In different growth stages crops  required phosphorus and calcium in the same  time ,but we avoid to add these  items together  or in short period to avoid precipitation of Ca & P as calcium phosphate which insoluble compound,

So in this group of special fertilizer you can solve this problem in using one compound with no restriction but with high efficient absorption and performance.

16-40-2+5%CaO

17-40-2+2%CaO

14-20-5+12%CaO