This issue is an example of one that needs to be addressed in the context of
an ongoing teacher/student relationship so that the fullness of the practice
and its related practices can be properly communicated,
BUT
since it seems that we're too quick here to casually dismiss misunderstood
practices as irrelevant, let me offer the following stuff in hopes of
inspiring more curiosity. This is just a way to get some thinking more
about the wider and important scheme of issues associated with soil
layering.

In the context where soil layering came from, it is recognized that...

- the soil components are very coarse and granular.
- the soil components do not generally contain any organic media.
- the optimum grain size for the lower root structure is not optimum for the
soil surface function.
- the cycle of moisture application/absorbtion/evaporation needs to be
fairly predictable and mangageable.
- there are seasonal conditions that are specific to that region of the
world.
- the mode of fertilization is with organic-based cakes (which degrade over
time - adding organics to the soil).
- the basis of in-pot horticulture assumptions are based on the specifics of
the soil medium (no organics).
- the degredation of fertilizer into the soil has to be controlled to a
certain extent (and managed afterwards with necessary techniques).
- the optimum grain size for the functional roots is not generally very
aesthetically pleasing (in most cases).
- the optimum grainsize for the functional roots is not conducive to the
support of decorative moss when needed (and the manner in which it is best
applied).
- proper repotting technique does not unduly disturb the
separation/distinction between grain size layers in the pot.
- roots colonize areas of larger particles differently than areas of smaller
particles.
- given the small acommodations, the roots need to generally be relegated to
a specific area of the pot (over a predictable span of time).

Now, these are not really "answers" to the question of why or why not to
layer soil, but they reference important factors that eventuate in the
practice. I suggest looking more deeply into these issues/practices in
order to discover the relevant issues and need for soil layering. Sometimes
the issue is a small one, but somewhat important nonetheless. You may deem
one or more of them to be irrelevant, but the fact that other do not is no
reason to believe them worthless. Hope this helps to some degree.

Kind regards,
Andy Rutledge
www.andyrutledge.com/
zone 8, Texas

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