They look like Liberty's, but as has been said, Liberty's don't normally grow on manure, they grow in feilds that have been fertilised by manure, but never (in my experiences) directly on the manure. Also the season, earliest I've seen Liberty's grow here in Scotland is around late August. Your spore print should come out a Purple-Brown colour if they are Liberty's. 1g Dried would be a good starting dose, Liberty's are pretty potent. Start at 1g Dried and work up.
well, because of the humidity at the moment, there has been alot of fungus everywhere for the last month, i work in a top garden centre in my area and every day we are having customers come in saying they are having fungus problems in their gardens. we have sold a years worth of fungus treatment stock in just over a month. so i think that explains why i have found them now, it seams to be perfect conditions for them. i will give them a go Saturday night and let you know what happens, the spore print is most definatly black though, no doubt about it, no brown, its possible its a very very deep purple. i shall perhaps return to the spot i found them and hopefully if they are still there i will take more pictures, and check for bluing
The fact they have a Black spore print, were found out of season, and found directly growing from manure SCREAMS "These are not libs". Eating unidentified mushrooms is completely irresponsible, I'd suggest you don't eat them. They're not libs.