RUBBER PLANTING 117 



upon a rubber plantation. The experience of the best 

 authorities in Ceylon shows that the annual application 

 of well chosen artificial manures leads to increased 

 growth and yield and to a better renewal of the bark 

 as well as to some immunity from disease. 



Green Manuring. 



Nitrogen is the most expensive of all the substances 

 required by growing plants. A sufficient supply of 

 nitrogen can most cheaply be added to soils, which 

 are deficient in this respect, by the practice of green 

 manuring. This method consists in growing some plant 

 which is capable of taking up nitrogen from the air. 

 The nitrogen is added to the soil by cutting down the 

 plants at the proper stage of growth and either 

 burying them or using them as a mulch. It is important 

 therefore that this process should only be undertaken 

 when there is plenty of labour available for dealing with 

 the green crop at the proper stage. The plants used for 

 green manuring belong to the natural order leguminosae. 

 They may conveniently be divided into (i) creepers and 

 climbers, (2) low growing bushy plants and (3) trees. 



Creepers and climbers are not generally to be recom- 

 mended. They are difficult to deal with, are liable to 

 smother the young rubber trees if neglected, and form a 

 convenient cover for snakes and other vermin. 



Among low growing bushy plants some of the best, 

 according to experiments carried out at Peradeniya, are 



