I absolutely let mine on the garden once I've harvested everything. They take apart whatever plants are left, till the ground for the following year and fertilize it as they go. I also dump a few buckets of horse manure on the garden and they love to pick through that as well, eating any grain and seeds they find. Within hours of a bucket being put out there, they have tilled it into the ground so much that you can barely see it. Mine are free range though. I leave the food/water where they are year round and just open the gate to the fenced off garden area so they go come and go as they please. So there is no scratch thrown out there. Over the winter, rather than throw stuff in the compost bin, where it just freezes, I throw it on top of the garden area. The chooks pick through it and eat what looks good to them. The rest (banana peels and so on), eventually gets scratched into the ground where it composts naturally. By putting the kitchen scraps on the garden, they are encouraged to continue scratching and tilling so they do a really thorough job.