Mrs H is correct about them drying out. Mine don't because it's humid here. Tomatoes and squashes will send down their roots to three or four feet deep, so they find water fairly easily, if you're growing lettuce you will need to water often.

They will shrink and separate some. I put a racheting tie-down around mine so I can tighten it as it shrinks

I read a post from a man in Florida on either the Market Gardener thread or Four Season Harvest who does the same thing outdoors with his lettuces in his cool season. He put the bales cut edges down on pallets and used a weed eater tool to carve out a depression in the bales. I think he used mushroom compost as a growing medium. He said he sells his greens for $6/# wholesale or $8/# retail.

Last summer I put a single straw bale, cut edge down in the yard. I put dried goat manure on it, watered it in and transplanted a volunteer pumpkin seedling into it--just opened a space in the cut ends and watered it. I emptied the chickens' waterer onto it every day when I gave them fresh water. It was a miniature pumpkin and produced a few fruits. The added benefit is that the whole bale composted nicely. The best thing is that all summer long, I didn't see one cucumber beetle on the vine or any other bug for that matter.

Since I have livestock, I have used leftover or spoiled hay with pretty good results. The trick since hay can have a lot of seeds is to water it well, let the seeds germinate then cover the whole business for a few days with clear plastic to "cook" the bale and seeds.

Yesterday (Oct 19) I put "books" of hay treated this way to make an experimental bed in the second hoop house, wet them down and put some good finished compost over the top. We'll put the cover on the hoop house this afternoon and then I can start transplanting my seedlings into the beds. The other two beds are finished compost and plain soil just in case the straw/compost bed isn't as effective. I am concerned about the layers freezing where the natural soil hasn't done so in the past, even in extended periods of cold. At least our cold here in central Missouri.

Hey, I'm a Master Gardener too and make soap as well. Also, cheese from our goats' milk, have the chickens, big gardens (about 5000 sq. ft.), orchard, etc.