As to the soil binding, I was referring primarily to P.  On leaching, I am referring to K, nitrate, sulfate, chloride, and on down the list.  Yes, if the nutrients are more available to the cash crop, they are also more vulnerable to leaching -- however, (a) the nutrients have been moved closer to the surface by the cover crop, and (b) there's hardly any time for leaching to occur, since the cover crop (if done properly) pulls most of the deep soil moisture.  I.e., if there's continual vegetative cover, far less leaching will occur.

There's plenty of data to support these statements, some of which have been posted on AgTalk recently.  Ray Weil has gathered good data from Steve Groff's farm, for instance.  Most of the mechanisms I've described have been long known in the soil science community, but few have glimpsed the implications or persuaded farmers to make use of it by growing cover crops.  That is changing.