I have some pretty clay heavy soil here and just a foot down is nothing but clay mixed with sand and gravel (like digging in concrete). I have been mixing in rough (unsifted) compost for the part 6 years we have been here and the garden soil is really showing a difference. Don't feel the need four s compost to look all black and crumbly - there's typically still bits of straw, shavings, etc in my compost when I spread it. Late Fall or early Winter is the best time to add the compost. After harvesting, I mix my compost into the top few inches of the raised beds and till it into the ground as part of the preparation for winter. Winter freeze and thaw cycles help to work the compost into the soil even more, loosening it up for Spring. The winter season also gives the compost time to "cool off" in case it is too "hot" with nitrogen.Maybe eventually with continuing to add chicken coop compost it will get to where I don't have to till