On Thu, 6 May 2010 23:01:12 +0100, geoff wrote:

OK until water gets in (which it will) and the post is permanently damp
and then rots away like a good 'un

I can see where you are coming from, rain and capillary action from
above or just capillary action from below but that's not quite the
same as the post in direct contact with the soil and the organisiums
in it. This band will also reduce the amount of oxygen available in
that critical length of post.

I doubt very much it's a "cure all", otherwise it would be common
practice to bandage posts at an below the soil boundary, after all
pitch and bitumen have been around for donkies years. I suspect it
may well slow the problem down, less wet, less oxygen but not stop
it.

--
Cheers
Dave.