Fertilizer comparison

After Paul Sears brought to my attention the composition of
Dupla fertilizers (as determined by George Booth) and
pointed out that various trace elements
were in short supply, I did a quick comparison of Dupla Drops,
Tropica Master Grow, my local trace element mix, and a trace element
mix that Douglas Skokna found in Houston.  The results are as follows,
normalized to give a relative iron concentration of 1.0:

Element  Dupla Drops  Tropica  My Mix  Doug's Mix
-------  -----------  -------  ------  ----------

   Fe        1.00       1.00    1.00      1.00
   Mg         (1)       5.57    5.00 (3)  1.35
    B          -        0.06    0.19      0.13
   Mn         (2)       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

(1) supplied by Duplagan; relative amount unknown
(2) supplied by Dupla tablets; relative amount unknown
(3) supplied by Epsom salts

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.

On the subject of K, can anyone tell me how much is in a Dupla 20L or 50L
tablet?  I have this gut feeling that the tablets don't supply enough
when used as directed.  If someone who uses the Dupla system and has
high nitrate levels would like to do an experient for me, add about 1/4tsp
K2SO4 per 500L tank water to the tank every day for a week and see if the nitrate levels drop. 
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"
Finger as332 at freenet_carleton.ca for PGP public key.