Hey
Head, powdered dolomite lime can be mixed into the soil at mix, a tablespoon per gallon of medium.
Wood ash can be a good source of Calcium as well as other nutrients (lots of K and a fair but of P), though it should be used with some care as it is very alkaline.
Check out these links:
Wood Ash Genral Information
Wood Ash in Context of Canna-Cultivation
SS