@Colinhendee the crop will not take up 1000 ppm of calcium, that Is just what is recommended to ensure that enough calcium becomes available during the crops growth. 1000ppm is 2000lbs per acre and your crop will only use a tiny fraction of that. If you are regularly applying a highly available source of calcium then the objective is to feed the crop directly rather then building your calcium reserves.

It does seem to me that the gsr application rates are far too low though.