362 



STATE BOARD OF AGRICULTURE. 



ceedingly tedious and uncertain experiment to prove an increase, while 

 the curve shows plainly that the nitrifying bacteria in the soil treated 

 with dextrose reached their maximum number at about the twentieth 

 day, while without dextrose this point was not reached until about the 

 twenty-seventh day. 



It seems quite probable from this discussion that dextrose has a 

 stimulating influence, not upon the nitrification process itself, but 

 upon the quantity of nitrifiers. It is probably used as food by these 

 nitrifiers, either directly or after having been broken up into simpler 

 compounds (e. g., CO2) by other soil bacteria. 



The next curve is an illustration for the necessity of determining as 

 many points as possible of a process to be analyzed by the form of its 

 curve. The data of Figure 12, representing the nitrification in soil with 

 ammonium salt, are taken from the paper of Coleman, mentioned above. 



NITRATE NITROGEN IN SOIL WITH AMMONIUM SALT. 



In the beginning 71.45 mg. per kg. of dry soil. 



After 3 weeks 316.82 mg. per kg. of dry soil. 



After 5 weeks 503.88 mg. per kg. of dry soil. 



After 7 weeks 501.91 mg. per kg. of dry soil. 



After 9 weeks 514.97 mg. per kg. of dry soil. 



The curve in straight black lines gives the actual result, and the two 

 dotted lines are two interpretations, both possible, according to the 

 given facts. If we did not know that the nitrification is really a pro- 

 cess caused by micro-organisms, and that the fermentation cuitc is the 

 only interpretation possible, the given data would not show this. It is 

 also evident that the determination of more points towards the end of 

 the fermentation does not improve our knowledge of the curve much. 

 The points of greatest importance are those which demonstrate the point 

 of inflection, and this necessitates several analyses at the beginning of 

 the fermentation. Comparatively little attention is paid generally to 



Fig. 12. Nitrificatiofi in Soil, and Two Possihle Interpixtations. 



