In article ,
"The Ranger" wrote:

OmManiPadmeOmelet wrote in message
news [snip]
If you have a guide book with a tried and true method,
what are you worried about???
[snip]

I believe he did in the OP. Something about experiencing problems
still...

Anyhow, there won't be any issues with using the Styrofoam cups or
having them biodegrade. The "collar" will allow you to maximize the
water while minimizing the effort (of control of weeds, rot, et al.).
The stepped system is already in place so now you should be looking to
figuring out why rot is taking place. A soil virus, maybe?

The Ranger

More likely a soil fungus.
Some pH regulation might be in order?
--
Peace!
Om

"My mother never saw the irony in calling me a Son of a bitch"
-- Jack Nicholson