Chicken safe way to kill fleas in yard?

Lately I have been having a severe struggle with my dogs having fleas. I have tried everything to get the fleas off of them, even going so far as the more chemical type flea bath. I usually try to stay all natural with everything, especially when it comes to my animals.
At this point I am thinking that the yard is infested. There is no way I have been totally unsuccessful in killing the fleas on their bodies. I have seen the fleas come out of their fur during treatment.
However, they go out to potty, a few mins later I check, and they are once again crawling with fleas.
I have seen these yard sprays to get rid of fleas. Problem is, my flock free ranges all over the place. I do not want to treat my yard with chemicals. Is there anything that is safe for chickens that will get the fleas out of my yard?

As I was in the yard last night I noticed fleas jumping on my legs. We had been delayed in getting a flea collar on the cat, since some of the chemicals are toxic to him (probably all are, but I cannot tolerate fleas). They're in the house and I've been dealing with that, and think we're winning. Now I also have to figure out how to get them out of my yard.

One natural remedy I used on my cat was food grade Rosemary oil diluted with light olive oil, and it worked to repel the fleas, along with a flea collar to kill the current fleas. He was flea free until he discovered during the snuggling time that I was putting some disgusting thing on him and he would jump off my lap shaking his feet.

Possibly planting Rosemary and clipping some occasionally to spread around the yard would help. I believe also I will plant some in my flower beds and around other areas. Tansy is another repellent herb. There are others, but I don't remember at the moment.

ETA: Herbs will only repel fleas; anything that kills the fleas will be toxic to chickens.