Hay bale gardening has been very popular for several years. I actually did this a few years back just to see how it worked. The tomatoes I grew were very good and flourished. Lettuce and English peas also thrived but the okra, peppers and carrots did not particularly like the hay bale environment. I also panted herbs all around the sides that fared okay but not great.

The bales have to be prepared with fertilizer and water for a couple of weeks before planting to begin the decomposition. All in all, I called it a general success but nothing I would do again. By the end of the growing season the bales decomposed so badly I had to prop them up in places. The hay seeds sprout and cause problems too.

But, I guess if you have awful soil this would be something to consider.