Iris Cohen wrote:

Brent at Evergreen Gardenworks wrote:
The major cause of soil collapse is loss of particle size due to
_composting_
of the organic portion. By using composted bark, you are using a
material that
already has one foot in the grave.

I'm a little puzzled at this. Fatal soil compaction results from using
organic
matter that is too finely ground or too soft, like peat moss. The pine bark
that is generally used in commercial bonsai soil, like Hollow Creek
Farms, is
only partially composted. This is to prevent the problem of bacteria in
fresh
bark using too much nitrogen.

Iris

I have commented extensively in the past about the phenomenon of 'nitrogen
lockup'. Briefly, it is of no concern to us IF, we use stable organic
materials such as bark. The amount of nitrogen temporarily locked up by
micoorganisms in a good soilless mix is miniscule, and completely overcome
by any sensible fertilizer program.

Also, if you repot on a regular basis, say every two or three years, the
organic matter won't have turned to mush that fast.

True, but there are those of us who don't get to every plant every two
years, and there are sometimes problems with plants that are growing too
slowly, or in pots that are too large for the plants to adequately root
colonize the volume in a reasonable period of time.

Another cause of premature
soil collapse is using an inadequately fired clay component, like cat
litter.
That is why we keep emphasizing the need to use a high fired product like
Turface.

Absolutely correct.

Iris,

Craig added:


I guess I'm as puzzled as Iris. I have begun to pot my deciduous trees in
2/3 -1/3
organic and inorganic soil, the organic being a combination of pine or fir
bark,
not composted, and my own compost. The inorganic is mostly turface and
some fine
gravel. It would seem that with regular repotting, as Iris points out,
the soil
compaction will not be a problem. If a person were to wait too long, like 4-5
years or more, then I could see it being a problem.

Exactly, and that is what happens. In a slow growing environment, even
three years can be a problem.

I'm not arguing that you _can't_ use composted materials in your soil, of
course you can. But you do have to be aware that you are _starting_ with
materials that are already well on the road to particle degradation without
any good reason that I can see. Given that, why not use fresh bark that
will last longer?


Brent in Northern California
Evergreen Gardenworks USDA Zone 8 Sunset Zone 14

http://www.EvergreenGardenworks.com

************************************************** ******************************
++++Sponsored, in part, by Chris Cochrane++++
************************************************** ******************************
-- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ --
+++++ Questions? Help? e-mail +++++