Ferrous sulfate question

Oz Oz at upthorpe.demon.co.uk
Sun Apr 16 16:49:24 EST 2000


In article <t89qeXApMi+4EwPP at tomgrower.demon.co.uk>, Robert
<robert at tomgrower.demon.co.uk> writes
>
>Growing tomatoes hydroponically we use a chelated form of iron, FeEDTA,
>and the last 4 years several other trace elements in chelated form.
>FeEDTA starts to drop out of solution above about pH 6.5. There are
>other forms of chelated iron which remain available at higher pH's but
>much more expensive.
>
>When we first stated using hydroponics we used ferrous sulphate, but
>even at a computer controlled pH of 5.8, it drops out of solution
>leaving a nasty deposit on the roots which was generally felt to be
>damaging or at least inhibitory. 

Just out of interest what pH do you set your system for and which
elements do you have 'trouble' with at that pH?

How did you decide on the pH you selected?

Have you ever considered making your own chelates? I did at one time
look into this but buying EDTA at (IIRC) 2000 ukp/T to mix with MnSO4 at
280ukp/T struck me as unreasonable and not worth the effort. However in
your situation this is probably not the case. Certainly it's the sort of
thing I would likely be doing, and for all chelated elements too, not
just Fe. Generally there's no magic to it, you could do it with an old
sprayer tank whose booms had long since rusted away.

-- 
Oz




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