Found this on an organic gardening page....

"Potatoes are on many dinner tables each day, and home gardeners often include them in the family garden. But instead of relying on mere dirt to grow your potatoes, try your hand at planting them in seaweed. Growers have used this organic material for centuries. Nutrient-rich seaweed feeds plants without the need for other fertilizer. It is sturdy enough to hold potato plants in place and can eliminate the need for soil altogether."