326 SYSTEMS OF PERMANENT AGRICULTURE 



Since the promulgation of much definite knowledge during the 

 first half of the last century, by such teachers as De Saussure, Davy, 

 Bousingault, Liebig, and Lawes and Gilbert, the increasing appli- 

 cations of phosphates, manures made in part from imported food 

 stuffs, and other fertilizing materials, including more or less po- 

 tassium salts and nitrates, and in more recent years a larger use of 

 legumes, are found to bear fruit in the corresponding increase in 

 the crop yields of western Europe, as will be seen from the follow- 

 ing crop statistics, compiled by Professor Wilhelm Kellerman 

 (Landwirtschaftliches Jahrbuch, 1906, page 289) and republished 

 by the United States Bureau of Soils (Bulletin 55) for the purpose 

 of showing that soils do not wear out. 



The data from Schmatzfeld are of interest because of the old 

 records, but they appear to represent in the main single years, 

 and in part selected years. Even the tenth-year records from 1830 

 to 1870 may signify but little. Thus the rye and oats for 1870 

 average less than for 1830. The late averages are, of course, very 

 significant. 



The Trebsen records have much value because they include 

 several ic-year averages which show no advancement prior to the 

 publication of De Saussure's work, which gave to the world the 



YIELDS OF CEREALS IN SCHMATZFELD, GERMANY 



