If you sink two really solid poles at the ends of a row,
either metal or 4x4s, with the tops 6-8' above the
ground, then run cable across the top of them, you can
use a single string per plant overhead support method.
You tie a piece of string to the stem with something
like a loose bowline knot (non-slip), then loop it over
the top cable with enough extra per plant to bring
it about halfway back down, and tie the end to an eye
made in the part of the string coming up from the plant.
As the plant grows, you untie the free end, untie the eye,
then loop the part of the string that starts at the plant
around the growing plant, make a new eye, higher up,
and loop the free end back over the top cable and tie
it to the new eye. As the plant grows, you continue this
process. If it gets beyond the top cable, just let it
droop back down (it has a long way to go to reach the
ground).
You would probably have to experiment with how much
extra string you really need (maybe double it all the way
back down to the young plant the first year, then
see at the end of the season how much was not
used). This will probably vary with cultivar.
I would use something like dcarch's cable anchors
on the cable that connects the tops of the poles.
He made an anchor about the size of a whole bag
of concrete with a steel eyebolt in it, then attached
cable between that and his poles with a turnbuckle
in it between the anchor and the pole, to tighten it up
without having to move the anchor. If the cable at
the top were connected to anchors like that at each end,
just beyond the poles, the top support would stay taught
and not sag as the plants got bigger and developed fruit
(plus you could adjust it with the turnbuckles).
I have seen pictures of setups like this in high tunnel
growing operations, where the infrastructure to support
the strings at the top was designed into the framework
of the tunnel. Someone posted a picture of something
equivalent here at Tomatoville where their rows were
short, and instead of cable at the top they used 2x4s or
2x6s with the long side vertical (less bend than pvc under
load), suspending the strings from those.
Here is a general summary of methods. Look at the "long row"
description, which is essentially what I described above:
http://content.garden.org/tomatogard...dex.php?id=347
I had a picture bookmarked of a leaning goat fence, which
you could just thread the plants through and let them
"sprawl upward", but that would be kind of expensive
and might be a pain to till around, too. It would have to
be at the edge of a row, not right in the center of it.
(Link brings up a blank page at the moment.)
Edit:
No experience with the tomato rings. I did find a piece of
Box Car Willie stem rooted into the ground this year, though.
It was growing on an angled string trellis that sagged in the
rain, letting this one stem trail on the ground. I didn't notice
it until I was pulling the plant at the end of the season.
You could always try *one* Japanese Tomato Ring and see what
happens. If you use indeterminates, how are you going to stake
them once they get taller than the tomato ring?