Relations of Higher Plants to the Formation of Nitrates 71 



the time of year is not the only determining factor in the formation of 

 nitrates; nor is the decrease of nitrates during the later stages of growth due 



(00 



BEFORE 

 PLANTING 



JULY 

 /5-20 



AUGUST 

 /'20 



SEPT 



OCT 



DIAGRAM XXI. — Relative nitrate content of soil undzr mzize -planted 

 July 5, harvested August 20, 1912 



80 



70 

 GO 



30 



20 



BEFORE iJC/NE 



JULY 



AUGUST 



SEPT 



OCT 



<) = — — -<r ^l 



DIAGRAM XXII. — Relative nitrate conteni of soil under potatoes, 1912 



entirely to the removal of easily nitrifiable organic matter, otherwise the 

 nitrate content would not have risen in the soil on which a regrowth 

 of maize occurred. 



