THE CALL OF THE LAND 



weights, measures, and coinage is to com- 

 merce. 



The most important problem in agricul- 

 ture is, and always has been, conserving and 

 increasing soil fertility. By good farming 

 you perform the miracle of eating your cake 

 and keeping it too. The principles involved 

 in this magic were laid bare by Liebig's in- 

 vestigations given out in 1840. Nearly the 

 entire commercial fertilizer industry, 

 amounting to millions of dollars in our 

 country alone, is based upon the doctrine 

 of this great teacher, that organic manure, 

 portions or the debris of plants and animals, 

 may be replaced by the inorganic com- 

 pounds into which it breaks up in the 

 ground. Supplementary to this came Hell- 

 riegel's epoch-making discovery that by 

 bacterial action on the roots of legumes 

 atmospheric nitrogen may be made avail- 

 able as plant food. The work of experiment 

 stations has been largely the application of 

 these fundamentals and the refutation of 

 erroneous conclusions from them. Hellrie- 

 gelism as worked out at the University of 



190 



