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