Hydroponics is tough to do on a small scale - as nutrient levels need to be constantly monitored because there is no soil to buffer the highs and lows. Now the tire tuber idea does work very well though. I had a neighbor who grew potatoes that way - he also would simply put the seed potatoes on the soil surface and simply cover them with a good bunch of hay. Water appropriately throughout the season and when it's time to harvest - there's no soil to knock off the new potatoes. My landlady in Miami grew tomatoes in a hay bale. Get one good hay bale - plant the seedling a few inches in the hay and water accordingly. The cool thing about this method - is that if you need to move the tomato plants - it's simply a matter of moving the bale of hay.

Dan