BOOKS AND CURRENT LITERATURE 



Soil Chemistry. — Perhaps the most important single phase of soil 

 science in the United States has been the violent controversy concern- 

 ing the theories of soil fertility announced by Professor Whitney, Dr. 

 Cameron and their associates in the United States Bureau of Soils. 

 Few factors, if any, have furnished equal stimulant to observation and 

 research in this field. Unfortunately, the point at issue has been too 

 frequently obscured by most regrettable personalities which have been 

 no more pertinent than they have been seemly. In the opinion of the 

 reviewer the point of difference is very simple and readily defined. 

 The older theory — opposed by the Bureau of Soils — assumed the soil 

 unchanging. Certain useful elements (plant food materials) got into 

 the soil when it was formed and stayed. These elements might, it 

 is true, be partially lost by leaching, but the only source of loss practi- 

 cally important was believed to lie in the removal of plant food ele- 

 ments in the garnered crops. This would constitute an actual and 

 artificial "depletion" of the food supply of the soil. From this theory 

 there follow two practical conclusions: (1) soil analysis ought to express 

 or indicate soil fertility; (2) soils will be exhausted or worn out by 

 cropping. 



Against this theory, then current, if not universal, Professor Whitney 

 and Dr. Cameron alleged that the two practical conclusions just stated 

 were not in accord with the facts of observation and that their falsity 

 was due to the incompleteness of the theory upon which the conclusions 

 were based. According to the Bureau of Soils the content of plant 

 food materials is not the only factor affecting soil fertility and frequently, 

 if not generally, it is not the main factor. Furthermore, the content 

 of plant food is not an unchanging value and it may increase as well 

 as decrease by natural processes. There is such a thing as self-enrich- 

 ment of the soil. 



It is perhaps significant that never, to the reviewer's knowledge, 

 has the essence of the Bureau's theory been attacked. Always the 

 attacks are against single supporting arguments or against more or 

 less secondary conclusions. For instance, the suggestion of organic 

 "toxic principles" present in soils and retarding growth received on 



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