The best site for the mango orchard is one which has good drainage together with soil of such nature that it will dry out thoroughly when no rain falls for a few weeks. In regions where the soil is deep and the trees consequently grow to large size, they should not be set closer than 35 by 35 feet. There are a few dwarf varieties, such as D'Or, which can be set much closer than this, but most of the Indian kinds ultimately make trees of good size. G. Marshall Woodrow recommends planting 20 by 20 feet, but in America this has not been found a good practice. Closer planting than 30 by 30 feet is undesirable except with dwarf varieties. Seedlings grow to larger size than budded or grafted trees, and need proportionately more space. On deep soils they will usually come to crowd each other in time if planted less than 40 or 45 feet apart.
April and May are considered the best months for planting in Florida. Midsummer planting is, however, much more successful than with the avocado. The principal point to be observed is the condition of the young tree at the time of planting. If it is not in active growth, it can be set at almost any season of the year, provided the weather is warm. In India it is recommended to plant at the beginning of the rainy season.
Holes 2 to 3 feet broad and deep should be prepared in advance of planting. Woodrow recommends that 20 pounds of fresh bones be placed in the bottom of each hole before filling in the soil. In Florida a small amount of commercial fertilizer is commonly used. The object in preparing the holes is the same as in planting other fruits, viz., to loosen the subsoil so that the roots can develop readily in all directions, and to place in the ground a supply of food for the young tree. It is sometimes recommended that stable manure be incorporated with the soil; this is a desirable practice, but it should be kept in mind that stable manure is not, generally speaking, suitable for bearing mango trees.
Well-grown budded or grafted trees, when shipped from the nursery, are eighteen inches to three feet in height, with stems one-half inch in thickness. They should be stocky and straight, with foliage of rich green color. Inarched trees are sometimes weak, crooked, and may have poor unions. While many inarched trees are produced and planted in certain parts of the world, notably in India, they seem much less desirable than the sturdy budded trees grown in the nurseries of Florida.
As soon as the young trees have been planted in the field, they should be shaded with a light framework covered with burlap or other cheap material. Palm leaves and pine boughs may be used for this purpose. The trees should, of course, be watered liberally as soon as they are planted, and in most regions the ground around the base of each should be mulched with straw or other loose material.
During the first four or five years, the trees should be encouraged to make vigorous rapid growth. After that the aim of the orchardist is to make them produce good crops of fruit. The object of early culture is, therefore, distinct from that of later years and somewhat different methods are required. The young growing tree can be given both water and fertilizer in liberal quantities; the mature tree, on the other hand, must be encouraged to flower and fruit by withholding water and fertilizer during certain portions of the year.
It must be admitted that the cultural requirements of the mango are not yet thoroughly understood. Varieties differ greatly in their reaction to the stimulus of tillage, irrigation, and manuring. A thorough study has not yet been made of the requirements even of a single variety. Horticulturists in India have devoted a limited amount of attention to the subject; but the mango seems to differ so markedly from other fruits which have been subjected to systematic cultivation that much further study will be needed before its habits are thoroughly understood.
The amount and character of tillage given to the orchard varies in different regions. In most parts of the tropics little attention is given to the mature tree. The soil beneath its spreading branches is often firmly packed down by the hoofs of domestic animals; or weeds may be allowed to grow unchecked. Needless to say, such treatment has little to recommend it. In Florida the land is sometimes given shallow cultivation during part of the year, and at other seasons leguminous cover-crops may be grown upon it, particularly if the orchard is not yet of bearing age. It is evident that the amount of nitrogenous fertilizer required by bearing groves is small. Over-stimulation results in vigorous development of foliage but no fruit.
Growers of grafted mangos in India resort to various expedients to check the vegetative activity of the tree and encourage the development of fruit. Thomas Firminger1 says: "The mango, like all other fruit trees, is much benefited by having the earth around it removed, and the roots left exposed for a space of two or three weeks. This should be done in November, and in December the roots should be well supplied with manure, and then covered in again with entirely fresh earth, and not that which had been previously removed." Woodrow notes that "the mango growers near Mazagon, Bombay, who produced such famous fruit before the land was occupied with cotton mills, applied ten pounds of salt to each tree at the end of September; this would arrest growth in October and November, and encourage the formation of flower buds. In a moist climate, and the intervening ground occupied with irrigated crops, this system is highly commendable, but with a dry climate it is unnecessary."
The failure of many varieties to fruit abundantly is often attributed to imperfect pollination, attacks of insect pests, and other causes which are discussed in a later paragraph. It seems probable that too much emphasis has in the past been placed on these factors, and that the problem is largely a physiological one, connected with the nutrition of the tree. It is for this reason that the two quotations above are illuminative. They show that the nutritional problem has been recognized by early students of mango culture; yet no one has taken up the subject in sufficient detail to master it.
1 Manual of Gardening for India.