Not a new method by far, but we are off to a great start on our place....
I was concerned about the rumor of txins in the tires...but could find no solid research on it (loads of opionion, but no research to back up the concerns). If anyone knows of any, please send it my way!
Anywho...you can find what we did with photos here:
Still - I see no real research about toxins (and a whole lot of opinions). I hope someone will do it one day to either squash the myths going around or warn us all off using tires forever.
I know I don't want to put my family at risk - but if I follow all the opinions on everything, I would never take a step in any direction Science is what is needed (and maybe I should see if I can convince someone to do it!)
heavy metals are mostly an issue when the soil ph falls really low since heavy metals are not sought actively by plants and must be dissolved in the soil solution to be forced into the plant
but i would think about all the other junk in the tires, and also the idea that tires are really recyclable now, so using them for potato farming doesn't make much sense in a conservation sense
and the method i heard that seemed like a real winner was to have four stakes about 4 feet or so out of the ground, build your box (4x4?) fastening to the posts at the corners --1x 8s or 1x6s, or whatever
then the next layer just put on two boards on opposite sides of the box
the next layer do the other two sides,
and at each level pull the greenery to the outside edge of the box so it can grow out and up and in the end you have a tall box that you can't see for the greenery
the trick is to get as much leaf area as possible, since it is the photosynthesis producing the starch for the potato and for the continued growth of the plant
so if you do go ahead and use the tires i'd put a spacer between them, enough to hold the soil, but still let the foliage out to the light