I use all of the horse manure I can get here, BUT that might not work for you! ---Compost is great, but takes a lot of it. Big-R stores here sell bags of composted cow manure, ( de- scented) and it works good for mixing into the soil.
If you can get some good topsoil, that would help too. When it dries out , till it several times as deep as you can go and let it sit a few days if you can then till again.---some of that stuff will rot down, but for the clay problem---really need to add good soil to the top few inches of it.
