Of these lime is by far the most prominent, forming about 60 per cent. of the whole.
I cannot help, therefore, arriving at the conclusion that, to cultivate coffee with any degree of success, the first-named substance must be present in the soil; or, if not present, must be supplied to it by some process.
Now it is a singular fact that the rocks and soils of Ceylon are greatly deficient in alkaline matter; and, taking this view of the case, one no longer wonders that many estates cease to produce coffee. That all, or nearly all the plantations did, in their first year or two of bearing, produce liberally in fruit, may readily be accounted for by the fact that the alkaline poverty of the soil was enriched by the burning of the vast quantities of timber which lay felled on all sides. Whilst this temporary supply lasted, all was well with the planter. Heavy rains, and frequent scrapings of the land with the mamotie, or hoe, soon dissipated this scanty supply, and short crops are now the consequence.
But nature, ever bountiful, ever ready to compensate for all deficiencies, has provided to our hands a ready means of remedying this evil of the soil, by scattering throughout most parts of the interior supplies of dolomitic limestone. The dolomite of Ceylon is not pure, far from it, being mixed freely with apatite or phosphate of lime. Even in this very accidental circumstance the coffee planter is aided; for the phosphoric acid thus combined with the limestone is the very substance required in addition. Some of the finest properties in the island are situated on a limestone bottom, and these no doubt will continue to yield abundant crops for a very long period.
It has been urged against this opinion that in some districts where coffee planting has proved a complete failure, dolomite is found most abundantly; but I have very little doubt that the dolomite here alluded to is only magnesian limestone, and which is most inimical to the coffee bush.
I am aware that already several manures have been tried on coffee with varying degrees of success. Guano has, I believe, quite failed, and is besides very costly. Cattle manure is said to be effective, and no doubt it is, but it is a costly and troublesome affair. Bones, ground fine, are now being tried, though they cannot but prove most expensive, especially when imported.
A ton of bone dust contains of animal matter, 746 lbs,; phosphates of lime, &c., 1,245 lbs.; carbonates of lime, &c., 249 lbs.
The virtue of bones lies in the phosphates far more than in the animal matter, and thus their action on soils is felt for many years after their application. The Singalese cultivators of paddy about Colombo and Galle, appear to have been long aware of the fertilizing effects of this kind of manure, and import the article in dhonies from many parts of the coast: they bruise them coarsely before applying them.
The partially decomposed husks of the coffee berry have been tried for some years, and successfully, but they are difficult of collection, and bulky to remove from one part of the estate to another.
In Europe it would appear that little is yet known as to the causes of the fertilising effects of oil cake: some suppose them to arise mainly from the oil left by the crushing process, but this is not at all clear. I do not, however, see that we must look for much assistance from Poonac as a manure for coffee: for the cocoanut tree it is doubtless most valuable, but we have yet to learn that, beyond supplying so much more vegetable matter, it helps the action of the soil on the roots of the coffee bush, which, after all, is what is really required.