80 



T. Lyttleton Lyon and James A. Bizzell 



fact that, while with incubation of the natural soil the rate of nitrification 

 is more rapid in the planted than in the unplanted soil, yet when nitrifica- 

 tion is independent of the native organic matter the rate is practically the 

 same for both the planted and the unplanted soil. 



Another question that presents itself is whether the rate of nitrate for- 

 mation in the milimed soil would be in the order named. In Table 29 the 

 quantities of nitrates produced during incubation, both with and without 

 dried blood, are stated for the unlimed soil from the alfalfa and the timothy 

 plats. It is seen from this table that the rate of nitrate formation is in the 

 same order as in Table 28. 



The nitrate content of alfalfa soil and of timothy soil 



Determinations of nitrates in soil growing alfalfa and in soil growing 

 timothy were made from time to time from the summer of 1906, when the 

 seeding was done, to the autumn of 1911. In 1910 and 1911 nitrates were 

 determined also in the unplanted sections of these plats. The nitrate con- 

 tent of the planted sections of the plats during the first year of growth of 

 alfalfa and of timothy, and of both the planted and the unplanted sections 

 during the last two years, are given in Table 30: 



TABLE 30. 



Nitrates in Soil under Alfalfa and under Timothy, and in Bare Soil 

 Previously Planted to these Crops (Parts per Million) 





1906 



1910 



1911 



Crop 



May 25 



July 16 



Septem- 

 . ber 6 



July 6 



May 10 



May 29 



July 31 



No- 

 vember 8 



Alfalfa 



None 



Timothy 



None 



37 

 ""31 



23 

 '""21 



11 



8 



21 



42 



4 



21 



11 



39 



4 



18 



10 



65 



6 



32 



8 



121 



1 



50 



5 

 145 



3 

 129 



It may be seen in Table 30 that the nitrates under timothy are somewhat 

 lower than under alfalfa, but that the difference is not great especially 

 when compared with the nitrates in the unplanted soil. The mdications 

 are, therefore, that alfalfa either absorbs nitrates from the soil or depresses 

 nitrate formation to a very great extent. If, however, the nitrates under 

 alfalfa are compared with those in the bare soil previously planted to 



