CHAPTER XVIII. 



THE PHYSICO-CHEMICAL INVESTIGATION OF SOILS IN RE 

 LATION TO CROP PRODUCTION. 



THE chemical constituents of soils have been incidentally 

 mentioned and discussed above, both in connection with the 

 processes of soil-formation, and with the minerals that mainly 

 participate therein. The manner of their occurrence and their 

 relations to plant life, so far as known, must now be consid- 

 ered more in detail. 



HISTORICAL REVIEW OF SOIL INVESTIGATION. 



While the obvious importance of the physical soil-conditions 

 has long ago rendered them subjects of close study by Schiib- 

 ler x Boussingault and others, the chemistry of soils was very 

 generally neglected for a considerable period, after the hopes 

 at first entertained by Liebig that chemical analysis would 

 furnish a direct indication and measure of soil fertility, had 

 been sorely disappointed in respect to the only soils then in- 

 vestigated, viz., the long-cultivated ones of Europe. The re- 

 sults of chemical analysis sometimes agreed, but as often 

 pointedly disagreed, with cultural experiences; so that after 

 the middle of the nineteenth century, but few thought it worth 

 while to occupy their time in chemical soil analysis. 



Popular Forecasts of Soil Values. In newly-settled coun- 

 tries, and still more in those yet to be settled, the questions of 

 the immediate productive capacity, and the future durability of 

 the virgin land are the burning ones, since they determine the 

 future of thousands for weal or woe. This need has long ago 

 led to approximate estimates made on the part of the settler, 



1 The early work of Schiibler on soil physics, published at Leipzig in 1838 

 under the title of " Grundsatze der Agrikulturchemie " and now almost inaccessible 

 outside of old libraries, is remarkable as having anticipated very definitely much 

 that has since been brought forward and elaborated anew. He is really the fathet 

 of agricultural physics. 



3 J 3 



