There are few cultivated crops that make less drain upon soil fertility than cacao, and few drafts upon the land are so easily and inexpensively returned. From an examination made of detailed analyses by many authors and covering many regions, it may be broadly stated that an average crop of cacao in the most-favored districts is about 9 piculs per hectare, and that of the three all-important elements of nitrogen, phosphoric acid, and potash, a total of slightly more than 4.2 kilograms is removed in each picul of cured seeds harvested. These 37 kilos of plant food that are annually taken from each hectare may be roughly subdivided as follows:

• 18 kilos of nitrogen,
• 10 kilos of potash,
• 9 kilos of phosphoric acid.

On this basis, after the plantation is in full bearing, we would have to make good with standard fertilizers each year for each hectare about 220 kilos of nitrate of soda, or, if the plantation was shaded with leguminous trees, only one-half that amount, or 110 kilos. Of potash salts, say the sulphate, only one-half that amount, or 55 kilos, if the plantation was unshaded. If, however, it was shaded, as the leguminous trees are all heavy feeders of potash, we would have to double the amount and use 110 kilos.

In any case, as fixed nitrogen always represents a cost quite double that of potash, from an economical standpoint the planter is still the gainer who supplies potash to the shade trees. There still remains phosphoric acid, which, in the form of the best superphosphate of lime, would require 55 kilos for unshaded orchards, and about 70 if dap-dap, Pionciana, or any leguminous tree was grown in the orchard. These three ingredients may be thoroughly incorporated and used as a top dressing and lightly harrowed in about each tree.

If the commercial nitrates can not be readily obtained, then recourse must be had to the sparing use of farm manures. Until the bearing age these may be used freely, but after that with caution and discrimination. Although I have seen trees here that have been bearing continuously for twenty-two years, I have been unable to find so much as one that to the knowledge of the oldest resident has ever been fertilized in any way, yet, notwithstanding our lack of knowledge of local conditions, it seems perfectly safe to predicate that liberal manuring with stable manure or highly ammoniated fertilizers would insure a rank, succulent growth that is always prejudicial to the best and heaviest fruit production. In this I am opposed to Professor Hart,1 who seems to think that stable manures are those only that may be used with a free hand.

We have many safe ways of applying nitrogen through the medium of various catch crops of pulse or beans, with the certainty that we can never overload the soil with more than the adjacent tree roots can take up and thoroughly assimilate. When the time comes that the orchard so shades the ground that crops can no longer be grown between the rows, then, in preference to stable manures I would recommend cotton-seed cake or “poonac,” the latter being always obtainable in this Archipelago.

While the most desirable form in which potash can be applied is in the form of the sulphate, excellent results have been had with the use of Kainit or Stassfurth salts, and as a still more available substitute, wood ashes is suggested. When forest lands are near, the underbrush may be cut and burned in a clearing or wherever it may be done without detriment to the standing timber, and the ashes scattered in the orchard before they have been leached by rains. The remaining essential of phosphoric acid in the form of superphosphates will for some years to come necessarily be the subject of direct importation. In the cheap form of phosphate slag it is reported to have been used with great success in both Grenada and British Guiana, and would be well worthy of trial here.

Lands very rich in humus, as some of our forest valleys are, undoubtedly carry ample nitrogenous elements of fertility to maintain the trees at a high standard of growth for many years, but provision is indispensable for a regular supply of potash and phosphoric acid as soon as the trees come into heavy bearing. It is to them and not to the nitrogen that we look for the formation of strong, stocky, well-ripened wood capable of fruit bearing and for fruit that shall be sound, highly flavored, and well matured.

The bearing life of such a tree will surely be healthfully prolonged for many years beyond one constantly driven with highly stimulating foods, and in the end amply repay the grower for the vigilance, toil, and original expenditure of money necessary to maintaining a well-grown and well-appointed cacao plantation.