I saw this idea last year . . well, kind of this idea.
At the Chicken Chicks blog she was showing how to turn used feed bags into planters for potatoes . . straw in the bottom, some dirt, potato :eyes" and more dirt. As the potato vine grew, roll up the sides of the bag and add more dirt.
I bought a bae of straw and we needed some more potting soil. The plants were $7 apiece at Save-a-Lot. So for about $30 I got this arrangement AND enough straw to put over the grass seed we need to plant in the back yard and enough potting soil for the rest of this year and next year . . . you know how it is . . .never know how much soil you are going to need.