Subject: Re: gardening chemistry question
From: wtmorgan@pilot.msu.edu (Bill Morgan)
Organization: Michigan State University
Date: Fri, 10 Oct 1997 14:46:48 -0400
Message-ID: <MOD$971010.29774@rec.gardens.ecosystems>
References: <MOD$971010.17474@rec.gardens.ecosystems>
In article <MOD$971010.17474@rec.gardens.ecosystems>,
gondwana@ix.netcom.com wrote:
> What would happen if equal parts coffee ground and fireplace ashes were
> placed together (with nothing else) and allowed to decompose?
>
> True, the resulting product wouldn't be nutritionally complete (or would
> it?), but might it be useful as a supplement (like, say, fish emulsion)?
> What would the chemical make up of the product be exactly, from a
> fertilizer standpoint (i.e. NPK and trace mins).
I can't answer that, completely. Wood ash contains a fair amount of the K
(Potassium) in NPK, and also include many trace minerals. Coffee grounds
are high in N (Nitrogen), and are similar to grass clippings in that
regard.
>
> Wood ashes are very alkaline, but very high in potash. Coffee grinds are
> (I have heard . . . please correct me if I am wrong here) highly acidic,
> but nutritionally empty.
As noted above, the grounds contain nitrogen, and of course some trace
elements, and also P (Potassium) and K, though I don't know how much.
Certainly, they contain quite a bit of carbon, and that adds to the amount
of organic matter in the soil they go into.
> Combining the two, I am guessing, would
> neutralize the severe alkalinity of the potsh in the ashes, and maybe
> make it mose useful. In fact you need to actually make the mixture
> slightly acid in order for the nutrients to be available to the roots of
> many plants.
Yes, they will tend to neutralize one another. I don't know what ratio of
grounds and ashes you need to get complete neutralization (to pH 7).
As for the effects on plants and nutrient availability, a lot of that
depends on the species of plant(s) you are talking about. Some plants
(Rhododendron, blueberries, many bog plants) like an acidic medium. Others
(Yucca, Agave, many cacti and other plants from the Western half of the US
/ other arid regions) like things more alkaline. Some bog plants
(especially the carnivorous forms) like a low nitrogen soil.
Be aware though, that it is hard to make large changes in soil pH. Anybody
who has tried to significantly alter the pH of their soil can tell you that
it takes a lot of ammendment to accomplish that. Remember that a change
from pH 6 to pH 5 takes a 10-fold increase in the concentration of H+ ions.
To go from pH 8 to pH 9 requires a 10-fold increase in OH- ions. Every
whole number change on the pH scale means an order of magnitude (10X)
change.
>
Most plants like something relatively close to neutrality (pH 6-8).
Chances are, you will have a hard time making big changes with the amount
of grounds or ashes available to most people.
Regards,
Bill
--
Bill Morgan
wtmorgan@pilot.msu.edu
Center for Room Temperature Confusion