Ferrous sulfate question

Robert robert at tomgrower.demon.co.uk
Mon Apr 17 15:26:03 EST 2000

In article <iyLdBtAkVj+4Ew$u at upthorpe.demon.co.uk>, Oz
<Oz at upthorpe.demon.co.uk> writes
>>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?
Generally set at pH 5.9-6.0. Usually no problem with any elements at
this level. We used to get  some problems with manganese deficiency
until we switched to a chelated form. (Actually its a ready made mix of
trace elements called Solufeed Tech). Managanese would appear to be
available to the plant from solution analyses, but not taken up. Today
we operate much lower levels of Mn by solution analysis, but without
deficiency. The plant takes it up rather than leaving it in solution.

>How did you decide on the pH you selected?

23 years of hydroponic experience and industry standard. It also falls
fairly well in the mid range for trace element availability. Some become
less/unavailable at higher and lower pH. Have to look it up for further
>Have you ever considered making your own chelates? 

No, but anything to save money
>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.
Last time I bought straight Fe EDTA, it cost  about £60.00 per 25kg
(£2,400/ton ) and no mixing
> 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.

I'm interested. But  we only use about 300kg a year. Copper and zinc
also chelated. Has to be mixed with Boron, and Molybdenum. its nice not
to have to weigh it out anymore.

Best wishes

Fundamentalist opposed to witchcraft

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