Use practices that discourage too much vegetative growth. When there is competition for Ca between vegetative growth and fruit, the vegetative growth is a much stronger competitor. Avoid excessive dormant pruning because this encourages vegetative growth. However, summer pruning may prove advantageous because of the reduction of vegetative growth. Encourage good pollination.
Seed number affects fruit Ca.
It appears that seeds help direct Ca to the fruit. Do not grow excessively large fruit. Fruit Ca decreases with fruit size for any given cultivar. Avoid water stress. For roots to absorb Ca, water must be present, and under severe water stress, the leaves can withdraw water and Ca from the fruit.