Also what can I use to kill the weeds inside the chicken run that is not weed killer and it wont harm the chickens ?
Interesting. My chickens ate everything down to the bare dirt in almost no time. I thought that was the ultimate weed control. Just eat everything!
I don't use any chemicals on my lawn at all. But I don't have a big weed problem. A fresh mowing will make everything look good enough for me. At the moment, my lawn is under one foot of snow, so it will not even be growing again until next April.
If your chickens do not eat the weeds in your chicken run, I would suggest just chopping/cutting down the weeds and throwing wood chips, leaves, and/or grass clippings on top of that patch to block the sun from the weeds and kill the growth.
I turned my entire chicken run into a compost system after my chickens ate the grass down to bare dirt. I think it was the best decision for me. I harvest $$$ worth of compost a couple times a year from the chicken run compost and use it in my raised beds and other gardens. Last year alone, I harvested over $300 in compost (big box store compost bags equivalent) for my gardens. My people food in the gardens is growing much better and I could not be happier. Also, my chickens love to scratch and peck the compost all day looking for worms and bugs to eat. So they benefit too as they make compost for me.
There are a number of us on the BYC forums that raise composting chickens and consider the eggs just a bonus. Anyway, if you decided to turn your chicken run into a compost system, I started out with a base layer of wood chips to cover the bare dirt. This will prevent your chickens from getting all muddy if it rains. Some people will just stop there as the wood chips look pretty nice in the run. But I continued to add grass clippings all summer long and then leaves in the fall. Last year, my chicken run compost was 18 inches deep after all the fall leaves were dumped in the run. Over winter, it went down to about 12 inches deep. But the compost under the top few inches is a rich dark black gold material that is great for my gardens. I spread out my grass clippings and leaves in layers, but the chickens will naturally mix up the compost as they scratch and peck around looking for things to eat. It really is a great system.
Since I don't use any chemicals anywhere on my lawn, everything I take off my lawn is safe to throw into the chicken run compost system. I would think that whatever chemicals you used on the lawn should have some kind of warning as to how long you should keep pets and small animals off the treated section(s). If not, maybe contact the company customer service and ask for a printout on the topic. Honestly, since you are concerned about the chemicals, and I think I would be too, I would look into other solutions like vinegar, already suggested. Also, I see some people using a propane torch to burn out/down the offending weeds. I have a dandelion stick that I use to pull them out by the roots, and then I feed the dandelion plants to my chickens. What they don't eat gets mixed up in the chicken run compost.
Because of hawks and Bald Eagles overhead all the time, I don't free range my chickens. But I cut the grass and collect the leaves and bring the range to them into the chicken run. It works for me and keeps my chickens safe. Chickens don't need to free range to be happy.