straw bale gardening
I didn't like it either. Plants do better in soil. I made a raised bed with strawbales once using the bales as a border with open space in the middle and filling that with soil compost mix. After the bales break down you're left with more of a mounded raised bed.
Some people have done it, but results will be highly variable. Plants need a certain level and ratio of minerals to grow good, if those minerals can be added to the bales it might work fine, The bales will compost while the plants grow and depending on the exact content of the hay or straw it can rob nitrogen, or it can get too hot if there's plenty of nitrogen. Alfalfa would overheat, straw might rob nitrogen to rot down. If hay is available free or real cheap, it might be better to compost it first and add that to the soil. Along with whatever minerals the soil is short on, and nitrogen if needed, composted alfalfa will be high nitrogen already, since protein breaks down to nitrogen. I prefer to work with the dirt, adding biochar and compost and minerals. But if the dirt has serious problems, as in severe overload of salt or something, or nothing but hard clay, or rocks, no dirt worth working with, maybe the bales would be a good alternative.
I had very good results using hay bales for potatoes and green beans. For the potatoes I just put the seed potatoes on top of the soil and set the hay bail on top. the plants came through the bale with no problem. I had no issues with dryness in the hot and dry North Carolina summer. The potatoes were very easy to harvest as well-just pull back the hay.
For the green beans I layed six hay bales two across in a rectangle and put some soil on top for starting the seeds. The plants were very vigorous and I had fewer problems with bean beetles. Again no moisture problems.