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Re: PMDD components



> From: Andrew Hamilton <andrewha at tafe_sa.edu.au>
> 
> I have been looking for fertilizers to mix into PMDD's and have found
> something that is close to the recipie. Im not totally sure that it is
> alright to use though so I thought I would post the ingredients to the list:
> 
> 11% Potassium as Potassium Sulphate
> 5% Iron as Ferrous Sulphate
> 5% Calcium as Calcium Carbonate
> 2% Magnesium as Magnesium Sulphate
> 2% Manganese as Manganese Sulphate
> 1.5% Copper as Copper Sulphate
> 1% Zinc as Zinc Oxide
> 2% Boron as Borax
> 1% Molybdenum as Sodium Molybdate
> 
> Questions: What purpose does Potassium provide? What effects will such a
> high percentage have? Is Potassium used excessively by plants?
>
	It is one of the major elements required by plants.  You will still
need more, if you make up a mix containing everything.
 
> No where does it say that any of these ingredients are chelated. Is Ferrous
> Sulphate the result of chelation? What will happen if I use this product and
> the ingredients are unchelated?
>
	It looks as if none of the four elements usually chelated is chelated
in this mix. (iron, manganese, copper, zinc).  The Fe++ ions that go into
solution when this material is dissolved will be oxidised quite rapidly, and
tend to precipitate out as Fe(III) oxohydroxides.  This may well result in
a shortage for the plants, even dosing daily.
 
> This product contains Copper. Has anyone else got copper in thier trace
> elements? Will Copper Sulphate poison the water or is it safe in this form?
>
	It is a required element.  There does seem to be quite a bit of it
in your mix, though.

> Will the Magnesium concentration be adequate or should I add to it?
>
	There may well be enough in your water.

> What provides the EDTA here? Is it vitally important?
>
	By the sounds of it, there is none there.  It is used to keep the 
four elements mentioned above in solution for a while.
 
	Try it, and see if the iron concentration in the water is O.K.
when you use amounts corresponding to the posted PMDD recipe.  If it
isn't, use a chelated mix, don't increase the amounts of this stuff, because
you may well then add too much copper and molybdenum.


Paul Sears      Ottawa, Canada