Last winter, I moved our chicken tractor all over the yard to give the chickens fresh ground often. But this year, I'm parking them on top of my raised beds to see if they can help the improve the soil. So far, they've been there about two weeks and have done a good job tilling up the dirt. I was wondering if there was some "ideal" length of time to leave the chickens in one spot for maximum soil benefit? Also, when spring rolls around, how long should the garden be chicken-free before planting? Thanks for your help!