I don’t know all the technical details of how this is achieved, but there are many instructions online. I do know that my brother’s tomatoes and onions and potatoes and peppers and broccoli(?) have taken pretty well. It looks like he has sometimes planted different plants adjacently. Also, that big group of plants in the the old dog crate are potatoes. And when they are ready to be harvested my brother will simply take off the crate and, dig out the potatoes from the mass of dirt. Pretty cool! You can see the remnants of one of the challenges of straw bale gardening in several of these pictures as in the early stages numerous mushrooms tend to grow out of the bales which need to be removed.