Searching the web I came up with this; a low tech
hugel wicking bed. What are your thoughts on it?
http://www.terraperma.com.au/blog/old-trials-new-updates-inground-wicking-hugelkultur-beds
My biggest concern would be it going anaerobic over time. I'm thinking that if I try this I would only use large
wood, closely packed, in the hole, and then top it with a layer of peat moss to keep soil from migrating down.
It would cut out the liner, etc. which is not cheap, especially if you actually want it to do a good job. And it would be more self healing then a plastic liner.
In a way, it is a sort of chinampa.