Re: K2SO4 and SO4 ion

[Thomas Barr <tcbiii at earthlink_net>]

> I was looking at http://www.nfis.com/~hartland/aqua/pmdd.htm
> K2SO4 is added. I know the use of K to plants. But what is the sulphate ion
> for? Is it a source of sulphur for the plants?
> 
> Wayne Wah from Singapore.

SO4 is the source that most plants take in for their sulfur needs. It is a
very common component of tap waters. If you have relatively moderate GH, it
is likely you have enough SO4 for the plants. If your source water is very
pure, you likely need some.......
S is needed in larger amounts(A macro vs a micro) than than Cl and seems to
have less adverse effects, _but_ at the normal usage of KCL this does not
seem to be a problem for many folks. The build up of Cl is likely not that
big of an influence. If using pure water, low SO4 level might be what's
being blamed as high Cl levels. Cl excess has been blamed for a number of
terrestrial plant problems and can produce adverse effects. Due to the water
medium, we may be able to handle higher levels and removal with regular
water changes.  I know I can have quite high levels of SO4 with no negative
effects. Some folks may be surprised at how high their SO4 levels are out of
their tap.
Regards, 
Tom Barr