INTRODUCTION. 



If an apology were needed for this compilation, the first public 

 document issued by the Department of Agriculture, after its elevation 

 to an executive department with a Cabinet officer at its head would 

 offer the same; for the report of the Committee of the Association of 

 Agricultural Colleges and Experiment Stations, therein quoted, con- 

 tains the following pregnant passages: "To one familiar with the 

 history of this sort of research, it is interesting to note how many of 

 the problems suggested for study by the different stations are nearly,, 

 or quite, identical with those with which the work of the experiment, 

 stations was begun when the first ones were founded, over thirty years 

 ago, and how large a proportion are, in fact, the same that have been 

 the object of the bulk of the study of these and other institutions of 

 research in this country, in England, and, to a far larger extent, on 

 the Continent of Europe, for half a century." And again: "The 

 difficulties which the newer stations have to meet are enhanced by 

 the fact that nearly all the accumulated experience is recorded in 

 foreign literature, and is accessible only to thofee who have at hand the 

 great accumulation of journals and other publications in which the 

 results of earlier and later research are set forth." Therefore, the 

 committee is strongly of the opinion that "one of the most useful 

 services to the cause would exist in the compilation of the main 

 results of this research in various special lines, and the putting of 

 them not only into English, but in forms conveniently suited to the 

 use of American investigators." 



An attempt to lay before the large body of intelligent American 

 farmers, in clear, concise, intelligible language, the latest practical 

 results of agricultural science in Germany, may, therefore, hope to be 

 not altogether unwelcome. Destined mainly to enlighten the tiller 

 of the soil about the great importance of soil nutrition, and to impress 

 upon his mind in a brief way the latest discoveries regarding the 

 problem of fertilization, this publication does not claim to enter 

 deeply into the scientific aspect of the subject matter, but to give only. 



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