At the orchard we have chickens that live in a movable dome that Toshio built. The dome is about 12 3/4 feet in diameter and made of PVC pipe and chicken wire. The roost is a lashed bamboo grid suspended from the top of the dome. The design comes from the book, "The Permaculture Home Garden", by Linda Woodrow.
We move the chicken dome every two weeks to a new spot. The floor is open, without wire, so the chickens help out the orchard by eating weeds, insects, and surplus fruit and vegetables, and by fertilizing the ground. Right now the chicken dome is in my garden, where the chickens are eating up weeds and insects and fertilizing the soil for the spring.
Last year I had the chickens stationed in the area that I later used to plant tomatoes. They left the soil loose and free of everything but the biggest weeds, and I didn't need to have the area tilled. After we moved the dome to the next spot I put down hay as mulch to keep down weeds until it was time to plant. I made beds by just pulling back the hay and hoeing in compost. Last year's tomatoes seemed to grow really well, so I hope to have time to station the dome in the areas for tomatoes, summer squash and cucumbers. The chickens need to be out of the area 120 days before ground crop harvest and 90 days before the harvest of vine crops.
We started out with 13 chickens, but now we have only 9, including the rooster. If we want to have more eggs to eat and sell, we'll have to buy a few more chickens that are younger. Ours are now about 4 years old and don't lay eggs very frequently.