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RE: Hydroponic Plant Food (long)
Josh has a question about the suitability of a particular soluable
fertilizer to act as a source of trace elements in a PMDD style regieme.
>I have a bottle of Hydroponic Plant Food and I was wondering if I would be
>able to use it for the trace element portion of PMDD? The breakdown is:
>Nitrogen...10.00%, Available Phosphoric Acid (P2O5)...8.00%,
>Soluble Potash (K2O)...22.00%, Calcium...5.000%, Iron... 0.200%
>Manganese... 0.100%, Zinc... 0.010%, Copper... 0.010%, Boron... 0.020%
>Molybdenum (Mo)... 0.005%
>The directions say to put 1 teaspoon in one gallon water, also add 1/4
>teaspoon epson salts.
Josh, you have answered your own question, even if you are not aware of
having done so. I suggest that you visit Steve Pushak's website
(http://home.infinet.net/teban/index.html) and follow some of the URL links
which he provides to learn more about nutrients. Specifically, I suggest
that you read Phillip Barak's material "Essential Elements for Plant
Growth", which may be found at the following URL:
(http://bob.soils.wisc.edu/~barak/soilscience326/essentl.htm).
All plants, regardless of whether they are terresterial or aquatic, need the
following elements in order to grow: hydrogen, oxygen, carbon, nitrogen,
phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, iron,
manganese, zinc, copper, molybdenum, and nickel. The first three - hydrogen,
oxygen and carbon are usually present naturally in every system and need not
be supplemented in the form of "fertilizer". The next six (N, K, Ca, Mg, P
and S) are needed in relatively large amounts by plants and are termed
"macronutrients". The remaining eight mineral nutrients are needed in only
trace amounts and are thus termed "micronutrients". While it might seem that
they aren't as important due to the relatively small amounts needed for
growth, each one of the elements listed MUST be present in order for plants
to grow well. Furthermore, not only must they be present, but they should
also be present in the proper proportions and in the correct ionic form.
Barak provides a breakdown of the relative number of atoms of each element
required by plants. He draws on material originally presented by E. Epstein
(1965).
Element Relative # of Atoms
Nitrogen 1,000,000
Potassium 250,000
Calcium 125,000
Magnesium 80,000
Phosphorous 60,000
Sulfur 30,000
Chlorine 3,000
Iron 2,000
Boron 2,000
Manganese 1,000
Zinc 300
Copper 100
Molybdenum 1
Nickel 1
The fertilizer you are proposing to use lists the macronutrients nitrogen,
phosphorous, potassium, and calcium in it's makeup. These are NOT required
in a "Micronutrient Source" for a PMDD style fertilizer solution (those
particular nutrients are supplied using other chemicals which make up PMDD).
Of the essential micronutrients, your fertilizer is missing Clorine and
Nickel. Now, it is possible that your other nutrient salts might contain
these elements as contaminents but then again, they may not. Also, the ratio
of the different micronutrients doesn't look correct to me - too much copper
and possibly not enough boron.
Karen recently commented about the overabundance of copper in a lot of
"micronutrient mixes" designed for terresterial or hydroponic agriculture. I
think that her caution is well placed and I have yet to see a formulation
which contains ALL of the micronutrients in their correct proportion.
I don't know if you are considering PMDD due to the cost factor or due to
the precision which it allows individual nutrients to be dosed, but without
a good grounding in just what elements plants need, you (and your aquatic
plants) might be better off with a commercial preparation designed
specifically for aquatic plants in aquariums (i.e. DuplaPlant & Duplaplant
24; Flourish, Flourish Iron & Flourish Potassium; Ferreal & Floreal; etc.).
PMDD can work very well - IF you know what you are doing. If you DON'T know
what you are doing, it is better to stick with commercial preparations which
are designed for aquariums. They don't cost THAT much.
James Purchase
Toronto