Subject: Re: Smoking compost. Is it not ripe yet?
From: wtmorgan@pilot.msu.edu (Bill Morgan)
Organization: Michigan State University
Date: Sun, 19 Oct 1997 15:05:26 -0400
Message-ID: <MOD$971019.8692@rec.gardens.ecosystems>
References: <MOD$971018.28855@rec.gardens.ecosystems>


In article <MOD$971018.28855@rec.gardens.ecosystems>, "dhs" wrote:

> I just ordered several cubic yards of compost (so called organic), from a
> local farmer who recycles garden refuse from the area. I put some in peony
> and new rose beds, and plan to cover 400 tulips in a new bed with it too.
>
> It is very dark, small pieces (it is sifted, I think), and smells lightly
> and wonderfully of forest. But I can see smoke when it is dumped from the
> truck, I suppose from heat generation from the decomposition process. Does
> this mean that it is not ripe? Does a pile of compost stop generating heat
> after it is all done? And is it ever all done?
>
> Should I use this compost???

Hard to tell from the information given. The steaming (not really smoking,
I hope) does indicate a degree of warmth relative to the surroundings. The
question is: where do you live and what was the weather when you saw it
steaming?

If you were near say, Tucson, AZ with the temperatures in the high 90's and
the humidity less than 10%, you were looking at pretty hot stuff. As you
reduce ambient temperatures and increase relative humidity, it requires a
higher compost temperature to show the same amount of steam. If you live in
the UP of Michigan and saw it steaming when the temperature was below
freezing, and the humidity was high, that doesn't necessarily mean it was
very hot at all.

When you break the compost up and spread it around, it will cool off
quickly regardless of how well decomposed it is. Spareading it before it is
truly finished just means that some of it will take a longer time to break
down. The main problems with doing this are with nitrogen balance: if the
stuff is hot and rich in something high in nitrogen (e.g., horse manure)
you might burn (chemically, not thermally) your plants. If it is very low
in nitrogen (unlikely if it is hot), then further decomposition will rob
nitrogen from the soil, especially if you work it in instead of applying it
as a top dressing.

Regards,
Bill

--
Bill Morgan
wtmorgan@pilot.msu.edu
Center for Room Temperature Confusion