Re: Fertilizer comparison

On Thursday, March 21, George Booth wrote:

> > [Kevin wrote:]
> > 
> > What's interesting about this table is that it shows that Dupla Drops
> > are a source of iron only; they are not a significant source of any
> > other trace element or micronutrient.  If you also use Duplagan and
> > Dupla tablets, Mg and Mn are supplied (as well as the macronutrient
> > K), but B, Mo, Zn, and Cu are still missing.

> Not to cast aspersions on Paul Sears or Keven Conlin, but how the 
> <explective deleted> did you manage to mangle the data so badly and
> then draw a conclusion from it?  "Trace elements in short supply"???

Read my posting, Giorge.  I said that "Dupla Drops are a source of iron only",
not that the "Dupla System is a source of iron only".  I'm specifically
comparing Dupla Drops to two commercial trace element mixes and to
Tropica Master Grow.  I'm entitled to make this comparison because, from
your own posting (available on the Krib),

  "Duplaplant 24 daily drops fertilizer
   Used daily to add trace elements that are either are unstable or are toxic 
   in large doses."

The statement says "trace elements", not "trace element", so anyone who
reads this is likely to believe they're getting more than iron (and how
could they know, since the package doesn't list the ingredients?).  Yes,
there are other elements in the drops, but at levels consistent with
contamination.  Levels far less than found in Tropica Master
Grow and two commercial trace element mixes.  Note carefully the use
of the word "significant" in my posting.

> Dupla drops are not designed to be used alone - they are designed to
> be used with DuplaPlant tablets.  The clause "If you also use Duplagan
> and Dupla tablets..." is a bit silly.

No, it isn't.  Since Dupla Drops advertise themselves as a source
of "trace elements", people might be tempted to save a few bucks and
find substitutes for the tablets and water conditioner, assuming that
the drops are supplying necessary trace elementS.  A very bad assumption,
it turns out.  My posting merely points out that the drops must not
be used alone.  It also points out that even if you use the system as
designed, you will likely be short of certain elements.

> If you are stupid enough to not
> pay attention to the dosage instructions, you deserve to waste your
> money and have your plants die.

True enough.

> Now how does one draw the conclusion that "B, Mo, Zn and Cu are still
> missing"?  Ah, apples and oranges were compared ("normalized to iron")
> and it was decided that the concentrations of these elements became
> small enough to be declared "missing".

Normalizing to iron is a reasonable approach since you're measuring iron
and adjusting the amounts of fertilizer relative to it.

From your analysis, it seems to make more sense to dose the tablets on a
daily basis and forget the drops.  Then the comparison becomes:

Element  Dupla Tabs   Tropica  My Mix  Doug's Mix
-------  ----------   -------  ------  ----------
   Fe        1.00       1.00    1.00      1.00
   Mg          -        5.57    5.00 (3)  1.35
    B        0.03       0.06    0.19      0.13
   Mn        0.15       0.57    0.29      1.00
   Mo          -        0.03    0.01      0.03
   Zn          -        0.03    0.06      0.38
   Cu          -        0.09    0.01      0.38
   Co          -          -       -       0.01

Here, "-" means "< 0.003".  Strangely, we still don't seem to have 
significant quantities of Mo, Zn, and Cu.  B is a little better
at half the Tropica concentration.

> Hey - these are "trace elements" not "bulk elements".

Exactly.  But "trace" doesn't mean "vanishingly small".

> What do you think "trace" means?

"Present in small but SUFFICIENT quantities."

> This
> also implies that Tropica, Kevin and "Doug" know more about the
> correct proportions of trace elements than Dupla.

There's no such implication.

>  Tropica maybe, but
> I doubt Kevin and "Doug" have done extensive research in this area
> other than, perhaps, their plants grow OK.

Douglas, Paul, and I use commercial trace element mixes.  The companies that
supplied the mixes have done their own research (probably better funded
than Dupla's, because the hydroponics market is larger than the aquatic
plant market), and they aren't ashamed to publish the compositions of their

Leave Douglas out of this.  He's an innocent bystander who simply mailed me
the composition of his trace element mix.

> I have been using Dupla solely for eight years and my plants manage to
> grow quite well, thank you.

No one denies this.  Mine grow quite well, too, and I spent about $CDN 40.00
for at least a three-year supply of ingredients.  And perhaps your plants
would grow even better if your rolled your own fertilizer (but you'll
never know, will you?).

> My tap water has nothing useful in it
> (pretty much pure Rocky Mountain snow melt) so the plants depend on
> Dupla for their needs.

I'm willing to concede this point, except to note that the plants are getting
N and P from somewhere, and it's not the Dupla.

> If Dupla products did not supply the proper
> nutrients, I probably would not have been able to sell $800 worth of
> plants last year.

You win.  I only sold $50 last month.

You're really cute with your hackles up.  Let's hear some more of those
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"
Finger as332 at freenet_carleton.ca for PGP public key.