Pam - gardengal wrote:

(clipped)

It is not necessary to work in organic matter to improve soil texture. The
action of the soil organisms, the decomposition process and even the
miniscule pulling action performed by plant roots will serve to eventually
work any soil additions well down under the soil surface.

(clipped)

Gotta ask about this... I have heavy red clay soil AND I have a deep
rich forest behind the house with tons of leaves left on the ground
every year, for at least 30 years. Lots of trees and bushes. If I dig
down out there over 4", I hit solid red clay.

By your reasoning, after all the years, I would have black dirt.

This red clay is the bane of every gardener around here. If this worked
as it obviously does in your area, it does not work here. I just cleared
out an area under the trees and this stuff is so dense, you could cut it
with a clay wire (like potters do).

I don't think one size fits all...