When pouring footings for bridge abutments, the elevation of the top of the footing was usually 2ft. below the elevation of the stream or river. After putting a rough finish on the top of the footings we would turn the dewatering pumps off and flood the entire footing. Best thing for curing concrete. If I was building this chicken run ,I'd did the holes large enough to accept dropping in a 60 lb. bag of premix so it would lay flat in the hole. Drop bag and all into hole . Place your post into the hole plumb it and fill it in with what you dug out. Moisture will get into that bag and do it's thing. 45 years ago I saw a 90ft x 60ft pole barn built this way and it's still standing today.
