538 



area is thus added to the area of soil available for rubber roots and the 

 growth of the trees is improved. 



In addition to arguments for clean weeding there is a local one, 

 the danger of the ground being taken possession of by "lalang" 

 (Imperata arimdmacea), a pestilent weed, which once allowed to invade 

 a plantation can only be eradicated at enormous expense. This plant 

 is ubiquitous, is always one of the first to cover newly opened land, 

 and by far the most difficult weed to eradicate. 



The experience gained in the use of tapioca as a catch crop in 

 rubber which obtains on some thousands of acres of rubber showing 

 excellent growth is another argument in favour of keeping the soil 

 covered up. Few, if any, crops take more from the soil than tapioca, 

 but this loss of valuable plant food in the soil is to a great extent 

 compensated for by the advantage of keeping the soil from the sun and 

 rain. The girths of young rubber trees grown with tapioca is in many 

 cases as large as those of trees in similar land, clean weeded, and with- 

 out any other crops. 



The position thus is : Clean weeding is a costly process, which 

 ensures quick growth of young rubber trees and prevents the land 

 being taken possession of by undesirable weeds. On undulating land 

 it causes loss of top soil, and on all land it means loss of moisture in 

 the surface layers of the soil. 



Eubber plants usually grow better in clean than in weed-covered 

 land, because the plant food and water present in the soil is all availa- 

 ble for the rubber and is not used by the roots of various other plants, 

 which are useless to the planter. 



The high cost of weeding and the fact that, with a not too 

 abundant supply of labour, the majority of coolies are employed at 

 this work, both point to the desirability of some other method not less 

 helpful to the growth of young rubber, if such can be found. 



Though figures of cost of weeding vary very greatly, on some 

 estates the cost two years after the land has been opened is not under 

 $2 per acre, per month, or $24 per year. This represents on an estate 

 of 1,000 acres a cost of $24,000 per year, and a probable cost for weed- 

 ing of nearly $100,000 before the rubber is in bearing. 



In labour it represents a continual force of about 250 coolies work- 

 ing for 300 days in the year. 



I have for the last three years been investigating the question of 

 a substitute for weeds which will reduce the wage bill without reducing 

 the rapidity with which the rubber trees grow, and mentioned in my 

 annual report for last year three plants which observation and experiment 

 show to be suitable and therefore worth a serious trial on everyestate. 



These three plants belong to the order Leguminosse, the clover, 

 pea and crotaloria tribe, a group of plants many of which are charac- 

 terised by the possession of bacteria on their roots. These bacteria, 

 the life history of which has been investigated fully by a large number 

 of botanists and agriculturists, live in what is technically called sym- 

 biotic relationship — i.e., both host plant and bacterium being of mutual 

 service to each other. In a report of this character it is unnecessary 

 to more fully explain this point, but it will suffice to say that the 

 bacteria which form characteristic nodules on the roots of the host 



