CHAPTER VII 



MANURES 



Exhaustion of the Soil. — It has been shown that grow- 

 ing plants take up certain substances from the soil in a 

 soluble condition, and these substances — which are called Active 

 active constituents — exist in the soil in a small proportion of'soIL^^"'"' 

 only. If land be continually cropped, therefore, and no 

 means be taken to restore the substances removed away in 

 the crops, the soil becomes gradually exhausted, and the 

 land loses its fruitfulness. In nature this does not happen, unculti- 

 for, in forests, the constituents of the soil are returned by ^?-'^^^ '^"'^ 



' J does not 



the decay of the leaves and branches and trunks which fall become 

 to the ground ; and, on prairies and savannahs where wild 

 animals roam, the return to the earth of the substances 

 eaten as food, is continually going on, for the animals 

 manure the land with their excrements in life, and with their 

 bodies when they die. 



The land must be regarded by the planter as a bank in The land the 

 which he has opened an account. If he continually draw ^^^^Jk.®'^ ^ 

 cheques on the bank, and make no fresh deposit to meet the 

 drain, he will sooner or later come to the end of his capital, 

 and the same argument applies to the soil. In cacao and Bad culti- 

 coffee cultivation in the West Indies, particularly on lands v^"°"- 

 of peasant proprietors, one often sees the planter take away 

 crops year after year, whilst he does next to nothing to 

 make up for the heavy drain on the land ; and, then, after a 

 time, he finds he gets very small crops, and he thinks the 



