the brassicas (rape, turnips) are a small seed so don't bury them too deep. If your ground is still very wet you could just broadcast them on the surface and drive over the seeds to "smash" them into the soil. What I do on my type of soil is till and then just broadcast then cover by dragging a homemade drag made from chainlink fence behind my ATV.--Lots of options but just don't bury deeper than 1/4 inch.