"David (Normandy)" a écrit dans le message de
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"Mary Fisher" wrote in message
t...

"David (Normandy)" wrote in message
...

The story you read sounds as though it were found in a sensational red
top,
professional gardeners still recommend the use of leached soot and
leached ash.

Mary

I can't remember where I read it now. I guess it makes sense if it is
left out in the rain to allow the noxious salts to leach out before it
is used on the garden. The problem only exists with coal ash/soot and
not wood ash/soot of course. Coal can contain all manner of toxic
minerals including arsenic, mercury, cadmium etc

David.

But only in very small quantities. Supposing they were absorbed by
plants - it would be in even smaller quantities and we wouldn't eat all
the plant anyway ...

I always leave wood ash in the open and wouldn't use it until it's been
rained on, it contains very caustic salts which can burn flesh and plants
until they're converted to the hydrated version.

Mary



Do I detect a fellow chemist? Potassium oxide (K2O) produced in the
burning, getting hydrated to become potassium hydroxide (KOH) which upon
exposure to carbon dioxide in the air eventually becomes potassium
carbonate (K2CO3).

To be chemically pedantic, it's bicarbonate (KHCO3).

The pre-war (WW2) gardeners' "bible", Gardeners Enquire Within, was very
much into soot. Enviro-friendly leaf mould was frowned upon.

I guess some of the components of soot would be insecticidal and/or
fungicidal, like coal tar spray (roses used to be easy to grow disease free
in big towns).

Regarding heavy metals, it's all in the dose. A kilogram of pristine soil
could contain a few micrograms of almost every element in the periodic
table, and arsenic is close to or above current safe limits in many parts of
the world. Sewage sludge, which contains some heavy metals, is dispersed in
a calculated manner. Gardeners don't have access to an analycal laboratory,
so the best advice is use soot and ashes, but use common sense and don't
overdo it.

Regards


David