190 AGRICULTURAL ECONOMICS 



algae, and with microscopic animal life, chiefly nematodes. The 

 species of the latter alone run up into the thousands. This branch of 

 science has only been entered upon. It may be scarcely said to have 

 been exploited at all. It is no exaggeration to say that a cubic foot 

 of ordinary garden soil presents more unsolved problems in biology 

 than the entire solved problems up to the present time, and these 

 problems are more difficult than the building of the Panama Canal, 

 including both its engineering and its biological achievements; more 

 difficult than wireless telegraphy, than submarine or aerial naviga- 

 tion, for these latter have in part been solved. If we may judge the 

 future from the past, while great things may be expected from soil 

 bacteriology and soil biology during the next hundred years, at the 

 end of that period new problems just as important will be clamoring 

 for solution. 



One strikingly important thing has already been brought out in 

 soil bacteriology. In this case the discoveries are partly linked with 

 plant physiological discoveries. I refer to the nitrogen-assimilating 

 organisms in the root tubercles of the Leguminosae. It has been 

 known for over a hundred years that clovers and some similarly 

 related plants possess a remarkable power in renewing soil fertility 

 when these plants are plowed under for the growing of subsequent 

 crops. It was finally discovered that this property depended on the 

 presence of minute tubers or tubercles that occur abundantly on the 

 roots and that the real function was performed by a tiny bacillus which 

 lives in these tubercles. The bacteria living in the tubercles are 

 able to force the free nitrogen of the air into chemical combinations 

 and build up nitrates subsequently readily converted into proteids, 

 the most valuable food of both plants and animals. Still later 

 investigations have developed practical methods of cultivating and 

 distributing these germs for soil inoculation. 



F. The Conservation of Nature's Agricultural Resources 



55. THE DEMAND FOR CONSERVATION OF THE LAND 1 

 BY JAMES J. HILL 



How are we caring for the soil, and what possibilities does it hold 

 out to the people of future support ? We are only beginning to feel 

 the pressure upon the land. The whole interior of this continent, 



1 Adapted from The Natural Wealth of the Land and Its Conservation, address 

 at the Conference of the Governors of the United States, 1908, pp. 67-71. 



