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Re: Organic matter's effect on soil bulk?



Tom wrote:
> 
> Here's a question that I'm hoping someone knowledgeable about soil
> can answer.
> 
> Imagine I had a plot of land on which I dumped six inches of wood
> chips every year.  Obviously this would cause the level of the plot
> to rise over the first few years.  The question is, after, say, ten
> years, would the level continue to rise, or would it stay constant?
> In other words, when the wood chips deteriorate, do the elements go
> into the air and water?



I would say that it depends in part on what you dump onto your plot. 
Wood chips are high in carbon and low in nitrogen, so the decay 
process is slow. My compost pile does reduce in size over the winter, 
but part of that is probably compaction. The products of decay (caused 
by bacteria and fungi) are primarily carbon dioxide and water plus 
some compounds from whatever other elements are present.

The soil is a combination of different things. People talk about 
topsoil and loam as if they were the same thing, but I have always 
thought that loam has a higher organic content than topsoil. Topsoil 
is just the soil on top, i.e. it is a combination of mineral and 
organic components. The organic components come from surface plant 
growth and decay processes and the mineral components provide the 
structure. If you sterilized a plot of land and kept anything from 
growing on it, the organic components would probably disappear from 
the soil (into the air and water) leaving mostly mineral soil.

As far as continually dumping wood chips onto your plot, I would think 
that it would take much more than 10 years to stabilize, possibly as 
long as 100 years. If you dump something onto your plot that has a 
more favorable carbon/nitrogen mix, the stabilization would probably 
be quicker. However, the decay process takes air and water as well as 
carbon and nitrogen, so the lower levels of your plot might decay very 
slowly.

Having said all that, I will now admit that I'm no expert on the 
subject and would like to hear from someone who is to correct any 
inaccuracies in the above.



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