I don't know where in your area but riding stables are often only too glad to see the back of it, though it is often mostly bedding material. Even that is good though.
A tip I learned a long time ago to "tame" solid clay (the type that you could really put on a potter's wheel) is to build a bonfire (quite a big one) and stack the lumps of clay onto it when it is burning well. Make a sort of igloo out of the clay lumps and leave the fire to burn out. Next day, the clay will have baked hard. You can smash it down into powder and it won't fight back and reform into gloop.