I've been intrigued with the notion of Straw Bale gardening for a while, and decided to give it a try this Spring. I decided to use the center space within my bales to do a version of the Potato bin method. I covered the grass inside the space with a sheet of heavey corrigated cardboad, and then a layer of compost from my chicken yard. My question is this- how deep should my compost be for my potatoes? I will fill the remaining space with loose straw, as the potato plants grow. My compost right now is about 4 inches deep. Do you all think that is sufficient? And how much compost should I put on top of the potato starts? Thanks!