If your tree does not have a disease,and if you are following the proper fertilizer regiment for your trees age (3 fertilizer applications a year), then to help the tree to flower, it is a common commercial practice to apply a 1 percent urea or a 1 percent potassium nitrate solution as a foliar spray to the tree's foliage approximately 1-2 months prior to your tree's expected bloom date. This procedure will help your tree's production.

Thanks very much. Where can I find urea or potassium nitrate?