170 COCOA CHAP. 



Before describing the manner in which manuring 

 experiments are carried out, one point regarding the 

 exhaustion of the soil by the crop grown on it has to 

 be discussed, as it has given rise to much confusion, 

 and even to erroneous statements in handbooks on the 

 subject. 



It is often said that manuring is indispensable to 

 every cultivation, because a certain amount of the 

 various necessary elements (in the first place, nitrogen, 

 potash, phosphoric acid and lime) are always taken 

 from the land in the crop. If therefore we desire the 

 land to maintain its original richness, we must return 

 to it the plant-food we take from it in this way. 

 Some writers on cocoa, indeed, go so far as to analyse 

 the seeds and to conclude from this analysis what sort 

 of manure has to be given to the soil. In this reasoning 

 one thing is always forgotten viz. the fact that every 

 year a part of the dormant (or non-available) plant- 

 food is converted into available food by means of the 

 different atmospheric (influences, and also by means of 

 the action of the plant roots themselves. 



Especially in the tropics, where weathering of the 

 soil goes on quicker than in cooler climates, it is not at 

 all exceptional for a soil to keep its original fertility 

 without manuring : that is to say, the quantity of 

 available plant-food converted every year from dormant 

 plant-food is equal to the quantity extracted from the 

 soil by the plants. If this quantity is sufficient to 

 make the plant give its highest yield, it will obviously 

 be impossible to increase the yield by manuring ; and 

 this will be the case not only in the first few years of 

 cultivation, but also after many years of production. 

 It is far from the author's intention to make planters 

 believe this to be the rule, and to encourage them 

 to regard manuring as generally superfluous, but it 

 cannot be too clearly stated that the quantity and 

 composition of the crop reaped cannot give any reliable 

 indication as to the particular kind of manure required 

 to increase the bearing power of the trees. The 



