What we found after pigs is that , because their feet all sink in the same amount, there is a hard pan a bit below the surface. Ideally this needs to be ploughed (a single furrow plough isn't expensive). After we let it stand for a while to weather, we would then go over it with a tractor driven rotavator (our little tractor is a Siromer). The rotavator is useful for all sorts of things, but doesn't work the soil deeply enough to break up the hard pan. It leaves it ready for planting straight afterwards.