158 COCOA 



CHAP. 



Planters are mostly agreed that in such circumstances 

 clean weeding is not to be advocated, as the weeds are 

 necessary to keep the soil together. The other influence 

 of weeds to be mentioned here is doubtless an important 

 one, but it is by no means so clear or so easily under- 

 stood. The detrimental effect of weeds on the growth 

 of trees cannot be attributed wholly to their drying 

 effect on the soil and to the prevention of the free access 

 of air. It has been proved by experiments that still 

 another noxious influence must exist, and the only 

 possible explanation seems to be that the roots of the 

 weeds produce some substance which is poisonous to 

 the tree. However interesting this subject may be, 

 there is no room in this handbook to go into further 

 detail. 1 



It will now be clear that the presence of weeds 

 has great disadvantages, but also a few advantages ; 

 that the system of " clean- weeding," i.e. the destruction 

 of all weeds as thoroughly as possible, is in some 

 cases advantageous but generally unsuitable ; and that 

 while sometimes the planter's motto should be " Kill 

 the weeds," there are more cases in which it should be 

 " Save the weeds." Which is the right one depends 

 wholly on local conditions. 



These conditions also control the question whether 

 the ordinary method or " clean weeding " is to be 

 preferred. 



" Clean weeding," i.e. the systematic absolute 

 destruction of all weeds, has advantages, and the reader 

 will understand from what has been said that it is 

 especially advocated when there is no fear of a deficiency 

 of humus or of the soil being washed away. This 

 is the case on flat lands or on not too steep slopes, 

 where cocoa is grown under suitable shade trees which 

 afford sufficient humus by their fallen leaves and 



1 Readers who take an interest in this subject may be referred to the articles 

 by Milton Whitney ("On Soil- fertility," and other Bulletins of the Division 

 of Soils of the U.S. Dept. of Agriculture, Washington). The subject is also 

 treated by Willis, Harpenden (Gardener's Chronicle, 1909, p. 337), and by 

 Fletcher (Memoirs of the Dept. of Agriculture in India, vol. ii. No. 3). 



