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Re: need help identifying deficiency

On Tue, 6 Apr 1999, Aquatic Plants Digest wrote:
> (ripped from water company web site)
> Hardness, Total mg/L 7.71
> Hardness as CaCO3 mg/L  5.34
> Sodium mg/L 0.003
> Calcium mg/L 0.002
> Magnesium mg/L 0.575
> Due to the utter lack of Calcium and Magnesium in my water, I supplement it
> with CaCO3 and MgSO4 to raise it to 80 mg/L of CaCO3 and 20 mg/L of MgSO4.

Hmmm.  If the analysis is right, then they're sending you some pretty
remarkable water.  Sodium is certainly low.  In fact, it would be low if
it were three orders of magnitude higher than reported.  Similar things
can be said about the calcium level.  Also, the calcium and magnesium
shown in the analysis aren't high enough - not even close to high enough -
to account for the reported hardness.  Something appears to be awry.

> I am assuming that isn't enough sodium to matter? I don't use Sodium Bicarb
> (which is a shame, I bought a very pricey pound of it from Hach)

Yep.  If the analysis is even close to being right, then high sodium
levels aren't the problem.

> My thoughts are that either:
> 1. I don't have the water hard enough yet.
> 2. I need to add Potassium Nitrate (Nitrate at 1-2 mg/L currently)

1.  A few months ago I asked the list how low the hardness could be
without encountering calcium and magnesium deficiencies.  I didn't get
very many direct answers at that time.  Anyone that's got some input here
might like to speak up now.  I suspect that others on this list are
growing plants with less calcium and magnesium than your supplying.

2.  Like I said in my first note,  I think the Dupla fertilizers carry
what they think is sufficient potassium.  I don't do Dupla myself, so
someone who has experience mixing KNO3 into a full Dupla regime might want
to pipe up.  Certainly you wouldn't need to add the KNO3 for the nitrate.

> I guess I am looking for some obvious error before I start adding Nitrates.
> Is there a form of Potassium other than KNO3 that I am overlooking?

I'm with you on that; it's best to know the problem before you start
adding things to solve it.  If you want to dose potassium you can also do
it with potassium chloride or potassium sulfate.

There are a couple other things you might think about.

Problems with K, Ca and/or Mg can be caused by an imbalance in any of Na,
K, Ca and Mg (this tidbit comes from a review of nutritional needs in
hydroponics - normal agricultural sources seem to indicate less
sensitivity to the problem).  Since your water apparently is very clean -
rather like RO water - you might try using one of the mixes used to
reconstitute RO water instead of dosing individual chemicals.  The
prepared mixes should give a balanced composition.

Think about reducing the light levels.  Anubias in general are rather slow
growing plants, and they may just lack (or underemphasize) the biochemical
equipment needed for rapid uptake of nutrients.  Their thick, rigid leaves
and coarse roots tend to make me think that they are well suited for
growth where light rather than CO2 or fertility is the limiting factor.
Maybe when light is not limiting they have a difficult time getting the
nutrients they need to come up to their potential growth rate. The result
is a deficiency symptom.  Probably the easiest way to reduce the lighting
levels is to put in some floating plants.  Then wait a couple months to
see what effect that has.

Roger Miller