194 SOIL CONDITIONS AND PLANT GROWTH 



to it since denitrification requires an absence of air. Yet 

 blowing air through the dung causes greater loss. Again, 

 nitrogen may be lost where no nitrification is observed, and 

 further, the effect of antiseptics on the extent of the loss is 

 not what might be expected from a knowledge of their effect 

 on denitrifying organisms. In consequence of these results 

 they gave up the alternate oxidation and reduction hypothesis 

 and accepted the direct oxidation hypothesis. Some support 

 was lent to this direct oxidation view by the announcement 

 that Wood and Wilcox ^ had isolated from bran infusions 

 an organism able to liberate nitrogen direct from nitrogenous 

 compounds : apparently, however, this has not been confirmed. 

 On the other hand, Miintz and Laine (208c), working on 

 sewage purification, and dealing with percolation filters, reject 

 the oxidation hypothesis. In the first instance they note that 

 loss occurs only in presence of organic matter : it is not seen 

 when a solution of ammonium salts is run on to the filter. 

 Secondly, they find that the addition of nitrate to the liquor 

 increases the loss of nitrogen. Laboratory experiments 

 showed that it caused an evolution of nitrogen, and by working 

 in a vacuum a complete balance was made as follows : — 



At Start. At End. 



Nitrogen as ammonia 16-3 i5'2 mgs. 



„ in organic compounds . . . 12*2 13 "i 

 ,, as nitrite . . . . . .1*2 0*5 



„ as nitrate ...... 30*6 8-o 



Total .... 60-3 36-8 

 Loss .... — 23*5 



But they found dissolved in the liquid : — 



Free nitrogen 38-1 c.c. at N.T.P. = 23-9 mgs., which thus 

 almost exactly balances the loss. 



This experiment shows that denitrification can take place 

 and cause loss of nitrogen, though it does not necessarily ex- 

 clude the hypothesis of a direct oxidation of ammonia. 



Adeney's (2) results are also inconsistent with the direct 

 oxidation hypothesis. When albuminose, asparagin, etc., are 



^Journ. Soc. Chetn. Ind., 1897, 16, 510. 



