According to the Horticultural Crops Development Authority (HCDA), mangos in Kenya are available from November to April (and sometimes to July). Because of less competition better prices are fetched in Europe and the Middle East between November and December (see Appendix 5 - Export Market Stats for Kenya). Many techniques have been used in other countries to improve productivity and to alter the cropping season. Smudging (moist organic material—grass, leaves, etc.—is slowly burnt under the tree canopies and the resulting smoke induces flowering) is an old technique reported from the Philippines for enforcing off-season flowering, but this has largely given way to chemical induction. The application of potassium nitrate has been commercially accepted. The reasons are obvious: to have an altered earlier harvest, to take advantage of the good market price, to fill the gap of under-supply and to have flowering during a dry spell with little or no fungal diseases.
The readiness of a tree to flower is an important factor for a successful operation. For best results, choose trees with leaves that are dull green or greenish-brown and brittle when crushed by hand. The trees should have an appearance of suspended growth or be dormant alive but not growing; a resting stage. It is easier to induce mango trees to flower towards the dry season, and older trees respond better than young ones.
It is recommended that a 1% potassium nitrate solution mixed with a sticker material added to a spray to increase retention on plant foliage agent (adhesive) be sprayed on to the tree, totally drenching its terminals and leaves. Make sure a knapsack sprayer has no residual herbicide any chemical used to kill plants in it before beginning to spray. If the timing is right, flowers will emerge 10–14 days after application. Tentative trials have been successfully implemented in Kenya.