PERNICIOUS WEEDS 47 



Weight 

 per acre, lb. 



70-8 

 211 

 94-8 



The figures in the third column give the weight of the 

 chief manurial constituents in the weeds contained 

 in an acre of ground, or in other words the quantity of 

 weeds growing on an acre would contain as much nitrogen, 

 potash, and phosphoric acid as there are in about 3341b. 

 of sulphate of ammonia, 171 lb. of sulphate of potash, 

 and 1 cwt. of basic slag respectively. 



The disadvantages associated with allowing weeds to 

 grow in young cocoa plantations may now be considered. 

 Unless the weeds are constantly cleared away from the 

 cocoa trees they will interfere with and check the 

 development of the young lateral roots of the cocoa 

 trees and rob them of a certain amount of available 

 plant-food. Shade trees and plants used as temporary 

 shading agents will be similarly affected. 



Many noxious perennial weeds found on cocoa plan- 

 tations are exceedingly difficult to eradicate if allowed 

 to grow unchecked, and rapidly spread in all directions. 

 The most pernicious are those which develop tuberous 

 or stoloniferous roots. Such plants cannot be destroyed 

 by cutting down the foliage-bearing portions. A striking 

 example of this category is the common nut-grass, 

 Cyperus bulbosus (rotundus). It is useless to cut down 

 this plant before it seeds to check its spreading, as its 

 roots frequently descend 3 or 4 ft. below the surface of 

 the ground and bear numerous " nuts " or bulbs, any 

 one of which is capable of producing a new plant. This 

 plant also develops lateral, nut-bearing roots which 

 frequently extend a foot or more from the parent plant. 

 A dense growth of this Cyperus, in the neighbourhood 

 of the roots of a cocoa tree, would be exceedingly difficult 

 to eradicate without seriously damaging the cocoa roots. 

 It would be almost impossible to extract all the Cyperus 

 bulbs from the ground at one time. By the time the 

 bulbs which had been left in the ground had produced 

 foliage their roots would have again become entangled 



