Feb., 1919] Nitrogen Content of Volcanic Ash 223 



The ammonia content of the tundra is about that of a normal 

 soil. Ordinary soils contain little ammonia, usually from 0.2 

 to 0.8 parts of nitrogen per 100,000. Rich garden soils may con- 

 tain up to 2 parts per 100,000, while Boussingault reports 50 

 parts in leaf mould from South America. Peat has been found 

 to contain as high as 18 parts per 100,000. 



The nitrite content is much higher than that found in the 

 samples of ash. The surface tundra has no nitrites, as was to 

 be expected in an area well under-drained and subjected to 

 frequent rains. The nitrite forming bacteria do not operate 

 near the surface but are found in the deeper, darker layers. 

 The presence of much vegetable matter in the tundra, upon 

 which the nitrifying bacteria may work, accounts for the 

 greater proportion of nitrous nitrogen over that found in the 

 ash. 



On the northerly slopes the winter frost had not left the 

 tundra by June 21st. Determinations made on the frozen 

 tundra did not indicate any marked difference between its 

 ammonia and nitrous nitrogen content and that already thawed 

 out. Nitrification is rather feeble at temperatures below 5° C, 

 and only begins to be really active at 12^ C. A determination 

 made on August 22nd gives no indication of any material 

 change in the rate of nitrification with the season. Evidently 

 the cold condition of the tundra produced no change in the 

 nitrite content throughout the long frozen period. 



The total nitrogen content of the tundra, 432 parts per 

 100,000, is considerably higher than that of the average culti- 

 vated soils. Illinois prairie soils contain 308 parts per 100,000, 

 while the abnormally high nitrogen content of the rich black 

 loam of the Red River Valley, in the neighborhood of Winnipeg, 

 contains but 373. This large total nitrogen content is probably 

 associated with a low rate of nitrification in the cold, shallow 

 soil of the tundra. 



Manitoba Agricultural College, Winnipeg. 



