148 



INFLUENCE OF SALTS ON THE SOIL 



calcium nitrate, potassium chlorid, potassium sulphate, magnesium 

 nitrate, and sodium sulphate. 



200 



100 



O o 



FIG. 21. Graphs showing the percentage of stimulation at the above noted molec- 

 ular concentrations (See Fig. 20), the untreated soil being counted as producing 

 100 per cent, of nitric nitrogen. 



o 



- ^ 6 o i 

 o o R w 5 







FIG. 22. Graphs showing the molecular concentrations at which the various salts 

 are toxic to ammonifying and nitrifying organisms in the soil. 



There were also six which failed to stimulate the nitrifiers, but 

 it is quite evident from the results given in Fig. 20 that in the 

 majority of cases these are different from the ones which failed to 

 stimulate the ammonifiers. This is remarkable when we remember 



