Backyard Aquaponics
A place to discuss aquaponics

If it breaks down that quickly, then if you have sun hitting your water it would be best to dose at sunset. Presumably, Moonbeams don't worry it Of course the container of it would need to be kept in the dark all the time too.

I see it - pretty dark indeed

Similar to, but worse than an overdosing of seasol, but at least that's not permanent


I did actually read all 11 pages of this thread, but just to confirm do you still buy your DTPA from http://www.duralite.com.au/hobby-growers ?

thanks

I do (did) Jono - lasts a while, though have not seen much in the way of iron deficiency since getting the ph down.

Well I have only bought it once from there, it last quite a while so I havnt had the need to buy again.. But I probably will as they were easy enough to deal with.

I found the ' The Aquaponic Source' (sylvia bernstein) is bagging up DTPA and selling it as 'AquaIron'.

Smart thinking Sylvia.

so you're saying when dtpa is exposed to direct sunlight, it precipitates in 30 minutes? thanks

this might explain my constant battle to keep Fe concentrations above 2ppm

Found this on DTPA - Haven't had time to read it yet

http://www.ars.usda.gov/SP2UserFiles/person/11847/albano_miller_2001_Hort%20Sc%2036%282%29_%20pp313-316.pdf

Edit: Skimmed it and it takes 96 hours for >90% of the Fe-DTPA to be lost (unavailable)

It's not instant but most of the Fe-DTPA will be unavailable after exposure to the wrong wavelengths of light. Higher temperature makes the reaction faster if I understood correctly.

did I read that they did all of their experiments under artificial lighting? How could we translate the study to growing outdoors...i.e. which wavelengths in natural sunlight that affect DTPA precipitation and which artificial lighting is most similar/relevant?

I found a study that was looking at Fe-DTPA in a lake. They had the half-life of 30 minutes for Fe-DTPA at maximum sunlight.

So does this mean more regular dosing at smaller quantities may be a better approach in AP?

It means keep your water covered as much as possible, or use Fe-EDDHA. Dosing with Fe-DTPA at sunset might also be a good idea.

I agree Tom , regular small dosing, at sunset and keep the water covered as much as possible. Also read iron absorption by plants is pretty quick.

FYI - EDTA is more photo sensitive

I never realised that iron was so quickly absorbed (by plants..excluding foliar spraying which I knew was quick) and/or changed/destroyed (sun exposure)… sort of makes my iron tests pointless unless it is within 24 hrs (just guessing maybe 48hrs) of dosing… also would seem to indicate that reacting to the plants may be better than regular dosing as there wouldn't be as much of a chance at wasting the iron or overdosing.

Are there certain plants that show iron deficiencies earlier than others… they would make good sacrificial plants (like a biological test kit) to show iron levels