Reduction in the size of mango trees would be a most desirable goal for the commercial and private planter. It would greatly assist harvesting and also would make it possible for the homeowner to maintain trees of different fruiting seasons in limited space.
In India, double-grafting has been found to dwarf mango trees and induce early fruiting. Naturally dwarf hybrids such as 'Julie' have been developed. The polyembryonic Indian cultivars, 'Olour' and 'Vellai Colamban', when used as rootstocks, have a dwarfing effect; so has the polyembryonic 'Sabre' in experiments in Israel and South Africa.
In Peru, the polyembryonic 'Manzo de Ica', is used as rootstock; in Colombia, 'Hilaza' and 'Puerco'. 'Kaew' is utilized in Thailand.
About 6 weeks before transplanting either a seedling or a grafted tree, the taproot should be cut back to about 12 in (30 cm). This encourages feeder-root development in the field. For a week before setting out, the plants should be exposed to full morning sun.
Inasmuch as mango trees vary in lateral dimensions, spacing depends on the habit of the cultivar and the type of soil, and may vary from 34 to 60 ft (10.5-18 m) between trees. Closer planting will ultimately reduce the crop. A spacing of 34 x 34 ft (10.5 x l0.5 m) allows 35 trees per acre (86 per ha); 50 x 50 ft (15.2 x l5.2 m) allows only 18 trees per acre (44.5 per ha). In Florida's limestone, one commercial grower maintains 100 trees per acre (247 per ha), controlling size by hedging and topping.
The young trees should be placed in prepared and enriched holes at least 2 ft (60 cm) deep and wide, and 3/4 of the top should be cut off. In commercial groves in southern Florida, the trees are set at the intersection of cross trenches mechanically cut through the limestone.
Mangos require high nitrogen fertilization in the early years but after they begin to bear, the fertilizer should be higher in phosphate and potash. A 5-8-10 fertilizer mix is recommended and applied 2 or 3, or possibly even 4, times a year at the rate of 1 lb (454 g) per year of age at each dressing, Fertilizer formulas will vary with the type of soil. In sandy acid soils, excess nitrogen contributes to "soft nose" breakdown of the fruits. This can be counteracted by adding calcium. On organic soils (muck and peat), nitrogen may be omitted entirely. In India, fertilizer is applied at an increasing rate until the tree is rather old, and then it is discontinued. Ground fertilizers are supplemented by foliar nutrients including zinc, manganese and copper. Iron deficiency is corrected by small applications of chelated iron.
Indian growers generally irrigate the trees only the first 3 or 4 years while the taproot is developing and before it has reached the water table. However, in commercial plantations, irrigation of bearing trees is withheld only for the 2 or 3 months prior to flowering. When the blooms appear, the tree is given a heavy watering and this is repeated monthly until the rains begin. In Florida groves, irrigation is by means of overhead sprinklers which also provide frost protection when needed.
Usually no pruning is done until the 4th year, and then only to improve the form and this is done right after the fruiting season. If topping is practiced, the trees are cut at 14 ft (4.25 m) to facilitate both spraying and harvesting. Grafted mangos may set fruit within a year or two from planting. The trees are then too weak to bear a full crop and the fruits should be thinned or completely removed.
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