Relations of Higher Plants to the Formation of Nitrates 77 



TABLE 26. Nitrate Formation in Soil which Had Previously Grown Alfalfa 

 AND Timothy, but which Was Kept Free from Vegetation during the Year in 

 WHICH Test Was Made 



Plat 



Soil treatment 



Previous crop 



Nitrates 

 produced 



in seven 



days 

 (parts per 



million) 



4001 A 



Limed 



Limed 



Not limed 



Not limed 



Alfalfa 



33 



4002 A 



4001 C . 



Timothy 



Alfalfa 



Timothy 



29 

 26 



4002 C 



11 







recorded the nitrates produced in fourteen days incubation. These figures 

 represent the differences between the nitrates at the end of the incubation 

 period and the nitrates in the soil as it came from the field, 



TABLE 27. Nitrate Formation in Soil from Plats on which Alfalfa and Timothy 

 Were Grown and from Unplanted Sections of these Plats 



Plat 



Crop 



Nitrates produced in fourteen days 

 (parts per million) 





May 10 



May 29 



November 8 



4001 A, 4001 C 



4001 A, 4001 C 



Alfalfa... 



None 



Timothy 



None 



48 

 48 

 50 

 42 



59 

 40 

 41 

 33 



48 

 16 



4002 A, 4002 C 



4002 A, 4002 C 



34 

 15 



Except in the first test made, the alfalfa soil showed a greater nitrate 

 production than did the timothy soil. In every case the bare soil previously 

 planted to alfalfa nitrified more rapidly than did the bare soil previously 

 planted to timothy. In the test of November 8 the nitrates in the bare 

 soil as it came from the field were so high that the increase during incuba- 



