IISrTRODUCTIOK. 9 



in a cubic foot of soil. But we must not imagine 

 that in order to be able to secure a certain yield of 

 any crop, it would only be necessary to ascertain by 

 analysis the exact amount of plant food in the soil, 

 and to supply the deficiency of the substances 

 needed to bring the aggregate amount in the soil 

 up to that required in the production of the intend- 

 ed crop. The subtle ways and agencies of nature, 

 the action of soil and life forces and forms in it 

 baffle the skill of the chemist, and force him to con- 

 fess that he has reached the end of his wisdom. 



Where chemistry fails to acquaint us with the 

 causes, from which we might expect certain results, 

 the experimenter must step in, observe the results, 

 and try to ascertain the causes in his way . The 

 chemist' s analysis and the farmer' s tests — these are 

 indispensable requisites of modern husbandry, and 

 the corner stones of success in profitable crop feeding. 

 No farmer can select and purchase fertilizers with 

 proper regard to economy and fitness, or apply 

 manures intelligently, unless he has some under- 

 standing of the principles that govern plant growth, 

 of the various elements of plant food, their action 

 and their values. 



The study of these problems has been a source of 

 much satisfaction and profit to me. I believe it 

 would also be so to other farmers and farmers' boys, 

 who in this era of low prices and " agricultural de- 

 pression" are trying hard to learn how, by the use 

 of improved methods, farming may be made to 

 yield fair returns for the labor and capital invested. 

 I am sure the task will be materially lightened by a 

 thorough understanding of the principles here in- 

 volved. 



These considerations have lead me to attempt. 



