162 



Plant Physiology 



89. Another view of soil fertility. In the discussion 

 of fertility thus far it is accepted that soils may be rela- 

 tively deficient in nutrients, that removal of nutrients 

 by crops tends towards practical deficiency, and that the 

 addition of fertilizers, although it may also affect avail- 

 ability, or balance, is a considerable factor in maintaining 

 fertility. Some investigators advocate another view. 

 This is in part based upon a method of observation and 

 experiment yielding results which seem to point to an 

 unexpected uniformity in the constitution of the soil solu- 

 tion from diverse types of soil. 



They conceive that the addition per acre of a few hun- 

 dred pounds of fertilizers to one or two million pounds of 

 earth (surface soil) is of no consequence in increasing 

 available nutrients, and they would ascribe the admitted 

 value of fertilizers to some more general effects upon the 

 soil, all of which are not understood. This view would 

 seem to demand that sodium chlorid would be, in general, 



