THE NITROGEN CYCLE 



453 



The amount of nitrogen removed by the maize crop 

 was greater than that removed by the timothy; conse- 

 quently the greater amount in the former soil cannot be 

 due to the effect of the crop. 



So far as the conservation of nitrogen is concerned, 

 sod is an ideal crop, for nitrates are formed very little 

 faster than they are used, and are not carried off in large 

 quantities by the drainage water. 



In the corn land as much as 175 pounds of nitrate 

 nitrogen was present in the first twelve inches of one 

 acre, or fully three times as much as was used by the 

 crop. 



372. Depths at which nitrification takes place. War- 

 ington 1 concluded from his experiments that nitrification 

 takes place only in the surface six feet of soil. Hall 2 

 has pointed to the fact that no more nitrates were leached 

 from the 60-inch lysimeter at Rothamsted than from the 

 one 40 inches deep ; which is very good evidence that in 



1 Warington, R. On the Distribution of the Nitrifying 

 Organism in the Soil. Trans. Chem. Soc., Vol. 51, p. 118. 

 1887. 



2 Hall, A. D. The Book of the Rothamsted Experiments, 

 p. 230. New York, 1905. 



