I don't know what your winters are like, but turning soil without bothering to break it up lets it weather and break up a bit, especially if it freezes. Try and work it when it is moist, dry it goes rock hard and you don't break it up well, too wet and the clay particles get closer together. Think of of the way they knead clay to make pots, it makes it more waterproof too, you can dig out a pond and spend an afternoon having a puddling party where everyone gets in the hole with a hose and puddles the clay all around the walls and bottom making it waterproof. Best on a sunny day with some alcohol, you all get very muddy.