SOILS AND FERTILIZERS 



A study of the composition of ash of plants led him 

 to propose the mineral theory of plant nutrition. 

 De Saussure had shown that plants contain certain min- 

 eral elements, but he did not emphasize their impor- 

 tance as plant food. Liebig's writings on the composi- 

 tion of plant ash, and his emphasizing the importance of 

 supplying crops with mineral food, led to the commer- 

 cial preparation of manures, which in later years devel- 

 oped into the commercial fertilizer industry. The work 

 of Liebig was not conducted in connection with field 

 experiments. It had, however, a most stimulating in- 

 fluence upon investigations in agricultural chemistry, 

 and to him we owe, in a great degree, the summarizing 

 of previous disconnected work and the mapping out of 

 valuable lines for future investigations. 



Liebig's enthusiasm for agricultural investigations 

 may be judged from the following extract : " I shall be 

 happy if I succeed in attracting the attention of men 

 of science to subjects which so well merit to engage 

 their talents and energies. Perfect agriculture is the 

 true foundation of trade and industry ; it is the founda- 

 tion of the riches of states. But a rational system of 

 agriculture cannot be formed without the application of 

 scientific principles, for such a system must be based on 

 an exact acquaintance with the means of nutrition of 

 vegetables, and with the influence of soils, and actions 

 of manures upon them. This knowledge we must seek 

 from chemistry, which teaches the mode of investigat- 

 ing the composition and of the study of the character of 



