PREFACE vii 



our soils, cropped for a scant three genera- 

 tions, contain only enough mineral elements to 

 continue producing food for seventy-five, one 

 hundred, or one hundred and fifty years. The 

 sole means offered to forestall this inevitable 

 day of doom is the use of chemicals as fertili- 

 zers, limited in supply themselves; a system 

 which carried to its logical conclusion consid- 

 ers the soil merely as a mixing bowl in which 

 food may be manufactured synthetically. 



Recently, however, there has been put for- 

 ward a more logical and less pessimistic hy- 

 pothesis concerning the fertility of the soil a 

 hypothesis fathered by the scientists compos- 

 ing the federal Bureau of Soils at Washing- 

 ton and backed by a long series of classic ex- 

 periments, as well as by the teachings of his- 

 tory. This theory assumes the mineral ele- 

 ments of the soil to be inexhaustible, an as- 

 sumption which the history of China, whose 

 soils are unimpaired, indeed are the richest in 

 the world after 4,000 years of intensive culti- 

 vation, seems to justify. 



An examination of this new hypothesis, in 

 the light of orthodox criticism, shares the 

 pages with a consideration of the extent of our 

 land resources. 



