416 



THE PRINCIPLES OF SOIL MANAGEMENT 



Table LXII. Nitrates Produced on Heavily Manured and 



on Unmanured Soil 



Land in timothy 



April 23 



May 3 



May 14 



May 30 



June 1 



June 13 



June 20 



July 24 



August 14 



Land in maize 



May 19 



June 22 



July 6 



July 28 



August 10 



NO3 in parts per million, dry soil 



282. Effect of soil aeration on nitrification. 

 Probably the most potent factor governing nitrifi- 

 cation in the soil is the supply of air. In clay and even 

 in loam soils, the tendency to compactness is such 

 as to exclude air sufficient to enable nitrification to 

 proceed as rapidly as desirable unless the soil be well 

 tilled. Columns of soil eight inches in diameter and 

 of the same depth were removed from a field of clay 

 loam on Cornell University farm, and carried to the 

 greenhouse without disturbing the structure of the 

 soil as it existed in the field. At the same time, simi- 

 lar-sized vessels were filled with soil dug up from a 



