Nurseries having been properly established, attention may next be turned to the preparation of the fields for planting. In the first place some kind of draining will nearly always be necessary. In tropical agriculture two totally distinct kinds of draining are to be distinguished. The first is the draining of swampy land for the removal of superfluous water, and the second is the cutting of transverse drains on sloping land, in order to check the washing away of the soil, which soon occurs when the original vegetation is cleared.
In the Federated Malay States rubber is frequently planted on alluvial flats where the water level is only a foot or two from the surface of the soil. In selecting land for an estate in such a situation it is important to remember that provision will have to be made for carrying off the drainage water to a river or to the sea. For this purpose canals of some size may have to be specially constructed, and it may be necessary to acquis the land occupied by the canal beyond the boundary of the estate proper. The necessary canals are usually^ cut by government before the sale of the land. In soil of this kind numerous open drains are required, which may be as much as three or four feet deep and two or three feet wide. In some cases a drain is needed between each row of trees, and the trees themselves are planted on ridges formed by the materials thrown up in digging the drains. In the Southern Province of Ceylon a certain amount of rubber has been planted in swamps similarly drained.
A large part of the rubber in Ceylon and other countries is however planted on comparatively steep hillsides, and here an entirely different system of drainage is required. Small drains about one and a half feet in width and depth are carried across the slopes with a fall of from 1 in 15 to 1 in 25. These are made to discharge into any natural ravines or watercourses which may occur. The distance between the drains varies, according to the slope, from 100 feet down to 20 feet or less. The earth removed in digging is thrown out on the lower side of the drain. Loss of soil may be further checked by interrupting the drains with catch pits at frequent intervals. On very rocky hillsides draining may be impracticable. In this case some kind of terracing is frequently attempted by building low walls of boulders below the trees. This method is strongly to be recommended where drains cannot be cut.
Irrigation has been little practised in the cultivation of Hevea. In a dry climate the tree appears to suffer more from the effects of sun and wind upon its young branches and leaves than from lack of water in the soil. Experiments in growing Hevea under irrigation in the dry zone of Ceylon have so far been unsuccessful, though it is possible that they might have fared better if an effective wind-break could have been found.
The laying out of roads and paths leading to the different sections of the estate is an operation which should be undertaken at the same time as the tracing of the drains, in order that the necessary culverts and bridges may be provided for. Except in the case of the principal tracks, little road-making is necessary beyond the provision of a drain on one or both sides of the trace, and the building of suitable culverts or paved watercourses to prevent breaching by floods.