I have found that when you have poor soil, like I did in these beds last year, you have more water stress in the heat of the summer, weaker plants and a greater likelihood of disease and insect pests. It's nature's way of making sure that we feed the soils. I don't expect the same type of problems to anywhere near that degree this year.
I grew some green manure crops of peas and beans and turned all that matter into the soil. I supplemented with an untold amount of leaves this last fall and several bags of compost from the garden center. We also mulched with alfalfa last year and turned that all in when we dug the beds. I am mulching with straw this year and am growing worms in my worm bed. I hope with all of that, my yields should be higher and my plants should be healthier. Feed the soil and the soil feeds the plants.
We'll do it again, but maybe not in tires.
If you try this, get a jig saw and cut off the sidewalls of the tires before you plant. That makes it more of a barrel and it is easier to break down in the fall when you harvest. It also removes a serious place for black widows to hide, a real concern in the desert.