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potassium in (hard)wood ash & re: K2O vs. K2SO4/KCl

John Wheeler <Jcwheel76 at aol_com> wrote:
> after having read the Sears/Conlin paper, and follow ups (yes, all of them), as well as the
> other archival messages dealing with fertilizer. I am still a bit in the dark about some
> potassium issues. Namely, why potassium sulfate or potassium chloride are recommended
> over simple potash (K2O). All of the readilly available commercial preparations indicate
> K2O, and the stuff sure is cheap! Is there a reason why I shouldn't use it? 

K2O isn't what's in the bag.  The potassium compound(s) in the bag is specified as though it
were in the form of K2O for reasons related to archaic methods of chemical analysis, and by
convention in the fertilizer industry, according to prior posts on the APD.  E.g., see:

The sulphate or chloride salts of potassium _are_ what's in some bags.  I gather there are 
at least some situations where either of these would be suitable sources of potassium, but 
at least some others where chloride might be less desirable than sulfate.  By the way, I 
assume after looking at 

etc (google search on +wood +ash +garden)

that the reasons people don't use ashes from their fireplace as potassium sources are
either the variability of amount of potassium in a given amount of say hardwood ash,
undesirable contaminants coming along at the same time (heavy metals?), or that most
of us don't have/use fireplaces?

Rockville, Md