The Chip Mill

Larry Caldwell larryc at
Wed Nov 5 13:48:31 EST 1997

In article <01bce8c3$9b7da220$2c8792cd at>,
"Ron Wenrich" <woodtick at> wrote:

> The problem with whole tree chipping is the effect on the soil.  I've been
> told that 90% of the nutrients are in the leaves and the fines.  This
> doesn't get returned to the soil in whole tree chipping operations. 

How do they handle bark in the whole tree chipping operations?  I've
heard about those mobile chippers, but if you haul a tree to the mill
it has to be 90% debarkable or the mill won't take it.  If you tried 
to sell them leaves they wouldn't even let you drive into the yard!

What do you sell the stuff for, hog fuel?  Nobody would make paper or
OSB out of it.

> Another impact is the carbon-nitrogen ratio.  With the removal of so much
> carbon, this should have an effect on the amount of carbon available to
> soil fauna.  There have been several posts to this NG about the benefits of
> soil fauna and tree growth, and I suspect that adding carbon would be just
> as advantageous as adding nitrogen.  I don't think that whole tree chipping
> is sustainable in the long term, and rarely recommend it.

I don't think carbon is a limiting nutrient.  Trees extract it from the
air with good efficiency to build their carbohydrates.  That's what
photosynthesis is all about.

Nitrogen, sulfur and trace elements are quite often limiting nutrients.
Local foresters tell me 250 lbs/acre of available nitrogen (450 lbs/acre
of urea) will boost forest growth for 7 or 8 years.  Evidently the
leaves and duff of an established forest are incredibly efficient at 
recycling nutrients and not letting them escape.  Trace boron is important
for mycorrhizal mushrooms, but use more than a pinch per tree and you'll
kill the tree.  Scalp the land and you create some pretty serious nutrient
shortages that you need to remediate.

-- Larry

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