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Re: Aquatic Plants Digest V3 #602
I don't think that there is a person alive, that can tell you, without
any contradictions, what the optimum N-P-K ratio is!
But since you are planning to experiment, here are the N & P ratios of
some of the phosphates you are interested in:
(NH4)H2(PO4) N = 12.18%, P = 26.93%
(NH4)2H(PO4) N = 21.21%, P = 23.48%
K2HPO4 K = 44.89%, P = 17.79%
KH2PO4 K = 28.73%, P = 22.76%
Ca(H2PO4)2 (superphosphate) P = 26.47%
CaHPO4 P = 22.77%
Ca3(PO4)2 P = 19.97
Hope that these numbers will help in your experimentation!
> Date: Sun, 25 Oct 1998 14:12:59 EST
> From: TomWood3 at aol_com
> Subject: Chemists - Need Advice Please
> I am currently using the PMDD method with some success. As you probably know,
> this entails dosing K2SO4 and KNO3 along with a trace element mix. I'd like
> to experiment with additions of these and some form of phosphate in the
> substrate. I note that the Jobe's fern sticks have a 16-2-6 N-P-K ratio and
> that the analysis says the nitrogen is N, the phosphate is P2O5, and the
> potassium is K2O.
> I have a hydroponics catalogue that provides phosphate in several forms - Di-
> Ammonium Phosphate (NH4)2HPO4, Di-Potassium Phosphate K2HPO4, Mono-Ammonium
> Phosphate NH4H2PO4, Mono-Calcium Phosphate Ca(H2PO4)2+H2O, Mono-Potassium
> Phosphate KH2PO4, and Triple Superphosphate CaH4(PO4)2.
> Whew. So, the question is - What form of the above phosphates would work well
> with K2SO4 and KNO3 and in what ratio should all three be mixed to provide an
> optimum N-P-K ratio for aquatic plants? Am I right in assuming that each of
> these compounds disintegrate into the required N-P-K elements according to
> some chemical reactions that can be calculated? To make the calculation
> easier, assume no inputs from the other sources in the tank.