I see that this is a bit of an old thread, but I was just reading through and thought I might tell you about my grandmother's solution to container gardening...
If you have, or have access to old cinder blocks (the gray cement blocks with the two holes in them that are roughly 4"x4") they can be used for great container gardens. She has grown peas, carrots, corn, okra, peppers, collards and many other vegetables that surprisingly do not require a large amount of space for the roots. I have a largish (yeah -ish) garden that measures approximately 400' X 115' that I plant every year and I have noted that a lot of the plants she grows in cinder blocks have roots that expand over quite a bit of area. Surprisingly though, hers do just fine within the confines of the cement blocks.
She just turns them on the side with the openings facing up and fills them with soil, then plants the seed directly into the potting soil. She says that the lime from the bricks assists the plants and allows them to grow in a more confined space.
I haven't tried this myself, but she always has a decent harvest with it.
She also plants squash and tomatos in old wash tubs and they produce quite well too. She doesn't have any special irrigation set up, she just waters her plants with a hose every day.
I believe she uses a slow release fertilize and puts about a table spoon to each cell of the blocks before planting.