The surface layer is rich in numus and available 
plant food; consequently, denudation is responsible 
for a reduction in fertility and of deterioration of 
the texture of the soil. It is doubtful whether green 
manuring and the application of artificial manures 
will ever compensate for this loss of surface soil 
by wash ; and, in any case, the expenditure involved 
in attempting to restore this fertility is heavy. 
There are several methods of conserving surface 
soil, the most common and effective being the 
growing of a cover crop. Other methods are strip 
weeding, circle weeding, catch pits, terracing, bund- 
ing, and the planting of strong growing grass in 
contour. On undulating land a leguminous cover 
is recommended. In the case of very steep slopes, 
catch pits are not very effective and it is frequently 
impossible to establish cover crops. The most satis- 
factory method is strip weeding in contour, or circle 
weeding around the trees. Terracing is an ideal 
system but it is difficult to construct a terrace in 
contour in planted areas without doing considerable 
damage to a number of the trees. 
It is frequently found that the surface of a soil is 
so hard that the rain water flows over it and only 
a small amount of moisture is absorbed. Catch pits 
are useful in such cases, as a considerable proportion 
of the water is retained by the pits and gradually 
passes through the soil. 
Drainage. On the plains, the water table is, as 
a general rule, near the surface'; but 
there is considerable variation in different soils and 
in various districts. Soils with a high water table 
require to be thoroughly well drained before any 
attempt is made at planting. In the case of the 
rubber tree it is essential to have the land well 
