Former Systems of Tapping.—To hark back ten years in the plantation rubber industry is equivalent to delving into history, since development has been so rapid. It was then thought necessary to place upon the trees a number of simultaneous cuts which the modern planter would judge to be inconceivably excessive. Were it not for evidence in the shape of photographs extant, it would be difficult to convince a young planter that such systems were employed.
It was not uncommon for trees to have from six to ten cuts, sometimes all placed on one half of the tree in a herring-bone fashion, and sometimes divided into two portions, each of which tapped the opposite quarter panel of the tree’s circumference. Such superimposed cuts were spaced from 1 foot to 18 inches apart.
On other occasions, a spiral cut was employed, commencing at a height of, say, 5 feet, and gradually descending to the cup at the base of the tree.
Later systems varied from several cuts on a half-circumference, or on a quarter of the tree, tapped either daily, or on alternate days, to cases in which one-third or one-fifth of the tree was employed. Also popular were the systems of the V and half-spiral cuts on half the circumference.
It did not take long to be recognised that with all these systems demanding a number of simultaneous parings from the same panel of bark, the rate of excision was so heavy that the period available for the renewal of bark was insufficient for continuous tapping.
As a result most of the systems specified have fallen into desuetude, and the tendency has since been to reduce the number of cuts, or the periodicity of tapping, so as to allow for increasing periods of bark renewal.
In the earlier days, a period of four years was thought to be an extremely generous allowance, whereas six years is now becoming recognised as a minimum necessity. Eight years is not regarded as extravagant, while with older bark on some estates periods of ten and twelve years have to be allowed for full renewal. Even so no finality has been reached, and no general rule can be laid down. Local conditions of planting and growth exercise great influence, and the writers have in mind instances in which a period of eight years has proved to be insufficient even for a first renewal after the excision of virgin bark.
In the main the most popular systems of tapping are:
(a) One cut on a quarter of the tree, tapped daily.
(b) One cut on a third of the tree, tapped daily.