CHANGES IN INORGANIC CONSTITUENTS 427 



gestion carried out of such data then, involves the addition of salts 

 to the toxic salts already contained in a given soil, and thereby im- 

 proving its ammonifying and nitrifying power. 



VARIABILITY IN SOIL FERTILITY INVESTIGATIONS 



Waynick has pointed out that the variations between different soil 

 samples taken from a small area may be of such magnitudes as to throw 

 doubt upon the validity of the experimental data obtained with one or 

 a limited number of samples. A single sample of any soil is of little 

 value as regards determinations which may be made upon it. A com- 

 posite may be considered of value only after the probable error to which 

 it is subject is known and this can only be determined by the use 

 of a large number of individual samples. 



