[APD] Re: Potassium Bicarbonate in the planted aquarium

[<jppurchase at rogers_com>]

"I wonder if KHCO3 could be substituted for the K2SO4 in the PMDD recipe, or
is there a requirement for macro quantities of sulfur? I read the
Sears/Conlin paper again and couldn't find any specific mention of a sulfur
requirement."

Douglas, check out the following URL:

http://www.soils.wisc.edu/~barak/soilscience326/essentl.htm

Sulfur IS a macronutrient, although one required in smaller quantities than
the others. Whether or not you could substitute KHCO3 for K2SO4 in a
fertilizer would depend on how much SO4 (Sulfur is apparently absorbed as
SO4) is present in the system already (check your water supply) and the
Alkalinity of your water (CO3 level). If your water is naturally very, very
soft and contains little Alkalinity, you would probably have to supplement
the CO3 level in some way (Baking Soda) if you switch from KHCO3. It might
be possible to go 50-50, using both KHCO3 and K2SO4. Potassium isn't toxic
even at higher levels than really necessary, so you are unlikely to do any
damage, and SO4 is also relatively non toxic at elevated levels (within
reason).

James Purchase
Toronto


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