Wonder how hard these are to do...
http://www.wuvie.net/tireplanter.htm
They look pretty good on the page, though I dunno that anything *I* did would come out like that. Gotta be pretty hard to cut reinforced rubber evenly without killing yourself.
What kind of soil do they have around there? You could always dig a place. You'd have to kill the grass first, though. Just put some plastic or newspaper down and leave it until the grass dies.
Steve and I did plant about 250 onions this past Sunday...you can also see our garlic, which is about 5 inches tall now and our radishes...