48 



b. Plants which improve the soil. 



To this category belong the Leguminous plants, which 

 are used for green manure ; they give a great quantity 

 of leaves which are rich in nitrogen. Sometimes Crota- 

 laria Striata or Tephrosia purpiirea are used on the 

 Estates in the Malay Peninsula as green manures ; most 

 planters however are not in favour of such a system, 

 thinking that these plants assist the distribution of fungus. 

 Considering that the land already contains a large pro- 

 portion of nitrogen and organic matter, green manure 

 does not appear to be of great importance. 



c. Plants which protect the soil 

 against wash. 



We have already seen that on the Malay Peninsula 

 plants are very seldom used to bind the soil. Only once 

 I saw this systematically carried out and in that case 

 ferns were planted in rows between the Hevea. On a 

 rubber estate in Sumatra, I saw Krokot, (Scstwium Por- 

 tulacastritm) used; {he cultivation was attempted on the 

 slopes, but without material success. In the mountains 

 of Java not unfrequently "Bajem merah" (Alternant hera 

 amoena) is planted out in horizontal rows, the stalks 

 grow close to each other and form a sieve, so that the 

 soil is kept together. Latterly also, Leucena Glauca is 

 used for this purpose, and this has the advantage of 

 improving the soil to a considerable degree ; it must be 

 cut down regularly, and the foliage must be left to rot 

 on the soil, or must be dug in (see fig. 9). 



