffectant. It took a while to get the ratios right but works well enough. Its an extra layer of work but the idea of foliar spray as a sole application for Fe in AP is very intriguing to me. Since we are generally defficient with K as well, it might be wise to include this as a combination foliar, you think?

If I drop a piece of rusty rebar into the fish tank, could it harm anything, fish or plants, people?

Vlad Jovanovic said:


Anoxic conversion of ferric iron (Fe3+, like rusty nails) to plant usable ferrous iron (Fe2+) may be the safest form of iron for an AP system if the chelates freak you out.

If I may, George...a rusty hunk of rebar down low in the tank would cause neither harm nor good. If it were in a current of oxygenated water, causing erosion and suspension of ferric iron, then the fish gills may suffer. If it is down low in the system, covered in mulm, anaerobic, and acidic, then it just may create a supply of ferrous iron for the plants.

It is possible for humans to have iron toxicity, but do you drink your AP water?

Thanks.  What about dropping a piece of rebar into the gravel bed - I suppose that would be a current of oxygenated water and would produce ferric iron too?  Not sure if this train of thought is worth anything but it occurred to me that it might be possible to buffer iron in the system.  There is no anaerobic zone in my tank so the tank is out.

Drink the water?  I'm weird, but not that weird.

Jon Parr said:

but do you drink your AP water?
The rebar won't help, and possibly hurt, unless it's in the anaerobic zone. So either get it to the bottom where muck builds, or add a specific device for anaerobic production of ferrous iron after FT, and immediately before GB, or even in the GB.

I'm not sure I'd use the word "preventative", but I do maintain my water at 1-3ppm of iron depending on the crop by testing the water once a week.  When using chelated iron, I prefer the EDDHA.  As a former hydroponics grower, I prefer to maintain the nutrients rather than wait for a deficiency to show up.  

Days, and even weeks worth of growth potential are lost by the time you can see a deficiency in the leaves.

Jesse,

   what do you use to test the iron levels in the water?  Are there any other nutrient tests you use in your operation?

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