Food for Plants. 



157 



can become available, and it seems that during these 

 transformations nitrogen as ammonia, nitrate or as ele- 

 mental nitrogen must be lost in considerable quantities. 

 As bearing on this it may be pointed out that Russell 

 and Richards (5) have shown by laboratory experiments 

 with manure that in addition to the loss of ammonia by 

 volatilization there is still a loss amounting to 15 per 

 cent, or more of total nitrogen, and they have gone fur- 

 ther and shown that during decomposition there is an 

 evolution of gaseous nitrogen. This they believe com- 

 pletes the account of- the loss. This loss, they claim, 

 does not go on under wholly anaerobic or wholly aerobic 

 conditions but under mixed anaerobic and aerobic con- 

 ditions which arise when manure is being produced. 

 The}' explain further that in the natural manure heap 

 nitrogen is also lost as gaseous ammonia as well as in 

 the form of nitrogen gas. 



It is very probable that in a more limited way, similar 

 changes take place when organic compounds are placed 

 in the soil and that a part of the loss of nitrogen noted 

 in our experiments must be thus accounted for. It is a 

 well-known fact that when an organic substance like 

 cottonseed meal or dried blood is mixed with soil and 



TABLE 2 

 Percentage of nitrogen recovered from difiererit materials 



♦ First ten years. 

 + Second ten years, 

 j Twenty years. 



