precipitate iron

[timwag2001]

if i don't need to dose iron, but my K comes with iron, can i dose it anyway with phosphate if i don't care what happens to my iron?

 

[fort384]

It is possible to OD Fe. Do you have an Fe test kit? Why do you not need to dose it?

 

[timwag2001]

because the K that i have has Fe in it. it's 3% K and .19% Fe. if i want to dose a lot of K it would put too much Fe in for me. so i figured if i added my K at the same time as my Fe, the Fe would precipitate out and i could dose Fe the next day. am i making sense?

where do you recommend my Fe be at?

 

[fort384]

0.5 or so ppm chelated iron is good. So if you dose to .5 Fe using your fert, that would give you somewhere around 8ppm K, if my math is right. This is why it is a good idea to buy your ferts separately so you can target dose each macro/micros to your desired level. So that it doesnt go to waste, you could buy some K2SO4 or I can get you a pre mixed bottle of it and just dose it in addition to your Fe/K mix.

 

[timwag2001]

just got my shipment in from rex today

 

[fort384]

oh ok cool, so you have it then. FYI if you got the plantex stuff too, it has Fe in it so don't overdose it if you combine it with your K/Fe mix.

 

[timwag2001]

i did. i got chelated Fe, csm+b, KH2P04, K2SO4.

 

[darkmule27]

I can't help with the plant part, but I can with the chem part.
Chelated iron isn't going to precipitate out easily. It's locked up inside another molecule. To get any to precipitate out, you would also to add a ton of extra iron, have incredibly basic water (we're talking pH >12, maybe even higher), and/or mix it with something that would precipitate it out (i.e. concentrated hydrochloric acid, NaOH, etc).

 

[timwag2001]

doesnt phosphate do that? or did i confuse myself... again.

 

[darkmule27]

If it was straight Fe2+ or Fe3+ it would, but since it's chelated, it's pretty unlikely. It would also have to be fairly concentrated. It also think it might require heat? Basically everything you're adding has the possibilty to precipitate out iron, but it's chelated, probably with a decently strong ligand.
The only way to find out (since you probably won't see the teensyweensy bit of precipitate that would be precipitated out if it were) would be to calculate the concentration you should have and then test it. In general, I'd think it would be better to assume it's in there and staying in there to avoid overdosing.

 

[krap101]

I thought rex and others said that you shouldn't dose kh2po4 along with fe because it would create something like fepo4 (precipitate)?

 

[darkmule27]

I totally missed phosphate in the original post, oops. Too much work and too little sleep lately.
I can't say for sure. It depends whether the PO4 ion is a stronger ligand than whatever the chelated Fe is bonded with.
Sorry for any confusion!

 

[krap101]

Understandable when you're use to seeing PO4 . Same thing with Dihydrogen monoxide