I have the same problem. On the advice of someone on here I tried sharp sand. It worked for a while till the heavens opened again and now they are ankle deep in mud again. So next step is to dig it all out to base ground level,weed membrane on top, then gravel on top. Sandy's hens and ducks are on gravel and I think it's the best thing I've seen. Grass might start growing again once I shift the ducks out of there too.