Manures in General 



their fertility, and sometimes even to the point of 

 ruining the land. 



Restitution. 



It is necessary to give back to the soil those 

 fertilising elements which the crops have taken from 

 it, and of which there are not enough reserves in the 

 soils, in the form of manure. 



This is usually done by means of farmyard 

 manure. But, even under the most favourable con- 

 ditions of formation and preservation, farmyard 

 manure contains and gives back far less than the 

 total quantity of the elements which the crops have 

 taken from the ground, and so the latter is incapable 

 of maintaining its fertility. Besides, simple restitu- 

 tion, even when complete, is no longer sufficient 

 for our progressive agriculture. We want to get 

 very large crops very economically. To supply 

 the deficit of the ordinary restitution, and to 

 increase the productivity of the soil we must have 

 recourse to 



Importation. 



This means that we must turn to outside ferti- 

 lising matters to restore or retain the fertility of the 

 soil, and to increase its capacity. This importation 

 is usually made in two different ways : 



1. By concentrated foods (cake, meal, etc.) which 

 are given to the cattle. 



2. By bought manures. This second way is 

 preferable because it is more economical. 



From the manurial point of view the first way is 

 not advisable because the units of nutritive matter, 



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