PREFACE vii 



more it implies, or should imply, skill and knowledge in 

 using them. 



If this book is to have any justification for its exist- 

 ence, it will be by helping men to a greater skill and 

 knowledge in the use of their fertilisers and manure. 

 There is no lack of books which give an account of 

 the origin and composition of fertilisers : my object is 

 rather to make the reader understand their mode of 

 action and their relation to particular crops and soils. 

 For it is only by understanding the why and the how 

 that a farmer can properly adjust his manures to his 

 soil and his style of farming ; he must to some extent 

 reason the scheme out for himself, he cannot simply 

 be told. 



The scientific man is always being asked to arrange 

 his experiments to demonstrate the best way of grow- 

 ing this or that crop, by the best being implied the 

 cheapest : farming visitors to Rothamsted are often 

 inclined to suggest that the plots, if interesting, are 

 not " practical." After sixty years of work they rather 

 expect to see the absolutely cheapest form of manur- 

 ing each crop set out once and for all. But in 

 practical farming there is no "best" way of doing 

 things ; the mere fact that the weather of the coming 

 season is unknown makes it impossible to specify the 

 absolutely right course either in cultivation or in manur- 

 ing. The question even of the best manure for a given 

 crop is complicated by the manner in which every farm 

 differs somewhat from every other, not merely in its soil 

 and climate, for these matter less than is commonly 

 supposed, but in its object and management. One 

 man aims at crops, another man gets his money 

 back by his stock; one man has only to pay 15s. 



