RUBBER PLANTING 113 



keeping the surface of the soil loose and powdery, in 

 the form of what is known as a dust mulch, since a 

 caked surface evaporates much more water than a loose 

 surface. A leafy crop however is capable of evaporating 

 three or four times as much water as. a bare surface of 

 soil. In times of drought therefore a thick covering 

 of living weeds is a special danger, since the weeds 

 draw off the supplies of water available for the rubber 

 roots, and the crop is liable to suffer severely in 

 consequence. 



On steep slopes a cover crop may be of distinct 

 utility in checking soil wash, especially if it is grown in 

 definite lines across the slope, and periodically cut down 

 and laid along the contours in order to form a series of 

 miniature terraces. For this purpose various species 

 of Crotalaria, Indigofera and Tephrosia may be used 

 with advantage, since these are leguminous plants which 

 also collect nitrogen from the air. 



Intercrops. 



If wide planting be adopted, some kind of intercrop 

 seems to be desirable in order that some revenue may 

 be obtained during the period before the rubber comes 

 into full bearing. In Ceylon, tea is commonly used for 

 this purpose, or more frequently the rubber is planted 

 at wide intervals through existing fields of tea. In this 

 case the growth of the rubber must be expected to be 

 slow. Rubber has also been planted somewhat widely 

 L. 8 



